This paper proposes a voltage clamping balance (VCB) method applied with battery power module (BPM) system. The VCB method, which indicates that battery balance is activated after the battery voltage reached its rated value, can save the cost of battery state of charge (SOC) estimation and increases system reliability while keeping the battery voltage in safe operating region. Otherwise, a VCB discharging experimental result shows that the proposed method can release more charge from battery than conventional discharging method in this paper. The proposed system composed of several BPMs and a system control circuit can provide energy as a DC voltage source in discharge mode, and can be charged by an external DC voltage source in charge mode. Meanwhile, the characteristics of BPM system such as high flexibility and capability of hot-swapping can be achieved by the proposed system. Finally, a 24-V LiFePO4 BPM system prototype containing 4 BPMs with 200-W power rating for each BPM is built to verify the feasibility of the proposed VCB method and the proposed BPM system.