This paper proposes a design method how to realize a digital-high-power (DHP) lead-acid battery (LAB) charger. The main control unit P89LPC933 real-time collects the voltage and current of the charger. Then the unit sends out the control signal to pulse width modulator SG3525A, controlling the voltage and current. It co-operates the external circuit as well. This paper innovatively proposes 4-stage charging control method and strategy. This paper compares the typical chargers on the market with the one proposed by the authors in terms of horizontal and vertical dimension.