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MickeyD
03-17-2010, 01:17 AM
I got lucky and was invited to test drive the Chevy Volt that was in town for the SXSW Interactive show last Sunday and I was blown away by it. The car was one of the first 50 pre-production test cars, but other than some additional sensors and software differences it is the car that will be available in the fourth quarter of this year. Both interior and exterior design and feel are very nice, the seats felt great and even the back seat was roomy and comfortable (I am 5'11" with short legs, big feet, and a barrel chest). The driving experience is a little different than a normal car. The motor is TOTALLY quiet under 50 mph (we were on a closed track that is all there was room for), the torque curve is flat and very strong, and handling is more like a gocart than a normal car due to the weight being so low in the chassis. The electric boost steering actually had decent feedback and the brakes were powerful but not in your face. With four adults in the car I would estimate zero to sixty in the eight second range. It felt at least as fast as our 5.3L Tahoe on ethanol (about 375HP but a lot more weight there). If GM can get production up and avoid too many teething issues they have a real winner.

dp
03-17-2010, 02:06 AM
What did you think of the AC?

MickeyD
03-17-2010, 08:19 AM
It seemed to work fine. One of the guys said that it was a variable electric compressor so that it would actually work in the south in the summer.

EVguru
03-17-2010, 08:42 AM
I drove a GM Impact (EV1 prototype) back in 1997 or so. I was really impressed by the job GM had done taking the Aerovironment concept vehicle and turning it into a production ready design.

If you can find a copy, read 'The Car That Could', which is the story of the development of the EV1 (written at the time with GM's permission).

kf2qd
03-17-2010, 09:14 AM
Hate to sound pessimistic, how much will it cost, how far will it go on a charge, and at US$0.13/KWH how much will it cost to charge?

And the bigger question, at least for those of us who aren't able to afford one new... How long will the batteries last and how much will it cost to replace them?

Or is the bigger question - How long til the current administration requires us all to buy one?

John Stevenson
03-17-2010, 09:38 AM
I would imagine they are expensive to run given you have to factor in they will have no resale value.

The owners will only get rid either when they start to give trouble / need new batteries and / or the manufacturers bring a new model out and stop supporting the old one, maybe with government incentives to upgrade like the scrappage project.

.

EddyCurr
03-17-2010, 11:26 AM
If you can find a copy, read 'The Car That Could', which is the story of
the development of the EV1 (written at the time with GM's permission).Then as a chaser, watch Chris Paine's 2006 documentary
"Who Killed The Electric Car" about the odd demise of the EV1.

The local library branch likely has a DVD copy or two.

.

MickeyD
03-17-2010, 12:30 PM
At what we pay here (about $.11/kwh) it would cost about $1.75 to recharge the battery pack for 40 miles of range. The engineer that I spoke with said that because they only charge the pack to 80% and only let it drop down to 30% the batteries should last ten years.

lazlo
03-17-2010, 03:23 PM
At what we pay here (about $.11/kwh) it would cost about $1.75 to recharge the battery pack for 40 miles of range.

That's assuming 100% energy conversion. You have to consider the power supply and charging losses. Then a VFD converts the DC power back into 3-phase to power an induction motor. More losses.

So you're paying roughly $2.50 - $3.00 per 40 miles of range, and most of our electricity in Central Texas is generated from coal.

EVguru
03-17-2010, 03:50 PM
My VW Scirocco conversion used 3KWh on the 10 mile commute to work along the M1 Motorway with speeds up to 65mph or so. That's measured at the power outlet, so includes charging losses.

http://www.compton.vispa.com/scirocco


Just went away and looked up the Volt specs. The used capacity of the battery pack is 8Kw/hr (16Kw/hr nominal), so a full charge would cost 0.11 * 8 / 0.85 (typical Lithium cell efficiency) = $1.04.

DICKEYBIRD
03-17-2010, 03:51 PM
Having gone through some terribly cold weather this winter, I have to ask how good does the heater work?

JCD
03-17-2010, 05:06 PM
Having gone through some terribly cold weather this winter, I have to ask how good does the heater work?


I also have to ask about the heat. If it is cold outside, It seems like it could take 1000 Watts +_ to heat or defrost/heat + heated seat, rear window defogger etc.
Is there a "Large Battery" option?

Davek0974
03-17-2010, 05:15 PM
Does it have an iPod socket on the radio ;)

pcarpenter
03-17-2010, 05:18 PM
Just went away and looked up the Volt specs. The used capacity of the battery pack is 8Kw/hr (16Kw/hr nominal), so a full charge would cost 0.11 * 8 / 0.85 (typical Lithium cell efficiency) = $1.04.

I think you just calculated the efficiency on the output side (battery only as it does not consider inefficiency due to hysteresis losses in the motor), but as Robert (Lazlo) pointed out there is plenty of inefficiency at the input side in the form of the charger itself. Just put your hand on the typical battery charger (and even the batteries) while charging and you can see that much is converted to heat by (typically) a transformer, or semiconductors in the case of a switching power supply. There's also a measurable loss in wiring on the charge side since you are pulling all that charging current through them. Thankfully, most of that wire inefficiency is on the other side of your meter and you don't get a separate bill for it. On the other hand, you are really paying even for that inefficiency as well in the overall rates and fees you have in your electric bill.

What really killed electric vehicles in the past is that there is just far more energy available in a pound of gasoline than in a pound of coal used to generate electricity--much of which is "spilled" between the point of production and the point of use in the case of electric vehicles.

Paul

MickeyD
03-17-2010, 05:40 PM
I asked about heat and for interior heat and it uses the ac system (I suspect like a heat pump). When it is really cold, the gas engine goes into generator mode until the batteries are warmed up (over about 0 F). Someone mentioned the grill, it is used for the radiator for the gas engine, the AC, and liquid cooling for the electric motor.

EddyCurr
03-17-2010, 06:53 PM
What sort of uptake rate of EVs can be supported by the existing
generating capacity and power grid infrastructure ? 5%, 10%
20% ?

What kinds of restrictions will there be for recharging EVs? Plug
it in anytime you wish for as long as desired? Or will there be
stipulations that charging occur during off-peak hours. Perhaps
surcharges for charging outside of OP hrs? Perhaps prohibitions
from charging during extreme hot/cold weather to ensure that
brown or blackouts do not occur?

According to an .XLS published by Nuclear Energy Institute (http://www.nei.org/filefolder/New_Nuclear_Plant_Status.xls), there
are license applications for 25 new nuclear plants with the earliest
submitted in late 2007. Even with fast track approval, those
submissions that are successful are years away from coming
on-stream.

And that is just the generation side of the equation. Repair and
upgrading of distribution infrastructure is another facet altogether.

It is great that an alternative to internal combustion powered
personal transportation is becoming available, but my belief is there
are a number of hurdles besides vehicle cost, depreciation and battery
replacement to be overcome before it will be practical to have
one or more EVs in every household.

.

MickeyD
03-17-2010, 07:10 PM
One of the cool things is the charger in the Volt is fully programmable. You can set the charge rate and time (do something like set it to draw 40 amps starting at 2:00 A.M.) when the demand is lowest. With all of the improvements in domestic natural gas production and gas turbine electric generators, electricity is a lot easier to produce now than it was 20 years ago.

All switching to electric really does is change the power source from oil that we mainly buy from people who do not like us very much to nuclear, coal, natural gas, and wind, all of which we produce ourselves. We produce enough oil here to make all the diesel and chemical feedstocks that we need, I want us to be able to tell Chavez and the Arabs to go frack themselves and have it not affect us. I remember the gas lines from the 70's and early 80's and what the oil price shock did to our economy a couple of years ago and don't want to go through that again.

EddyCurr
03-17-2010, 08:18 PM
... from oil that we mainly buy from people who do not like us very much
to nuclear, coal, natural gas, and wind, all of which we produce ourselves.
We produce enough oil here to make all the diesel and chemical feedstocks
that we need, I want us to be able to tell Chavez and the Arabs to go frack
themselves and have it not affect us.Mainly?

Venezuela and Saudi Arabia are somewhat down from the top of
the US Energy Information Administrations's most recent list of
figures.

Total Imports of Petroleum (Top 15 Countries) (http://www.eia.doe.gov/pub/oil_gas/petroleum/data_publications/company_level_imports/current/import.html)
(Thousands of Barrels Per Day)
December 2009

Canada: 2,649
Mexico: 1,204
Nigeria: 1,029
Saudi : 893
Venezuela: 849A considerable portion of Canada's contribution comes from my region.
According to one source, "Alberta heavy oil/bitumen provides one
of the three largest contributions (Saudi Arabia and the Orinoco heavy oil
region of Venezuela being the others) to developable world oil resource
potential. As of 2006, the proved undeveloped reserves of Alberta heavy
oil/bitumen were approximately 155 billion barrels ... The undeveloped
technically recoverable potential was an estimated 295 billion barrels"
And serious commercial extraction is only really just getting underway.
Until the '08/'09 world economic meltdown, efforts were ramping up
to boost production of heavy oil from tarsands here by a factor of four.
More recently, there is a move afoot to put a stake through the heart
of the effort by US interests citing the environmental costs of such
efforts.

Meanwhile, changes in attitude regarding US domestic shale oil production
is opening taps on sources that were previously off limits in the interests
of lesser dependency on foreign imports from unstable regions.

On the conservation side, In 2007, President Bush signed off on legislation (http://www.msnbc.msn.com/id/22326795/)
that


"requires automakers to increase fuel efficiency by 40 percent
to an industry average 35 miles per gallon by 2020. It also ramps up
production of ethanol use to 36 billion gallons a year by 2022. ... The
legislation increases the federal standard automakers must meet to an
industry wide 35 mpg for passengers cars, SUVs and small trucks. The
standard for cars today is 27.5 mpg and for trucks and SUVs 22.2 mpg.

It requires refineries to increase the use of ethanol from about 6 billion
gallons a year this year to 36 billion gallons by 2022 and mandates that
by then at least 21 billion gallons are to come from feedstocks other than
corn."Imagine pickups that get 35 MPG !

I predict that the vehicles in showrooms in ten years will look and perform
a lot differently than those on the road and in dealerships in my town
today.

But to get back to the point about the demands on the electrical
generation and distribution system - I stand by my assertion that
the current infrastructure is near capacity. In my province alone,
there is a bill to upgrade the power grid over a ten year period that
anticpates expenditures of $8-10 billion dollars. Yes, billion.

.

J Tiers
03-17-2010, 11:35 PM
The conversion efficiency of chargers and VFDs can easily be over 95%. The main inefficiency of the battery system is the battery.

There is a built-in chemical loss, plus the resistive losses which depend on the square of current draw. A lead-acid battery has about a 20% energy loss in charging. The charger, if it is halfway decently designed, can be a very great deal better than that.

I don't have reliable values for the losses in other newer battery types. but all will have losses...... otherwise your laptop battery would not get hot.

Power grid? has problems with peak demand, but average is still well under capacity, given overnight low demands. The main new problem is that much needs to be replaced, and also distributed generation is now putting power sources in areas poorly served by transmission.

As for the source of oil..... yes Canada... And of course the US has as much or more right here at home, under much of the west...... in the form of oil shale and tar sand. We will never use it, environmental laws will see to that.

I think that is a mistake, we should develop the technology to use it now, and sit on it until it is needed. That way we cannot be driven down by oil shortages.

You have to remember that oil pricing is global....... if the price is high, it is high for Canadian oil as well as for that from Achmedinejad, or Hugo Chavez. Only if we were a communist totalitarian state could the oil be "free", as it was in the Soviet Union. Free in the sense that the communist totalitarian state owns everything, so charging money is just moving money from pocket to pocket.

mbensema
03-18-2010, 07:41 PM
How many people will actually plug these cars into the grid each night instead of using the gas engine to charge the batteries? Since the engine is going to charge the batteries while driving, I would not expect many full charges needed on average so the benefit of plugging into the grid is lower then the advocates of these cars are claiming.

EVguru
03-19-2010, 05:44 AM
How many people will actually plug these cars into the grid each night instead of using the gas engine to charge the batteries? Since the engine is going to charge the batteries while driving, I would not expect many full charges needed on average so the benefit of plugging into the grid is lower then the advocates of these cars are claiming.

