Abstract: The electric potential output from a battery and generator assembly is monitored by three electric indicator circuits, one of which includes a first indicator which is activated to indicate excessively low battery voltage when the normally deactivated transistor switch in said circuit is activated by deactivation of a bias control transistor resulting from deactivation of a zener diode when the output voltage from the assembly drops below a predetermined minimum; a second indicator circuit of which includes a second indicator which is activated to indicate excessively low generator charging voltage when the normally activated transistor switch in parallel with said second indicator is deactivated by deactivation of a zener diode when the output voltage from the generator drops below a predetermined minimum; and a third alarm circuit of which includes a third indicator which is activated to indicate excessively high generator charging voltage when the normally deactivated transistor switch in said third circui