The invention provides a method for power management for a computer system. In one embodiment, the computer system comprises a system controller, a chipset, and a battery coupled to the chipset via a system management bus. First, a timer of the chipset is used to calculate an accumulated time value. When the accumulated time value exceeds a threshold value, the chipset is directed to send a system control interrupt to the system controller. After the system controller receives the system control interrupt, the system controller is triggered to detect a power level supplied by the battery via the system management bus.