In certain transport aircraft, how are batteries kept charged if no DC generators are operating?

Batteries in certain transport aircraft can be charged when no DC generators are operating by using rectifiers connected to the aircraft's AC generators. These rectifiers convert the alternating current (AC) produced by the generators into direct current (DC), which is required for charging the batteries.

When the aircraft's AC generators are operating, they supply power to various systems and also have the capability to charge the batteries. The rectifiers ensure that the AC output is properly converted to a usable voltage and current for the battery system, thus maintaining the charge and functionality of the battery even when DC generators are not in use. This process is essential for ensuring reliable operation of electrical systems, especially in scenarios where continuous power availability is critical for safety and operational efficiency.

The other options do not accurately describe how the charging process occurs under these circumstances, as solar power and alternators do not typically play a direct role in charging the batteries in transport aircraft, and while inverters are used to convert DC to AC, they do not serve the purpose of charging batteries from AC sources.