One of the great joys of electric car driving (or a plug in Hybrid) is the fact that you've got your own filling station at home. The car is ready to go every morning without having to make a special trip to put fuel in.

That's my experience and is also mentioned in most studdies of EV use. Even when the available range doesn't meet a particular housholds needs, they still like not having to put in fuel.

mbensema
03-19-2010, 08:53 AM
One of the great joys of electric car driving (or a plug in Hybrid) is the fact that you've got your own filling station at home. The car is ready to go every morning without having to make a special trip to put fuel in.

That's my experience and is also mentioned in most studdies of EV use.Even when the available range doesn't meet a particular housholds needs, they still like not having to put in fuel.

I find it interesting that people with hybrids actually plug them in each night to charge, I can understand with electrics since you do not have the engine as a backup and want to make sure you have a full charge. I guess it is the perception of these cars, I see the hybrid as potentially more efficient then a conventional car and not as something I would want to, or need to, plug in each night to get the best efficiency.

lazlo
03-19-2010, 09:43 AM
The conversion efficiency of chargers and VFDs can easily be over 95%.

VFD's are 3 or more FET's synthesizing the three-phase power with Pulse-width Modulation. They're not very efficient, which is why they have giant heat sinks.

MickeyD was invited to drive the Chevy Volt because he's machining giant heat sinks for the drivers for a prototype electric vehicle. All that heat is loss of efficiency.

EVguru
03-19-2010, 09:53 AM
Just put your hand on the typical battery charger (and even the batteries) while charging and you can see that much is converted to heat by (typically) a transformer, or semiconductors in the case of a switching power supply.

My 2.8Kw battery charger had a loss of about 200w at full power.

Don't confuse heat and temperature.

EddyCurr
03-19-2010, 01:09 PM
Edited by EddyCurr

Not related to machining

.

Alistair Hosie
03-19-2010, 04:47 PM
Ten years ? seems to me that's a good long life these days.Electricity is the way to go for the future no doubt,and in fifty years most cars will be probably this way. And as far as not having resale value I think things will improve on this front maybe after ten years of use the companies might buy back the cars themselves for recycling batteries etc.In the meantime just like when steam came out most sailing ships were designed as hybrids and that's for peace of mind, so the cars might do the same for a decade or so to build up customer confidence.One thing is for sure this technology can only improve and we will eventually see the cost benefits to be an advantage in the long run .MY2 cents anyway.Kindest regards Alistair

Too_Many_Tools
03-20-2010, 07:13 PM
Ten years ? seems to me that's a good long life these days.Electricity is the way to go for the future no doubt,and in fifty years most cars will be probably this way. And as far as not having resale value I think things will improve on this front maybe after ten years of use the companies might buy back the cars themselves for recycling batteries etc.In the meantime just like when steam came out most sailing ships were designed as hybrids and that's for peace of mind, so the cars might do the same for a decade or so to build up customer confidence.One thing is for sure this technology can only improve and we will eventually see the cost benefits to be an advantage in the long run .MY2 cents anyway.Kindest regards Alistair


I agree.

Many of the comments I am hearing reminds me of what horse owners likely said of the early horseless carriages.

FYI...

http://en.wikipedia.org/wiki/Chevy_Volt

TMT

danlb
03-20-2010, 08:11 PM
One of the nice things about a plug in hybrid is that you can take advantage of the cheap rates when you plug them in overnight, and still have plenty of range for those trips that exceed the battery capacity.

Many people are confused about the NEED to charge nightly. Batteries are like gas tanks. Once it's full you can not put more charge into it. If you have an EV and get 100 miles per charge, an average (non commuter) will only NEED to charge it once or twice a week. What people tend to do is get in the habit of topping off the charge each night. If it was only driven 5 miles, then it's charged in less than an hour. If the battery was nearly depleted, then it might take 8 hours.

An acquaintance has an idea setup. A electric mini suv ( Toyota Rav 4EV, a production vehicle built by Toyota) and a solar panel installation. The solar panels feed his car was well as his house. His power bill and gas bill are both virtually non-existent. The cost of the solar installation, paid over 15 years, is less than his electricity bill used to be.

Dan

darryl
03-20-2010, 08:55 PM
Lately, I've been finding the solar part interesting. I used to see solar cells capable of amps of output. Not any more, in fact the last time I tried to use a solar cell, it didn't have enough output to move the needle on a cheap voltmeter. Granted, this was from a solar cell on a calculator, which probably doesn't need more than several microamps to run- but my point is, any of the solar panels I'v seen lately have been atrociously expensive for the meager power output. A 12v panel giving only 80ma costing $100 or so- ? How about 30 cells wired in series costing say $200- but giving more like an amp or so of output- or two amps as one cell I'm thinking of was rated at- in 1968 or thereabouts.

Where do you find solar panels that do give a substantial output for their footprint, without being in the thousand dollar and more range- I just can't see the current amorphous solar cell arrays being suitable for battery charging for anything high-use -

J Tiers
03-20-2010, 09:55 PM
VFD's are 3 or more FET's synthesizing the three-phase power with Pulse-width Modulation. They're not very efficient, which is why they have giant heat sinks.

MickeyD was invited to drive the Chevy Volt because he's machining giant heat sinks for the drivers for a prototype electric vehicle. All that heat is loss of efficiency.


I think not...... With reason, as I both design inverters, and use commercially available ones.

Motor drives with 96% efficiency are common. Your statement "they are not very efficient" is an error............

And I do NOT see "giant heat sinks"..... not on the inverters I see/use.

While there ARE losses, losses directly in the switching devices, you must consider the percentage.... A typical 60 kW inverter, from Vacon (Cutler-Hammer in the US) suggests using as the cabinet cooling requirement, 3% of output.... That is 97% efficiency in the actual inverter. Add control stuff, and filters (not necessary in a "sealed system" like a car), and you may lose a couple more percent.

The sources of inefficiency in a switching device are basically two......

1) switching losses...... losses due to shifting charge around in the devices. The charge is due to the inherent capacitances. Rather similar to the frequency-dependent losses in CMOS devices. These losses do NOT strongly depend directly on power, although with IGBTs there is a power-dependency due to "tail current", and other effects

2) resistive and 'voltage drop" losses in the devices, or associated items such as filters etc. This usually is directly power-related, and increases as the square of current.

Switching losses are drastically reduced with resonant and quasi-resonant operation, where the inherent device capacitances are resonated with inductors to return the energy to the supply, and/or switch with zero voltage across (or zero current through) the device. Changing the frequency lower also directly reduces loss, as with CMOS, and reduced capacitances, such as with newer silicon on sapphire devices etc, directly reduce loss as well..

But a motor drive is not an inefficient device, unless used at far below max power.... There is an ubavoidable "base loss" which looks horribly inefficient at low power, but virtually disappears at high power.

Resistive etc losses are reduced by reducing the resistance, reducing voltage drops, etc. It is all in the choice of devices, and the cost the product will stand, vs the losses that are acceptable. Without going to a higher voltage, obviously the current is not something that can be changed.

Bottom line is that excellent efficiency, far lower than battery losses, is quite possible and actually common, in motor drives even without fancy resonant converters. And the electronics to drive the motor generally cost way less than the battery, so some care and cost taken to gain efficiency is not a major factor in total cost.

Your information, I am afraid, is rather out of date.

JCHannum
03-20-2010, 10:38 PM
One of the nice things about a plug in hybrid is that you can take advantage of the cheap rates when you plug them in overnight, and still have plenty of range for those trips that exceed the battery capacity.
Dan

It will be very interesting to see how the motels and hotels are going to handle this. I doubt that you will be able to casually plug your auto into a wall outlet for free as part of your nightly stay, particularly if your room is on the fourth floor.

The other consideration not yet mentioned with "free" fuel is that the government will most definitely find a means to extract taxes for the power used or mileage driven to offset losses from gasoline purchases. They will have to do this to maintain the highways plus their usual exhorbitant overcharges to support themselves. Look for black boxes to record mileage and send data to the appropriate agencies, which will send monthly or yearly billings to extract their due.

I sincerely doubt that over the useful life of a hybrid or electric auto, once all the true costs are factored in, that there will any real economy in the ownership of one versus a comparable gasoline powered car.

MickeyD
03-20-2010, 10:40 PM
The motor controllers that I have been working on actually do have giant heat sinks to handle worse case scenarios (they are for large box and panel trucks) like creeping up hill in traffic on a 115 degree day. They are running in the 94% to 97% efficiency range, but 6% of 750 amps is still a lot of heat to get rid of.

steve45
03-20-2010, 10:41 PM
A few points:

If everybody charges their vehicle during off-peak hours, guess what? You now have another peak hour!

Regarding heating, it would take a lot more than 1000 watts to heat the interior of the car. A typical hair dryer is rated at about 1500 watts, a coffee maker about 10,000 watts.

Solar chargers? Well, the sun gives us about 125 watts/square foot, so that's the absolute limit for a 100% efficient solar charger. Most are about 10% efficient or less.

People won't replace the batteries in these things, they'll junk them. The cost of a Prius battery is about $8000.

I can see these being popular in larger cities because they move pollution sources outside the populated area. Not practical for many people. I drive about 250 miles per day for work, so it doesn't appeal to me.

J Tiers
03-20-2010, 10:56 PM
A few points:

A typical hair dryer is rated at about 1500 watts, a coffee maker about 10,000 watts.

I do NOT think so....... most complete electric stoves with ovens are only maybe 5 kW, half of your coffeemaker figure........ A coffeemaker is a few hundred watts.


I can see these being popular in larger cities because they move pollution sources outside the populated area. Not practical for many people. I drive about 250 miles per day for work, so it doesn't appeal to me.

To me, the huge issue with the Volt is that it is NOT a hybrid, and it is NOT an electric car.

it is a little of both, but lacks the advantages of either. That looks like an issue, but I suppose it could be OK.

The Volt goes about 80 miles, IIRC before charging, if you never use the engine.

If you run the engine, it goes 300 miles, but then you are dead in the water, no battery power, and have to recharge, DESPITE having an engine.. The engine is JUST SHORT of being able to keep up with driving.

In other words, it aaaaallllllmost has the features of a pluggable hybrid........ but falls short.

AND, it has an engine, so it is not an electric car, and is not "zero emission", so it falls short there too.

MickeyD
03-20-2010, 11:19 PM
The engineer from chevy said that between a fully charged battery and then switching over to the motor/generator for power you had about 300 miles before you had to stop for gas. The fuel tank in the stripped down power train model did not look like it was very large - my guess was in the 8 gallon range from eyeballing it.

Too_Many_Tools
03-20-2010, 11:42 PM
Hate to sound pessimistic, how much will it cost, how far will it go on a charge, and at US$0.13/KWH how much will it cost to charge?

And the bigger question, at least for those of us who aren't able to afford one new... How long will the batteries last and how much will it cost to replace them?

Or is the bigger question - How long til the current administration requires us all to buy one?

You don't sound pessimistic...you sound like a Republican who is still stinging from the November 2008 defeats.

If you recall, as an American taxpayer you are now part owner of GM.

Now wouldn't you like to see your investment do well?

And FWIW...the BIGGEST question IS when will the United States give up its addiction to foreign oil that has cost this Country trillions of dollars and thousands of American lives.

Cars that are actually efficient like the GM Volt are a small step towards that reality.

TMT

Too_Many_Tools
03-21-2010, 12:12 AM
I do NOT think so....... most complete electric stoves with ovens are only maybe 5 kW, half of your coffeemaker figure........ A coffeemaker is a few hundred watts.



To me, the huge issue with the Volt is that it is NOT a hybrid, and it is NOT an electric car.

it is a little of both, but lacks the advantages of either. That looks like an issue, but I suppose it could be OK.

The Volt goes about 80 miles, IIRC before charging, if you never use the engine.

If you run the engine, it goes 300 miles, but then you are dead in the water, no battery power, and have to recharge, DESPITE having an engine.. The engine is JUST SHORT of being able to keep up with driving.

