Didn’t find much in the way of discussion with this topic. So I figured we should start one up because power issues seem to be pretty common.
Any ways, my charger says my battery pack is charged. I go for a ride and I notice diminished range. What the hell is up? I get home charge the pack, I pull out my multimeter and measure some voltages. Results? Hold your horses.
12s Li-ion battery, Bestech D140 charge BMS, 12s 5a charger. Fused charge port(8a) and charger(10a).
First we need to check the voltage on the main terminals of the pack. My readings show 47.6v at the main terminals on the battery pack. Then leaving the positive probe of the multimeter at the main terminal and taking the negative probe to the B- on the bms. Readings show as expected 47.6v. Continuing to the P-(or C-) of the bms with the negative probe I read 45.6v. A -2 drop in voltage. Yet my charger says pack charged.
Connections including physical inspection of cells? Good.
Temp readings on each cell with laser temp gun? 74-75°F, ambient 75-80°F.
Individual series voltage? S1 4.01v, S2 3.96v, S3 3.97v, S4 3.89v, S5 3.96v, S6 3.95v, S7 3.97v, S8 3.95, S9 3.95v, S10 4.1v, S11 3.95v, S12 3.79v. Seems ok, nothing a bestech D140 can’t charge.
Conclusion, faulty BMS because of -2v difference?
Anyone able to chime in on anything I might have missed?
PS, clear heatshrink is nice for visual confirmation of good connections.