1. Inadequate first charging or long interruption time of charging;
2. No sufficient charging for long time;
3. No timely recharging after discharge;
4. Often excessive charging or deep discharge with small current;
5. Electrolyte density or temperature is too high so that lead sulfate will form and hard to decompose.
6. Lay the battery aside for a long time and without any regular charging;
7. Electrolyte is not pure and large self-discharge;
8. Internal short-circuit or leakage of electricity caused by the water on the surface of battery.
9. Barely plate partially sulfated because of low Level of internal electrolyte liquid surface.