A power system for managing charging, discharging and protection of rechargeable batteries is disclosed. The power system mainly includes a power system. The power system includes a switching circuit coupled to the rechargeable batteries to charge and discharge the rechargeable batteries. The power system includes a power management unit to control the switching circuit. The power system includes a temperature sensing circuit to monitor a temperature of the batteries, voltage detectors to monitor voltages of the batteries, and current detectors to monitor a current of the batteries. If an abnormal condition is sensed by the power management unit when the power system is in an operating mode, the power management unit will terminate the operating mode by switching off the switching circuit to protect the batteries and the power system.