Power supply providing longer lifespan of battery modules

A power supply providing longer lifespan of battery modules, comprising:

• a main power supply system which is electrically connected to an external power source and outputs a first power;
• a redundant power supply system including at least one battery module to receive and save the first power and output a second power parallel with the first power;
• and
• a state switch control module including a power supply switch unit to obtain a first electric potential of the first power and a second electric potential of the second power, and a state switch unit connected to the main power supply system to output a first signal and a second signal alternatively at a preset time interval to the main power supply system;
• wherein the power supply switch unit includes a first power supply state in which the state switch unit outputs the first signal to the main power supply system to output the first power to charge the battery module, and a second power supply state in which the state switch unit outputs the second signal to the main power supply system to stop outputting the first power to charge the battery module, and the battery module outputs the second power when the first electric potential is lower than the second electric potential.