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flylo
01-24-2016, 05:36 PM
Buying a very large 48 volt forklift battery & charger for a solar system. Just found out the charger is 36 volt so for a couple years it's been kept charged to 36 volts only. My question is do you think it's sulfated the battery of if I charge to 48 volt it will be OK? It'sin a forklift which seems to operate fine so I was gping to use the forklift until the panels are up. The battery weighs almost 4000# Thanks for the help!

J Tiers
01-24-2016, 05:55 PM
Buying a very large 48 volt forklift battery & charger for a solar system. Just found out the charger is 36 volt so for a couple years it's been kept charged to 36 volts only. My question is do you think it's sulfated the battery of if I charge to 48 volt it will be OK? It'sin a forklift which seems to operate fine so I was gping to use the forklift until the panels are up. The battery weighs almost 4000# Thanks for the help!

It's perfectly possible, maybe even probable. What KIND of charger?

The question is really, is this a "charger for 36V batteries"?

Or does the charger use 36VAC rectified?

If the former, then, there is a good chance that there is "degradation" in the battery, since it will not have been fully charged, and there may be "sulfation". At least it has been charged, so it's possible that there is less damage than might be.

If it is a rectified 36VAC, that's different. The peak voltage would have been about 50V, and that could at least maintain a 48V battery at a reasonable state of charge. It would not recharge one well, but given time it would probably happen.

Get a good temperature compensated specific gravity tester, and check all the cells. Bad ones will never come up to a good gravity no matter how much voltage you apply, and they will gas off more water than any others.

And, on discharge, they have low capacity, so they will discharge and then will likely reverse charge, doubling the net loss of voltage. You will probably end up bypassing any of those if you can do that and still use the battery.

flylo
01-24-2016, 06:17 PM
I think it's a recified 36v 3 phase charger & the owner did keep it charged to 36v. I've had good luck with deep cycle batteries but wasn't sure where sulfation would start as it's been 25% low on charge for a long time. The forklift runs & operates fine but I'm sure would not run as long as 48v would.
Here's another question thus model lift truck was offered in 36 or 48v in the same model. What would they have changed between the 2?

J Tiers
01-24-2016, 06:23 PM
They would have to change number of battery cells and probably cell size, also most likely motor ratings for drive and pump motors.

Maybe something about the way the lights and other "housekeeping" stuff is powered.

flylo
01-24-2016, 06:26 PM
Another question, if it's a rectified charger starting at 50v shutting off at 36v can I change something to make it shut off at 48v?

J Tiers
01-24-2016, 06:36 PM
I should have considered the 3 phase... ours were single phase.

With 3 phase, the 36V may BE just a bit higher, maybe 42 to 45V. That's about the bulk absorption voltage for a 36V battery. The average voltage for 3 phase rectification is different from single phase, given same input.

if it is an electronic type, there may be a way to make it the other voltage, because it probably starts a bit higher than needed and electronically adjusts the voltage output. That much higher may be too much difference though.

If it is an old style timer type, the voltage will be what it is, set by the transformer tap, but you may get a higher voltage by selecting a higher current tap, if the thing has a choice..

if any damage could have been done, it already was done, so it may just be what it is.... have you measured the battery output voltage to see?

flylo
01-24-2016, 06:41 PM
Only with a voltmeter, I'm checking it with a hydrometer in the morning. I know the cells come apart, the plates are thick & they rebuid them so I wonder how hard it would be to rebuild any bad cells? I'm sure I can sell the charger for enough to get a 48v golf cart charger.

J Tiers
01-24-2016, 07:00 PM
What did you get as a voltmeter reading?

flylo
01-24-2016, 07:04 PM
36.6

J Tiers
01-24-2016, 07:05 PM
Well then, most likely the battery is substantially sulfated.

flylo
01-24-2016, 07:19 PM
But it was only charged to 36v so to really know I'll have to put a 48v charge to it. Can you take the cells apart & desulfate them?

darryl
01-24-2016, 07:43 PM
What will be interesting is whether you can get the pack voltage back up. I don't know what the cell configuration is, but if you can access it at 6 cell, or 12 volt intervals you can use an ordinary battery charger. Those are probably 100 ah cells at minimum, maybe much more than that, so something around say 10 or 20 amps would be a tickle, and should bring the voltage back up to nominal- if that's going to happen. Give each section about the same amount of time until each has been tickled up to the nominal voltage. Fully charged that pack should reach about 55 volts or so. It will be best if you can tease it for awhile to get the pack voltage up to at least 48 volts before applying the standard rate of charge for it.

Can you use the existing charger- depends on whether the secondary voltage is above about 60 volts or so, before the regulation circuit. If it's not that high, then no you can't. But I'm not sure of what the charger does with the secondary voltage- it could be rectified and maybe filtered, but your voltmeter reading may not show the full value of the voltage unless it's filtered. There could perhaps be enough voltage to allow it to be readjusted for the 48 volt pack.

