Solar powered street lights are full of electronics. The solar panel converts the sun's energy to dc electricity. Voltage is then regulated to a specific value by an electronic circuit to charge the battery. A solar controller protects the battery from too low and over charge. Now for the lighting. Contrary to LEDs, HID and CF lamps require a high voltage, particular current, and frequency to work. It is the ballast's task to feed the lamp properly. We now need to control the lamp. To do so, a timer or photocell does the job of switching the light from dusk to dawn. On some advanced solar powered street lights models, intensity and color can even be adjusted.