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diy solar

Advice needed to safely draw-down overcharged cells?

traymor

New Member
Joined
Jul 23, 2021
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Over the last 9 days I have been charging (hopefully top balancing) a 16P set of 280 AH Eve batteries. I thought I had the charger set to 3.6 volts but apparently not. I have been recording voltages every 12 hours trusting that the amps would drop off at 3.6 volts. At 4:30pm today the voltage on multiple cells was 3.384v. An hour later the voltage was 3.930v. They are resting now at 3.795v. The cells are compressed and show no bulging. The charger was a Long Wei 3010DF (I must have bumped the settings over the last week?). Looking for a safe way to handle the cells from this point. Very new to this and thought the go slow approach was best. Any advise would be much appreciated. Thanks
 
Draw them down with 1-5 amps. load. Do it as soon as possible. Should not take too much time to drop them down as there is little actual capacity in that elevated voltage range.

An hour at 3.9v should not have done any significant damage as long as cell temp was not above 40C.. Things go south quickly above 4.3v.
 
I've used a small headlight bulb from a pickup to draw down high voltage stuff like that. It doesn't take much, like mentioned above.
 
Thank you! I found an old 12v computer fan and an old headlight and they are slowly drawing the power down. Once I get to 3.6v and let them sit awhile, if they are all close voltage wise, can I consider them to be top balanced or is there something else I should consider? This is the first of 10 48v batteries I intend to build, so hopefully I can make all the mistakes on the first one. Thanks again for the help, I do try to read as many threads as I can to learn from others.
 
I found this method very effective to quickly and safely lower the voltage of any size cell.

 
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