Are these 4s Multistar batteries killed?

[Mammalian04]

I left them on the Adaptto BMS to balance for a week and they were slowly adjusting. Then they tanked. I know I know, my fault for not watching more closely. Could have turned out BAD.

So are the batteries gone? They are 4s 20ah Multistars.

I am pretty sure the one that dropped to 2.86v is gone. I think that bad one drained the others.
The other 4 batteries are 4.5v to 5.6v.
EDIT: these voltages are for the WHOLE 4S battery, not per cell.

Are they salvageable? If so, what should I do?
Just throw them individually on the balance charger at a low charge rate?

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[dogman dan]

At first I thought you meant 2.8v per cell. No, the whole pack.

Uhh,,, not killed till they actually puff, but they are 10x more hazardous now. Can't have em in your house or garage anymore. Wouldn't use them on anything you can't have catch fire.

 

[miuan]

I applaud that 5.6V cell. I once overcharged a Turnigy 20C cell past 4.9V and it went into thermal runaway in seconds.

 

[Mammalian04]

At first I thought you meant 2.8v per cell. No, the whole pack.

Uhh,,, not killed till they actually puff, but they are 10x more hazardous now. Can't have em in your house or garage anymore. Wouldn't use them on anything you can't have catch fire.

Ok, thanks Dogman. If they are dangerous I'll get rid of all of them.

Ouch. That was a $600 lesson....

I applaud that 5.6V cell. I once overcharged a Turnigy 20C cell past 4.9V and it went into thermal runaway in seconds.

Nope, those voltages are for the whole 4s pack!

 

[Ykick]

Cheap BMS would've likely saved you from this disappointment. I don't quite follow how the Adappto BMS killed 'em?

You might be able to revive some of them but only in a monitored and fire proof location. And even if they did revive, I wouldn't ever trust them enough to run them on a commuter.

 

[wineboyrider]

If the bms was designed to maintain the right voltages then the BMS is suspect for sure. Also, they might have been dud cells to begin with :?

 

[Mammalian04]

Yeah, one cell in one battery was definitely bad but I didn't think it would crater the whole 20s pack (5 4s batteries). Sucks. $600 bucks up a hogs rump.

 

[dogman dan]

Not the bms's fault it seems? A trickle short in one pack drew down all the others in the string?

Or was something connected that was trickling down the whole pack?

I understand a bad cell can drain all other cells in parallel connection with the bad cell. But I didn't think that happened when cells were in series.

I would like to understand why all the cells drained themselves.

 

[nutnspecial]

I would like to understand why all the cells drained themselves . . . something connected that was trickling down the whole pack?

I def think that's important too, and think it sounds like leaving plugged into a charger that was off. . .
I did the same thing last year with similar results, although I did revive the cells.

____
Mammalian, I wouldn't do a normal charge on that pack with potential cells/strings below an avg of 1v or less. (in fact, I don't even recharge anything ~3.6v @ 1C or above). First find levels of all 20cells/strings, and confirm what happened before going further.
A slow trickle discharge doesn't necesarilly harm cell structure, but recharging back up the cliff too fast most likely will, and could even start thermal runaway. I had revival success with <1v cells using <1% C charge rates - and it was amazing how fast the cells wanted to come back up with such a light charge.
They are still okay today, and I still trust them the same as any pouch cell of this chemistry on my bike. . . . I don't.

 

[wineboyrider]

Yeah, one cell in one battery was definitely bad but I didn't think it would crater the whole 20s pack (5 4s batteries). Sucks. $600 bucks up a hogs rump.

That's why you have to cull the bad cells from HK packs, but once you do they are really nice batteries.

 

[Ykick]

Lesson learned, can’t go into hobby cells blind or inattentive. Also gotta collect few tools/supplies to test, qualify, connect and maintain. Spare brick ain't a bad idea starting out.

Once you have all that and practice a good neighbor use policy, RC Lipo has been a decent source of high power battery packs for many of us.

It ain’t for everybody though and as the 18650 DIY market grows, need for Hobby Lipo will likely become a thing of the past for eBikes.

 

[Mammalian04]

Thanks for the advice guys. I already dropped the batteries off for disposal/recycling. Expensive lesson but a lot cheaper than it could have been!

The charger was not plugged in. I just had the Adaptto turned on for balancing. I don't think the Adaptto could kill a battery in a week. I think the bad cell had something to do with taking out the others. The 4s packs batteries were wired in series so the BMS balance wires had to have something to do with it.