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aostling
11-24-2007, 10:27 PM
I've read about the Tesla, a $100,000 car which uses laptop lithium-ion batteries. I've searched, but can't find much info on what the hang-up is in bringing lithium-ion technology to the automotive market in an affordable vehicle. I understand there is a fire hazard. Is that close to being solved?

sch
11-24-2007, 11:09 PM
The rapid discharge problem is sort of solved: ie multiple developers have
lots of prototypes that seem to solve the problem, but no major auto
maker is likely to commit til there is more surety of this. Cost and size
of batteries is also a problem. Attaching and packing 6800 AA cells as
a power supply like the Tesla does is a non starter, as the Tesla people
will shortly discover at the $100k price level. The really deep doodoo
around Sony is something no auto maker will want to get anywhere near.

macona
11-25-2007, 12:14 AM
Lithium ion battery fires can be pretty spectacular. Several model airplane enthusiasts have lost their cars and garages from batteries spontaneously combusting. This is caused by one of two thing. First is improper charging or discharging. This will not be a problem in a car as they will have the appropriate safety circuits (Then again so did those laptops that were blowing up). The second is physical damage. All it take is damage to one cell to start a chain reaction that will set off the next battery. Each explosion will get greater than the last too.

And those batteries are darned expensive. Here people are bitching about changing the LiPo battery in their iPhones. Can you imaging what it will be with one of these cars?

http://youtube.com/watch?v=QJCZ4ayioCU

Doc Nickel
11-25-2007, 01:56 AM
The batteries are only a small part of it. The other part is that very few people will buy a $100,000 electric car.

Fewer still will buy a $100,000 electric car that whose batteries lose roughly 30% of their capacity a year, and for that car, will cost somewhere around $30,000 to $50,000 to replace.

Third, even the few rich yet still diehard "greenies" won't buy it because they know hat electrics simply displace pollution, not reduce it, and that the mining of lithim and production of batteries at large scale, is often "dirtier" than oil development and refining.

That leaves a market of perhaps a half dozen more-money-than-brains types who'll be more than happy to buy it, run it hard for a couple of years, get bored with it, and sell it off for a song later.

That's really not a good demographic to try and aim an entire auto industry at. :D

Doc.

Your Old Dog
11-25-2007, 07:24 AM
That's really not a good demographic to try and aim an entire auto industry at. :D

Doc.

I wouldn't say that. Not given the touchy-feely world we live in today :D Heck, they might really clean up.

When they do get this magic bullet to solve this perceived energy problem, how are they going to get the really poor people to sign on. Buying a new car on welfare might break us all? Better to get us all to drive (Oh this hurts) a Hugo then start down this road.

Ed P
11-25-2007, 09:30 AM
For all of those who have said that Lithium ion batteries are
impractical, I would like to point out the new Toyota Prius
is coming out with just such batteries in about one to two years.

Ed P

J Tiers
11-25-2007, 10:09 AM
And, we can expect to see the results in burned-out hulks perhaps.

Depends if they solve the problems.

The basic issue is that ANY really good battery that stores lots of energy in a small package MUST use very reactive materials. Lithium is one such.

With a Lithium based battery, you face a problem. It is, very grossly and somewhat dramatically, similar to that of having a very high mileage vehicle which however requires you to have the gasoline tank with walls made of 3 mil plastic, with an open flame just outside of the tank.........

Interestingly, the hybrid vehicles have VERY SMALL batteries.

I interviewed with one of the top companies making equipment for production battery testing and initial charge. They obviously have many automotive suppliers as customers world-wide.

In the interview they mentioned the actual size of the batteries in a couple of the hybrids, and I was shocked at the small size. I can't repeat to you the dimensions, that is somewhat confidential.

However, the difference in battery volume between a hybrid such as Prius, and an all-electric is large.

If an all-electric battery pack "went up" like the laptops, it very possibly would rapidly incinerate the occupants. Especially if they had to stop from highway speed in traffic before they could bale out.

In a hybrid, the same fire would be unpleasant, but if the battery were properly located, it would be far more likely to be survivable.

And, with smaller batteries, it would be possible to make them a bit more robust without a major impact on the overall size and weight.

Not so with a "maximum effort" all-electric. That faces a problem equivalent to the laptop battery issue.

IOWOLF
11-25-2007, 02:18 PM
Captain,We have a Warp core breach,prepare to eject the core. :)

Spin Doctor
11-26-2007, 10:16 AM
How much work is being done on flywheel battery systems now. I know they were "hot" a few years back. One side effect is that you need them in pairs that counterrotate to cancel torque effects

planeman
11-26-2007, 10:22 AM
Lithium-Ion batteries are in constant use in the radio controlled model plane hobby with excellent results (http://www.rcgroups.com/batteries-and-chargers-129/). Yes, they do catch fire if improperly charged and handled but they don't explode. So does gasoline. They do require a special charger. The most expensive computerized battery charger is only about $120 (US) - I have one - with non-computerized chargers in the $25 to $40 range. Today's batteries take very high discharge rates but have relatively long charge times, generally about a half an hour with a computerized charger and much longer with non-computerized chargers. This lengthy (for us) charge time is about to change to under five minutes or less with new technology which is about to come online - about the same time it takes to gas up a car. The batteries are not particularly expensive and if you have ever seen what they are made of and how they are manufactured you wonder why they cost as much as they do. The price is bound to come down considerably.

General Motors is set to introduce a plug-in rechargeable hybrid in a year or two with the aim to have half of its line with this technology shortly after.

I had the opportunity to drive a number of full-size electric automobiles at an electric automobile symposium, one of them a Chevrolet SUV, and I guarantee you won't be hurting for performance!

The electric automobile is truly arriving at our door!

R. Carswell

J Tiers
11-26-2007, 11:03 PM
I keep hearing about "if improperly charged"......

