Ever come across a single cell that won't discharge?!

[Haohmaru]

Anyone ever come across a cell that won't discharge?! If so I'd love your troubleshooting advice.

I mistakenly attempted to parallel charge packs with my BC168, which resulted in a big spark that melted the JST plug of the 2nd battery I attempted to connect. I have since replaced the JST plug but
Cell #3 3.86v) won't discharge but will charge. Cell #4 discharges more/faster (3.74v) than #1,#2, & #5 (3.80v). Discharge set to 3.80v at 1A. When the discharge stops on all the other cells except #3, #3 remains at 3.86 but #4 continues to discharge (even though BC168 shows 0.0A drawn from #4).

It has been a couple months since this accident with no change (attempting to discharge as I write).

Dumb newb mistake I recognize.

I am in the process of building my first ebike, so have yet to use this battery. No charge/discharge through main bullet leads.

Since this 9s pack was a bit pricey for me, my hope is that it will discharge/charge normally through the bullet connectors (I was hoping I could just use the BC168 but am now shopping for a bulk charger. Likely from BMSbattery.com but considering Meanwell). If $ weren't an issue I would discard & replace.

My thoughts are to connect this pack on it's own to the ebike, discharge it some, then check to see if the #3 cell is still stuck at 3.86.

Any advice/recommendation/tips/flaming(do people still call it that lol) would be greatly appreciated.

Thank you in advance, ES community. I really like this place. Great people; great pursuits.

 

[cal3thousand]

I think that something is wrong with the cell balance connections.

I think that maybe when you charge it, actually 2 batteries are taking the charge and it eventually gets back to the target cell. But when you discharge, you are trying to pull from 2 separate cells and it won't work.

Just a guess.

 

[dogman dan]

Something fried in the KFF spark. Is that a through the balance wire type charger? If so, it will charge, but the discharge side has a tab vaporized.

 

[Ykick]

We may have a language thing going on here? I wasn't sure how to exactly interpret the problem but something is fried and probably gonna need to cut the end open to see what's going on with the balance/power leads or battery tabs?

This is where CellLog comes in real handy to quickly see if all the balance leads are intact and/or quick read of cell voltages.

Pics might help too? keep 'em under 100kb, 640x480.

 

[Haohmaru]

Thank you @cal3thousand @Ykick. It's nice to speak into the void, & get an answer back. Can't say enough good things about the ES community.

Thank you @dogman especially, I have read numerous posts of yours & have been educated by them. What's a "KFF" spark?

Update: Cell #9 (on the 2nd 4 cell JST balance plug, now only showing 3 cells) no longer registering on BC168 balance charger! :-( Noticable puffiness now. The attached pic is to reference puffiness. I've heard puffing is bad, but not enough experience to gauge severity of my pack. Is this puffing mildly bad, or code red fallout bad?

I wish I had taken a picture of the melted 5 cell JST balance plug. Alas, I quickly snipped & tossed & replaced it.

I searched for repairing lipo tabs & found that zinc solder is recommended to stick to the aluminum tabs. I found this video infomative:
http://youtu.be/RCsNQszo--E

If anyone has a tutorial / standard operating procedure SOP I'd love a link/share.

I am preparing to cut the shrink wrap off of the battery to take a look at the tabs. Wish me luck or warn me of common pitfalls.

Mostly, is the puffing alarming?

Thanks again everyone
Haohmaru

 

[cal3thousand]

That puffing is a bit concerning to me. I would keep a keen eye on that thing and store is somewhere fireproof.

If you would like to know more about LiPo pack repairs, Ypedal does a decent job:

http://www.ypedal.com

 

[Haohmaru]

Thanks for the recommendation @cal3thousand. I'm actually going to take it to a local hobby shop tomorrow who said they could repair it. Evette's Model Shop in Los Angeles. On one hand I feel like I should repair it myself, on the other hand I think it'd be safer to have it repaired professionally. Hopefully I can watch & pick up a trick here or there.

Currently stored in individual lipo bag in metal cabinet.

 

[DAND214]

9s, what are you going to use it on,a 24v system?

Dan

 

[Haohmaru]

Hi @DAND214 -

My intention is to form a 2s3p pack with 6 of them for 66.6v 12,000mAh, possibly reconfiguring to 3s2p 100v 8,000mAh pack later if power feels limiting. Please let me know if this is a bad idea.

 

[dnmun]

professionally? what's that?

to open them i use scissors and cut the shrink wrap off by starting it at the top and slitting it to pull the top free and down off the entire pack, cut the heavy plastic ring wrap at the top in the center with the scissors and pull that back to reveal the top of the tabs. be careful not to short the scissors on the tabs when the top is exposed.

 

[Haohmaru]

Thanks @dnmun. I may try if I get an ES consensus of optimism.

Just back from Evett's Hobby Shop. Consensus was that puffed cell was unrecoverable, although the staff there were unfamiliar with larger packs. No repair work was done.

I am slowly but surely biting the bullet of recycling & replacing.

What does the Endless Sphere community think about recovering this pack?

 

[Ykick]

Thanks @dnmun. I may try if I get an ES consensus of optimism.

Just back from Evett's Hobby Shop. Consensus was that puffed cell was unrecoverable, although the staff there were unfamiliar with larger packs. No repair work was done.

I am slowly but surely biting the bullet of recycling & replacing.

What does the Endless Sphere community think about recovering this pack?

My small part of community sez it's worth a look to see what's gone wrong. It's probably better for all if you learn/know what's gone wrong as opposed to blindly guessing what's behind the shrink wrap.

Use good judgment, common sense, be prepared, etc. Post pics when stumped if you wish to do cell surgery get a hammerhead soldering tip + 60W iron and learn what to do.

Bricks like that can almost always be re-worked. I use plastic wrap and Gaff tape (real stuff although duct tape works too) in order to seal them back up after surgery.

Surgery isn't even that important as you mostly need to qualify balance/power wiring and get to the bottom of what's wrong. Probably a blown main tab but until you can trace what's what, everything's a best guess.