In a charging system, external AC power is converted into direct current suitable for battery storage, and related components and circuit systems are charged at a slower rate. The charging power of slow charging modules is relatively small, generally 3.5kW or 7kW, long charging time, suitable for charging at night or when parking for a long time; And slow charging usually uses the trough electricity price at night to charge, and the cost of equipment is relatively low, so the charging cost is low; The slow charging process has a small current, less heat generated, less damage to the battery, and is equipped with perfect safety protection mechanisms, such as leakage protection, overvoltage protection, etc., which is safer.