Battery Cell Identification

Nils

10 mW
Joined
May 11, 2020
Messages
21
I have a 7s battery originally supplied with an outboard motor that is in need of repair. One of the 7 cell pairs is totally dead (0mV) and has rendered the pack unusable in its current state. If I could sort out what the cell is/where I might find one I could hopefully get this thing back up and running. I've searched for what little labeling there is, but to no avail. This is my first foray into pouch cells and I am admittedly unfamiliar with what is out there and/or readily available. I was wondering if anyone here had an idea for what it could be.

I am somewhat nervous able taking the cells out of their plastic housing, though I guess they should not pose a risk if they are at 0V. Please correct me if I am wrong! It might help with identification. The BMS is labeled atpow which seems to be a chinese manufacture, though it doesn't really help.

Many thanks for any help!

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Nils said:
I have a 7s battery originally supplied with an outboard motor that is in need of repair. One of the 7 cell pairs is totally dead (0mV) and has rendered the pack unusable in its current state. If I could sort out what the cell is/where I might find one I could hopefully get this thing back up and running. I've searched for what little labeling there is, but to no avail. This is my first foray into pouch cells and I am admittedly unfamiliar with what is out there and/or readily available. I was wondering if anyone here had an idea for what it could be.

I am somewhat nervous able taking the cells out of their plastic housing, though I guess they should not pose a risk if they are at 0V. Please correct me if I am wrong! It might help with identification. The BMS is labeled atpow which seems to be a chinese manufacture, though it doesn't really help.

Many thanks for any help!

This is a tough nut to crack. Mixing old and new cells is generally not a good idea, even if you get the exact same cell (which will be hard). Then again, you just might get lucky and find the cells if they are name brand cells like LG or Samsung.

It’s a strange battery to me; Looking at the 25.9V 144 Ah label it seems to be a 7S pack of lithium cells. What is the max charged voltage? Around 7*4.2 so 29.4V?

I have never seen a 7S battery used, do you have two of them in series for 14S?

Since there are 6 pouches in parallell in the blocks then each cell is 144/6 so it’s a 24Ah pouch.

You can open the dead cell module without a major risk. Wear protective gloves and eyewear and be in an open place where you can let it burn if it bursts into flames. Shouldn’t be a risk since at 0V there’s no energy in the battery. Just be careful when handling it, don’t use anything conductive (screwdriver etc) to nudge the cells out if they are compressed and stuck in the box

Now that one of the cells are dead there’s the question if the BMS has worked or not. You can check it for any obvious burn marks, loose wires or loose components, corrosion and such.

One way forward for you will be to just use the remaining 6 cells as is. This would require a new bms or a reprogramming of the original bms low and high volt limits, possibly also a reprogramming of the motor controller, it depends on the rest of your system and if you can accept the 6/7 difference (14% shorter range and 14% lower max speed). And a new charger..
 
Your guess is right that it is used in series with another pack to make a 14s battery. From memory the fully charged voltage is right around 29V per pack.

After posting yesterday I had a halfhearted attempt at removing the plastic module cover, though didn't get too far. Either the foam or the cells themselves are exerting a decent amount of pressure on the plastic case, making them hard to pull out. I will give it another try when I get the chance and might have to resort to more destructive methods. But I am now quite curious about what they might say on them!

It sounds like there might not be an easy fix to use the pack in its "as built" state. Unfortunately I don't have the ability to reprogram the controller, or the bms. I'll see what I find, but it might be that it ends up being reconfigured into something else, though it would save a lot of time and effort if I can use it as originally configured!
 
Programming a bms or controller doesn’t have to be hard, it’s done through a software and since atpower are contactable you could reach out to them and ask for a replacement bms or programming support. A problem might be that the softwares could be in chinese.

What motor controller is it? Name, and picture would help. What kind of motor?

That’s a pricey battery so repairing it will be worth some efforts :wink:
 
I believe it’s a sevcon controller but I’d have to double check and am unsure on model. I remember looking into reprogramming options a couple of years back and it looked infeasible without shelling out a bunch of cash for the the license/software.

I still need to open up the module but I noticed what might be damage to one or more of the FETs(?) on the bms. The cracks don’t look great, not sure if that is related to the battery issues.

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j bjork said:
One option to get the battery working could be to take one cell from each of the cell groups and use them instead of the dead cells.
Making it 7s 5p instead of 7s 6p.

That's an option I hadn't really thought of. If the modules weren't such a pain to open It seems it could be a good fix. I just found the time to open them up and it was quite destructive to the module housing. Not much labeling on the cells themselves. Interestingly one of the cells was quite a bit puffier than the others, is this a sign it was the problem?

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That's pretty likely. Every puffy cell I've ever encountered was problematic in one way or another.

But you can create a puffy cell by damaging it from external causes, too.
 
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