Why there is no over-charge protection with your Battery ?
A. Insufficient battery power with the customer’s multimeter which leads to a large value measured by the multimeter. After fully charged with multimeter battery, the actual test value with each series single cell is the normal 4.20V, but the multimeter shows 4.30V or bigger. The customer mistakenly believes that the battery is overcharged without protection.
B. Check if the welding position of C- wire is correct or not. If the B- and C-wires are welded reversely, the protection board has no charge-discharge protection function; and also when user solder the C- wire to the P- position ,there will be no charge protection function.
C. The charger is abnormal. A damaged charger may deliver a high voltage of above 100V, which caused the damage against the BMS and resulted in overcharge of the battery.
D. The charging MOS tube on the BMS was damaged (the resistance between C- and P- after disconnected the BMS with Battery , if its resistance is infinite with unit of M above ,it means the charge Mosfet is OK and normal; but it shows value with unit of Ω and K,it means the MOS tubes was broken). The common reasons for the damage of the charging MOS of the BMS are: 1. The charger, especially the high-power charging cabinet, it still deliver a high voltage while the BMS starts over-chare protection function, which will shock the charge Mosfet and let it broken; 2. The current is greater than the maximum current that the protection board charging MOS can withstand. The charging MOS is overheated and damaged. For example, the BMS with different charge and discharge port which can bear a maximum charging current of 5A and a maximum discharge current of 15A. If the customer connects the BMS as the BMS with the same port, the charging MOS will bear 15A when the BMS discharge at 15A current.