But then the batteries that burn seem NOT to be under charge at the time of failure, they may be in use being discharged, or in storage.

Can you explain that?

Does the "improper charging" damage them so they are 'going to" fail and burn later at some unknown time?

This has not been explained. Nor has any means to detect a damaged battery been explained.

Then also, the rapid charge times..... Sounds very good. There are some details.

The energy input rate to get the rapid charge is relatively high, and corresponds to high currents etc. Pretty much a 'don't try this at home" deal, as you need a solid mains supply line to do it. For special charging stations only.

Then, if the special charger goes awry, and damages the battery in such a way as to (apparently) turn it into a time bomb, how can you tell?

It would be unpleasant to find out that the charger had just ruined $20,000 worth of batteries.

It would be much more unpleasant to find out as they incinerate you and your family

The comparison to gasoline is natural, but meaningless. Gasoline has known hazards, and the presence of fumes is obvious to anyone whose nose works. The hazards are generally "mechanical" and are understandable / accessible to the average person.

Not so with a battery.

Even less so with a battery which may be undetectably damaged so as to guarantee a catastrophic flaming failure at some unknown future time.

mayfieldtm
11-27-2007, 09:45 AM
Interesting note...
The Lithium Batteries in a Prius Hybrids are never charged above 80% and never allowed to discharge below 20%.
Toyota claims this gives the maximum life for a Lithium battery.

I did a query on a couple of Prius Forums about battery fires.
No one has ever reported one, so the engineering seems to be on top of it.
I'm thinking the charge/discharge profile might have something to do with it, also.

My average annual mileage has very slightly increased over the last 5 years, so, the battery efficiency must not have diminished much, if any, over that time.

Tom M.

Wirecutter
11-28-2007, 01:28 PM
Uh, one problem with lithium ion batteries is cost. Take for example, my latest gokart the Neurotikart 2.
shameless plug:
http://www.youtube.com/watch?v=pl0xeX2xwLE

This kart runs 6 Optima yellow-top batteries, which weigh about 300 lbs and cost around US$1100. If I'd used NiMH for the same energy capacity, it would have cost me $3500-5000. For lithium ion, it would be closer to $25,000. Now mind you, LiON batteries are %40-%50 of the weight of those monster lead acid beasts, but geez, 20x the price.

Now piling on - with NiMH and LiON, you need to have special charging and balancing circuits if you want optimum safety and battery life.

The simple fact is that storing electrical energy in batteries is difficult, and whenever you have that kind of energy density, you have danger. Safe storage and transport of equivalent energy in petroleum-based fuel is comparatively very easy. There are some that don't consider electricity "energy" - it's just a vehicle for moving it around.

I repeat - most people don't realize the amount of energy is represented in a tank of good old gasoline. That's one (just one) reason we're finding it so hard to replace with other energy sources.

-Mark

aostling
03-11-2008, 09:48 PM
Toyota may be having trouble keeping the 2009 Prius on schedule. Lithium-ion batteries are likely postponed. Making it a PHEV (plug-in hybrid) is going to increase the total volume of the battery compartment, reducing luggage space.

With the skyrocketing price of gasoline I find this a little frustrating. Anybody have any inside information on these developments?

batt-man
03-12-2008, 06:09 AM
There's a couple of problems with using li-ion and (to a slightly lesser extent) li-polymer batteries in a car

First problem is charging (and where a large number of the reported fires come from). Assuming you use the proper charging algorithms for these cells they are very reliable and safe if the cell stack is cold/cool. As soon as you start moving enery in/out of a cell it starts to heat up. These types of cells do not like being charged if they're warm. Typically you charge this type of cell using a constant voltage; stopping when current flow drops below a certain point.

Problem is the warmer the cell the lower it's internal resistance and so the more energy that will flow into the cell before this minimum current limit is hit. However whilst your charging the cell it's internal temperature is going up and so it's internal resistance is going down; more energy will go in before the limit is hit.

So with warm/hot cells you can easily get into a cascade effect; more energy than designed goes into the cell, cell warms up meaning still more energy, cell overheats/ruptures catches fire.

So, the reason behind many of these li-ion fires was that people were either using a charger that was not fit for purpose (ie didn't use correct charge voltage, current cutoffs), or they were charging batteries that were still hot from being used.

The second problem will be the lifespan of the cell-stack; typically cell manufacturers advertise in the region of 70-80% capacity after 300 charge/discharge cycles; what they don't normally tell you is that this is based on a very "easy life", ie discharging at 1/10th of rated cell capacity to probably no less than 20% charge, and then charging to maybe 85% capacity. It's when you take the batteries into the end portion of the charge/discharge cycle that you quickly eat up the batteries life.

Even if you do give the battery an "easy life", by the time you go beyond 400 cycles if charge/discharge just about every cell that i've seen quickly starts loosing capacity. I should mention that i do a lot of design work for a battery company that literally uses in excess of a million li-ion/li-pol cells a year so i've got some experience with this technology.

I don't know what a replacement battery would cost for a hybrid but i can't imagine you'd have to do many miles in a day before you've completed a charge/discharge cycle. 400 days of driving and you need a new battery.....


Sorry for the long-winded post - i learn so much from you guys it's nice to be able to give a bit of knowledge back once in a while... :)

Cheers
Sledge

Evan
03-12-2008, 07:25 AM
We won't be doing any wholesale switching to electric cars any time soon. It doesn't matter how good or safe the batteries are, we don't have the electric generating capacity. We won't have it in the foreseeable near future either.

There are some very significant problems with electric too. They just don't work at -40 no matter what sort of battery you use. The cold weather problem ensures you won't see all electric in wide use in Canada even if the extra kilowatts were available.

Environmental issues are also very serious. How do you recycle a used up Li-Ion battery? They aren't designed for easy disassembly like a lead acid battery. What is the energy cost of making those batteries? What is the energy cost of recycling such batteries? In order to be at all acceptable they MUST be recycled. Landfilling isn't an option.