In other words, it aaaaallllllmost has the features of a pluggable hybrid........ but falls short.

AND, it has an engine, so it is not an electric car, and is not "zero emission", so it falls short there too.

It is a solution...for now.

Again read this....

http://en.wikipedia.org/wiki/Chevy_Volt

And note the following....

"With fully charged batteries, enough electrical energy will be stored to power the Volt up to 40 miles (64 km). This distance is capable of satisfying the daily commute for 75% of Americans, whose commute is on average 33 miles (53 km)."

That means that the Volt is a solution for 75% of Americans...and that is a MAJOR step towards weaning America off foreign oil.

TMT

Too_Many_Tools
03-21-2010, 12:18 AM
I would imagine they are expensive to run given you have to factor in they will have no resale value.

The owners will only get rid either when they start to give trouble / need new batteries and / or the manufacturers bring a new model out and stop supporting the old one, maybe with government incentives to upgrade like the scrappage project.

.

Hmm..you will have to explain to me what you are saying here.

If history is any example, the Volt will have a great resale value...just like the Toyota Prius as.

TMT

danlb
03-21-2010, 12:33 AM
It will be very interesting to see how the motels and hotels are going to handle this. I doubt that you will be able to casually plug your auto into a wall outlet for free as part of your nightly stay, particularly if your room is on the fourth floor.

Motels solved this problem years ago. They use street level parking lots now. :) But seriously, motels are not a big problem. They've figured out how to charge $8 for a $4 can of nuts in the honor bar, and $8.95 for a single pay per view movie. They'll figure something out.



The other consideration not yet mentioned with "free" fuel is that the government will most definitely find a means to extract taxes for the power used or mileage driven to offset losses from gasoline purchases.

What makes you think that those taxes will only be for alternative energy vehicles? Any tax that is successful will eventually be spread as far as possible.


I sincerely doubt that over the useful life of a hybrid or electric auto, once all the true costs are factored in, that there will any real economy in the ownership of one versus a comparable gasoline powered car.

That all depends on how you want to slant the numbers. You can PROVE that a Boeing 747 is better for the environment than a bicycle if you pick the right things to stress and the right ones to ignore. I've got 100K on mine, it's still worth 1/2 of what I paid for it 8 years ago. So far I've saved about $7,221 in gas compared to the Chevy Impala . That's assuming the Impala could get 22 MPG in stop and go driving. The ones I've rented got only 18. The purchase price for my car and an impala were about the same. The Impala resale is almost nothing at 100,000 miles.

I'd say I'm ahead even if you don't count the fact that I enjoy the car. :)

Dan

danlb
03-21-2010, 12:51 AM
A few points:

If everybody charges their vehicle during off-peak hours, guess what? You now have another peak hour!

That is the whole idea. Commercial power plans over produce at night. Adding load will allow that extra energy to be used.



Regarding heating, it would take a lot more than 1000 watts to heat the interior of the car. A typical hair dryer is rated at about 1500 watts, a coffee maker about 10,000 watts.


Wow! a coffee maker that draws 83 amps! I'm impressed! But really, if you compare the output of a hair dryer with the heat produced by your car's heater you might find they are similar. The hair dryer is moving a lot of volume too.



Solar chargers? Well, the sun gives us about 125 watts/square foot, so that's the absolute limit for a 100% efficient solar charger. Most are about 10% efficient or less.


Not sure what the point is. My house has a roof that presents over 1000 sq feet to a southern exposure. Using your figures that gives me 12,000 watts or 100 amps at 120 volts. My home only has a 100 amp service.

Realistically, a solar setup only generates top power for 6 hours or so per day, so it's not perfect.




People won't replace the batteries in these things, they'll junk them. The cost of a Prius battery is about $8000.

Cool! Where are you? I can get them here for less than $4000 new and used (from auto accidents) for under a thousand. I want to sell them in YOUR neighborhood.



I can see these being popular in larger cities because they move pollution sources outside the populated area. Not practical for many people. I drive about 250 miles per day for work, so it doesn't appeal to me.

I can't speak for the Volt; I drive only 60 a day in my commute, over a small mountain range and lots of stop and go interspersed with the high speed parts. My Prius handles it well. There are hybrids that do work.

Dan

MickeyD
03-21-2010, 01:28 AM
I think that a lot of people are missing the point on the Volt. For trips under 40 miles it has the capability of being a pure EV if it was fully charged by being plugged in. For longer trips it acts more like hybrid (although one that just runs off of the electric motor) cycling the gas motor/generator combo to maintain sufficient charge to drive the car. Performance wise it was a real blast to drive with acceleration being much stronger than a Prius and Honda Civic hybrid that I had driven in the past. Another impression that I was left with after driving it was that the car really felt solid, and this is from someone who drove Volvos for many years. The doors had some weight and thickness to them and the car felt like it had good sound proofing to keep out the tire noise. The Prius and Honda also had nice fit and finish but they always reminded me more of the old school imports that had a lot of road noise and felt like the design priority was being light vs. solid. I guess the Volt is the next step in the hybrid evolution. What is going to be really fun is when the next generation motors get paired up with newer battery technology and we get some serious performance.

lazlo
03-21-2010, 10:35 AM
The motor controllers that I have been working on actually do have giant heat sinks to handle worse case scenarios (they are for large box and panel trucks) like creeping up hill in traffic on a 115 degree day. They are running in the 94% to 97% efficiency range, but 6% of 750 amps is still a lot of heat to get rid of.

Mike, considering the frequency that they're burning-up their drivers, the worst-case scenarios are apparently more frequent than you'd imagine...


Motor drives with 96% efficiency are common. Your statement "they are not very efficient" is an error............

And I do NOT see "giant heat sinks"..... not on the inverters I see/use.

Your information, I am afraid, is rather out of date.

OK, let's see :rolleyes:

Mitsubishi A500, state of the art, 3.7 KW Variable Frequency Drive, with IGBT FET's (same power transistors used in electric vehicles). Sells for about $2,500:

http://i164.photobucket.com/albums/u15/rtgeorge_album/Mitsubishi/Mits1.png

Take the cover off:

http://i164.photobucket.com/albums/u15/rtgeorge_album/Mitsubishi/Mits2.png

Now remove the plastic chassis:

http://i164.photobucket.com/albums/u15/rtgeorge_album/Mitsubishi/Mits3.png

lazlo
03-21-2010, 10:38 AM
Now separate the driver from the giant heatsink:

http://i164.photobucket.com/albums/u15/rtgeorge_album/Mitsubishi/Mits4.png

The silver MCM is the FET package -- all three phase (U, V, W)FET's plus the dynamic braking resistor FET. You can see it's mated socket in the heatsink.

To put the sizes in perspective, that's a 1/2" socket cap screw in the top of the picture. The heatsink weighs 5 1/2 lbs, and that's a 60mm fan blowing forced air across it. The VFD will turn off the output drivers if the fan is disconnected or shorted.

John Stevenson
03-21-2010, 10:47 AM
I love those blown inverter drives, the heat sinks are ideal for mounting a set of steppers drives on.

Keeps them cool and looks cool to boot, the rewind guys send me all their dead units.

Sorry for the hi-jack.

lazlo
03-21-2010, 10:51 AM
I love those blown inverter drives, the heat sinks are ideal for mounting a set of steppers drives on.

Sorry for the hi-jack.

You are correct, as usual John! :p The FET burned-up...

J Tiers
03-21-2010, 11:04 AM
Your "giant" heatsink is really fairly small for a nearly 4 kilowatt device.

AND it doubles as the BASE for the drive, which sets the size as equal to the PWB . It appears to be a casting, which limits the options for fins, etc.

if I have the size right, the whole inverter is about 13" tall, and 6 or so wide.....

For comparison purposes..... for an audio amplifier of just over 1 kW, we would have needed a heatsink at least that big, with tall fins at close spacings....... and we were NOT required to operate under all industrial conditions of temperature, nor did we have to produce an average over about half power......

Also for comparison purposes..... A 3 phase IGBT module that we used in a 200KW system......... this inverter module handled 3/5 of 200 kW, or 120kW (it was a 5 phase system)..... and the total volume occupied by heatsink was about twice as big as that 4 kW drive..... FOR 120KW.

A Vacon frame 7 inverter, which handles 72kW (87A) at 480V, is about 24 x 10 x 9 inches...... half of which is connection and control space. About half the remainder is occupied by an inductor, and a fan.

You do the math.......

it appears the Finns are a tad smarter than the Japanese at Mitsubishi..........................

And that is for a general-purpose drive, which cannot use the fancy zero-voltage switching type operation, because the unknown connected load could mess up the timing.

For an automotive "sealed" system, where everything is under the control of the designer, added efficiency could be had if a quasi-resonant or similar design is used. Whether that would pay back economically when the efficiency is already at 96%+ is a question.

Sorry, Robert, they are quite efficient, if designed competently.

lazlo
03-21-2010, 11:11 AM
Your "giant" heatsink is really fairly small for a nearly 4 kilowatt device.

Sorry, Robert, they are quite efficient, if designed competently.

I don't know what your point is? A 5 1/2 lb heatsink isn't giant? Scale that 5 1/2 lbs for a 5 HP motor up to 100 HP...

Inverters for motor drives have giant heatsinks because there's considerable loss. An IGBT can have a 96 - 99% efficiency under "ideal" (i.e., laboratory conditions): when the FET are fully saturated and driving hard in one direction with maximum Vgs and the Tj (junction temperature) is room temperature.

But motor controllers have to constantly start and stop the motor, ramp the speed up and down, and the junction temperature is 80 - 90° C range. In those cases, the FET's are not in saturation and the efficiency drops way off. That's the reason for the giant heatsinks.


if I have the size right, the whole inverter is about 13" tall, and 6 or so wide.....

10" x 6"

J Tiers
03-21-2010, 11:15 AM
And note the following....

"With fully charged batteries, enough electrical energy will be stored to power the Volt up to 40 miles (64 km). This distance is capable of satisfying the daily commute for 75% of Americans, whose commute is on average 33 miles (53 km)."

That means that the Volt is a solution for 75% of Americans...and that is a MAJOR step towards weaning America off foreign oil.

TMT

Sorry, TMT, but it just WON'T WASH.........

it's worse than I thought.... 80 miles would be usable, almost, 40 miles is NOT.

The assumption is that people would be happy to have a car for commutes only. drive to work, drive back, plug in, wait for tomorrow.

That is SUCH BS

REAL people buy ONE car..... and they expect to use it for everything. They do that because they CAN'T afford to buy a car for commutes and a car for everything else.

REAL people drive to the store after work..... they don't want to wait for a recharge.

REAL people drive places on weekends, they go out at night after work... they don't want to wait for a recharge.....

REALITY IS that they will drive using the engine.... THEY WILL HAVE TO.

Edit: And of course the car is only a "urban car"..... you couldn't drive to the in-laws in it, if you will be going more than maybe 200-250 miles....... or you will have to stop for a recharge. Even the smallest IC engine car can go for as long as you are willing to refill the gas. I have even seen "Smart cars" on the highway.

And, speaking of "smart cars", I USED to see a number of them. I have not seen one in at least two months, even where I KNOW there were regularly driven ones.... the gloss must have worn off.... The practicality issue always comes up.... And it may likely come up with the Volt as well. There needs to be a sequel.

So, what was that about oil? Most of which is not "foreign" in the sense you mean, as in coming from Iran, etc.


If teh average fuel economy of the US "fleet" could be doubled....... which has at least as much to do with getting rid of the inefficient 18 wheelers as it does with autos, much/most of the foreign oil contribution from out-of-hemisphere would be removed.

And, don't forget, the automotive contribution from people buzzing around the city in small 35-40 mpg cars (as they do now) is NOT the big deal. So the Volt displaces only the MARGINAL contributors........ The REAL gas hogs are the folks with 40 mile one-way commutes..... jammed in traffic on the highway in their outsized V-8 SUVs, getting 12 to 18 MPG on a good day, and near zero in stop-and-go traffic.


THE VOLT FALLS SHORT IN ITS CONCEPT.

Sooooooooo close, but no cigar.

It might still be reasonably successful, but it is NOT the 'answer".

