Which component recharges the battery when the engines are running?

• A. Battery
• B. EPU
• C. Generator
• D. Starter generator

Answer: (D)

The device that recharges the battery while the engines are running is the starter-generator. It’s built to do two jobs with one unit: it acts as a motor to crank the engine during start-up, and once the engine is turning, it switches to generating electricity to power the electrical system and charge the battery. This dual role means the battery is kept charged by the same component that's turning the engine. The Emergency Power Unit provides power only in emergencies, not during normal operation. A separate generator could charge the battery, but in this setup the component designed to both start the engine and recharge the battery while running is the starter-generator.