Depending on the configuration you may be able to access each cell terminal and thus determine what voltage each cell is at. You might find that some are at zero volts, potentially shorted. If it were me, I'd be trying to get each cell to come up to more than a volt and maybe up to two volts before applying a charge to the pack as a whole, or in sections if that works for you. Sometimes a capacitor discharge can shock a dead cell into becoming chargeable.

flylo
01-24-2016, 08:05 PM
What will be interesting is whether you can get the pack voltage back up. I don't know what the cell configuration is, but if you can access it at 6 cell, or 12 volt intervals you can use an ordinary battery charger. Those are probably 100 ah cells or something like that, so something between a trickle charge and say 10 amps should bring the voltage back up to nominal- if that's going to happen. Give each section about the same amount of time until each has been tickled up to the nominal voltage. Fully charged that pack should reach about 55 volts or so. It will be best if you can tease it for awhile to get the pack voltage up to at least 48 volts before applying the standard rate of charge for it.

Can you use the existing charger- depends on whether the secondary voltage is above about 60 volts or so, before the regulation circuit. If it's not that high, then no you can't. But I'm not sure of what the charger does with the secondary voltage- it could be rectified and maybe filtered, but your voltmeter reading may not show the full value of the voltage unless it's filtered. There could perhaps be enough voltage to allow it to be readjusted for the 48 volt pack.

Depending on the configuration you may be able to access each cell terminal and thus determine what voltage each cell is at. You might find that some are at zero volts, potentially shorted. If it were me, I'd be trying to get each cell to come up to more than a volt and maybe up to two volts before applying a charge to the pack as a whole, or in sections if that works for you. Sometimes a capacitor discharge can shock a dead cell into becoming chargeable.

A lot of IFs. The great part is I can buy it for the scrap value of the battery & it looks & runs great, has great components & could be parted but I don't know how long it will run on a charge & I don't have room for it & still have a bunch to pickup from "the buy".

PStechPaul
01-24-2016, 08:21 PM
Is it possible that the battery pack is actually 36V nominal? 36 volts on a 48V pack is about 9 volts for a 12V battery, and that is essentially dead.

Here is some good information on lead-acid batteries and charging:
http://www.evdl.org/pages/hartcharge.html

http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery

http://www.mpoweruk.com/chargers.htm

http://www.mpoweruk.com/life.htm

http://www.mpoweruk.com/soc.htm

That last link shows a fully discharged 12V battery has an open circuit voltage of about 11.5V.

http://www.mpoweruk.com/images/soc_voltage.jpg

So, I don't think it is possible for a 48 VDC lead-acid battery pack, charged to 36 volts, to be able to operate a fork lift (even a toy!) There are other possibilities:

1. One or more of the batteries (or cells) is totally shorted or bypassed, so that only 36V of battery are used.
2. The cells are some other chemistry, with a nominal 1.5-1.7 vpc, such as Nickel-Zinc (https://en.wikipedia.org/wiki/Nickel%E2%80%93zinc_battery).

jimmyc
01-24-2016, 08:46 PM
A lot of IFs. The great part is I can buy it for the scrap value of the battery & it looks & runs great, has great components & could be parted but I don't know how long it will run on a charge & I don't have room for it & still have a bunch to pickup from "the buy".
the voltage you read with a meter is the E effective or average , if you multiply 36 x 1.414 you will get the peak of the ac cycle and that should be 50.9 volts then take 3 phase 120 degrees apart and you almost have no ripple. full wave rectification of 60 cycles give 120 positive pulses , 3 phase would give you 360 pulses at 50.9 volts. You should read a lot higher voltage with 3 phase rectification than with 1 phase. Unless like Jtiers said it is wired to give 38 volts out with 3 phase in. 5o.9 volts would be like a trickle charger on a 48 volt battery. that's what I think anyway wish I could help you more. Jim

koda2
01-24-2016, 09:04 PM
Guess I am missing something here. A lead-acid system is 2.1V per cell in the charged state (and supposedly 1.75V in the discharged state).

So you should have either 18 or 24 cells, if they are visible, like this one.

http://www.alibaba.com/product-detail/Forklift-battery-48v-lead-acid-battery_60408322013.html?spm=a2700.7724857.29.1.Ob KZDL&s=p

At the end of a busy day the voltage in a 48 v system should drop to around 42V??

If it is an older open-style lead acid battery, each cell should be accessible for measuring the specific gravity and water level. The newer gell cells or recombinant batteries are sealed but sometimes you can still surmise the voltage. You should be able to tell if a cell is bad by using a hydrometer, right?

