Answer: Although the lead-acid battery has been strictly selected when it leaves the factory, after a certain period of use, the non-uniformity will appear and gradually increase. The charger does not have option and recognition, and can not supplement the undercharge Restricting the amount of overcharge and how to balance the battery capacity must be performed by humans. The user measures the open circuit voltage of each battery periodically and irregularly during the middle and late periods of battery pack use. For lower voltages, recharge separately to make the voltage and capacity consistent with other batteries, and try to reduce their gap.