So I just killed my lipo pack...what to do now?

[Finnster]

Originally Posted by BrianG

^ +1. Even with the BEC disconnected, the ESC draws power, albeit very little.

Yeah, in my case the Rx was off, so rx/servos weren't powered, just the small current drain over a few days on flat packs drained the minimal amt of pwr left and killed the batts. :( I've prolly done it before, but on charged batts it can prolly go for a very long time before it discharges enough to kill the batts.

Won't do that again

[zeropointbug]

Yeah, just remember that A123's are just as likely to die if drain right to zero volts. I have drained my pack until the vehicle came to a snail crawl, charged them back up and still full power, didn't do anything.

A while back I had a post of my pack with roughly 100 cycles on it, the cell capacity was still over the rated 2300mah, it was IIRC 2375mah @ 2.0 cut-off. This is after a pack that had been used in a 10 minute discharge, as well as being accidentally shorted out, twice. IMO, they were born for R/C.

HERE is the test.

[silentbob343]

Guy named charles over at rcgroups has beaten the snot out of his A13 packs even bringing them to 0 volts and has managed to bring them back with minor performance degradation.

[zeropointbug]

Well there you go!

[silentbob343]

Originally Posted by zeropointbug

Well there you go!

very impressive cells, can't wait for the 1100mAh cells for 1/18 scale.

[Finnster]

So I took apart my 3S2P 8K pack and made it into a 2S2P pack to match the other 2s2p 8K pack I had to make my 5S pack (2s+3s.)

It was a pain to take apart, as all the packs had double sided tape holding them together and I had to coax them apart. It was pulling the silver wrapper so hard on a couple I used a blade to gently score the tape so it would peel apart. Unfortunately I did get a tear in two of the cells.

It smelled a bit odd, so its what made me look, and that's when I saw one tear. The other one got cut as well as careful as I was. I sealed them back up, and did not puncture the batt, as I could see an inner lining, but does anyone know what would happen when the outer wrapper gets torn? Smelled liek hydrogen or something. I'm going to dispose of the cells regardless, I don't need them and its not worth the risk using them, but I would like to know what would happen if they are used like that.

Small rocks get under the cells/batt tray and scratch at the lining. If it ever did tear it so I couldn't see it, is that highly dangerous? I can't think it would be so much so as many ise lipos in cars and these things will just happen, but then again...:032:

Otherwise pack went together ok. Now I have 1 4S 8K pack (2*2s), which is good enough for me. I'll be looking at A123s down the line, but I'll get by on one batt for now.

[zeropointbug]

Yikes, that's not good at all. Tearing the lipo packaging is very dangerous indeed, and is highly likely that it will expand/start on fire, maybe not right away, but it will over time for sure.

i did this: http://img174.imageshack.us/my.php?i...6030594of1.jpg

followed up:
http://www.rc-monster.com/forum/show...054#post110054

[zeropointbug]

What exactly happened to that cell A4DTM? Looks like something hit it? That looks nasty, I take it that's the cell that died?

[Finnster]

Well I didn't bother testing it out. They also went for a saltwater bath today too. However these packs were both fully charged, so several hours of some nice electrolysis displays. Made some cool patterns in the water w/ the salts or bubbles (hard to tell what it was, but looked like it was following the current.)

Well a sad and expensive wkend, but still have a pack, so all is good.

[zeropointbug]

Well if you want to go to A123 packs anytime, HERE is a great link showing a DeWalt 36v pack being taken apart and made into other packs.

I just bought two of these packs as I am going to 7s2p pack and a Neu 1512/3D/F at 1700Kv., this pack is capable of 3000 watts.

Originally Posted by zeropointbug

What exactly happened to that cell A4DTM? Looks like something hit it? That looks nasty, I take it that's the cell that died?

the pinion slid off the motor shaft, until it hit the battery. threadlock fixed that problem.. I'm guessing that's the cell that's bad, because cell #4 (from the positive balance lead) is the cell that dropped to 1.8v. The cell that's damaged would either be #2, or #4, so i'm guessing it's #4, as it is slightly puffed more than the others.. meaning the other's are all wrinkly*sp, and that cell looks "filled" completely.

[Finnster]

I left the pack to soak overnight so it can get disposed today. I looked and both packs had puffed (silver jacket was expanded.) Good to have those safely away, and I guess that solves that mystery. FWIW, the packs that went low voltage did not puff, so its reasonable to think it was due to the torn lining.

[silentbob343]

Originally Posted by Finnster

Well I didn't bother testing it out. They also went for a saltwater bath today too. However these packs were both fully charged, so several hours of some nice electrolysis displays. Made some cool patterns in the water w/ the salts or bubbles (hard to tell what it was, but looked like it was following the current.)

Well a sad and expensive wkend, but still have a pack, so all is good.

When you can smell that sweet li-poly smell it is wise to do what you did.

[zeropointbug]

Yup, that's the highly unstable graphite in the cathode reacting with the anode when the SEI layer breaks down. It might just slowly puff up when you charge it... the ultimately it will expand and very high risk of it exploding, and igniting. Guess what, it's hard to put a lithium cell fire out, because the oxidizer is right in with the battery.