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replacing bad cell

Old 05-08-2009, 06:04 PM
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louisben36
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Default replacing bad cell

Hi all

I have a couple of Li-po packs (3s) that contain 1 damaged cell in each pack. I was wondering if anyone has replaced such a cell for a good one to make up a complete pack?
And, if so , how difficult is it?

thanks

Louisben
Old 05-09-2009, 01:35 PM
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el_xero
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Default RE: replacing bad cell

What you're asking about is VERY dangerous!!!! but yes it is possible if you know what you are doing... I can't tell you how because i've never done it I have read about people doing it i do know you need some kind of aluminum solder to do it though... But be warned!!! VERY dangerous stuff!
Old 05-10-2009, 08:19 AM
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louisben36
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Default RE: replacing bad cell

Yes..the solder is Aluminium and has a high melting point, so you need a good iron. I might have a go at it.....we`ll see.
Old 05-10-2009, 08:34 AM
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el_xero
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Default RE: replacing bad cell

Id suggest getting the correct melting points online try googling also i 've read else where that people practiced on foil before attempting to work on their batteries. You should use a temp controlled iron too. dont use the cheap radio shack stuff you'll be happy you got a good iron.
Old 05-13-2009, 12:14 AM
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jdetray
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Default RE: replacing bad cell

Louisben -

I'm sure it has been done and done successfully. Aside from the soldering difficulties, my concern would be matching the existing cells with the new one. That seems like a recipe for trouble.

Obviously, you need to match capacities. But even if the new cell is of the exact type and stated capacity as the others, a new cell may behave differently from a used one. It might have a different discharge curve, for example, which could result in balance problems every time the pack is discharged.

A safer course might be to convert the packs to 2S packs and thereby avoid the matching problem altogether.

- Jeff
Old 06-03-2009, 05:40 AM
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Default RE: replacing bad cell

A safer course might be to convert the packs to 2S packs and thereby avoid the matching problem altogether.
That's what I did, at least the pack is usable & safe . - John.
Old 06-03-2009, 02:39 PM
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el_xero
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Default RE: replacing bad cell


ORIGINAL: jdetray

Louisben -

I'm sure it has been done and done successfully. Aside from the soldering difficulties, my concern would be matching the existing cells with the new one. That seems like a recipe for trouble.

Obviously, you need to match capacities. But even if the new cell is of the exact type and stated capacity as the others, a new cell may behave differently from a used one. It might have a different discharge curve, for example, which could result in balance problems every time the pack is discharged.

A safer course might be to convert the packs to 2S packs and thereby avoid the matching problem altogether.

- Jeff

Good Call! I wasnt thinking along those lines and totally forgot that was an option. Thanks ill do that with mine too hehe
Old 06-04-2009, 05:48 PM
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PatternFlyer
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Default RE: replacing bad cell



I've tried separating 4200mAh 3S2P packs to 2 of 3S2100 couple years ago.
pack was new.  Two separate packs didn't last long.   LiPo cells are wrapped with aluminum, but the output tabs often has small tin strips on them for soldering purpose.

If you decide to disassemble the packs, make sure to have the tin strips still on them to solder.  Some manufacturers, spot weld them at the end and roll the tin strips.  So make your decision after checking how the packs were assembled.

Old 06-05-2009, 06:13 PM
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el_xero
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Default RE: replacing bad cell

Thanks! I've not tried yet. No time.. but ill be keeping that in mind.

ORIGINAL: PatternFlyer



I've tried separating 4200mAh 3S2P packs to 2 of 3S2100 couple years ago.
pack was new. Two separate packs didn't last long. LiPo cells are wrapped with aluminum, but the output tabs often has small tin strips on them for soldering purpose.

If you decide to disassemble the packs, make sure to have the tin strips still on them to solder. Some manufacturers, spot weld them at the end and roll the tin strips. So make your decision after checking how the packs were assembled.


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