Power panels typically put out a pulse of 12 volts for 1 millisecond then nothing for 9 to 10 milliseconds then repeats. This averages out to about 1.2 volts. If you use an oscilloscope you can see this pulse train. You must have a load on the unit to have it work. The pulse is usually generated by an LM555 set up as a pulse generator with its output driving either a power transistor or Power FET.