A power supply system for portable equipment has a lithium-ion secondary battery as a power supply, a temperature detection portion for detecting a temperature of the power supply, a voltage detection portion for detecting a voltage of the power supply, a memory portion, and a forced discharge portion. The memory portion stores a control operating temperature, a control operating voltage and a control termination voltage. The forced discharge portion recognizes an abnormality of the power supply when the temperature of the power supply is at least the control operating temperature and the voltage of the power supply is at least the control operating voltage. Then, the forced discharge portion electrifies the notification portion and makes it inform a message indicating that the abnormality is being avoided. The forced discharge portion forcedly discharges the power supply until the voltage of the power supply reaches the control termination voltage.