Rebuilding 2 Battery Packs for 2013 Zero XU - Advice, Experience Sought

[robby]

I have two Zero XU packs that are in deep discharge. I would like to rebuild them to get the bike working again. I have a few questions:

1. Has anybody rebuilt a 2013 pack? If so I would love if you could walk me through it. I am willing to compensate you for your time.
2. Does anybody have suggestions on which cells I should use to rebuild the pack? Obviously a number of factors here -- geometry, chemistry, voltage ratings.
3. Does anybody know what the tolerances (or specifications) are for the built-in BMS system? I'm wondering how much leeway I have to rebuild the modules at different nominal voltages (depending on which cells I can find). Or should I replace the BMS, too?

Many thanks in advance for any guidance that people can offer.

 

[amberwolf]

What cells do they have in them now?

What voltages are the individual cells at?

If they are the EIG NMC pouch cells (I don't rmemeber what year they used them), then you may be able to trickle charge them at a few dozen mA, until they get closer to full than empty.

Then you can try the regular charger, and let the BMS balance the pack. It might take a while.

Do this with one pack, just to test it out, then if it does charge and balance, test it on the bike and see if it works and how much capacity / performance it gives.

I've recovered a small 4s pack of the EIG cells that were drained to zero by this method, and they are still working years later (albeit by now at reduced capabilities).

If they're the Farasis cells, they'll probably work similarly, but I have no experience with them.

 

[robby]

They're original so I assume it's the Farasis 25Ah pouches. I started to open it up, and when I got half the torx screws off, the pack lurched outward (even breaking apart some of the metal). It's possible that they're just stuffed tight, but I'm worried the cells are bloated and under pressure from the confines of the pack. What do you think? If the cells are indeed bloated, is it risky to open the pack and check, or at this point does it not matter much? Am I better off building a new 116V battery from scratch?

 

[amberwolf]

If they're that puffed up, I'd call them toast. :/

My EIG cells didn't puff when drained to zero, but I did have one once that got reversed, and that DID puff. I still ahve the cell in a metal box, to destructively test someday.

I do however have a number of RC LiPo packs that are puffed, some of which appear overdischarged, and some of which had zero charge, and some of which had normal charge levels.

 

[robby]

I'm not worried about the cells so much as my appendages.

Is there a safe way to disassemble a pack in that condition? I assume the cells will stay whole as I pull them out, but these are by far the biggest potential I've dealt with, and without much experience I'm erring toward caution. I'd love to salvage the cases if possible though to house rebuilds. And also because I expect the BMSs are fine.