help with battery balancer

Thread Starter


Joined Apr 11, 2016
hello everyone,
i got one of those Bird-style scooters and i'm 90% convinced that the battery controller is failing.
it's wired up like so:
2P7S battery <---> balancer <---> BLDC <---> motor
i test it by
1 - connect VOM leads between the balancer and the BLDC "brain", read 29V
2 - switch on the brain, LEDs light up, motor runs correctly
3 - grasp the balancer and shake it around, VOM reading drops instantly to 4 - 7 volts, LEDs and motor die.
4 - voltage between 2P7S and balancer is still 29V
5 - voltage between balancer and BLDC starts to slowly rise, like after 2 minutes it's about 17V (BLDC has 470uF input cap).
6 - disconnect and reconnect balancer from BLDC, V between balancer and BLDC is at 29 again.

the brain must be switched on for the symptom to appear. if it is off i can shake the balancer around all day and it's output voltage remains at 29.
when i 1st got the scooter it was working fine. this problem didn't start until about 4 days later.
here's a pic of the balancer.