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        Question Damaged 6S Lipo; One cell bad; Need help with discharge and disposal

#1 Arcturus97 Jun 19, 2012 09:40 AM

Damaged 6S Lipo; One cell bad; Need help with discharge and disposal
 
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I've got a 6S-3000 that was in a crash. There is small but visible physical damage to cell #3 (pic attached, wrapper peeled away by me for view). Post crash all cells had pretty much equal voltages at around 3.8
I charged the battery, charger really struggled getting it balanced (took a long time), to get cell #3 up to 4.2 volts. I was suspicious so after a break I put it on a 1C discharge, set to go down to 3.6v per cell to see much capacity came out. About 45 minutes later the charger started alarming, I was in the room the whole time ran over and saw that it terminated due to low voltage on (you guessed it) cell #3. #3 was at 3.1v while all the others at 3.7v

I've had this battery in a lipo bag by itself on a concrete floor for the last week or so wondering what to do with it. In that time cell #3 has now dropped to 2.9v, others still at 3.7v. Using the charger to discharge is not an option - I suppose I could fool the charger (icharger 306b) by not plugging in the balance port but that doesn't seem like a good idea - I'm not looking for a fire on my workbench.

The whole point - how can I discharge this battery safely so it can be disposed of?

I've read different things about the salt water bath: some say do it, others say do it after discharged, and others say it will not discharge a lipo.

#2 rampman Jun 19, 2012 10:14 AM

Salt is a no-go.
For a 6s you will have to make a series light bulb discharger. Put 2 automotive light bulbs in series. An 1157 or 2057 will work. Simply go from your battery plug to a mating plug + to bottom contact/contacts of bulb 1. Solder a short wire from brass side to bulb 2 contact/contacts. Another wire from bulb 2 brass side to the - of plug.
These will get hot and may take all night to fully discharge this pack. Do this in a safe area as you will not be there to monitor it that long.
Just because the light bulbs are not lit the pack may not be fully discharged. Once ALL heat is gone + 1 hour it should be discharged to a safe disposal state.

Rick

#3 Mark Wood Jun 19, 2012 11:46 AM

^^ What Rick said.
If your charger has a discharge function you can put it into Nicad mode, set for .1 volts at max discharge and do that a couple of times to affect a complete discharge.
Either way, once the pack is discharged, strip and twist the leads together to prevent voltage rebound in the pack.

mw

#4 feathermerchant Jun 19, 2012 12:15 PM

FWIW when I discharge packs, I put them on the grill outside and close the lid. I have never had any issues but if one does flame it won't hurt anything.

#5 pgk Jun 19, 2012 12:32 PM

Quote:

Originally Posted by feathermerchant (Post 21939287)
FWIW when I discharge packs, I put them on the grill outside and close the lid. I have never had any issues but if one does flame it won't hurt anything.

Except if you were planning on grilling burgers that day! (: lol... Sorry, couldn't resist...

Pete

#6 feathermerchant Jun 19, 2012 04:52 PM

Well If I see it flame up, I just go get the patties and start cookin. (JK)


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