Help my battery might be damaged and im not sure what to do

[ceasium]

A little context: 10s4p p42a. My voltage meter is klein tools and is new and the first time using it. For some reason the voltage is shown as 0 but when I set it to max it records the real voltage( I tested it on a AA battery and it had 1.57v) so the readings are not perfect but I took them multiple times and they relatively the same each time.

Now back to the problem.

I was charging my board and when I unplugged it after a few hours, it (my remote) still said it was dead. (Like it would work but it showed low battery) So my first thought was to check the charing port but no luck. So I checked my battery and the voltage was weird, each group was around 3.23-3.24v. Except for one group that was 3.1v. When I checked each cell of the low voltage P group three of them where about 3.15v and the fourth was about 3.37v. The welds on the fourth cell look fine but when I was checking it was a tiny bit warm. Now If I push the nickel down nothing happens and it doesn’t get warm. What should I do? How unsafe is it as is ( its unplugged from the board)? Should I be worried it might catch fire or is it something I can fix in week when I have access to my tools? Is there anything I can do to save the battery? My ek8 is main mode of transportation and how I get to my classes. So I need to fix as soon as possible. Thanks in advance for help

Update: [quote=“ceasium, post:5, topic:84929”]
Thanks for all the help so far. I got a new multi meter and did some more tests. Turns out the reason it wasn’t charging was the charging port wire was disconnected under the heat shrink.

All the P groups are at 3.44v and the bad one is at 3.37v (when pushed down on the nickel it goes to 3.42v). The 3 cells are at 3.37v and the 4th is at 3.48v.
[/quote]

[tuckjohn]

Sounds like the bms is refusing to charge because of the low-p group voltage. (Typically it’s not good for battery health to run down to BMS cutoff)

Do you have pictures/videos that you can share of the board? Wdym by

@ceasium

Now If I push the nickel down nothing happens and it doesn’t get warm.

[ceasium]

@tuckjohn

Sounds like the bms is refusing to charge because of the low-p group voltage

What should I do then?

@ceasium

Now If I push the nickel down nothing happens and it doesn’t get warm.

When I pushed down on the nickel over the (potentially) bad cell it felt warm. But later when I pushed down on the same place it wasn’t warm.

Also I ordered a new multi meter so I can get better measurements.

@tuckjohn

Do you have pictures/videos that you can share of the board?

What specifically do want pictures of?

[SternWake]

A 4p parallel group without broken welds, will show the same voltage on all 4 cells within that P group.

The only way you can measure different voltages on cells within a Parallel group, is if there are broken welds, and thus they are not in parallel anymore.

When you pushed down on the nickel, you re parallelled that one cell, a bunch of current flowed from the other cells within that P group into that separated cell, heating the nickel under your finger.

3 cells of that p group likely have been doing the work of 4, for a significant while, and have aged far faster, and only recently have they degraded so far as to alert the bms.

Those 3 cells likely rise to and exceed 4.2 v when charging, far faster than all other 9 p groups triggering the bms High voltage disconnect, and under load, that p group would drop to 2.5v first too, triggering the LowVD.

Even if you were to reweld that 4th cell, returning it to parallel with, the other overworked 3, That p group would still be compromised with a fraction of the capacity of the other p groups.

I think it is unlikely any recommended course of action other than retiring the pack will be approved by the community.

You do have 40 cells. it is likely 36 of them from the 9 otger P groups are all similar states of health.

Your 10s4p battery could be made into a 10s3p, by someone with the skills and tools to do so.

If you want to post a pic of the cell and Pgroup with broken weld, and the general construction quality/method of the entire battery, It could help thwart substandard practices in the future.

[ceasium]

Thanks for all the help so far. I got a new multi meter and did some more tests. Turns out the reason it wasn’t charging was the charging port wire was disconnected under the heat shrink.

The all the P groups are at 3.44v the bad one is at 3.37v (when pushed down on the nickel it goes to 3.42v). The 3 cells are at 3.37v and the 4th is at 3.48v.

Is there any chance that the weld popped recently? Would it still be safe to fix? If not would it be possible to turn it in to 9s4p instead, I manly use the board to get to campus so I don’t mind losing a little speed, need be.

Also side point, but this is pretty much the lowest I let my battery get to. I usually dont let it get close to this low before I charge it.

Current photo

!
Photos from when it was built

[massy]

@ceasium

Thanks for all the help so far. I got a new multi meter and did some more tests. Turns out the reason it wasn’t charging was the charging port wire was disconnected under the heat shrink.

