My GoPro Hero 7 black broke, and i'm trying to fix it.
To do so i want to emulate the original battery. This should be possible by using theBMS chip of an original battery.

My problem:
The untampered original battery reads 4.1 Volt between + and -

The moment i disattach the BMS chip, and feed it to the battery with wires. I do not read 4.1 volt over the output pins anymore.
I do read 4.1 Volts between ground and several components on the chip though.
A youtube link of the concept i am trying:

@ 1:11

Why this route ?
All other routes of trying to revive the GoPro are a dead end.
When i insert the battery into the original battery case, and connect the battery case to the motherboard, everything works, even the touchscreen.

My question ?
Why on earth do the output pins not give voltage after disattaching the BMS and feeding it just like it would have been fed when it was still attached to the battery ?

 

Sometimes a protection module ("BMS") will detect a fault and disconnect the cell, and won't reset until it has been connected to a charger. I don't know if that applies to your situation.