We will have to wait and see what japanese-designed, chinese made car comes in and cleans GM's clock......

And who buys the bankrupt assets of GM in a few years.

J Tiers
03-21-2010, 01:09 PM
I don't know what your point is? A 5 1/2 lb heatsink isn't giant? Scale that 5 1/2 lbs for a 5 HP motor up to 100 HP...

Inverters for motor drives have giant heatsinks because there's considerable loss. An IGBT can have a 96 - 99% efficiency under "ideal" (i.e., laboratory conditions): when the FET are fully saturated and driving hard in one direction with maximum Vgs and the Tj (junction temperature) is room temperature.

Nonsense

I have already shown that the heatsink for a 60kW (80HP) drive is not a lot more volume than that 4 HP drive 'appears"to occupy.

A competent design has its rated efficiency under FULL LOAD. At light load the percent efficiency goes down due to relatively constant losses, like switching loss, and controller overhead, etc. Under overload (temproary) conditions efficiency can go down. There may be an area of even better efficiency at around 70% or 80% load, where the resistive losses have not risen yet, but the switching loss is at a near-minimum vs total output.....

I KNOW what the efficiency is, I have done heat runs under full load for the Vacon inverters.... If anything, it was BETTER than claimed.



But motor controllers have to constantly start and stop the motor, ramp the speed up and down, and the junction temperature is 80 - 90° C range. In those cases, the FET's are not in saturation and the efficiency drops way off.


the "fets" actually IGBTs, are ALWAYS in saturation when load current is flowing............ If they EVER come out of saturation with repetitive load current through them they are toast... quite literally.

In fact, one reliable overcurrent sense method is the 'desat" circuit... if the device comes out of saturation, the voltage across it doubles or triples, and the dissipation does the same. So the circuit instantly cuts off the drive if a higher than normal voltage occurs. Cuts it off in microseconds.....

De-saturation can NEVER be tolerated except as a transient condition during switching off/on of the device.

The rise in voltage with temperature is a known factor, and must be taken into account in the design. So what?

I won't try to teach you processor architecture.... don't try to teach me inverter design........;)

vincemulhollon
03-21-2010, 02:36 PM
The cost of a Prius battery is about $8000.

My wife has had one for five years. The whole car, I mean, not just the battery. I looked into it before purchasing, and also spot checked about a minute ago. A quick google search shows they are STILL about $500 used, $1000 for a rebuild, and claims that they're $3000-ish factory brand new OEM from Toyota. The prices have not changed much since the initial rollout, if that gives any hint as to what will happen with newer electric vehicle batteries.

I was advised when I bought it that the battery costs "about as much as a transmission" and that seems to hold true.

If you're in the market, and willing to cough up $8K per, I'll gladly sell you as many as you want for $8K and pocket the difference...

MickeyD
03-21-2010, 05:44 PM
Robert- on the one that I have been working on the IGBT's are mounted on a water cooled heat sink on the top side of the "box". The passive heat sinks that I have done (as well as the rest of the enclosures) are for the rest of the electronics in the control.

J. Tiers - The battery range is the range before the generator kicks in. You can actually drive the car as long as you want. The one that I drove is actually driven from demo to demo on the highway and range is limited to your butt going to sleep or stopping for gas.

Dr Stan
03-21-2010, 09:07 PM
Or is the bigger question - How long til the current administration requires us all to buy one?

Looks like a number of people are just using this thread to rant. In addition, some of the info regarding battery recharging applies to lead-acid, but not to the lithium ion batteries used in the hybrids.

As to the load on the grid as it has been pointed out anyone with any sense will charge during the night which is when many power plants throttle back. Consequently implying it will overload the grid is just a red herring.

As to pollution from power plants it is more efficient and cost effective to have pollution control equipment at one energy generating plant, rather than millions of polluting cars. Hopefully in the long run this will help revive the US nuclear power industry. Just as an aside coal fired power plants release much more radiation into the atmosphere than do nuclear plants due to the radioactive materials naturally contained in coal.

Bottom line it will take several years and the use of multiple technologies to wean the US off its petroleum addiction with hybrids being only one part of this solution. Fuel cell vehicles powered by hydrogen or ethonol from switch grass are just another possibility. Let's hope US and European manufacturing companies take the lead and do not let this opportunity to slip through our hands.

100mpg carburetors, cars running on water, magnetic gas line ionizers, and lots of other urban legends/out and out BS that the gullible scientific illiterates swallow just will not cut it.

J Tiers
03-21-2010, 09:35 PM
J. Tiers - The battery range is the range before the generator kicks in. You can actually drive the car as long as you want. The one that I drove is actually driven from demo to demo on the highway and range is limited to your butt going to sleep or stopping for gas.

The information I have is a hard limit at 300 miles..... that the engine "helps" but cannot keep up with the electric demand, so you run out of range.

Are you saying that the vehicle does NOT run dead at 300 miles?

Because that is a change from initial data, and would make it FAR more useful. If that change has been made (and it would be a BIG change if initial data was correct), the Volt may be a much more useful vehicle than the information that has been published in our newspaper suggested.

Liquid cooling is an excellent way of compacting the drive, getting lead lengths and inductances, etc down. It need not imply anything about total power dissipation, and in fact can be a way of improving efficiency.



Looks like a number of people are just using this thread to rant. In addition, some of the info regarding battery recharging applies to lead-acid, but not to the lithium ion batteries used in the hybrids.

I have mentioned that...... do you have the charge efficiency numbers for Lithium ion as used in the cars? I don't have that, although I could probably get it from a guy I know who works for the company that makes the battery test equipment for the Volt. However it may be covered by a non-disclosure agreement.



As to the load on the grid as it has been pointed out anyone with any sense will charge during the night which is when many power plants throttle back. Consequently implying it will overload the grid is just a red herring.

or just misinformation..... There has been so much info in the media about the "aging, crumbling" power grid, that people can be forgiven for believing it......

However, there WILL be an impact, since overnight power demands will use the grid to more of its total capacity, make maintenance occur more often, etc, etc. Plant downtimes will be more frequent due to more time under load. presently, overnight is used for quite a bit of maintenance, and that may no longer be possible.




Bottom line it will take several years and the use of multiple technologies to wean the US off its petroleum addiction with hybrids being only one part of this solution. Fuel cell vehicles powered by hydrogen or ethonol from switch grass are just another possibility. Let's hope US and European manufacturing companies take the lead and do not let this opportunity to slip through our hands.



I hear a lot of that "wean the US off its petroleum addiction" and "pry people out of their cars", etc, etc...... And I see large cutbacks in every system that could replace cars and "fuel".......... The bus system here has shut down 30 to 40% of its routes semi-permanently...... expansion of light rail has been delayed or cut from budgets, etc, etc.

There will probably ALWAYS be a need for fueled vehicles..... The electric car is an "urban-only" animal, no good to you when it is 50 miles to town, no use to an area salesman, and worthless to short and long-haul trucking, mining, etc. Railroads could be electrified, but who will pay for it?

A power outage means no way to get to your job..... at least not after the first day.... We fairly regularly get 3- 5 day outages in the city..... there have been several since hurricane Ike.

And, it is worth pointing out that the product of burning hydrogen is a far more potent greenhouse gas than CO2..... yes, water vapor is a VERY strong greenhouse gas. the greenies haven't caught up with that yet........ just wait.

As for taking the lead, it would be best if you got used to the idea that all the new technology will be coming from china....

China has a national push to lead the world in every environmental technology, and they already do. They have more wind turbines planned for construction within 5 years (and built in china of course) than the rest of the world has ever built in history.

dfw5914
03-21-2010, 10:02 PM
One question I've always had regarding the batteries, is what sort of risks do they pose in a serious accident.

J Tiers
03-21-2010, 10:22 PM
One question I've always had regarding the batteries, is what sort of risks do they pose in a serious accident.

The newer high voltage ones, especially of less stable batteries like the lithium, can pose hazards. Lead acid may inundate the victims with sulphuric acid..... Lithium batteries if shorted may burn, and I understand they burn very hot..

However, the gasoline tank poses quite a hazard also..... volatile, explosive, highly flammable........ not a good thing if you are for any reason unable to get out of the vehicle.

Face it..... ANY "compressed energy", be it fuel, batteries, flywheel, etc, poses a serious risk if the energy is released in an uncontrolled manner. And, with containments breached in an accident, it likely WILL be released, one way or another..

the main hazard right now may be the unwillingness of 'first responders" to approach a vehicle that may have unseen shock hazards, invisible hydrogen or alcohol flames, etc. I understand that you can walk right into a hydrogen or alcohol fire without knowing it until you are being toasted, and that standard procedure is to wave a broom ahead of you to see if it catches fire.....

dfw5914
03-21-2010, 10:41 PM
I guess that was what I was getting at, is how well emergency crews will be able to respond to the risks associated with new battery technologies.
35 gallons of gasoline is a huge potential hazard, but is well understood.

MickeyD
03-21-2010, 11:01 PM
What the chevy engineer told me was that if you did not recharge from the grid or refill the gas tank the range was around 300 miles (which is about the same range my pickup has and I always have needed to stop before it does). The generator output is about 53kW and pushing the car down the road takes 10 to 20 HP depending on speed and accessories running, so unless you are just driving like a maniac or trying to recreate the Cannonball Run, I don't see how it is range limited other than by the size of the gas tank. As far as battery protection goes, they are in the centerline tunnel (the interior feels more like a traditional rear drive car with a big transmission and driveshaft hump). If think that if you smash the car bad enough to breach it you have other things to worry about.

J Tiers
03-21-2010, 11:08 PM
I would expect that with the Prius, etc that training is starting, although it may not be universal.

However, teh Prius has a very tiny battery.... I interviewed with the battery test company some time ago (and didn't take it, to the disappointment of the guy I know, who worked with me at my previous employer), and at that time was told that the individual cell size for the Prius was at that time close to 'D-cell" size, although there were a lot of them.

The stored energy in that size cell is a lot different from the energy storage to get a 40+ mile range. And the potential hazards are obviously greater in the latter case.

Not only that, as the battery pack gets bigger, the "target" is larger, and battery damage will be more likely.

The proper process for "letting down" the battery pack, to "safe" it for vehicle salvage or recycling may be an issue..... more so for a damaged battery than for a whole, undamaged battery.

Mistakes are more spectacular at hundreds of volts and high peak available current than with a 12V battery. and the energy from a 12V cranking battery can already cause burns etc....

This may be a case for "socialism"...... developing nationally standardized battery packs which are certified to safety requirements. The procedures for dealing with standardized packs would be known to all responders, mechanics, etc. That would make everything much safer than it would be with dozens of different types of battery packs.....

A response to a damaged "type K" pack would be quicker and less hazardous than a case where the responders have to flip through a manual of some sort to find out what to do about a "Hao Chang" pack in a partly squashed "Great Wall Tiger" car, which would be different from a "Go Binh Tall Dragon" vehicle, etc, etc.

darryl
03-21-2010, 11:37 PM
Well, we really have a problem. It's high energy use per person. We still have the 2000 lb car transporting the 200 lb person, and we still jump in that car and screech off to the corner store and the coffee shop, etc- plus to work and back most of the week. Many of us go hot footing it around just to listen to the stereo. And it seems to me that it's getting worse.

We can look at and go with alternate technologies all we want, but in the end what we're still doing is using up a lot of energy and adding the subsequent heat to the environment. It won't matter if the end form of the fuel we use is electric, gas, hydrogen- every one has its cost to produce and will in total add up to our steady, and steadily increasing, use of the planets resources. Those who are in the business of supplying us with the various fuels will continue to rake in the money, supplied by us, in ever increasing amounts, and continuing to tap the planets resources- whether it be to produce gasoline, or hydrogen, or electricity, and all the materials needed to produce the systems we use to burn that fuel.

I find it hard to believe that we'll see an improvement in the environment through electric vehicle use, or hydrogen vehicle use. It doesn't appear likely that smog levels over large cities will change much, especially when you hear things like water vapor being a potent greenhouse gas, and production of electricity needed for electric vehicles having to be supplied by fuel burning plants. Maybe less of the smog will be produced in the cities, but it will be produced nonetheless in another area, and close by if the logistics of power transmission are taken into account. I think the upstream costs to the environment are just as severe as that from producing and using gasoline.

