What is battery power used for on subway cars?

Battery power on subway cars is primarily used for supplying energy to the emergency lights. This function is critical for ensuring passenger safety during situations where primary power sources may fail, such as during outages or emergencies. Emergency lights are essential for illuminating the interior of the train and evacuation routes, helping passengers navigate safely in the event of an incident.

In contrast, operating the main engine typically relies on other power sources, such as overhead electrification or third rail systems, which are designed for traction power rather than battery supply. The car's computer system is usually powered through the main power supply, not directly from the battery. Heating the passenger compartment is generally achieved through dedicated electric heating systems that operate off the main power, rather than from battery power.