Discharged Lithium cells

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Grumpy-b
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Discharged Lithium cells

Postby Grumpy-b » Thu Mar 17, 2011 8:24 pm

WHat are the issues of recommissioning lithium (not sure which version) cells that have dropped so far the BMS has ceased to function. The discharge has been because of standing for a year + rather than being run down under load.

Grumpy-b

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retepsnikrep
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Re: Discharged Lithium cells

Postby retepsnikrep » Thu Mar 17, 2011 9:07 pm

You can't revive them asfaik. Time for the skip.
Regards Peter

Two MK1 Honda Insight's. One running 20ah A123 Lithium pack. One 8ah BetterBattery Nimh pack.
One HCH1 Civic Hybrid running 60ah A123 Lithium pack.

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Jeremy
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Re: Discharged Lithium cells

Postby Jeremy » Fri Mar 18, 2011 7:54 am

It depends very much how low they've gone and what type of cells they are. There are plenty of examples on ES where some types of LiFePO4 cells have been resurrected from near zero volts successfully. I have a pack of Headway cells that accidentally got discharged down to around 1V per cell and they came back to life and have been working at full capacity for several months now. Others have found the same with A123 cells.

The same isn't true for LiCoO2 cells though, once these die they are dead for ever, it seems. It may also be that some other types of LiFePO4 cells don't recover - there's some evidence that pouch cells are poor at recovering from over discharge.

It's worth trying though. I'd aim to charge each cell individually and monitor them to see how well they pick up. You may get a nice surprise and get back a fully functioning pack, or at least one with enough capacity to be usable.

Jeremy

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ChrisB
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Re: Discharged Lithium cells

Postby ChrisB » Mon Mar 21, 2011 10:47 am

Must admit I've generally found they wont come back once they have dipped to low.

One of the annouying things with them, I've got some old Nicad camcorder batteries that are decades old now, yet a couple of cycles and they are nearly as good as new, yet my lipoly in my stills camera went flat because I didnt use it for about 8-9mths and now wont even hold a charge for 5mins :(

ChrisB
I reject reality and substitute my own !!!!!!


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