The only thing that seems plausible to me if we are to have a real impact on the overall pollution and greenhouse gas picture is to use less energy overall. But looking slightly ahead, you might see that the world economy may not be able to handle that. If our personal costs became reduced, that would probably translate directly, if not immediately, into lost jobs- and here is another runaway effect- a decending into poverty. Chinas big push to rise out of it seems destined to fall back when the world fails to buy their product in sufficient quantity to cover the costs they have incurred in order to be able to produce the products.

It almost seems ludicrous to talk about electricity being so green, or hydrogen being so green- it's a grand scale delusion and we're buying it- and man, are we going to pay for it:(

gmatov
03-22-2010, 12:08 AM
Fuel tax wise, many states and the US Gov are already considering a mileage based tax, mostly BECAUSE people are "getting away" with not paying a "fair share".

I drive a 10 mile per gallon pickup, I pay 44 cents per gallon, 4.4 cents per mile. You drive a 40 MPG toy, you pay 1.1 cents per mile.

Problem arises when everybody drives a 40 MPG vehicle and road taxes are quartered, and can't maintain the road system. Money has to come from somewhere.

Don't have to be snoops checking your odometer. Many jurisdictions have annual Inspections. Numbers wired to the DMV. They know how many miles you have driven. Multiply by 2 or 3 cents per mile, send us the money.

I wonder if the battery pack is a monolith, or if it is "cells"? (Batteries, if you prefer.) The Tesla uses some 6,000 cells in its battery pack, XX of them in series, and XX of them in parallel to make their voltage. COULD be equivalent to replacing one bad battery in a 6 battery golf cart. Pull the "bad" battery, replace with a good one, pull that one apart and replace one or more bad cells, back on the market as a "rebuilt" with a specified warranty.

6,000 cells are not going to all go bad unless you have a catastrophic short of some kind. Lithium is not as rare as it has been reported. One of the most abundant metals in the Earth's crust, but nobody spent money to mine it because there was little demand for it, until now.

What IS a 600 amp diode worth? I think they are 600. I think 1 5/16 across the flats, 7/8-14 or 16 thread. My 230 amp Ac welder has a bridge built of them, and I have some extras. Probably well out of date, today.

I would consider an electric car. I don't HAVE to be anywhere at any given time

Cheers,

George

gmatov
03-22-2010, 12:30 AM
Darryl,

You are absolutely correct that "green" does not mean what WE think it means. "Green" might mean wind or solar, but you still pollute making the solar cells and the wind generators.

Granted, possibly less than the ongoing means we have now, build, use energy and pollute, burn fuel and continue to pollute.

Wind or solar will, I think, pollute to build, then pollute less during the life of the plant.Fuel powered plants, whether coal, oil, gas, nuclear, will demand gigawatts of energy to produce the fuel to run them, AFTER the gigawatts of energy to produce them.

Never ending cycle. Fuel cells are not the answer, unless we can put crude into them and get power out of them. Never going to happen.You have to refine the crude to Hydrogen to feed today's experimental "fuel cells". GREAT for oilmen. It's STILL pumped oil at 80 bucks a barrel, and losses all along the way, and fewer MPG than you would get burning straight crude oil.

Bush II, if you recall, was all for Hydrogen economy when he first came into office. He knew that it would require even more oil than we were then importing to meet the demand for hydrogen.

We are getting screwed left and right on the energy front, and it will only cost more in the future, whether cost of production rises or falls. We are near 3 bucks a gallon for fuel, and I wonder why the Diesel drivers are no longer bitching, as they were a year or more ago. 3 bucks is OK?

Cheers,

George

Too_Many_Tools
03-22-2010, 01:12 AM
Looks like a number of people are just using this thread to rant.

The same people who are sore about losing the November 2008 elections.

TMT

Too_Many_Tools
03-22-2010, 01:15 AM
Sorry, TMT, but it just WON'T WASH.........



Oh but it will.

TMT

Too_Many_Tools
03-22-2010, 01:18 AM
My wife has had one for five years. The whole car, I mean, not just the battery. I looked into it before purchasing, and also spot checked about a minute ago. A quick google search shows they are STILL about $500 used, $1000 for a rebuild, and claims that they're $3000-ish factory brand new OEM from Toyota. The prices have not changed much since the initial rollout, if that gives any hint as to what will happen with newer electric vehicle batteries.

I was advised when I bought it that the battery costs "about as much as a transmission" and that seems to hold true.

If you're in the market, and willing to cough up $8K per, I'll gladly sell you as many as you want for $8K and pocket the difference...

And with more electric cars in use the price will go down.

TMT

danlb
03-22-2010, 01:56 AM
I guess that was what I was getting at, is how well emergency crews will be able to respond to the risks associated with new battery technologies.
35 gallons of gasoline is a huge potential hazard, but is well understood.


The risks are really very small. There has been training to teach the emergency crews what not to touch. All high voltage wiring is in bright orange casings. All high voltage (in my car, and I suspect most others) is transported as DC, and converted to AC within the components that need AC. 300 volts DC can give you a jolt, but is rarely serious. I've been bit by it when working on 'anaconda' circuits at the phone company. Not fun, but not THAT bad.

The batteries are all built up of cells, and the cells can be replaced in modules. There are short circuit protection circuits at many points. If the 300 VDC line shorts to ground the power is cut off at the battery.

And (of course) the main lines are run far away from door sills and other places were emergency crews might use the jaws of life.

Dan

danlb
03-22-2010, 01:58 AM
I forgot to congratulate the OP on being able to check out the new car. I'm quite envious. I am intrigued by all new technologies.


Dan

J Tiers
03-22-2010, 08:12 AM
The risks are really very small.

........
All high voltage (in my car, and I suspect most others) is transported as DC, and converted to AC within the components that need AC. 300 volts DC can give you a jolt, but is rarely serious.
Dan

DC Should be quite a bit WORSE.

The reason is that AC does not penetrate a conductor, like a person, as well as DC. People are high enough resistance that the effect is reduced, but it still exists.

DC can be conducted through your entire cross-section, meaning that there is a good chance it will penetrate to teh heart and stop it.

Plus, according to my sources, DC, if you are not thrown clear by the initial muscle contraction, may cause you to "freeze on" to the conductor for longer. AC does that also, but is probably a bit easier to get away from. I've had both, don't want either, didn't like 450V DC one bit. It blew little holes in the skin.



Oh but it will.

TMT

That's nice, dear.......

vincemulhollon
03-22-2010, 09:28 AM
I would expect that with the Prius, etc that training is starting, although it may not be universal.

Again, another topic I researched before my wife and I bought ours half a decade ago. Specific Prius training only began about a decade ago. There is, however, really nothing to really "learn" in that its just a set of procedures the firemen already know... Kind of like machining, every job is different, but once you know "how to face on a lathe" pretty much every facing job is similar, more or less.

Here's a link to a 2001 training manual that Toyota has been distributing to firemen. Its 33 pages of mostly irrelevant and common sense stuff, a single page or less would have been completely adequate. The 3-D "blueprints" are kind of cool.

http://www.firehouse.com/mz/images/2008/07/moore_erg/ERG_Toyota_Prius_2001.pdf

The electrical switchgear is basically comparable to the SRS (airbag) stuff. The usual, pull the battery and/or a specific relay, wait a couple seconds, and you're all safe. The delay is waiting for tiny little electrolytic caps to self discharge. The prius stuff is safer than airbags because there is no explosive like airbags have. Nothing they haven't dealt with since airbags in the 80s.

The battery itself is full of potassium hydroxide gel adsorbed into the plates. Admittedly, given the location of the battery, explosive disassembly of the extremely heavily built and centrally located battery would imply there's no hurry, its just a leisurely corpse removal job. The gel means it doesn't leak when cracked or shot, so the only worry is literally blowing it to pieces, like if a railroad train ran it over. The firefighters have been doing alkaline hazmat since the railroads invented tank cars, pretty much, although a prius is on a dramatically smaller scale. Nothing they haven't dealt with since the 80s, 1880s I mean.

As for the electrics, they know what to do when a power line falls on a car, and thats the absolute worst case. In practice the battery has multiple internal fuses and also a normally open set of relays on + and - leads and what amounts to a DC GFCI that trips if either power lead contacts the chassis. I though it interesting when I learned the whole DC traction system is "no ground chassis" I had assumed it was neg ground chassis like a conventional car. I guess its safer that way in that if anyone somehow contacted either lead while touching the chassis, the DC GFCI would instantly trip. The simplest way to deal with it is to "shut off the car normally" and the output of the battery goes open circuit. Also the battery goes open circuit if an airbag has deployed. Or you can pull a certain relay much like disabling the airbags. Or you can pull the 12 volt battery and the N.O. relay goes open. Really, its hard to come up with a scenario where a FF on a call would approach a vehicle that doesn't already have an open circuit battery. The battery safety circuits are pretty amazing compared to a simple old fashioned 12 V lead acid battery. Worst case, nothing they haven't dealt with since the first aerial electric power "telephone pole" back around 1900.

Really J Tiers, it says a lot about the high quality of the machine design, that a desperate hatchet job is filled with such... desperate claims.

lazlo
03-22-2010, 09:38 AM
the "fets" actually IGBTs,

Yes, I've referred to them as IGBT's several times. Regardless, an IGBT is just a FET with a bipolar gate. Spice models an IGBT as a Darlington pair with a bipolar transistor driving the gate of a FET.


are ALWAYS in saturation when load current is flowing.

So you're saying that an IGBT has no linear region? That there's no overshoot or undershoot on an IGBT?

IGBT manufacturers all have 40 page app notes showing various techniques on how to drive their IGBT's to minimize power dissipation, there's a huge market in IGBT drive ASIC's to actively manage the gates:

Adaptation of IGBT Switching Behaviour by Means of Active Gate Drive Control for Low and Medium Power (http://www.tf.uni-kiel.de/etech/LEA/dl-open/epe2003-active_gate_control.pdf)

In any event, rather than bore everyone with transistor switching theory and IGBT S-curves, why do you think that VFD's have giant heat sinks? Mike's prototype electric car has water-cooled drive heatsinks.

Try this: turn on your VFD, and let it run for awhile. Now run the motor speed up and down, with your hand on the (giant) heat sink. You won't be able to hold it there very long :)

Comparing the size of the 5 1/2 lb forced-air heatsink on the Mitsubishi to a processor or GPU heatsink, I'd estimate it's rated for 500 - 750 Watts. That works out to around a 15% (peak) power loss on a 3.7 KW VFD.

In any event, my point is that you can't calculate the cost of driving 40 miles by taking the battery capacity divided by the Kilowatt/hour electrical cost. You're losing power in the battery charger, you're losing power in the drive circuit, you're losing power on the motor itself (which is a water-cooled induction motor), plus you have the friction and braking losses than any vehicle has.

Still, electric vehicles are vastly more efficient than a conventional car. The most efficient IC engine (fuel-injected diesel) is around 40% efficient.

vincemulhollon
03-22-2010, 09:45 AM
And with more electric cars in use the price will go down.

I expected that for a decade, but it turns out the nickel is an expensive commodity and NiMH cells are pretty much an off the shelf commodity item.

I'm told the scrap value of the nickel in the Prius battery varies a heck of a lot but averages just a wee bit less than the cost of a used prius battery.

So, in theory, if there were any real demand for Prius battery replacements (apparently there is not), then the Chinese could sell them at walmart for a wee bit more than the cost of the nickel, but they'll never drop below, say, $400 a piece because then you could flip them to scrappers for a profit.

The "materials times ten" that Toyota charges is a wee bit steep even for a foreign OEM, but the "materials time two" that the independent rebuilders charge is probably a lower limit on still being able to make a profit. "materials times two" probably depends on recycling dead cells to make all the profit, kind of like the stories I've heard that screw machines only run a profit by recycling their swarf.

lazlo
03-22-2010, 09:53 AM
I expected that for a decade, but it turns out the nickel is an expensive commodity and NiMH cells are pretty much an off the shelf commodity item.

