Due to the constant charging voltage, the initial charging current is too large. With the constant voltage charging process, the electrolyte density and electromotive force of the battery will increase, and enter the end of charging period, the current’s GONNA get smaller. Its disadvantage is that when the battery is charged, the current is high, which easily causes the electrolyte inside the battery to heat up, which causes the internal temperature of the battery to change too much, and it is easy to cause the electrode plate of the battery to bend, if the input voltage value is reduced, the charging time will be longer and the storage battery can not be filled quickly, which will aggravate the aging of the storage battery and shorten its service life. Therefore, the constant voltage charging method