BMS won't charge beyond 47V

ESK8 Electronics
1

Hi folks, I recently made my own battery pack (12S3P) but i’m facing an important problem i couln’t solve. I’m using a 50.4v charger but the BMS seems to stop, stucked at 47v. The light turns green.

I’m using this 40A model that I bypass. B- to the antispark P- to charger port.

700×850

First, i thought about soldering issue or bad connection somewhere but it doesn’t seem to be the root of the problem.

I also checked every cell voltage, everything looks ok (some group cells §have a 0.02 v difference).

Now I’ve to admit i’m a bit confused, if any of you guys already had this problem and know how to solve it.

Thx !

2

Do you have a wiring diagram how you wired everything up? Or maybe as min some pictures of the bms installed and maybe a link to the bms. That would help a lot.

Did you also check if your charger really output 50.4V?

1 Like
3

I found this one on the internet, i can’t tell if it’s correct. Someone on the forum already asked about bypassing this particular BMS, and they told him to connect battery minus to B- and P- to battery positive.
rBVaVVxPSoOAQFCVAAE0cC8GMcg022

Otherwise, my charger is brand new and fine (50.4v) output. I also checked each cell while bms plugged in

4

If you bypass a bms you don’t connect the main + from the battery at all to the bms. Charge - goes to B- and the P- goes from the bms to the battery -. The charger + goes directly to the battery +

5

My bad ! I made a mistake. In fact P- is connected to charger port -. And as you said main + isn’t connected to anything except charger port +.

Anyway charging works fine until I reach 47 V where BMS seems to cutoff.

6

Did you ever figure this out? I’m having the exact same issue. I’ve even tried two different chargers. Both chargers read 50.4v with the multimeter when they are not connected to the board.

Then when I connect either one to the charging port of my board, I can leave it all day and it never goes over 47.4 volts, and usually averages about 47.0 volts.

This is so weird.

Any suggestions would appreciated. Thanks.