Then of course there is the safety issue. When lithium batteries first came out in the late 60s they were almost immediately seized on as the answer to cold temperature operation of ELTs, Emergency Locater Transmitters for aircraft. They work better than any other type of battery in cold weather although still not well enough to use at -40 for long. While it seemed like an excellent idea it became apparent the having an exploding/flaming device near the pilot's head in a light aircraft was a bad idea. After a number of incidents they were all recalled and replaced by more reliable nicad technology.

It doesn't matter what the motive power for a vehicle is. If it has sufficient energy density to be practical then it is equivalent to a bomb.

Tuckerfan
03-12-2008, 07:48 AM
We won't be doing any wholesale switching to electric cars any time soon. It doesn't matter how good or safe the batteries are, we don't have the electric generating capacity. We won't have it in the foreseeable near future either. Yup. According to a powerplant engineer I know, if you could suddenly make all the paperwork hassles disappear, it'd take 74 years just to replace the coal fired powerplants currently in use. (Which is very near the kind of volume of plant construction we'd have to undertake to make the switchover to electric cars.)


There are some very significant problems with electric too. They just don't work at -40 no matter what sort of battery you use. The cold weather problem ensures you won't see all electric in wide use in Canada even if the extra kilowatts were available. Nope, and according to people who've dealt with electric cars, they don't care for any kind of cold weather, so folks in the much of the US could be nearly in the same boat as their neighbors to the North.


Environmental issues are also very serious. How do you recycle a used up Li-Ion battery? They aren't designed for easy disassembly like a lead acid battery. What is the energy cost of making those batteries? What is the energy cost of recycling such batteries? In order to be at all acceptable they MUST be recycled. Landfilling isn't an option.This one's easy. We ship the batteries off to China, where they promptly mix the stuff in with the foods and toys they ship back to us. ;) The mining of the raw materials for the batteries (as well as the manufacturing of them) tends to be done in places with lax environmental laws, so they chew up the environment both ways.


Then of course there is the safety issue. When lithium batteries first came out in the late 60s they were almost immediately seized on as the answer to cold temperature operation of ELTs, Emergency Locater Transmitters for aircraft. They work better than any other type of battery in cold weather although still not well enough to use at -40 for long. While it seemed like an excellent idea it became apparent the having an exploding/flaming device near the pilot's head in a light aircraft was a bad idea. After a number of incidents they were all recalled and replaced by more reliable nicad technology.Most people don't realize how sensative these things are to such problems. I did some work in the Nissan plant last year, and they were training the employees on how to deal with the hybrid cars that they were going to be manufcturing there. Basically any problem would result in the car being literally roped off, hazard signs being placed around it, and only specially trained employees would be allowed near the car, as the risk of electricution was considered so great.


It doesn't matter what the motive power for a vehicle is. If it has sufficient energy density to be practical then it is equivalent to a bomb.Quite true. The only question is: How "easy" is it to detonate? Some fuels are more volitale than others, and are more predictable than others. Chevy has quietly been making noises that they'll be delaying the introduction of the Volt because they can't solve the battery issue.

And it looks like if you live in a drought stricken area, hybrid/electrics aren't exactly a good idea. (http://www.sciencedaily.com/releases/2008/03/080310094555.htm)
Eco-minded drivers in drought-prone states take note: A new study concludes that producing electricity for hybrid and fully electric vehicles could sharply increase water consumption in the United States.

In the study, Carey W. King and Michael E. Webber note that policy makers often neglect the impact that fleets of hybrid and electric vehicles could have on already-scarce water resources. They calculated water usage, consumption, and withdrawal during petroleum refining and electricity generation in the United States.

Each mile driven with electricity consumes about three times more water (0.32 versus 0.07-0.14 gallons per mile) than with gasoline, the study found.

J Tiers
03-12-2008, 08:23 AM
So with warm/hot cells you can easily get into a cascade effect; more energy than designed goes into the cell, cell warms up meaning still more energy, cell overheats/ruptures catches fire.

So, the reason behind many of these li-ion fires was that people were either using a charger that was not fit for purpose (ie didn't use correct charge voltage, current cutoffs), or they were charging batteries that were still hot from being used.



JUST ONE PROBLEM WITH THAT

Many, if not most, of the computer fires occurred while the battery was IN USE, NOT BEING CHARGED.

THE COMPUTERS USED THE "RIGHT"CHARGER and so the batteries "could not have been damaged by improper charging"..... (quotes indicate possible doubts).

While the R/C equipment fires occurred potentially due to improper charging, they occurred in storage.

Somewhat like storing a rag oily with some "drying oil".....the problem occurs hours or days after the original cause.


Each mile driven with electricity consumes about three times more water (0.32 versus 0.07-0.14 gallons per mile) than with gasoline, the study found.

I find these sorts of water use statistics to often be outright LIES.

The "use" of petroleum fuel DOES in fact "consume" the petroleum. It disappears in being "used".

VIRTUALLY ALL USES OF WATER` DO NOT "CONSUME" THE WATER.

MANY of the so-called "truthful statistics" about water use treat "process water" as if it were "destroyed" by being used, while in most cases it is in fact recovered and re-used. They attempt to put forth the LIE that each gallon used must be pumped from the ground, and is then "lost". Example: ethanol production.

HOW CAN PROCESS WATER WHICH IS RECOVERED BE COUNTED AS DESTROYED?

Now, I don't know how much process water is used in electric generation. Cooling water if evaporated is not destroyed, but it surely may be "moved" to elsewhere. In an arid climate that may be equivalent, locally. But it is not the only way to to the colling job, just one of the more effective ways.

The only processes immediately coming to mind which truly destroy the water are:

1) Hydrogen production

2) at least one type of coal gasification


Naturally, hydrogen is being touted as the save-all fuel, and the destruction of water is not discussed, presumable because in both of these cases water is re-created elsewhere by the use of the fuel. So even there, the water is "moved" and not "destroyed".

