Question Laptop Battery problem (Possibly BMS problem)

JackFrostSekhose

Prominent
Feb 12, 2019
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Hello so I have a laptop battery pack that is about 12.20v in series (3 cells), It came that way from the factory.
Now I removed the BMS and resoldered it to the batteries and tried putting it back to the laptop and now the battery doesn't give any backup..it was working fine before I tried changing BMS. Why?

I had a couple of Lenovo pcr batteries of a higher capacity I wanted to use instead of the cheapo Chinese INR I got. All are 18650 cells by the way. Turns out that doesn't work so I reverted back to my old INR and the original BMS, but for some reason now it doesn't give any voltage reading or backup at all.
It stays at 99% and upon unplugging the computer dies instantly.

What could have gone wrong?
The test leads on the multimeter reads 0.9 volts (NOW 0V) when I probe the connector that goes to the laptop...

It is supposed to read 12.20 or something - right?
 

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