The all the P groups are at 3.44v the bad one is at 3.37v (when pushed down on the nickel it goes to 3.42v). The 3 cells are at 3.37v and the 4th is at 3.48v.

Is there any chance the weld popped recently and it would still be safe to fix. If not would it be possible to turn it in to 9s4p instead, I manly use the board to get to campus so I don’t mind losing a little speed, need be.

To me the “pushing down changes voltage” sounds very much like there is a bad weld in that group.

Could be that the 4th cell is stuck at 3,48 becuase it is not connected. Meanwhile the other 3 has had a slight discharge. Now if you’d charge it, let med guess the 3 cells would charge and the 4th still be stuck at 3,48 V as it is not connected anymore.

Sounds safe to repair, but then I’m just speaking in “electronics terms”, it would also need to hold up and be well repaired physically, which might be harder and require some skills and tools.

[massy]

@SternWake

Those 3 cells likely rise to and exceed 4.2 v when charging, far faster than all other 9 p groups triggering the bms High voltage disconnect, and under load, that p group would drop to 2.5v first too, triggering the LowVD.

Logically, about a fourth faster as that group holds a fourth less capacity.

(given this problem is relatively new and skewed wear and tear hasn’t messed it up further)

[hummieee]

Every weld looks too hot.

[SternWake]

That one photo showing the sides of the 4 cells, and the buckled nickel, indicates that there has been physical stress on the pack there, which broke the welds.

A new battery would likely break the welds in the same spot as board and enclosure are flexing in a manner which is stressing the battery itself.

Perhaps a thicker gasket and more interior paddingwould allow board to flex/twist and not stress the battery.

[ceasium]

All the photos are from before I put the battery together except for the first one labeled current.

[SternWake]

Is the broken weld on that pgroup with the buckled nickel?

Could be the camera lens, but it looks a bit cupped.

The nickel looks exactly how id expect a welded p group to look if one tried to bend it

[ceasium]

This is where the broken weld is.

[SternWake]

The picture where you lifted the nickel to test the welds, none of those dots left behind inspire confidence.

When my test welds using 0.15 pure nickel looked like that, the nickel peeled off way too easily.

[ceasium]

Those welds on the test were done hotter then the rest, when I reweld the battery I did them a lot cooler.

[SternWake]

Check out this thread:

P42A pack damage - WTF happened?

Well, I’m not certain, but could this have something to do with it? It looks like you essentially had no padding or protection on it, and it suffered a lot of abuse (both electrically and mechanically) before some point of the pack gave up and led to failures elsewhere.

[ceasium]

Ok thanks, I read the thread.
So my next question is, if I can get my hands on a good spot welder would it make sense to reinforce the welds of each group, or would I have to take off all the nickel and replace it. If I do have to replace the nickel would I be able to turn my pack in to a 12s3p.

My board is pretty stiff and there is a soft foam between each group to allow the battery to flex. If that makes any difference.

Hypothetical: I fix the bad weld. A) is there a way to test to see if the group is safe( like the capacity didn’t deteriorate too much). And B) what is the danger of using the battery, like will it catch fire sitting in my house?

Also I don’t think I’ll be able to do anything to the battery for a while. It is currently at 3.44v should I fix the charging port and put some sort of clamp to hold down the bad weld to top up the battery to 3.6v?

[SternWake]

It is my opinion, your welds look very inconsistent.

Im reluctant to offer advice, that those with more experience, might find insufficient, regarding adding more welds.

Id not try to charge it. most cells are shipped in 3.4 to 3.5v range.

Probably take months for self discharge or parasitic draw of bms to drag them down to the sub 2.8v zone.

Im racing a clock for rest of the day.

[hummieee]

@ceasium

or would I have to take off all the nickel and replace it.

I can think of no reason to remove what’s on there. Just reinforce with more welds but not as hot. Maybe glue the nickel to the cell as well if it’s being strained in that spot or use more/better foam

the cell that was becoming disconnected shows within a safe voltage still. I’d just charge it and see if that p-group is still showing good

[jack.luis]

@hummieee

Maybe glue the nickel to the cell as well if it’s being strained in that spot or use more/better foam

[hummieee]

Remember when u said I was an idiot because I said you can still charge cells that went under 2v… then I showed it in the data sheets? And then you said it’s still not possible but you can’t tell about it because of ur non-disclosure agreement?! Can you give a hint? Can you tell which battery company you have a non disclosure agreement with …or is it all of them?