Focbox reporting wrong voltage and BMS overcharging


I just noticed a very concerning problem with my build. I got an Enertion Focbox (4.12), 10S Lipo battery and a Bestech charge/discharge 80A BMS.

So firstly, I just unplugged my balance connector to manually check on the individual cell voltages. All are reasonably balanced (+/- 0.05V), however, they are overcharged, with the max cell at 4.39V! Im using a 42V adapter to charge. Total pack voltage was roughly 43.7V.

Then I hook the board up to VESC tool, and the ESC is reporting 39.5V? What’s going on here? Any help would be deeply appreciated, I really dont want to burn my house down :sweat_smile:

Looks like you have set the balance charger to 11s?

Unfortunately not, the BMS is a Fixed 10S.

EDIT: Might have found the source of the overcharging, my adapter suddenly gives 46V out (while not charging). However, the BMS should still have cut off the charging…

Still odd that the esc reports a lower voltage. Where are you reading this voltage from the esc?

Yep, very odd. Reading from the VESC tool, but also via UART to the my DaveGA monitor. image

EDIT2: False alarm. Turns out my multimeter is broken. When having the display illumination on, the meter reads way to high! Pack voltage now reads 39.2, more reasonable! Max cell at 3.96V, min cell at 3.91V.

Ha,ha. Maybe try new batteries in your multimeter.

1 Like

Will do haha! Got my heart pounding real good when I saw those measurements :sweat_smile:

1 Like