LIPO open heart surgery (worked, but be careful)

Batteries, Chargers, and Battery Management Systems.

LIPO open heart surgery (worked, but be careful)

Postby bart_dood » Mon May 10, 2010 12:19 am

I had a bad cell in one of my zippy flightmax 5000mAh 6S packs, so I bought a 2S 5000mAh turnigy pack from ebay with the same C rating to repair it. When I opened up the pack with the bad cell it was obvious which one was bad, it had slightly ballooned (marked with black sharpie in photo).

As the cells in the pack are kind of glued together with strong double sided adhesive I decided to slice open the pouch and remove the insides, so avoid risking the two neighboring cells......not a good idea...as soon as I cut into it it flared up and went haywire, see video.
Fortunately it didn't damage the other cells, so I simply pulled the remains out and re-soldered the new cell in place. I will be doing some tests and re-balancing over the next few days to confirm it works ok.
I have one spare cell left, if I get another bad cell I can replace it, but a bit safer next time!!! these things stink when they go!!

:shock:

(the vid will be added in a few mins, youtube is slow)http://www.youtube.com/v/U7n_ZSl256s&hl=en_US&fs=1&
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Re: LIPO open heart surgery (worked, but be careful)

Postby Hyena » Mon May 10, 2010 5:23 am

bart_dood wrote:As the cells in the pack are kind of glued together with strong double sided adhesive I decided to slice open the pouch and remove the insides, so avoid risking the two neighboring cells

Riiiiiiight...

bart_dood wrote:not a good idea...as soon as I cut into it it flared up and went haywire

How unexpected!
I'm glad you're ok but seriously, what did you think would happen ?!
That's like trying to clean up spilled diesel with a match.
I think you need to change your name from bart_dood to bart_noob
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Re: LIPO open heart surgery (worked, but be careful)

Postby bart_dood » Mon May 10, 2010 11:00 am

On a side note, when a lipo cell goes bad, during recharge they balloon up right? is this accompanied by an increase in temperature? or do they stay at the same temp as the good cells until they really fail and turn into a ball of flames?

I was working on a safety system based on temperature monitoring, if bad cells don't show themselves up with increased temps my system won't work.

thanks
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Re: LIPO open heart surgery (worked, but be careful)

Postby Bazaki » Mon May 10, 2010 2:36 pm

I had the same yesterday ! But my knife went into the bad cell that was really dead. I read somewhere how to remove the double tape between the cells, I don't how they did it exactly.

PS How did you solder the aluminium tabs ?
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Re: LIPO open heart surgery (worked, but be careful)

Postby bart_dood » Mon May 10, 2010 7:25 pm

Bazaki wrote:I had the same yesterday ! But my knife went into the bad cell that was really dead. I read somewhere how to remove the double tape between the cells, I don't how they did it exactly.

PS How did you solder the aluminium tabs ?


The new cell I spliced in was from a good new pack, so it was pre-tinned. All I had to do was de-solder it from it's pack, I used two soldering irons at either side of the tab to heat it quick and get it removed without dumping too much heat into the cell.

I didn't bother de-soldering the old pack, I just sliced the tabs and solder away with a sharp box cutting knife.
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