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Apr 29, 2012, 09:35 PM
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CJRAY's Avatar
Help!

6S with a bad cell


OK, I know that I'm probably posting in the wrong section, so maybe a mod can move it for me. I tried searching to no avail, so here goes. I have a Gens Ace 6S 5300mah with maybe 20 cycles on it that has apparently dropped cell #6. When charging, it appears fines, charges fine, however, under load, that cell drops off first, heats up, and has puffed slightly. After sitting, it will come back up in voltage to equal the other cells. Anyone ever see that? Any ideas? What i was thinking about doing, was to removing the Number 6 cell and change it to a usable 5s pack? Any thoughts? Any help is appreciated.
Last edited by CJRAY; Apr 30, 2012 at 01:14 PM.
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Apr 30, 2012, 09:27 AM
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dedStik's Avatar
I'm sure it can be done, but given the volatile nature of lipo's I wouldn't try it, as it's just not worth the risk.
Apr 30, 2012, 01:05 PM
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CJRAY's Avatar
Quote:
Originally Posted by dedStik
I'm sure it can be done, but given the volatile nature of lipo's I wouldn't try it, as it's just not worth the risk.
Yeah, I've separated a different bad 6s pack that I had, just to look and check it out. I don't think it would be too bad considering it's an outside cell. I'm just looking for some pics or a thread with pics for reference or a step by step, I guess.
Last edited by CJRAY; Apr 30, 2012 at 01:16 PM.
Apr 30, 2012, 04:41 PM
ShopCzar
Endlesslag's Avatar
If it's an outside cell, it's doable. i did it with a 3s pack that had a dead cell, made it a 2s. I just desoldered the dead cell and removed it's balance wire from all of them. still had to plug into the 3s balance port but functioned as a 2s fine.Just be careful. It's not impossible, but it's tough to solder the wires and tabs together, especially when it's an aluminum tab. They have to use a special solder and flux, and the tabs are tack welded together.
Apr 30, 2012, 06:49 PM
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CJRAY's Avatar
Quote:
Originally Posted by Endlesslag
If it's an outside cell, it's doable. i did it with a 3s pack that had a dead cell, made it a 2s. I just desoldered the dead cell and removed it's balance wire from all of them. still had to plug into the 3s balance port but functioned as a 2s fine.Just be careful. It's not impossible, but it's tough to solder the wires and tabs together, especially when it's an aluminum tab. They have to use a special solder and flux, and the tabs are tack welded together.

Yeah, i fixed it when I got home from work. Just unwrapped it, clipped the positive wire and balance tap wire off, removed the cell and re soldered the positive wire back on. All done, Very simple with it being the last cell. Would be a problem in the middle or on other end where you would have to rearrange all of the balance leads. Now I have a good 5s pack for my Patriot.
Apr 30, 2012, 07:28 PM
ShopCzar
Endlesslag's Avatar
Quote:
Originally Posted by CJRAY
Yeah, i fixed it when I got home from work. Just unwrapped it, clipped the positive wire and balance tap wire off, removed the cell and re soldered the positive wire back on. All done, Very simple with it being the last cell. Would be a problem in the middle or on other end where you would have to rearrange all of the balance leads. Now I have a good 5s pack for my Patriot.
Cool, glad it worked out charges and balances ok?
May 01, 2012, 03:39 PM
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CJRAY's Avatar
Quote:
Originally Posted by Endlesslag
Cool, glad it worked out charges and balances ok?
Yeah, which is the strange thing as it did that anyway. After a few minutes of flying, #6 would start dumping. The way I noticed is that I lost power on my 550E and when I brought in in to land, it was twitching. I immediately checked the cells and 1-5 were are like 65%, 6 was at 30% and hot. Let it sit for a while and it would revive itself and they would all show to be in the 65% range. Tried sloooow charging it, but kept getting the same results. Kind of strange. Anyway, removed the cell, balance charged it, and hooked up the Patriot for some power system testing and it worked great as a 5S. Money saved! The Patriot needs more cooling holes though.
May 09, 2012, 10:28 PM
Registered User
Whoa! Don't fly with a bad LiPo cell!!

These internal cells are usually in series, which means that the pressure of all the individual cells gets pushed through the bad cell (so it heats up). Bad news.

I have had a 4S battery lose a cell and read as a 3S. I don't trust doing the surgery to remove the bad cell, so discard these.
May 09, 2012, 11:37 PM
Registered User
Done it before when lipos were expensive, even the crappy ones from HK. If you search over at Runryder or Helifreak, there are threads showing how.
May 10, 2012, 07:41 AM
Registered User
CJRAY's Avatar
Quote:
Originally Posted by wuest3141
Whoa! Don't fly with a bad LiPo cell!!

These internal cells are usually in series, which means that the pressure of all the individual cells gets pushed through the bad cell (so it heats up). Bad news.

I have had a 4S battery lose a cell and read as a 3S. I don't trust doing the surgery to remove the bad cell, so discard these.
Well, it was # 6 on the end, so it was as easy as removing the covering, clipping the positive wire off of number six, un-soldering it from 5 and re-soldering the positive wire back on to # 5 and wrapping the pack back up. If it was another cell, I probably wouldn't have messed with it.


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