Troubleshooting dead battery?

[Chris Maluszynski]

Hi

I was given a spare battery (36v 10ah), that seems to be dead. It does not seem to charge at all.

I'm thinking it might be worth trying to troubleshoot it, to see if I can get any life out of it. Could it be defective cells ?

How would you go about such a process, if it's even worth it?

Thanks!

Chris

 

[wheeliepete]

Measuring the voltage at the output is a good place to start.

 

[Nealh]

What battery ?

A part as mentioned from checking voltage ouput, any ext fuse ?
Other wise batteries usually men opening them to get all the gubbins and may mean removing heat shrink or any insulation. Issue may be a wire or bms fault.

If defective cells then not worth mixing new and old cells, though if you had the right resources to hand you could remove any duff cells and reconfigure as 7.5ah battery or use the cells for torches etc.

 

[Chris Maluszynski]

Hey folks, thanks for the response, and sorry for my absence.

I should probably clarify a few crucial facts:

They key I got for the battery fits, but doesn't turn, so it's probably the wrong key. Hence I cannot turn it on. But i took off the top, and measured voltage between the thick red wire going into the key mechanism and the bottom (-) contacts on the battery, and voltage shows 30.0V.

When I hook up a charger to it, it does not seem to be charging though (and normally the switch wouldn't need to be on to charge? Also not sure I have the right charger, but it fits, and is also for a similar 36V battery.

There are two fuses: 30A and 5A, both are ok.

I could potentially cut the wires to the lock and just connect them, having the battery permanently on. (or mount some kind of power switch on it)

Another way is to try to pick the lock maybe?

or any other ideas?

But voltage should be higher than 30 right? and what could be causing it not to charge?

 

[wheeliepete]

Some batteries need the switch to be in the ON position to charge, so this may be the problem. Also not all charger pin outs are wired the same, so the charge voltage may not be reaching the battery pack. As you have the pack open, check the pins and polarity are the same. If the cells are still balanced, then 30v is 3v per cell, which may be a little low for the BMS in the pack to allow charging. If you can, connect the charger to the output terminals and bring the pack to around 34v, then try charging through the charge connector.

 

[Chris Maluszynski]

If you can, connect the charger to the output terminals and bring the pack to around 34v, then try charging through the charge connector.

Really? That sounds dangerous? Not exactly sure how I would do this, but I guess I could somehow manage if I am relatively sure I won't blow anything up in the process?

I will check polarity of charger connection first.

Thanks

chris

 

[wheeliepete]

Yes, check the charger and battery charging connector first to make sure they match. No real increased danger with part charging through the discharge connectors, although I would not leave the battery unattended.

 

[Chris Maluszynski]

Ok, I can report this: Polarity is same on charger as battery, so this is not the problem. I hooked up the charger to the output terminals and charged for around 2 hours last night. But that did almost nothing. Voltage jumped from 30.0 to 30.1 I'm thinking I'll try it for much longer this afternoon/night to see if that makes a difference. Or is this a lost cause?

 

[wheeliepete]

There's a very good chance that if the battery is older and has been left lying around uncharged that the cells are not in great condition, but I would have expected some voltage increase after 2 hours. I don't see any point in trying it for longer. 30v would suggest some hope of recharging, any lower and I would say forget it. If you want to go further and you have the pack open, measure the voltage of each group of cells. you may need to remove the inner cover to do this. A photo will assist with helping you with this.

 

[vfr400]

When your battery won't charge, you need to do two things to find out why. Measure the voltage on the battery's charge socket and measure the voltage on the charger's connector when it's switched on. Those two results will indicate what's causing your problem. My ransom guess says there's no voltage on the charger.

For a 36v battery, the battery voltage needs to be between 29v and 42v and the charger needs to be 42v +/- 1v.

 

[Chris Maluszynski]

Update:
After charging the battery for another couple of hours I got it up to 34V, but as I was measuring, the voltage steadily dropped by .1V about every 2 seconds. I think it eventually returned to 30V. Maybe some capacitor retains the voltage immediately after charging?

Anyway, I finally took the cells out - and to my big suprise it looks like below. What kind of battery is this?? Big plates, and it says it contains lead I believe?

Is this complete junk?

 

[Chris Maluszynski]

I still have not manage to turn the ignition lock to ON. Not sure if this may still prevent me from charging the battery correctly. But this projects starts to look a bit hopeless I think?

 

[Chris Maluszynski]

When your battery won't charge, you need to do two things to find out why. Measure the voltage on the battery's charge socket and measure the voltage on the charger's connector when it's switched on. Those two results will indicate what's causing your problem. My ransom guess says there's no voltage on the charger.

For a 36v battery, the battery voltage needs to be between 29v and 42v and the charger needs to be 42v +/- 1v.

So you are saying the battery may actually be fully charged at 30.0V? Is that why it is not charging?

The charger maintains a steady 41V.

 

[wheeliepete]

They look like lithium polymer pouch cells, but as you say if they will not hold any charge, then they are useless. bit of a shame, but never mind, nothing ventured and all that.....At least you have an idea of what the inside of a battery pack looks like for next time.

 

[Chris Maluszynski]

Ok... so you think this is where I should give up? Or maybe try forcing the lock first before I toss the whole thing? But I suppose it would have charged when I hooked it up to the outputs anway? And what about vfr400 suggestsion -that it may be fully charged at 30V?

 

[wheeliepete]

what about vfr400 suggestsion -that it may be fully charged at 30V?

I'm not sure vfr was suggesting that it was fully charged, just that it needed to be 29-42v to take a charge. Just a thought, but it's not a 24v battery is it? Fully charged would be 29.4v. Carry on if you wish, you've nothing to lose and maybe learn some more. One word of caution, those cells do tend to swell up when they get old, so now you have the pack open, if the battery appears to expanding, I would remove it from your house immediately.

 

[vfr400]

We got the charger voltage but what's the voltage on the battery's charge socket?

 

[Nealh]

Without more battery info it is hard tell, but you mentioned the word LEAD.
It could be possible that your 36v 10a battery is a Lifep04 pouch battery and then the max charge is 3.65v per cell or 43.8v per pack as it will be 12s for Lifepo4.
I tried blowing the pic up to count the ripples of pouch cells and believe there could be more then 10, if this is the case you will need a dedicated lifepo4 charger.

 

[Chris Maluszynski]

It says Lithium-Polymer 36V 10ah on the case. I counted the pouch cells and there's 10 rows of them. Voltage on the charge-port is the same as on the output terminals now 30.5V. So it may be the case of not being able to charge with a charger for Li-Ion, if it's a Li-po battery?

 

[vfr400]

One of your cells is down, so the management system has switched off the internal charging switch. You have to pull back the blue heatshrink until you can get to the multipin connector. Unplug it and measure the voltage on each pin. Each pin is for one of the 10 cells. the difference in voltage between adjacent pins is the cell voltage. At least one of them will be lower than what's allowed for charging. Somewhere around 2.5v is the minimum allowed. Tell us what they are so we can see if you have a chance of bringing it back to life.