Inefficient Charge
If the charge is inefficient after partly discharging, the electrode will be covered with a layer of lead sulfide, and the electrode plates that generate electrical energy are insulated from the electrolyte, which will make the chemical effect of producing electrode lower. In case there's a large number of discharging (such as the moment of engine startup), a great amount of current will damage the middle of the lead plate due to high thermal expansion of the lead sulfide plate. When the lead plate is damaged, the battery will be over as well.
Note: When driving, the generator of the vehicle has enough power to supply all the electrical devices on the car, and the balance is charged into the battery.
Lack of water
The water in the electrolyte will decompose to hydrogen and oxygen, and then vapor due to the chemical reaction when charging. Therefore, the moisture content will decrease in the battery. Check the moisture content once in every 2 weeks will be needed. If the moisture content is not enough, the sulfuric acid concentration will be too high, and erode the inner construction of the battery; on the other hand, due to the incomplete covered of electrode plate, the amount of current flow will also be reduced.
Impurities in the electrolyte
If you use tap water or groundwater instead of distilled water, the mineral content will invalid the chemical reaction in the battery.
Excessed charge
Excessed charge will lose great amount of water in the battery and make the electrolyte too thick. Over-concentrated electrolyte will erode and damage the lead plate. Excessed charge will also increase the temperature of the battery, the lead plate will be deformed and failure in the end.