Lew Hartswick
03-12-2008, 08:51 AM
For all of those who have said that Lithium ion batteries are
impractical, I would like to point out the new Toyota Prius
is coming out with just such batteries in about one to two years.

Ed P
I wonder if this is sort of like the ads from Chrysler back in the 60's
"Turbine engines are about 10 years away" then in the 70's it was ,
"Turbine engines are about 10 years away" then I havent heard a
word about turbine engines since. :-)
...lew...

Evan
03-12-2008, 09:48 AM
"Turbine engines are about 10 years away" then I havent heard a word about turbine engines since. :-)

Simple reason too. A turbine just can't compete with a piston engine in a sole prime mover application with variable duty cycle. With a piston engine full torque is no more than half revolution away, with a turbine it's about 50,000 revs away. There might be a comeback though since the turbine wins on efficiency in a constant full power duty cycle application. A turbine hybrid does make some sense since turbines are cleaner and more tolerant of fuel variations. They also burn cheaper fuel with a higher energy content per liter than gasoline. They are very light weight too. A turbine suitable for a hybrid could easily be lifted by one person, probably with one hand.

darryl
03-12-2008, 04:28 PM
I read a 'fact' the other day in Motor Trend about using gasoline- they said that burning one gallon of gas produces 19.3 lbs of CO2. Interesting. One gallon of gas weighs less than that.

There was also some stuff about hybrids and one that I found interesting is the pickup truck. It uses a pair of electric motors, alternators basically, inside the tranny, and a relatively small battery pack. Another interesting article was about the use of flywheels in race cars. They use an 11 lb wheel turning some 65,000 rpm, and it's capable of delivering 80 horse for 11 seconds- something like that.

In either case it's an augmented IC engine still doing the work, just relying on an 'accessory' to help with peak demands. I've always thought that is the way to go, since it's pretty hard to beat the gasoline engine in so many ways. I'd be happy with a pure electric since that's kind of in my blood, but it's way more problematic than I ever thought it would be. If the battery is a bomb waiting to go off- so is a gas tank, so is a flywheel, so is a wound up spring, so is--- So is Toshibas latest offering, a mini-reactor capable of powering an entire apartment building for decades, or a vehicle-

I personally use a power source that so far is renewable, is pleasant to use, is NOT a bomb waiting to go off (as far as I know) and would make good use of agricultural land reserves- it's called food, and it runs my legs. But I guess we'll never see the day that we go that far back to basics.

Hmm. I'm going to use this fuel right now- to get my body into the gas guzzler and over to where I can obtain some electrically intensively produced material for my project- aluminum- which has taken a lot of fuel use to earn the money to pay for. Just can't win.

Evan
03-12-2008, 04:41 PM
they said that burning one gallon of gas produces 19.3 lbs of CO2. Interesting. One gallon of gas weighs less than that.
Oxygen has mass too and isn't included in the gasoline. It still sounds too much though although most of the weight of a gallon of gas is the carbon. Could be close.

Tuckerfan
03-13-2008, 06:41 AM
I wonder if this is sort of like the ads from Chrysler back in the 60's
"Turbine engines are about 10 years away" then in the 70's it was ,
"Turbine engines are about 10 years away" then I havent heard a
word about turbine engines since. :-)
...lew...
At one point, they were days away. (http://www.allpar.com/mopar/turbine.html)
When the Corporation was in such dire straights, back in 1979, we all know what happened, or do we?

Chrysler got some loans from the US Government...that much is certain. That Chrysler (as a condition of those loans) had to sell off Chrysler Defense and the M1 turbine-powered tank program is somewhat lesser known, but still public knowledge.

What is known only to a priveleged few is that the government killed a dream of a lifetime for a group of 70 people at the Chrysler "skunkworks" in Highland Park.

Believe it or not, Chrysler was days away from making a production decision (one which Iacocca favored) on a rather unique vehicle....

1981 Chrysler New Yorker Turbine car (M-body)... the car was ready to be tooled according to the head of the program, Mr. George Scheckter, whom I met when I got to see and touch the 1963 Turbine Car again in 1989. There was no more design work to be accomplished, just tool and start production.

The Turbine Engine was a fifth generation (not a 3rd generation like the 1963 car) engine capable of 22mpg in the EPA test cycles. To really make this sink in, one of the prototypes is still in existence (at least it was in 1989), stored in the same building as the 1963 car, its tooling and all the remaining spare parts (enough to build 3 more of the '63 cars).

Your government thought it was too much of a risk and ordered the car cancelled as "too risky, from an economic standpoint." Just imagine what COULD have happened!:(

J Tiers
03-13-2008, 08:08 AM
Simple reason too. A turbine just can't compete with a piston engine in a sole prime mover application with variable duty cycle. With a piston engine full torque is no more than half revolution away, with a turbine it's about 50,000 revs away. There might be a comeback though since the turbine wins on efficiency in a constant full power duty cycle application. A turbine hybrid does make some sense since turbines are cleaner and more tolerant of fuel variations. They also burn cheaper fuel with a higher energy content per liter than gasoline. They are very light weight too. A turbine suitable for a hybrid could easily be lifted by one person, probably with one hand.

Another efficiency improvement which is IMPOSSIBLE with a piston engine but quite possible with a turbine is:

Regenerative heating. You take exhaust heat and pre-heat the input to the combusters. Because this is AFTER the compression "cycle" it counts as heat input, same as fire. So you can use less fuel.

