A. check whether the C-wire welding position is correct, B- and C-wire welding is reversed, then the protection board does not have charge and discharge protection function.

B. the full sub-port architecture and charging end can discharge the protection board, in the charging end of the discharge is no discharge protection.

C. the protection board discharge MOS tube breakdown (protection board power down to measure the resistance between B- and P-, if it is infinity, M above is OK normal, Ω and K is MOS tube is bad). Protection board discharge MOS damage common causes are: 1, the load, especially high-power discharge cabinet in the protection board discharge protection moment P + P- have negative high voltage (P- terminal than P + terminal voltage tens of volts) lead to discharge MOS high voltage breakdown; 2, the current is greater than the protection board discharge MOS can withstand the maximum current leads to discharge MOS overheating damage.

D. the protection board discharge protection control circuit or discharge MOS driver circuit damage.