Abstract: A generator-battery DC power supply system comprises a plurality of sub-systems each including a battery and a temperature sensor sensing the temperature of the battery and controlling the generator regulating means to decrease the generator output voltage in response to an increase in the sensed battery temperature, to thereby prevent overheating of the battery by over-charging same. The system further includes a bus-tie-contactor for connecting the sub-systems in parallel, and control means effective to control all the generators in response to the highest-sensed temperature of any battery in the sub-systems. The illustrated system is particularly useful in electrical power supply systems on aircraft.