It's not a technology issue either -- electric cars are surprisingly low-tech. The motors, batteries, and drive circuits haven't changed much in the last ten years. The Chevy Volt, for example, uses the same motor and drive electronics that the EV1 used.

It's become popular for hobbyists to retrofit gas vehicle with electric motors. Someone posted a really nice Honda conversion where they literally used a stock induction motor with conventional VFD's.

What's limiting electric vehicles is the economics of charging the vehicle. In most places in the US, electric vehicles are coal-powered, so the pollution savings are minimal.

Willy
03-22-2010, 10:34 AM
What's limiting electric vehicles is the economics of charging the vehicle. In most places in the US, electric vehicles are coal-powered, so the pollution savings are minimal.

Good point Lazlo.
The economics of charging, and of course the the all too real issue of energy density. Battery technology has a long way to go before people relinquish their addiction to liquid fossil fuels.
As it stands today, a 1000 lb. battery pack contains roughly the energy equivalency of a 1.2 gallon, or 8 lb. container of gasoline.

vincemulhollon
03-22-2010, 12:02 PM
As it stands today, a 1000 lb. battery pack contains roughly the energy equivalency of a 1.2 gallon, or 8 lb. container of gasoline.

Without even doing the math or looking anything up, my finely tuned engineering brain says that's way, way off. Not by a whole order of magnitude, but pretty close.

So, 1000 pounds is about 450 kg, pounds to kg is a wee bit less than "just divide by 2". My estimate is probably low.

So 450 kg * about a tenth KwH per kg, which is about right for LiFePo battery used in a Chevy volt, yer black and decker cordless drill, or heck just plain ole any lithium battery out there. That gives about 45 KwH in that pack. My estimate is probably low, the lab/marketing numbers are Much better like 0.150 or even higher, but a tenth is pretty easy to remember and calculate.

45 KwH times the rule of thumb of about a third liter of diesel per KwH. Thats going to be about 15 liters of diesel to charge that dude. Thats for a "cruise ship" sized engine running continuously at full throttle. My estimate is pessimistic, a real cheapo tiny gen running at various throttle positions (like a car engine) is probably closer to a half liter of diesel per KwH.

15 liters of diesel add a quarter because diesel has "about" a quarter more energy than a similar amount of gasoline. Thats gonna be about 19 liters of gasoline. I think real diesel is closer to a fifth more so I'm estimating pessimistic, but the math is simpler for a quarter.

19 liters divided by 4 because a liter is about a quart, and four quarts in a gallon, thats darn near 5 gallons. 1 gallon is actually more like 3 and 3/4 liters but that math is harder so I'm sure its well over 5 gallons, again my estimate was really pessimistic.

So, not even breaking out the calculator or looking any of this stuff up, I think you're off by at least a factor of 5. Given that I was super pessimistic in all my estimates, I would not fall out of my chair were I to find that a 1K pound battery is closer to ten gallons of gasoline. If it does turn out that 1 kilopound of battery equals about ten gallons of gas, that would be a convenient rule of thumb to memorize.

Besides, it just makes sense, that you can beat up a "kilopound" of electric forklift about as long as you can beat up "ten gallon tank" of propane forklift, more or less.

Maybe 1 gallon is close for 50 year old lead acid batteries technology, like on an antique forklift. Maybe not even then. I think it a fair bet that an individual battery with performance as poor as you specify would have to be older than I am, or be some very special case like an edison cell or something.

lazlo
03-22-2010, 01:03 PM
As it stands today, a 1000 lb. battery pack contains roughly the energy equivalency of a 1.2 gallon, or 8 lb. container of gasoline.
Without even doing the math or looking anything up, my finely tuned engineering brain says that's way, way off. Not by a whole order of magnitude, but pretty close.

You're both right :) Willy is saying that the Chevy Volt can drive 40 miles on a full charge. That's roughly 1.2 gallons of gas.

Part of the discrepancy is because the LiPo battery in the Chevy Volt weighs 400 lbs. The other complication is that, in order to optimize the life of the batteries, GM is using a 16 kWh battery pack in the Volt but only use 55% of the theoretical capacity to power the car. So they only charge the battery up to 85% and switch to internal combustion when it falls to 30% charge. GM claims that will provide a 10-year lifespan of the batteries.

If you do the math, that works out to 50 Wh/Kg of useable battery capacity, about the same as a high quality lead-acid battery.

Willy
03-22-2010, 01:34 PM
The real world practical energy that actually drives the car, works out to about 7 or 8 lbs of liquid fuel, gas or diesel, to provide enough energy to do what a 1000 lb batty pack provides in the form of "fuel" to propel a vehicle an equivalent distance.
Both systems will of course have energy losses in the form of heat and of course they also have other "issues" in the form of manufacturing, and environmental footprints. But this is essentially what the conversion breaks down to in practical terms.

Here is a good read (http://www.caranddriver.com/features/10q1/electric_supercars_audi_e-tron_tesla_roadster_m-b_sls_amg_edrive_charge_to_production-feature) on some very exclusive all electric concept cars from MB/AMG and Audi.




Owners wishing to tap into this performance—why else would you spend all that money on a supercar?—will find that the batteries just don’t have the energy density to cope with the power demands. Audi claims the 53-kilowatt-hour battery pack powering the e-tron is good for a 154-mile drive. However, the car uses only 42.4 kWh of its total output for propulsion, in order to lengthen the life expectancy of the battery. That total usable capacity of the battery pack, which weighs more than 1000 pounds, contains the same amount of energy as about 1.2 gallons, or eight pounds, of gas. In the Benz, three 16-kWh lithium-ion battery packs add up to 48 kWh, the energy equivalent of about 1.3 gallons of gas. So Mercedes doesn’t expect its electric SLS to travel more than 100 miles on a charge even when driven slowly


I could point to other links citing the same energy levels, but unfortunately these are the real world values that one has to face when it comes down to current battery technology.

Dr Stan
03-22-2010, 01:54 PM
Well I see Chrysler is jumping into the hybrid market:

http://www.industryweek.com/articles/chrysler_announces_new_fiat_500_electric_vehicle_2 1386.aspx

saltmine
03-22-2010, 02:13 PM
Having been a victim of Chrysler and FIAT's "Engineering", I would expect them to sneak into a golf course, steal a golf cart, cut the bottom out of a FIAT 500, and weld it onto the golf cart chassis. Presto! FIAT electric vehicle.

Dr Stan
03-22-2010, 03:54 PM
Having been a victim of Chrysler and FIAT's "Engineering", I would expect them to sneak into a golf course, steal a golf cart, cut the bottom out of a FIAT 500, and weld it onto the golf cart chassis. Presto! FIAT electric vehicle.

I understand your sentiments, but on a trip to Italy 4 or 5 years ago I was able to get a new look at Fiat's offerings. They were far superior to the old Fiat's imported into the US and were equal to any of the other European cars of the same price class.

J Tiers
03-23-2010, 12:58 AM
Yes, I've referred to them as IGBT's several times. Regardless, an IGBT is just a FET with a bipolar gate. Spice models an IGBT as a Darlington pair with a bipolar transistor driving the gate of a FET.


A "minor technical error" there...... IGBT = Insulated Gate Bipolar Transistor.
A mosfet driving the gate of a bipolar transistor would be a much more technically correct description of an IGBT.....

For high voltages, the saturation voltage of the IGBT is much lower than a similar voltage Mosfet. For LOW voltages, the Mosfet is far superior, with milliohm "on" resistances.




So you're saying that an IGBT has no linear region? That there's no overshoot or undershoot on an IGBT?


All switching type parts are optimized to make the linear (high dissipation) operation minimal........ which generally means high "gain".

You CAN operate them in linear, I have done that with certain mosfets, but in switching you want to avoid that at all costs.... You are stuck with it in transitions, for various technical reasons which I shall not bore everyone with.....

You avoid it by "zero voltage" or "zero current" resonant switching.

"Desaturation" is a known killer of switching parts, and NO power switching device I know of is operated out of saturation, they are carefully protected against it.

Old time high speed bipolar computer circuits were carefully operated at the 'edge" of saturation, avoiding the stored charge/minority carrier problems of heavy saturation.... but they were not "power" circuits.

Overshoot and undershoot are a different issue, usually related to outside stray/parasitic components.




In any event, rather than bore everyone with transistor switching theory and IGBT S-curves, why do you think that VFD's have giant heat sinks? Mike's prototype electric car has water-cooled drive heatsinks.


Water cooling, as I already mentioned, is for COMPACTING the drive...... shortening the wiring, which often IMPROVES the efficiency...... the IGBTs in large drives can be the size of books...... they don't lay out well when combined with heatsinks that can deal with 2 or 3% of drive output........ So water cooling lets the drive be small, and the heatsink be *elsewhere*.

IN NO WAY does water cooling imply enormous losses....... You are sounding like Evan, only Evan usually makes sense even when he is wrong.........




In any event, my point is that you can't calculate the cost of driving 40 miles by taking the battery capacity divided by the Kilowatt/hour electrical cost. You're losing power in the battery charger, you're losing power in the drive circuit, you're losing power on the motor itself (which is a water-cooled induction motor), plus you have the friction and braking losses than any vehicle has.

No argument there..... it's just the claim of HUGE losses in conversion that I object to.



Still, electric vehicles are vastly more efficient than a conventional car. The most efficient IC engine (fuel-injected diesel) is around 40% efficient.

Oh, really? I suppose you will consider the generation process, and the transmission losses from power plant to the plug as "zero"?

the overall efficiency is not that radically different..... if you start with a plant heat efficiency to the generator shaft of of 50%, which is decent...... and figure a 95% generator efficient, with 4 layers of transformers at 97%.....

Then incorporating charger and drive at 97% efficiency, the net BEFORE the inefficiency of battery itself is now about 39%.... neglecting transmission losses and poor power factor, etc.......

if you start with 60% heat efficiency, you get 47% efficiency WITHOUT the battery losses... again without considering transmission losses, poor power factor, etc.

While you have to deliver gasoline, you also have to deliver coal to the plant.... or gas, which is likely at least a wash..... Hydro has a huge fixed energy cost to build the plant......

Sorry, no free lunch today.





it says a lot about the high quality of the machine design, that a desperate hatchet job is filled with such... desperate claims.

hatchet job?

Bull$hit.......... not by me......

I LIKE the idea, and I am extremely pissed off that GM apparently blew it, as the reports seem to indicate. The main issue is the claimed 300 mile hard range limit, engine included... it turns a useful car into an urban toy...... a few extra HP would have probably made the difference.....

But one poster seems to claim they do NOT have that hard limit...... if so, that would be far better.....But maybe he just never had to drive more than 300 miles in a day...... I do 600+ in a day going to relatives, and it wouldn't work for me, I'd ahve to afford a second car.

As for your claims about responders..... With possible energy sources including batteries, fuel cells, hydrogen, alcohol, and even flywheels....... YOU BET THERE IS AN ISSUE. I dismiss your claims of "no problem" out of hand.....

The responders I know do NOT want to have to deal with hydrogen or alcohol fires, they HATE those types...... they'd much rather deal with gasoline fires. I would argue gasoline is more hazardous to the occupants than the usual battery etc. Hydrogen CAN be stored in better ways, but then the tank is heavy and has less usable volume (adsorbed storage).

danlb
03-23-2010, 01:58 AM
DC Should be quite a bit WORSE.

The reason is that AC does not penetrate a conductor, like a person, as well as DC. People are high enough resistance that the effect is reduced, but it still exists.

DC can be conducted through your entire cross-section, meaning that there is a good chance it will penetrate to teh heart and stop it.

Plus, according to my sources, DC, if you are not thrown clear by the initial muscle contraction, may cause you to "freeze on" to the conductor for longer. AC does that also, but is probably a bit easier to get away from. I've had both, don't want either, didn't like 450V DC one bit. It blew little holes in the skin.


I think you got your facts backwards. AC will freeze the muscle and burn you. DC will just burn you, but you can turn loose of a DC line. If you'd hit a 450 AC line you'd be a gonner.

Hi-freq AC involves the skin effect. Not sure where you got the notion that it makes much of a difference at lower frequencies. Maybe from welding classes?

