According to the seller when charging 1 or 2 batteries at the same time blue switch needs to be pushed in . When charging 3 batteries at the same time blue switched should be pushed out . I will test and charge this bat and let you guys know
That's tough to keep note of every time and not make a mistake, also reading the circuit, i would not trust it because of the way its designed using resistors as a load balancer for batteries at different levels.....