For high-power applications such as electric motorcycles, batteries in series to provide the required voltage is fairly common. The 48V is 12V connected four cells in series for lead-acid batteries of electric motorcycles. After charging and discharging of lead-acid batteries several times, the voltages are often imbalance. Without proper protection, may cause an excessive discharge of lead-acid batteries for early damage. Therefore, lead-acid battery module requires a simple balance circuit to improve battery life in order to avoid over-voltage or under-voltage condition occurs. Energy balance circuit to improve lead-acid battery module matching problems, make the safety and cycle life of lead-acid batteries to improve. This research intends to complete balanced circuit design of lead-acid batteries.