This is essentially impossible in a "batch processing" engine but fairly easy in a "flow" engine.

darryl
03-14-2008, 12:18 AM
My own thinking on the matter of electric vehicles has evolved to the point where a somewhat ideal system could be the gas engine/cvt/alternator/electic motor package. Although every step in the power train is lossy, some of that loss can be compensated for by eliminating much of the standard power train componentry. An elecric motor these days can be very compact, light, efficient, and powerful. Use one per wheel, and no drive shafts. Make the alternator a four stage unit, with each stage driving one motor. The field current can be varied to each stage to alter the output to suit the speed and torque required from each motor. As you turn for instance, the outside motors need to go faster than the inside ones, so increase the voltage to those during the turn. Controlling four field windings is going to be easier and cheaper than controlling four direct high current outputs, so there's a savings in cost and complexity. A control module will be needed of course, but in these days of anti-skid wheel speed sensors it wouldn't need a lot of further development. An input from the steering column would modify the algorithm feeding the field coils so that each wheel motor still 'pulls its weight'. Input from the 'gas' pedal still controls accelleration, and braking energy recovery can be taken up by the alternator, which would have to act as a flywheel to do so. Because it doesn't need to drive the vehicle for miles on its own, it hasn't become overly heavy, and can be electrically brought up to some speed by a single 12v battery in order to clutch in the engine for starting.

There you have it. The alternator is key to this proposal, as it is a four part unit, and must act as a flywheel for part of the cycle. It will be driven by the gasoline engine through a cvt, which will only need to have a range of about 3-1 at most. The engine can be kept in an efficient rpm range and wouldn't have to deliver any peak torque, so in theory, a 20 hp engine can drive a full sized car.

It appears that I've basically traded off the battery pack for a flywheel/alternator/gas engine combination. If we are to consider gasoline to still be the fuel of choice, this could be the way to go. As stated by many before, the dynamics of having to provide a country-wide way to charge all those battery operated electric vehicles will be avoided. I've also avoided the cost, weight, and replacement cost of a fair sized battery pack, and some of the high current electronics that must necessarily go with it. The flywheel effect of the alternator has taken care of that. Because it will still need to be a substantial size, that also suggests that it will be capable of delivering quite a large amount of energy to the motors, so it isn't like the vehicle needs to be anemic in performance.

One issue nags at me, and that is the lack of the direct connection between motor rpm and vehicle speed that we are all used to. Chances are that no matter what system or systems we end up using, we'll have to get used to that disconcerting separateness where, for example, the engine might be revving, but you're stopped. When you hit the 'gas', the engine doesn't respond like your brain says it should. This is an esthetic that a muscle car driver for instance would probably never get used to.

Anyway, I'm just trying to find a way to :
eliminate the battery pack
keep the engine size down
eliminate much of the need for high power electronics
keep much of the thrill of shooting from 0 to 60 in 1.4 seconds alive
reduce fuel usage
etc.

Evan
03-14-2008, 12:28 AM
One issue nags at me, and that is the lack of the direct connection between motor rpm and vehicle speed that we are all used to.

Ever driven a 2 speed Hydramatic? :D

aostling
03-14-2008, 12:37 AM
so in theory, a 20 hp engine can drive a full sized car.


Darryl,

I don't understand where the energy will come from when you need 100 hp or more. Are the alternator flywheels storing significant kinetic energy which can be tapped?

darryl
03-14-2008, 03:33 AM
Allen, that is the idea. The gas engine does its best to keep the alternator rpms up, while the stored kinetic energy supplies the peak demand to run the wheel motors. The controller would have to slowly increase the field currents as the rotor rpms dropped to keep the output power constant, or at least in relation to the depression of the gas pedal.

I see the rpms being in the 10 to 15k range, similar to regular automotive alternators, with each alternator section being larger of course. The output power would come from the stationary windings on the stator, which would also act as a measure of containment should the rotor come apart.

In one sense, I'd like to see this being an outer rotor, since the potential is there to store more kinetic energy with the same size structure. There is of course no inherent containment there should the rotor come apart, and a separate housing would have to be used. And also, of course, the system is a bomb like any of the others.

In basic terms, I like the alternator concept because a small field current will control a much larger output current, and the output is not totally dependant on the rotor rpms. Essentially you can feed your drive motors a voltage which is regulated to what they require at the moment, and not a higher voltage which would have to be stepped down through high current switching electronics to achieve the same thing. Kind of like tapping a string of batteries where each and every tap you make would deliver a smooth dc voltage without switchmode noise, voltage spikes, etc, not to mention further losses in the electronics.

macona
03-14-2008, 12:17 PM
The motor in the wheel concept has been around for a long time. But your design needs to be brought into this century. Motors in each wheel would be 3 phase brushless PM motors. One generator provides buss power (~300VDC) for the motor's drive electronics. 3 IGBT half-bridges per motor. All would have to be water cooled.

Figure about 10KW motors in each wheel minimum. But thats going to be hard to fit in a normal size wheel. And you still have to leave room for mechanical brakes.

This gets very expensive quick to build. Expensive to repair. Requiring specially trained techs.

darryl
03-14-2008, 09:23 PM
Yes, that's the type of motor that I had in mind. I've seen iterations of it in the past, including one that stands out in memory, made by Unique Mobility. 40 hp in a roughly 5 inch cubed area, weighng less than 10 lbs (and costing a couple of limbs each). I've been trying to think of a way to eliminate the high current transistors entirely, but currently they would still be required at each motor to do the commutating.

It would be interesting to find a way to supply each phase directly from an independant alternator section by having field current keyed to the motor shaft rotation. I believe that all the control electronics could be made as one unit, receiving shaft position information from each pm motor being driven, and outputting the required field drive signals. Regenerative braking could be had very easily with a system like this. It would merely be some phase shifting of the control signals.

