No power output from BMS

[z3leg]

Hello,
I just put together my DIY E-bike and i have an issue with my BMS. It wont output any power from P- or C- , therefore I cannot even power on my ESC, the battery is fully charged, all individual cell pairs are at 4.3v, whole pack is at about 55v and all balance connectors are connected. I have no idea why that is.

*The motor runs when connected directly to the battery (skipping the BMS)
*Charging works thourght the BMS (through its P- and not C-)
*When connecting the battery + to ESC + and BMS P- to ESC - there is a huge voltage drop from around 53v to around 5 - 10v and ESC
won't turn on

The BMS is most likely the problem, its a cheap one bought from banggood.
https://www.banggood.com/13S-35A-48V-Li-ion-Battery-Protection-Board-BMS-PCB-with-Balance-For-E-bike-Scooter-p-1286039.html?

Also: On the sellers page a picture is included where it shows to connect the negative charge cable to C- on the BMS but when doing so the batteries don't charge.

 

[amberwolf]

all individual cell pairs are at 4.3v,

That's probably why; the cells are too high, for typical Li cells. 4.2v is the usual max per cell.

Try draining them down to below that, and see what happens.

(the BMS, if it has balancing function, should be doing this on it's own, so if it doesn't, the BMS may not be working at all, damaged or potentially miswired).