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Old Jan 17, 2015, 12:55 PM
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Question
Do I have a weak cell?

I'm kind of new to this Lipo thing. I have a new 4S/5000/20C battery that I am playing with on the bench just to get experienced with my charger, battery, watt meter, and voltage alarm.

I was attempting to discharge down to 3.7 V per cell with the intention of then performing a balance charge to see how long it took, how many mAh went back in, and how well balanced the cells ended up. I was applying a discharge load of about 20 amps which is very low for this battery. I have a voltage alarm connected. When the alarm sounded the cell voltages were:

3.79 3.80 3.80 3.69

I turned of the load and let the battery rest for about 5 minutes. The cells then measured:

3.81 3.81 3.80 3.80

I put the load back and within 5 minutes the voltages were back to about the first set with cell 4 triggering the alarm. Is this amount of difference between cells normal? Especially under such a light load?
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Old Jan 17, 2015, 01:09 PM
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Normal in a discharged condition. What's important is how well the cells are balance fully charged.

mw
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Old Jan 17, 2015, 01:22 PM
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Originally Posted by Mark Wood View Post
Normal in a discharged condition. What's important is how well the cells are balance fully charged.

mw
Ok thanks. Am I ok discharging down to where the cells are about 3.7 after being allowed to rebound?
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Old Jan 17, 2015, 01:38 PM
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Yep. That is widely considered the lowest range for storage mode.

mw
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Old Jan 17, 2015, 01:52 PM
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Quote:
Originally Posted by Mark Wood View Post
Yep. That is widely considered the lowest range for storage mode.

mw
Thanks again. I did a search and found some good posts on where to set my voltage alarm. I am gonna carry on with discharging to 3.7 resting and then do a balance charge to see capacity and final cell balance. Then I will put it back to about 3.8V for storage.
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Old Jan 17, 2015, 09:01 PM
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Perfect!

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