The service life of ordinary car batteries is usually about two years. The life span of maintenance free vehicle batteries is twice that of ordinary batteries. But in real life, car batteries can not be used to design life expectancy. There are many reasons for the damage of the battery, such as excessive discharge, long storage without charge, no electrolyte or electrolyte, too high, polluted by dirt, and so on. Now the author makes an analysis on some common reasons. I hope that it is helpful for us to maintain the car battery correctly.