Oops, bought the same cheap BMS for charge only again, connected it, attached the charger and saw sparks. A mosfet was clearly destroyed. Last time I believe the problem was connecting balance leads before ground, but this time I am not sure.
I measured voltages on the balance leads, which ranged nicely from 4.2 to 33.6v. The problem occured when I connected my magsafe connector. I use the two outer pins for negative and the inner ones for positive, I measured the voltage on the charger pins and checked for shorts on the plug and there does not seem to be any problem. When I first connected the connector, the charger LED did not change to red (indicating it’s charging). Not sure why, but when I connected the magsafe the other way around, sparks appeared.
The BMS is not expensive but this is the last step for my build and it is getting frustrating. Did I make a mistake? Should I invest in a more expensive BMS? Or should I ditch the fancy magsafe?
The BMS:
The way I connected it: I actually did not use the balance negative but the main lead to connect to B-