Is the battery labeled as a 48 volt battery? If you are only getting 36V you must have some dead cells.

flylo
01-24-2016, 09:36 PM
I'll know more tomorrow & post back what I find. Thanks for all the help, I really appreciate it.

J Tiers
01-24-2016, 09:52 PM
But it was only charged to 36v so to really know I'll have to put a 48v charge to it. Can you take the cells apart & desulfate them?

You pretty much know already.... it was used only partly charged for at least a year or two, I think you said. In that time, the unused sulfate will generally recrystallize as what is often called "inaccessible" sulfate, material that is not possible to get a current through in normal charging. No current, no participation in the charging cycle. Capacity is lower, and specific gravity will be low.

Could affect all cells evenly, but probably some are pretty dead, and others are more normal. A state of perfect balance is rare.

When the battery is charged, all the sulfate is in sulfuric acid, and gravity is high. As you use electricity from it, some acid becomes lead sulfate as it gives up electrons. If recharged soon, that is reconverted to acid. If not recharged soon, the sulfate, which is not very soluble in water, will slowly become inaccessible, a non-participant. Then the battery is lower capacity by that amount of possible electrons. In a year or two, a battery can easily become nearly worthless if not charged, or not fully charged.

Some pulse chargers claim to fix this, by forcing current through the water, and thus supplying electrons to reconvert the lead sulfate to negative ions of acid. It does seem to work, I have used that sort of system to at least partly recover a small battery or two. But larger batteries would take a long time to fix, if they were even "fixable".

As mentioned, you can count up the cells, and multiply by 2 to find the nominal (quoted) battery voltage.

flylo
01-24-2016, 10:49 PM
I tried desulfaters & it fixes 2 but not for long, I think it knocks the sulfate off but then it settles to the bottom & shorts things out again.

J Tiers
01-24-2016, 10:52 PM
yes, there can be shorts, but most deep cycle batteries have enough space under the plates that any material which is dislodged can fall clear.

I had another thought.... Could the users have bypassed some cells so it really IS now a 36V nominal?

old mart
01-25-2016, 10:23 AM
Since a normal car 12V battery has six cells and is charged at 14V by the alternator, then a 48V battery would have 24 cells and require 56V available for proper charging. I find it hard to believe that a forklift truck would run at all at 36V.

Black_Moons
01-25-2016, 10:36 AM
yes, there can be shorts, but most deep cycle batteries have enough space under the plates that any material which is dislodged can fall clear.

I had another thought.... Could the users have bypassed some cells so it really IS now a 36V nominal?

Possable. Or just 6 cells have shorted out already and PO didn't care to even bypass them (Very dangerous to be running hundreds of amps through a dead cell.. better to discharge it fully then short it out (and ideally, remove it from the pack)

Georgineer
01-25-2016, 12:15 PM
There's something here which doesn't add up. A fully charged lead-acid cell discharges at a fairly constant voltage for most of its discharge time, then the voltage drops off rapidly. When drawn as a graph this is a nearly horizontal line (the useful bit ), then a rounded knee as the voltage starts to drop, then a nearly vertical line as the battery turns its toes up. A 48 volt battery would be well below the knee at 36 volts, so would be nearly discharged. Connecting it to a 36 volt charger would not recharge it (beyond possibly a few percent of its capacity) because it would not get up over the knee. The battery would not be able to do any useful work in that state, and it has nothing to do with the age or condition of the battery.

If the forklift works, then it must have either 36 volt battery and charger, or 48 volt battery and charger. Unless there are some sneaky electronics in between, or they have rewritten the laws of science since I studied them.

George

flylo
01-25-2016, 12:23 PM
The guy bought it 2 or 3 years ago from a company using it like this. The battery is 48 volt for sure & the charger is 36v. I'm thinking now someone has disconected 6 cells to make the battery 36v then all would be fine. He had to take his wife to the doctor & postpone.

sarge41
01-25-2016, 01:28 PM
flylo: Can you a use stepup transformer to get the 56 volts you need to fully charge the battery? How many amps does the 36V charger put out?

Sarge

flylo
01-25-2016, 01:53 PM
That's the plan if the battery is 48v & not cut back to 36v. Thanks everyone for all the help. I'll report when I know more.

J Tiers
01-25-2016, 02:48 PM
That transformer plan only works in some cases..... Most electronically controlled chargers either won't change voltage that way, or will be damaged.

The Artful Bodger
01-25-2016, 04:50 PM
So lets see if I have this right, the forklift is a 48V machine and operates fine, the battery is 48V and the charger is only 36V, is that right?

