Below are graphs of dynamometer test results. NOTE: All Sun levels referred to are based on full Sun in December here in Melbourne NOT AM 1.5 which will be the 100% Sun level used in futurities. Feb 2010 onwards.
The tests were conducted with a Faulhaber 2232 6 volt motor powered by a Solarex SX 10 panel configured either with all cells in series, 2 lots of 2 strings of cells in series then paralleled and 4 strings of cells in series paralleled. These configurations giving exactly the same power but at different voltage and current levels.
Examination of these graphs shows the narrow RPM band we must work within to stay near maximum power when electronics is not used. Other interesting and important observations:
- Solar panel configuration ie. voltage and current available to the motor can have a significant effect on maximum power output available from the motor. (Up to about a 35% variation)
- The power output of the motor when an electronics unit is used is always greater than the power output without electronics. Do remember an electronics unit will probably make a poorly constructed car move. But it will NEVER turn this car into a winner.
There are several electronics units on the market produced specifically for use in model solar cars. They all operate by switching power to the load (the motor in this case) on and off rapidly to maintain the solar panel output voltage within a narrow pre-selected range, around the maximum power point voltage. Generally you must select the required voltage and adjust the circuit to operate at this selected voltage.