As for resistance.... DC and AC see electrical paths the same. Path of lowest resistance wins (not counting reluctance in tuned circuits). If you stand with one foot on the DC negative and one on the positive, your brain does not cook.

But that was a neat post anyway. :) Entertainment value way up there. http://bbs.homeshopmachinist.net/images/icons/icon14.gif

Dan

OldRedFord
03-23-2010, 04:09 AM
At what we pay here (about $.11/kwh) it would cost about $1.75 to recharge the battery pack for 40 miles of range. The engineer that I spoke with said that because they only charge the pack to 80% and only let it drop down to 30% the batteries should last ten years.


40 miles? Thats a one way commute to college.

J Tiers
03-23-2010, 08:25 AM
I think you got your facts backwards. AC will freeze the muscle and burn you. DC will just burn you, but you can turn loose of a DC line. If you'd hit a 450 AC line you'd be a gonner.

Hi-freq AC involves the skin effect. Not sure where you got the notion that it makes much of a difference at lower frequencies. Maybe from welding classes?

As for resistance.... DC and AC see electrical paths the same. Path of lowest resistance wins (not counting reluctance in tuned circuits). If you stand with one foot on the DC negative and one on the positive, your brain does not cook.

But that was a neat post anyway. :) Entertainment value way up there.

Dan

If you are suggesting that facts are wrong, it is up to you to disprove them.......

per skin effect.... The effect of skin depth varies with frequency, of course. But it also varies with resistivity, and the overall depth to which conduction is desired to penetrate... even at the low frequencies of power circuits, the so-called skin effect is effective.

In good conductors, the average depth of conduction can be as low as 1 cm at 60 Hz. People are not such good conductors, but then the conduction depth needs to be around 7 cm, so there is a balance.

DC has NO skin effect, and conduction in the conductor core lags only slightly, fractions of a second. However, DC also requires somewhat more current to affect the heart. That current is available if the voltage can drive it, since full conduction will occur in well under 1 second.

As for DC and "freezing", my understanding (and to some extent my own experience) is that DC produces a continuous muscle contraction, which would seem to be the DEFINITION of causing you to "freeze" onto a conductor. And, in fact, a short internet search produces confirmation of that from various sources.

In ANY case of electrical contact, muscle contraction may cause you to eitehr freeze onto, OR be thrown clear of, the live part..... it's the luck of the draw what happens.

And, I am not at all sure that the matter is overly relevant to electric cars.... Aside from the direct fire hazards (refer to the "burning laptops" of a couple years ago), or dumping electrolytes onto victims from breached battery cases, the direct hazards of battery vehicles are probably less than those associated with a fuel vehicle.

The problems of any unfamiliar technology out in the sticks is simply poorer training, and possible delays in rendering assistance due to perception of hazards.

The problem of "invisible flames" is apparently quite real, though, according to my contacts at the FD.

lazlo
03-23-2010, 08:37 AM
Water cooling, as I already mentioned, is for COMPACTING the drive...... shortening the wiring, which often IMPROVES the efficiency...... the IGBTs in large drives can be the size of books...... they don't lay out well when combined with heatsinks that can deal with 2 or 3% of drive output........ So water cooling lets the drive be small, and the heatsink be *elsewhere*.

Sorry Jerry, but that's just flat-out wrong. The company that's making the prototype electric truck started out with conventional aluminum heatsinks on the IGBTs. They burned them up. Then they went with giant aluminum heatsinks. Burned them up. Then they went with giant copper heatsinks, burned them up.

The only way they can keep the IGBT's cool under operating conditions is with giant water-cooled heat sinks.


IN NO WAY does water cooling imply enormous losses....... You are sounding like Evan, only Evan usually makes sense even when he is wrong.........

Jerry, you're getting wrapped around the axle like you usually do when you get into these brain lock flame-wars with Evan.

Answer the question: why do VFD's have giant heat sinks?

Why does the heat sink on a VFD get really freaking hot when you run the motor speed up and down?

Why is the induction motor on the Volt water cooled?

Why does the power supply for the volt have big heat sinks?

Why are the Volt's batteries water cooled?

No, they're not boiling water for tea :rolleyes: It's because they all represent losses in the system.

By the way, here's a picture of the Chevy Volt's battery pack being charged. The nylon-reinforced orange tubing at the bottom are the forced coolant. That's not a lab setup, that's how it's configured in the car:

http://www.blogcdn.com/green.autoblog.com/media/2009/12/volt-battery-shake-1260997355.png

Richard-TX
03-23-2010, 09:55 AM
Both interior and exterior design and feel are very nice, the seats felt great and even the back seat was roomy and comfortable

I find it hard to believe that Chevy/GM can actually make a proper seat. As of two years ago they still have not been able to make a proper seat.

J Tiers
03-23-2010, 08:51 PM
Sorry Jerry, but that's just flat-out wrong. The company that's making the prototype electric truck started out with conventional aluminum heatsinks on the IGBTs. They burned them up. Then they went with giant aluminum heatsinks. Burned them up. Then they went with giant copper heatsinks, burned them up.

The only way they can keep the IGBT's cool under operating conditions is with giant water-cooled heat sinks.


Answer the question: why do VFD's have giant heat sinks?



In general THEY DO NOT.....!!!

You keep harping on this "giant" thing..... it's GIANT GIANT GIANT...

VFDs do NOT have outsized, or "giant" heatsinks.... That's just a bunch of loaded words that you choose to use, we have no idea what your use of "giant" means.

If you would take the trouble to see what heatsinks are used in modern VFDs, such as the Vacon/Cutler-Hammer units, you would see that rather small boxes, including heatsinks, IGBTs, control circuits, filter capacitors, etc, control huge power.

A 200 kW 5 phase inverter I know of (and cannot discuss in detail due to confidentiality) has an air-cooled heatsink about 5" x 10" x 24" in size. I don't call that "giant" for 250 HP of continuous output.

Look at the total size vs power of the Vacon units. They are on-line, so you can educate yourself easily.

As for the truck people, I don't know why they have such trouble, but they might have a space problem locating heatsinks where they need to be..... because I know perfectly well that hundreds of HP worth of inverter is fittable in a decently small package, WITH good cooling. but maybe not fittable where they decided to PUT the IGBTs.

Water cooling doesn't cool BETTER..... you STILL need to remove the heat to the air somewhere..... and you must do that at a reasonable temperature, because the water is only a transfer medium, it isn't a miracle cure. The cooling problem is merely moved, to a place that presumably is more convenient.




Why does the heat sink on a VFD get really freaking hot when you run the motor speed up and down?

It will get hot whenever you supply significant power .... All power circuitry has losses..... the question is HOW MUCH in losses..... And what you call really hot....

Boiling water is really freaking hot to your hand, but it's a good running temperature for an IGBT junction.

Good motor drives are 95% or more efficient including filters etc. perhaps 97% in the switching section alone.

Ask yourself what 3% of output represents, and that is what you must dissipate, if you have a good inverter, like the Vacon units I am familiar with.

Now, specific drives may be designed to a cost.... and the heatsink may be cheaper than using a small number of special IGBT modules for one specific product only.



Why is the induction motor on the Volt water cooled?

Why does the power supply for the volt have big heat sinks?

Why are the Volt's batteries water cooled?


Well, old son, I don't know for sure.... in that I don't know what the tradeoffs are in the design.

But the usual reason for water cooling is because it is a lot more compact than blowing air through whatever is being cooled. if you need to cool a battery, and the battery usually DOES need to be cooled if it is jammed into tight spaces, air cooling works against fitting it in. But water cooling carries heat away to a radiator..... And radiators are well understood. A reasonable-sized radiator carries off most of the 60% of the heat energy that your IC engine wastes.

I say again.... the usual reason for water cooling is to carry a LOT of heat from a SMALL SPACE..... a lot in that it is much more than air cooling that same space could be expected to do.

Water cooling allows you to put the fins wherever you want, instead of them having to be on the parts you want cooled....

As for the Volt, since high efficiency drives are commercially available, the designers, if they had any sense, equaled commercial practice in efficiency, especially given their strong motivation....

So I will go with water cooling for compactness.....

It is usually desired that a car should be of a reasonable size, carrying people and stuff. A car that was a big lump with room for one person and no "stuff" would not be considered an unqualified success......

And a car that looks generally like an IC engine vehicle is preferred.... which does not leave a lot of room for batteries plus cooling fans and vents, ducts, etc.

Water cooling allows the designer to put things wherever they fit, and still cool them with a conventional radiator, perhaps located (gasp, choke) up front where they have always been......................

lazlo
03-23-2010, 09:31 PM
You keep harping on this "giant" thing..... it's GIANT GIANT GIANT...

VFDs do NOT have outsized, or "giant" heatsinks.... That's just a bunch of loaded words that you choose to use, we have no idea what your use of "giant" means.

The $2,500, state of the art, 5 HP Mistsubishi VFD I posted has a 5 1/2 lb heatsink. That's 10" x 6 ", x 2", or 120 Cubic inches, with force air cooling. That's a giant heat sink by any definition.

Have you run your VFD up and down with your hand on the heat sink yet? :)


If you would take the trouble to see what heatsinks are used in modern VFDs, such as the Vacon/Cutler-Hammer units, you would see that rather small boxes, including heatsinks, IGBTs, control circuits, filter capacitors, etc, control huge power.

As it turns out, I have two Cutler-Hammer VFD's. In fact, I sold one to MickeyD (Mike). Guess what -- the 5 HP Cutler-Hammer heat sink is the exact same size as the Mitsubishi. No surprise, since IGBT's all dissipate the same heat under the same conditions.

People were asking how much mileage the Chevy Volt will lose to turn on the car's heater. No worries there, since practically every system in the Volt, from the charger, to the LiPo batteries, to the drive system, to the motor has a water-cooled heat sink.

There's no free ride, even on electric vehicles.

J Tiers
03-23-2010, 10:27 PM
Have you run your VFD up and down with your hand on the heat sink yet? :)


Does a several hour heat run on a 60kW grid tie inverter count? because I HAVE done that, with a few dozen thermocouples all over it...... or are you holding out for the "manual test"?

I'd have to look it up to give hard numbers, but the heatsink entrance and exit air, in a closed cabinet with 300+ CFM of air exchange, was low enough to be of no concern for operation... and remember that was for 60kW of inverter, PLUS all the ancillary stuff for grid tie applications.

Remember what 3% of 60,000W is..... it's 1800W... Very efficient, but still heat to be dissipated.

The actual inverter size I have given elsewhere, and it isn't so big. I think you have a very odd definition of giant....... but then you work with micro-chips... ;) Remember that the inverters are specified to operate up to at least 122 deg F, which is already too hot for humans..... And that is teh ENTRANCE air temp that they must be able to handle........ hence the heatsink.

if you want "giant", .....any linear amplifier device , operating at that power level, would have a heatsink that would be many times bigger, and would REALLY be a "giant" heatsink.......



As it turns out, I have two Cutler-Hammer VFD's. In fact, I sold one to MickeyD (Mike). Guess what -- the 5 HP Cutler-Hammer heat sink is the exact same size as the Mitsubishi. No surprise, since IGBT's all dissipate the same heat under the same conditions.


hardly.......

IGBTs are quite different from each other.......

* They differ in voltage drop at rated current, which directly influences dissipation.

* They differ in "tail current" which affects speed of switching (an effect of their basic bipolar transistor structure)

* They differ in total gate charge requirements, which affects their drive requirements

There are a considerable number of different characteristics of different IGBTs which directly affect the total dissipation.

And, then there is a basic problem in extrapolating from low power VFDs....... THEY ARE MADE TO A COST GOAL.

That cost affects their efficiency, as the very smallest IGBTs which can do the job are used..... NOT the most efficient, just the cheapest. Typically a module, which includes the IGBTs, rectifiers, commuting diodes, and the brake IGBT, is used, which come in only certain sizes, unless you use millions and can get a custom.

It is also a lot cheaper to slow the switching down to reduce EMI, than it is to put in an expensive filter...... All you do is change the gate drive resistor, and add some heatsink...