This would require the alternator to respond very quickly, giving an output voltage locked in step, and reversing voltage as well during the cycle. In other words, it puts out a sine wave tuned to the motor being driven, but independent of the alternators own rpm. It might be required to work with an output frequency as high as 400 hz, maybe a bit more. If you hear the whine from any ordinary alternator, you'll hear the frequency being much higher than that. It would seem that the only mechanism limiting the response time is the speed at which the field magnetism can be cycled. In a standard alternator this is a problem because the rotor is not a laminated structire, but solid steel. Eddy current losses would be large is the field had to change this quickly, but the frequency I've suggested (400 hz) is well within the capabilities of a laminated rotor structure. These days a high magnetic field density steel is available and would be a natural for this application.

Maybe if we use some other term to describe this device it would help. I've been calling it an alternator, but think of it as a rotary magnetic flux translator instead. I would not be surprised to find that there is an existing device that does just what I've been describing, though I'm drawing a blank on that right now.

darryl
03-14-2008, 09:42 PM
Interesting- in todays paper I read about an electric vehicle using motors in each wheel. (a swiss development, I think it was) . They talked about a total of 30 hp, or 7.5 horse per wheel, and 0-60 times of 7 seconds. This was Li-ion powered- don't recall all the details- was this the sQuba- I really must get a memory-

As I walked, I though again about the motor in the wheel, but it would be just about as efficient to have two motors back to back where the differential would normally be, and use half shafts as in four wheel independent suspension. Front drive would be done pretty much as is already with cv joints and half shafts. You don't necessarily have to locate the motors in each wheel- why not integrate them with the suspension in this manner. You still eliminate differential gearing and drive shafts fore and aft.

Something else that occured to me as I walked is that some older volkswagon vans used a geared drive right at each rear wheel to put the drive shaft higher than the wheel centerline, and of course brakes are included in that housing. If one were to allow for some type of gearing or belt drive per wheel, then that opens up more options for the motor that drives it- though from an efficiency standpoint direct drive still seems the way to go.

J Tiers
03-14-2008, 11:56 PM
If you use a VFD to drive the wheel motors, AND you pole-shift them, you could effectively have an electronic gearbox.

Pole shifting, changing the number of poles in the motor on the fly electronically, allows a speed range change that is better than a frequency change alone. There can be a power consequence, but you can control which setting is optimized.

Use of a VFD drive loses a little efficiency, but allows very agile speed control, and relatively easy phase changing.

Wheel gearing , like the "Humvee", is a good way to raise the axle, and may allow some speed/torque trades that are better than direct drive.

macona
03-15-2008, 03:50 PM
I think that 5" cube 40HP is peak HP. Not continuous. The servo motor I am installing to replace the spindle motor will put out about 20hp for a very short time but continuously it puts out near the 3hp mark.

Your alternator idea wont work. The motors are operated like a stepper motor or three phase motor and the frequency of the input power is what controls the motor, that with either hall effect or encoder feedback to make sure the rotor is where it is supposed to be.

Dont think you would want a VFD. Definitely permanent magnet brushless DC or AC motors with full commutation feedback. Higher power density than a induction motor.

darryl
03-15-2008, 06:05 PM
Macona, you've suggested that my idea won't work- I'm assuming that's because you don't see the capability of the alternator to output signals (power level of course) that can be kept in tune with the requirements of the 3 ph motor, independent of the alternators rpm. I'm aware that the motor requires its 3 inputs to be sequenced to the rotors position at all times. I see that as control signals, and like you say, that's determined by hall sensors, encoder feedback, optical devices, or whatever method is used. Those signals can either control the h-bridge at full voltage and current, or they can control any other method which is capable of delivering the voltage and current to operate the motor.

If we see that other method as simple amplifiers with their own power source, it becomes easy to see that a higher power output would follow the low power input signal, and that output would satisfy the need to lock the delivery of the power to the motor winding in step to ensure rotation, and in the desired direction. Here we have three windings, so three amplifiers and three control signals derived from the motor itself.

My idea has the alternator acting as an amplifier. I referred to alternator sections- three sections woud be needed to supply three separate outputs. The power supply for this 'amplifier' is the rotation of the alternator, which is firstly from being driven by an engine, and secondly by it having some kinetic energy when at speed. Consider just one section and how it operates- as with a regular alternator, if you don't supply any field current, there's no output. If you pulse the field, the ouput pulses in step. If you supply a continuous field current, the output remains just as constant, with the degree of output depending on the field current and the rpm. The standard alternator has to supply voltage in one direction only, so there are rectifiers. Each of those windings also goes negative for half the cycle, but current is not drawn during that part of the cycle. Each winding supplies a positive pulse through it's rectifier, and those pulses overlap so the output is a composite of three phases superimposed.

For my application, we need the output to go negative as well, so as we reverse the direction of the field current, we also have to reverse the direction of the rectifiers. Perhaps it is this part that causes you to say that the idea won't work. I see it as being a circuitry issue, and in this case it's replacing the rectifiers with transistors, and switching one bank of three off while the other bank is on, controlled by the polarity of the field current. This can be a zero-crossing switching, and each bank of transistors is either on or off for the duration of the half cycle of the field current. Essentially, this becomes a 'smart' rectifier package.

Maybe there's a major flaw in my thinking, and if so I'd like to hear someone point that out in as much detail as is appropriate. For the moment though, I need a coffee, so I'm going for a walk to Java Hut. :)

Ok, back from coffee. That didn't take long did it- :) Anyway, now I figure the rectifiers for the alternator windings can be replaced directly by triacs, so the part count in the high current pathway remains the same. The triacs can be switched at the appropriate time during the cycle to supply either a positive or a negative voltage output. What the motor will see on each winding is sine wave with a ripple component on it. The frequency of that ripple is directly related to the alternators rpm, but will vary from about 5 times the sine wave frequency to maybe 1000 times that frequency. Where it is 1000 times higher is when the alternator is up to full speed and the vehicle is stopped or moving very slowly, and when it's 5 times higher is when the alternators rpm has been dragged down to the minimum design speed and the vehicle is travelling at its highest design speed. The frequency being produced by the alternator is always going to be at least 5 times higher than the frequency the motor requires on its windings. Whew! Good old caffeine

J Tiers
03-15-2008, 08:53 PM
The VFD won't work?

