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7.4v 8000mah balloning (slightly)

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Old 04-29-2007, 04:15 AM
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killjoyken
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Default 7.4v 8000mah balloning (slightly)

I've had this pack in my Tamiya TRF415 for about 4 months. It's always been run with a Mamba Max 7700 with lipo cutoff at 6v. I haven't run the car for a few weeks and when I went to take it out tonight I noticed that the top cell was slightly puffing in the middle. I checked the voltage and it's over 8v. Last time I put it away it had more than half a charge left in it. (I think only once did I ever hit voltage cutoff, it lasted that long!)

My questions are: Is the pack ruined? And if so, what caused it? I've always done everything right when it comes to lipo care so this is really buggin me! Also, if only one cell is ruined, can I save the remaining cells to make a lower mah pack?

BTW, it's a great pack at a great price!

PS. I use an MRC 989 and charge the pack at 8A.
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Old 04-29-2007, 03:13 PM
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Default RE: 7.4v 8000mah balloning (slightly)

There are a few causes to a pack swelling....over amping, charging at to high a rate (I always charge at less than max...you say 8 I would go 6....It's easier on the cells) And always store cells at half of there capacity..........Again these are just some causes.......without all of the info I really don't know what caused yours to puff "slightly", Are you balancing the pck when you charge it?? Check the reading from each cell and see where they stand........
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Old 04-30-2007, 09:49 PM
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Default RE: 7.4v 8000mah balloning (slightly)

Hey Jason, thanks for the tips. From what I had read in magazines, they said just to charge at 1A per 1000mah. From now on I'll drop the amps.
I always store them at half to full capacity. Is it bad to store them fully charged? I've also heard that balancing wasn't necessary so I've never done it. Guess I should invest in one.

I'll pull the shrink wrap off and test each cell.

Thanks again for your help!

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Old 05-01-2007, 05:43 PM
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Default RE: 7.4v 8000mah balloning (slightly)

Some balance every time they charge others do it after a couple of charges..........I do it all of the time.Let me know what the cells check out at.........
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Old 05-02-2007, 12:52 AM
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Default RE: 7.4v 8000mah balloning (slightly)

Ok, took the pack apart and one cell in the center was balloned but was still putting out about 4.3v, same as the others. Nothing looked like it was shorting out and the other cells looked fine so I reconfigured them into a 3s 4000mah pack. Can't wait to test it out!
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