FAQ: The capacity of the pack after the initial charging and assembly

Question: I have made the initial charge of the battery pack to full voltage level and installed the BMS123. Why is the BMS123 software showing the capacity left only at 62%? I think the capacity should be some 95% or perhaps 100%. 

Answer: The BMS does not estimate SOC (State of Charge) by the total voltage of the pack, because this method is very imprecise for LiFePO4 cells. The BMS counts +Ah when charging and decreases -Ah when discharging. To calibrate the capacity meter you must perform at least one full cycle from the full charge to the full discharge. (Provided you have made the correct settings of the BMS values.) Please take in mind  that during the first few cycles the capacity meter will be more precise with every cycle.

The initial installation procedure should be in these steps:  1) make the initial charge of the cells (one-by-one to the full voltage), 2) assemble the pack with the BMS, 3) when your system is working, make the full discharge and full charge cycle. This way you can also 4) verify the proper function of the BMS including the deep discharge voltage levels and full charge levels warnings.