Odd....... there is one working at my work now. Different app, 200KW power level, but much the same thing. Sensorless vector type system, using a PM motor.

Nice thing about the deal is that with a minor adjustment of timing you can generate a lot of torque, no torque, braking (with re-generation, i.e. energy recovery), etc.

So much for "it won't work".

macona
03-15-2008, 09:25 PM
I was replying to darryl's idea about not working.

I hadnt seen a PM type motor ran with a VFD. Well, now that I think about it the brushless motor used in models dont use feedback. In a velocity mode where you really dont need to know exactly where you need it position sensing other than flux vector wouldnt be needed.

One other problem with engine driven alternators is that the AC waveform is pretty terrible. Skewed laminated rotors can help but its still pretty cruddy compared to mains AC.

The alternator design would for your idea would be a nightmare! At least 12 sliprings and brushes to match. Then separation of the fields and rotor sections. I have a hard time seeing this fitting under a hood.

jkilroy
03-15-2008, 09:33 PM
It blows the mind that people want to preach about the dangers of Li batteries but they don't have a problem driving around every day in a car with a tank full of liquid explosive. I wonder how many of those same folks will change there tune when fuel prices really go up? You have to figure in ten years we will be looking back on $3 a gallon with fond memory! Or how about telling our grand kids, "Why I can remember when you could buy a gallon of gas for three dollars!" when the price is over $10.

J Tiers
03-15-2008, 11:04 PM
We would think very differently about gasoline if it would change to an explosive liquid and randomly "go off" if it got slightly too cold, or too hot, etc.

As it is, it is kept in a fairly safe container, with known hazards that are reasonably controllable. It is NOT nitroglycerine, or greek fire.

The problem with the Li batteries is that right now, it seems that they can turn into extreme incendiaries with no visible change or discernible reason.

It's all very well to say that improper charging damages them etc, blah, blah...... But the computers that went up were presumably charged correctly, by their own internal chargers.

So there was a defect in the battery. An invisible, undetectable defect that made the battery unstable.

Who wants to be driving along on the highway when the thing goes up?

You'd get cooked, no choice. The batteries are distributed around, under seats, etc. If you stop, you get creamed. If you don't get creamed, you get killed as you bale out. Or you can fry.

By the time you DO stop, you will probably be well cooked, and if not the people who hit you will injure you and your passengers so that you will be stuck there frying.

Not a pleasant prospect.

Remind me again why this is a good thing?

darryl
03-16-2008, 12:46 AM
It doesn't sound all that palatable to be stuck (physically unharmed otherwise) to a melting battery and frying. I would probably choose option B. And I think I'd rather be pureed than creamed :) If my spinning rotor blows apart, I'd probably get shredded and tenderized- might not be too bad :)

Yes, I agree the alternator design would be a multiple complexity. I have looked at it as a single complexity which would then just be duplicated multiple times- but it still has to be compact and rugged ,and not have to contain thousands of dollars worth of high current electronical parts or a dozen or more slip rings. It seems in my quest to eliminate as much of the high current electronics as possible, I may have done the opposite, and I've created a mechanical nightmare. Bad coffee, BAD. :)

I think there's still hope for my concept if the vehicle design uses a single PM drive motor. I have eliminated the battery and the need for a chopper-type speed control, I've gotten rid of the alternators rectifiers, but added some triacs in their place. All that's left now is to design away the slip rings-

J Tiers
03-16-2008, 08:45 AM
You need the battery to increase the efficiency...... Hybrid-wise. that avoids the need to idle the engine for short stops.

It frankly sounds like you have eliminated almost all the items that make it efficient, and to some extent re-invented the IC-electric locomotive.

Evan
03-16-2008, 11:52 AM
Jerry,

Locomotives and other large diesel electric equipment are rapidly moving to VFD/AC drive systems. They are more efficient and controllable.

Seastar
03-16-2008, 12:41 PM
We simply cannot end our dependence on oil and coal by changing to electric cars.
Where will the electricity come from?
We can't build enough wind and solar to even begin to power our vehicles.
Hybrids and very small vehicles may increase our mileage but they are still "oil" powered. The number of vehicles grows every year as the world population expands..
Here is the limitation on nukes:
http://bloomberg.com/apps/news?pid=20601109&sid=aaVMzCTMz3ms&refer=home
Things are going to go down hill very quickly as we run out of oil.

Evan
03-16-2008, 12:51 PM
We won't run out of oil. Just wait and see how fast people ditch those 5.7 liter Jeeps when the gasoline costs the same as a bottle of Johnny Walker.

aostling
03-16-2008, 01:25 PM
Just wait and see how fast people ditch those 5.7 liter Jeeps when the gasoline costs the same as a bottle of Johnny Walker.

This is going to result in automotive V-8 engines available for scrap prices. Could such engines be converted to something useful, without melting them down?

dockrat
03-16-2008, 02:12 PM
This is going to result in automotive V-8 engines available for scrap prices. Could such engines be converted to something useful, without melting them down?

Allan see my post LOL :D

http://bbs.homeshopmachinist.net/showthread.php?t=28078

J Tiers
03-16-2008, 10:06 PM
Jerry,

Locomotives and other large diesel electric equipment are rapidly moving to VFD/AC drive systems. They are more efficient and controllable.

Which would be why I immediately suggested the VFD system as per an above post.

Efficiency may be debatable in some operational modes, since the VFD type controls add losses which are far from insignificant. But over the full spectrum of operational modes, on average the efficiency should be higher.

Would it help your understanding of my statement if I had said "TRADITIONAL IC/electric locomotive" ?

The technology being discussed as "simpler" is from the 1930s.