There is only one explanation I can conclude and that is the charger is not a 36V charger, maybe it was once but someone moved a tranformer tap to up the voltage to something higher, maybe it really is a 48V charger but the labels or other indicator is wrong and reads 36V. Maybe it is a 36V charger but all the regulation circuits have been bypassed either by a fault or design. Maybe it has adjustable regulation which someone screwed up to the max until they saw charging current on a 48V battery.

It is not a 36V charger which operating normally can charge a 48V battery and have the forklift operate normally.

Of course there is always the possibility that the mains connection is incorrect and the charger is operating at much higher primary voltage than designed for.

J Tiers
01-25-2016, 05:41 PM
He said somewhere above that the battery measures at 36.6V, which looks like a number of cells are not working. It may not actually even be quite a 36V nominal battery anymore.

old mart
01-26-2016, 10:46 AM
Perhaps looking at the battery and counting the cells would solve the problem, or not, if this is just a great windup.

J Tiers
01-26-2016, 10:53 AM
I get the impression that Flylo has not got it in-house, but is looking at buying it, so he can't just go out and have a look.

With all the funny stuff that seems to surround it, and the fact that Flylo wants a 48V battery apparently, I suggest forgetting about it. Far better to get a bunch of Trojan T-105 golf cart batteries. Those have been the most economical choice among respected types for a number of years.

One string will provide about 220 ampere-hours at 48V,which is a considerable amount of stored power. Two such strings would likely equal a forklift battery. When you buy that many at a time, you should get a quantity discount.

Forklift batteries are expensive items, you can often get an electric forklift for scrap price.... without a battery. The battery may be several grand, a grand or two even for a used, but working one.

flylo
01-26-2016, 04:30 PM
Mystery solved! I posted that the lift truck could have 48 or 36 volt batteries. The truck says 48v but the battery is 36v hence the 36v charger. I drove it , ran the forks up & down several times to knock off any float charge then checked them with a multimeter & hydrometer & every cell checked fine. The charger put out 44v with no load & turned off in about 10 minutes after using the truck then plugging the charger. I counted the cells & told the owner it was 36 volt & he said no it wasn't so I offered him a stupid amout (the scrap price of the battery which covers the forklift & the cost to have it hauled) & bought it. I called a dealer who said there is a switch you flip to change 48 to 36v. He also said a 48v truck wouldn't move on 36 volts. This will allow me to take my 5500# Cat forklift to the hanger at the airport to unload the rest of the "Buy" that won't fit in the hanger at home. Thanks guys for all your help, I really appreciate it!

darryl
01-26-2016, 05:53 PM
Just out of interest- the switch to go from 36 to 48 volts, this is on the forklift or the charger? If on the fork truck, then you're either losing speed on the lower setting, or somehow managing the motor wiring to maintain speed. Be interesting to know what's being done there-

flylo
01-26-2016, 05:59 PM
I asked the dealer & he said it varied with model but it's on the computer & I didn't have the model #. When I get it home I'll try to get a service manual. The battery case is full so the only reason I see to offer both is to match the voltage of other trucks or chargers you already have.

ulav8r
01-26-2016, 09:02 PM
About 10 years ago I ran a reverse auction to buy several forklift batteries. We got them for just over $3000 each. Some were initially quoted at just under $5000.

Black_Moons
01-26-2016, 11:18 PM
Just out of interest- the switch to go from 36 to 48 volts, this is on the forklift or the charger? If on the fork truck, then you're either losing speed on the lower setting, or somehow managing the motor wiring to maintain speed. Be interesting to know what's being done there-

Im guessing the switch is more for turning the 'low voltage cutout' to 36v (well, to 30v) so it does not turn off prematurely to protect the battery from over discharge.

a 48V DC motor won't run too badly at 36V, and likely develop/deliver similar torque under load, just at (30%?) less RPM.

Also could be VFD/Brushless motor, and then it could run at the same RPM, just less max HP

J Tiers
01-27-2016, 12:38 AM
If it is a PWM controller, as the traction motor almost certainly will be, then it can allow essentially the same performance either way. It just depends on what the native motor voltage is. It could be a 24V motor, with the PWM compensating for the different voltages.

The switch would be as simple as telling the controller which PWM constants to use, plus adjusting any other controls or readouts to relate to the voltage in use.

The pump motor is another issue, but may also use PWM to adjust the lift rates.

flylo
01-27-2016, 06:12 AM
Lift & drive speeds seem the same as ones I've driven if that helps at all.

flylo
01-27-2016, 11:47 AM
It doesn't seem to matter with travel or lift speed if the battery is 48v or 36v as per this which is a different model http://www.forkliftaction.com/equipment/specifications.asp?itid=3136
Here's the specs on the battery I believe I have, Plenty of capacity for a solar system if I go that way & I can leave it in the fork lift & have the best of both:cool:
36v
1360 6/amp hr
2144 20/amp hr
3930#
$8,329