Is my BMS working - connected correctly?

Hi Guys,

I have assembled my first battery and connected it with the balancer cables. Now I just wanted to charge the battery. How do I know, if my bms is working on a preloaded battery. I preloaded every cell before point welding, thats why my 10s battery is preloaded.

my setup: 10s4p samsung 30q battery bms: 10s 20A bms for charge only

On my bms is no signal LED or comparable. Are there any voltages that I can measure during charging that tell me BMS is doing its job correctly?

And secondly, do i connected the BMS correctly for charge-only?

I want to build it according to this sketch:

kind regards and happy easter

That diagram doesn’t look to be for a charge only BMS configuration. Also, why are you using such thin wires?

The wires are only for testing. Later i will be using for battery connections 8-10 awg but for charge port you don’t need such big wires if the voltage drop is lower than 3%.

This diagram would be correct for a BMS for discharging, too where C- = charge and discharge (same port). But in your case that’s a wrong sketch, give me some minutes to correct it.

voltage drop isn’t particularly relevant to wire size. The primary factor is current

For charging 20AWG is totally fine. For Battery wires 12AWG (90A) should be enough, 8-10AWG is overkill and harder to solder.

This is the corrected sketch how you should connect it for bypassing/charge only.


thanks for the corrected sketch :slight_smile:

There are so many bypassing sketch’s, that i got a little bit confused.