Then also, often the choice of switching frequencies means that the highest frequency will have considerable losses, but you have to have it to satisfy low noise requirements. That also adds heatsink, but is not a strictly technical requirement

Now, once you get out of the low power 1 to 20 HP stuff, you start to get to units where the efficiency is a concern, and attention is paid because efficient drives are cheaper.

Switching frequency can be low, it is typically 3600 Hz in the 72 kW Vacon drives....... where it may be up to at least 16 kHz in a 2 or 5 HP drive. Cheap IGBTs are slower, and heat more at higher frequencies.

I suggest you look it up.....Educate yourself.... check these manufacturers for the TOTAL size of the units...... not all of which size, of course, is heatsink..... But, I suppose you might still persist in labeling them "GIANT"....... you must suit yourself, of course.

http://www.vacon.com/

http://www.invertek.co.uk/

lazlo
03-23-2010, 10:41 PM
Does a several hour heat run on a 60kW grid tie inverter count? because I HAVE done that, with a few dozen thermocouples all over it...... or are you holding out for the "manual test"?

I'm holding out for the manual test Jerry. You know damn well the giant heatsink on a VFD gets really hot when it's accelerating or decelerating, because it's a lossy system. I don't know why you're so persistently pursuing this argument.

Based on a 5 HP VFD with a 500 - 750 Watt heat sink, it's designed for around a 85% worst-case efficiency.

So take the Volt's 16 KWh battery battery pack, GM's stated they're only using 55% of that capacity for battery life, then assume a 85% efficiency of the drive system in typical traffic where the motor is accelerating and decelerating, a 90 efficiency of the water-cooled induction motor, ... which explains the 40 mile range from a 16 kWh battery pack.

J Tiers
03-23-2010, 11:10 PM
The "economically sized" heatsink on a VFD gets hot under load...... I never denied that....

My problem with your claims is this assertion of "gross ineffciency", and your persistent use of emotionally loaded terms such as "GIANT heatsink"....... You are only being silly, and ought to know better.

Since we have ESTABLISHED that motor drives are commercially available with efficiency in the 95% plus range, it is puzzling why you persist in apparently claiming that huge water cooled heatsinks are a requirement due to the poor efficiency of motor drives..... 95% or 97% would be considered pretty good...... and surely exceed the efficiency of any of the rest of the system barring the wiring....

MOTORS and BATTERIES are much less efficient than drives.

As for your "750W" heatsink....... let's look at it.

100 deg C is a good operating junction temperature for reliability...... now whatever heat is dissipated must be transferred from the IGBTs through an electrical insulator*, to the heatsink base, and then to the fins. A reasonable temperature drop for that is 20 deg C..... might be a little less, or a little more.

Then the transfer of heat to the air requires a temperature difference........

From 25C "consumer equipment ambient", that leaves 100-20-25 = 55 deg C to be taken up in the effective thermal resistance from sink to ambient..... great, that's liberal.....

But WAIT...... the INDUSTRIAL environment requires a 50C ambient (or higher)........ woops..... 100-20-50= 30!

Now we have to do the same dissipation with only 30C allowed rise.......

THAT is a lot of the reason for your so-called "giant" heatsink..... it isn't the dissipation alone, it is the fact that the allowable temperature rise is so darn low.....

You can expect an industrial heatsink to be bigger than you think it should, because it has to be much BETTER than a consumer one such as your stereo receiver has...... not because of some enormous heat load, but because of the high ambient temp.

Given the controlled power, the size of the device overall is pretty low. Even for crummy VFDs.

Too_Many_Tools
03-23-2010, 11:57 PM
40 miles? Thats a one way commute to college.

The daily commute for 75% of Americans is on average 33 miles (53 km).

That's round trip...there and back.

Your commute is not the average.

With the Volt your gas engine would run...as it should.

FWIW...the longer commute, the better a solution a hybrid car is.

What do you drive now and what is its gas mileage?

TMT

lazlo
03-24-2010, 12:42 AM
Since we have ESTABLISHED that motor drives are commercially available with efficiency in the 95% plus range, it is puzzling why you persist in apparently claiming that huge water cooled heatsinks are a requirement due to the poor efficiency of motor drives.....

Who has established that motor drives are available with "95% plus efficiency"

I've posted pictures showing disassembly of the state of the art in VFD drives, with a 5 1/2 lb, 120 cubic inch heat sink.

I also own the Cutler-Hammer VFD you use as a counter example, which has an equally large heat sink, indicating similar inefficiencies. Would you like me to post pictures of that giant heat sink as well?

Can you explain, if the drives and motors are 95% efficient, how the Chevy Volt, with a 16 KW power supply, only has a range of 40 miles at best?

oldtiffie
03-24-2010, 05:44 AM
Any help/interest?

http://www.gizmag.com/porsche-911-gt3-r-with-hybrid-drive/14148/

http://www.gizmag.com/porsche-911-gt3-r-with-hybrid-drive/14148/gallery/

http://www.gizmag.com/chrysler-to-produce-fiat-500ev/14590/

J Tiers
03-24-2010, 08:32 AM
Can you explain, if the drives and motors are 95% efficient, how the Chevy Volt, with a 16 KW power supply, only has a range of 40 miles at best?

16 kW whats? 16KW maximum rate? 16 kW-hours? Kilowatts are a rate, not an amount of energy....... So you are lacking some units data here...... but we will make an assumption.... I am NOT going to pre-calculate this, we'll just see where it goes, first pass gets posted.

Taking the number as kW-hours..... First, we are told that the battery cycles between 40% and 85% of capacity...... i.e. it is intentionally limited to use only 45% of its energy content. Right there 16 * 0.45 = 7.2 kW-hours.

Now, 7.200w-hrs / 746 = 9.6 HP-hrs.....

And I understand that the Volt is rated for range at 50 mph or so.

Most older vehicles require about 12 to 20 HP to maintain a highway speed, on average, and 50 mph is a highway speed.

let's assume that the Volt requires only 10 HP due to good design.....

40 miles at 50 mph would take 0.8 hour.... So using 10 * 0.8 = 8 HP-hours to go 40 miles...

We found above that the available enrgy is 9.6 HP-hours, and we have extracted 8 hp-hours as useful work, AFTER all losses.

8/9.6 = 83% efficiency....... which is the PRODUCT of all the individual efficiencies..... E(battery) * E(motor) * E(drive) AND includes all the other power drains that don't drive the vehicle, steering, brakes, control systems, etc......

If the three systems, Battery, Motor, and Drive, EACH have a 94% efficiency, their product gives 83% overall efficiency.

Since that doesn't include ancillary systems, and extraneous power draws incidental to operation, at least SOME of the efficiencies MUST be greater than 94% IF the battery holds 16 kW hours total.

Now, I am using YOUR 16kW hours figure, so if you don't like the result, or you gave me a bad number, it's not my deal, it's yours......


Who has established that motor drives are available with "95% plus efficiency"

The application literature for the LARGER Vacon/Cutler-hammer drives.... it is available on-line..... Air exchange estimation for enclosures is STATED TO BE based on 3% of total drive output...... And efficiency is also STATED.

Don't go by the little ones like yours, they have other issues.... as I have already mentioned.

And, YOU TOTALLY IGNORED the requirement of operating at high temps, where the heatsink is required to have half the temp rise as at 'consumer" temps....... meaning it will be about twice as big.....




I've posted pictures showing disassembly of the state of the art in VFD drives, with a 5 1/2 lb, 120 cubic inch heat sink.

I also own the Cutler-Hammer VFD you use as a counter example, which has an equally large heat sink, indicating similar inefficiencies. Would you like me to post pictures of that giant heat sink as well?

I suggested you go and look at the very large drives, and see their quite reasonable overall size, including heatsink, inductors, and everything else.... Look at their quoted efficiency....

You apparently refuse to do that, preferring your pet personal predjudices to facts.

Further discussion with someone who refuses to look at or accept facts is useless, so I think it is nearly time to let you stew in your own predjudices.....

lazlo
03-24-2010, 09:54 AM
16 kW whats? 16KW maximum rate? 16 kW-hours?

Yes, KWh. Should be obvious that was a typo (missing the 'h') since I've posted the Volt's battery info several times in this thread :rolleyes:.


GM is using a 16 kWh battery pack in the Volt but only use 55% of the theoretical capacity to power the car. So they only charge the battery up to 85% and switch to internal combustion when it falls to 30% charge.


Now your typo: GM cycles the Volt's battery between 30 and 85% capacity, so it's 55% of 16 KWh. But despite that, you're on track for exactly the point I've been making...


Taking the number as kW-hours..... First, we are told that the battery cycles between 40% and 85% of capacity...... i.e. it is intentionally limited to use only 45% of its energy content. Right there 16 * 0.45 = 7.2 kW-hours.

Now, 7.200w-hrs / 746 = 9.6 HP-hrs.....

Using the correct 55% capacity, it's 8.8 KWh / 746 = 11.8 hours. But keep going, you're getting there! :)


let's assume that the Volt requires only 10 HP due to good design.....

40 miles at 50 mph would take 0.8 hour.... So using 10 * 0.8 = 8 HP-hours to go 40 miles...

We found above that the available enrgy is 9.6 HP-hours, and we have extracted 8 hp-hours as useful work, AFTER all losses.

So correcting for the correct battery capacity, you have 11.8 HP hours in the battery, and 8 HP/Hours of work.

And finally, here's the punchline about giant heatsinks, water cooling, and system losses I've been making for 6 pages:


8/9.6 = 83% efficiency....... which is the PRODUCT of all the individual efficiencies..... E(battery) * E(motor) * E(drive) AND includes all the other power drains that don't drive the vehicle, steering, brakes, control systems, etc......

If the three systems, Battery, Motor, and Drive, EACH have a 94% efficiency, their product gives 83% overall efficiency.

So correcting your math for the actual Chevy Volt battery capacity, 8 / 11.8 = 68% percent efficiency.

The three systems, Battery, Motor, and Drive, therefore EACH have ~88% efficiency. What do you know, I ball-parked 85% efficiency of the VFD by eye-balling the size of the Mitsubishi heat sink :D

So now that you agree with the point I've been trying to make, we can go back 6 pages in the thread, and re-read this:


Comparing the size of the 5 1/2 lb forced-air heatsink on the Mitsubishi to a processor or GPU heatsink, I'd estimate it's rated for 500 - 750 Watts. That works out to around a 15% (peak) power loss on a 3.7 KW VFD.

In any event, my point is that you can't calculate the cost of driving 40 miles by taking the battery capacity divided by the Kilowatt/hour electrical cost. You're losing power in the battery charger, you're losing power in the drive circuit, you're losing power on the motor itself (which is a water-cooled induction motor), plus you have the friction and braking losses than any vehicle has.

J Tiers
03-24-2010, 10:31 PM
Dude.....

I have been agreeing with THAT part all along....

I merely keep objecting to you pointing at the DRIVE as the source of all inefficiency, when there is a very good chance that it is the MOST efficient part of the system, and quite good on an absolute basis as well.

I expect the BATTERY to be the very worst, well below either the motor or the drive. It will be better if a low consistent current is drawn, and will probably get worse as the square of the current draw... the same rate as many other losses in the motor, etc go up.

Oddly, the drive will be pretty flat, most likely, horrible at low power due to "fixed losses", then flat near peak over a wide range, and somewhat lower near maximum short-term power out.

So we can expect the efficiencies to NOT be equal.

The battery will be the worst... maybe 84%

The motor next...... maybe 92%

The drive the best. probably 95%

Lets see where THAT goes, with no editing and correcting.... I'm playing fair, I'll accept whatever comes out of the calculation using my estimates.

.95 * .84 * .92 = 0.73

I'd suppose 2 or 3 % for all the extra stuff, cabin ventilation, steering assist, etc. Even if there is a separate battery, it's all part of the system, probably charged off the big one.

The gets to 70% , pretty close to the numbers with the corrected 30% to 85% capacity figure.

Of course, BOTH of us are WAG-ing unashamedly....... As probably neither of us knows the real HP requirement of the Volt at the speed of best distance...... So our numbers may not be real, neither the original, not your corrected ones.