For what purpose does the storage battery on each passenger subway car supply power?

The purpose of the storage battery on each passenger subway car indeed encompasses various functions, but its primary role is to ensure the operation of critical systems when the main power supply is unavailable. One essential function of the storage battery is to supply power for emergency systems, which include tail lights. Tail lights are crucial for safety, particularly when a subway car is stopped in a tunnel or station and needs to be visible to other trains. Ensuring that tail lights are operational helps prevent accidents and enhances the safety of all passengers and crew on board.

While interior lighting, heating systems, and air conditioning units are important for passenger comfort and safety, these systems typically rely on the main power supply during normal operations. In the event of a power failure, the storage battery primarily activates emergency systems such as tail lights to maintain visibility and safety standards.