AZSORT
03-17-2008, 12:40 AM
I don't know what the rest of you are going to do, but me and my converted toyota EV can live without gas, and I admit the range sucks but am waiting for the CAT spinoff called Firefly Energy to finish development on their new lead foam battery that weighs 1/3 of a regular deep-cycle.

I'm not worried about the extra electric load on the grid argument, cause as soon as the economy declines following a peak in liquid fuels (haven't surpassed the oil production peak in June 2006 yet), electric demand will go down as well.

Lithium batteries violate the keep-it-simple-stupid rule.

Tuckerfan
03-17-2008, 12:54 AM
I don't know what the rest of you are going to do, but me and my converted toyota EV can live without gas, and I admit the range sucks but am waiting for the CAT spinoff called Firefly Energy to finish development on their new lead foam battery that weighs 1/3 of a regular deep-cycle.

I'm not worried about the extra electric load on the grid argument, cause as soon as the economy declines following a peak in liquid fuels (haven't surpassed the oil production peak in June 2006 yet), electric demand will go down as well.

Lithium batteries violate the keep-it-simple-stupid rule.
Only about 9% of US electricity is produced from oil.

darryl
03-17-2008, 04:00 AM
I'm not sure exactly how diesel/electric locos work, but it wouldn't surprise me if they're still using some kind of rheostat to adjust the flow of power- like the old mine cars. Simple, fairly rugged, fun to play with, hotter'n double overproof cajun chili. Maybe it's used to adjust field current in the big alternators, I don't know. Moving to vfds would probably be a step forward from that.

I also don't know what efficiency to expect from a vfd- anyone have any specs on that? The thing that really bothers me about using those for say, the 40 odd kilowatt range, is that they must be complicated and full of expensive high current, high switching speed parts (read expensive). Have they really come of age at that power level?

Evan
03-17-2008, 04:37 AM
AC VFD drive isn't new. high power devices have been available for decades. About 15 years ago they converted the LORAN C transmitter down the road from here to all solid state. It switches 500 kilowatts at 100 khz in a pulse modulated mode.



AC Traction vs
DC Traction


AC TRACTION



The AC (alternating current) Drive, also known as Variable Frequency Drive, has been the standard in industry for many years. While it has been used in locomotives for over two decades (especially in Europe), it has only been recently that the price of the drives has allowed them to be used in most of the new diesel-electric locomotives in the United States.

AC traction for locomotives is a major improvement over the old DC systems. The primary advantages of AC traction are adhesion levels up to 100% greater than DC and much higher reliability and reduced maintenance requirements of AC traction motors.

The tractive effort of a locomotive (whether AC or DC) is defined by the equations:



Tractive effort = Weight on drivers x Adhesion


Adhesion = Coefficient of friction x Locomotive adhesion variable



The friction coefficient between wheel and rail is usually in the range of .40 to .45 for relatively clean, dry rail in reasonable condition and is essentially the same for all locomotives. The locomotive adhesion variable represents the ability of the locomotive to convert the available friction into usable friction at the wheel rail interface. It varies dramatically from about .45 for old DC units to about .90 for modern AC units. This variable incorporates many factors including electrical design, control systems, truck type and wheel conditions.

First generation DC locomotives such as SW1200s, GP9s, SD40s, and GE center cabs typically have adhesion levels of 18% to 20%. More modern units with adhesion control such as SD60s and Dash 8s have adhesion levels of 25% to 27%. The newer AC traction units such as the SD80MAC and the C44AC are usually rated at 37% to 39% adhesion. Thus, the newer locomotives have about twice the adhesion of the older units and the Class I railroads are, in fact, typically replacing two older units with a single new AC unit.


The rest here
http://www.republiclocomotive.com/ac_traction_vs_dc_traction.html

J Tiers
03-17-2008, 08:25 AM
I also don't know what efficiency to expect from a vfd- anyone have any specs on that? The thing that really bothers me about using those for say, the 40 odd kilowatt range, is that they must be complicated and full of expensive high current, high switching speed parts (read expensive). Have they really come of age at that power level?

Efficiency can be quite good.

200kW, which is not in the locomotive class, can be switched with LOSSES in the 2% to 4% area without special trouble and hassle. 96% to 98% is quite a bit better than a rheostat.......

With more efficient switching (the losses are at least 1/2 in actual switching losses, not conduction) the efficiency can go up from there.

Electric utilities use switching systems for DC to AC conversion at similar efficiency, so yes it's possible.

darryl
03-17-2008, 04:31 PM
'efficiency can be quite good'- well those figures are high enough that it's not really an issue. Back to my alternator application then, a fairly normal single stage device would be fine. A battery pack would augment the system- but with all the problems batteries come with, I still want to eliminate that-

I have to stop thinking about this for awhile.

Rich Carlstedt
03-17-2008, 09:49 PM
A Harvard Physics Professor did a study 4 years ago and it isn't pretty if you like electric cars.
To replace all the cars and trucks on the road with Electric or Hydrogen power, would REQUIRE that 3 and 1/2 times the number of power plants we have now, be built to provide the electrical energy, and even that would only allow 2 hours a day of motor vehicle operation .

We can't hardly build a power plant here in the USA ..NIMBY !
China starts up a new coal fired plant EVERY day !

Rich

Tuckerfan
03-18-2008, 05:11 AM
A Harvard Physics Professor did a study 4 years ago and it isn't pretty if you like electric cars.
To replace all the cars and trucks on the road with Electric or Hydrogen power, would REQUIRE that 3 and 1/2 times the number of power plants we have now, be built to provide the electrical energy, and even that would only allow 2 hours a day of motor vehicle operation .

We can't hardly build a power plant here in the USA ..NIMBY !
China starts up a new coal fired plant EVERY day !

Rich
You know who did the study? I'd be interested in reading it. China is adding more powerplants (many of them illegal and totally unregulated as far as emissions go) every year than are in the whole of England!