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Non-working battery - #1 series cells are a full volt (2.9v) lower that the other 12 groups (3.9v).  

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Andrew Smith
(@evolvedbicycles)
Street cred = 100 mAh
Joined:2 years  ago
Posts: 15
07/05/2019 3:38 pm  

I built a 13s5p 65 cell ebike battery.  It worked for 5 to 10 rides (way under 200 miles) and then lasted shorter and shorted periods. The BMS just stops randomly.  I can't touch the throttle, that ends it right there.  The BMS shuts off when the battery has a nearly full charge which is SO madding about this problem. 

So I removed all the shrink wrap and padding and checked the voltage balance. Sure enough  I had 12 series groups in perfect balance at 3.9 v before charging and 4.1 after.  The 13th series group was a full watt out of balance at 2.9 v .  This series group is #1 and has my black leads attached in two places.

Here in the forums I read another poster (permalife) with a 10S4P battery with the identical problem.  The advise given to that poster was a question: Did or do you routinely leave the battery attached for long periods so that the BMS can balance the cells. 

When I read that I thought that was MY PROBLEM for sure.  I don't want to burn down the house for when the fan stops I unplug it.

But no.  I have now had my battery (red/blue caps version) on my Luna advanced 300 watt charger for 72 straight hours.  After a short initial charge of maybe 30 minutes with the fan running,  the fan stopped and it has remained in a resting-stage?  with a solid red light and the green light blinking and making a clicking sound.  For 72 hours of the charger being plugged in, the #1 series group increased from 2.9v to 3.0 volts which the other 12 groups are all perfectly 4.0 volts. 

This battery will not run long enough for me to discharge it very far.  I feel like if I could get the rest of the pack before the voltage of the low group maybe the BMS would have a shot at balancing the group.  Is that correct at all? 

Should I buy a new BMS and replace it?  That would be easy enough.  

Any help anyone at all can give me would be so much appreciated.   

 

 

Edited: 2 weeks  ago

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