I made a 52V battery but it’s cutting out @ 51v ?

Pskin132

100 mW
Joined
Aug 6, 2022
Messages
39
Hey guys,

I made a 52V battery out of tested laptop batteries.

Battery chargers to 58.8 which is perfect.

I have hooked a BMS up which is all connected properly, when it gets to 51V on my handlebar volmeter the LCD display goes off and the voltmeter dies. When I switch it back on it fluctuates to 10-20-30v then goes off again.

Is it something to do with balancing ?

Bad cell ?

Little bit stuck.

Be great if you guys could point me in the right direction I’d be very grateful.

Thank you

Nathan

This is the BMS I have got - https://m.aliexpress.com/i/32977028591.html
 
Likely (at least some of) the cells are past EoL.

How stringent were your tests, what sirt, using what gear, what cut-offs for go/no-go?

Best to start out with quality new cells from a trusted vendor, all matching Grade-A, ideally frim the same production run.
 
I would guess bad cell(s). Can you get to the pack and check voltages of each of the 14 banks when this happens? Could explain quite a bit. I built a pack from laptop batteries. Only lasted part of one summer then had the same problem you are describing. Laptop batteries aren't very good for ebikes. They can't take the high discharge rates and if they are used then they are already on their last leg. I've used Tesla "S" cells for the last couple of packs I've made. They test out at ~3600 mah which is off the charts for 18650s. Definitely worth the couple buck$ each.
 
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