A motor that wants more current to drive its load than the panel can supply will pull the panel voltage down and reduce the power available to drive the car. The car will then run slower. Depending on the magnitude of the load, the panel voltage could be pulled to near zero and the panel “STALLED”. The panel and motor will stay in this state till the motor load is reduced or the panel produces sufficient current to get the motor moving again.
Increasing current will increase the torque produced on the motor shaft.) Conversely, if the load on the motor is low, it will not take all the current the panel is capable of producing and will not be using all the power available from the panel to drive the car. The car will be running slower than its potential. This is why it is critically important to match the motor load to the panel output. In real life this means that for a particular light level and car speed there is a gear ratio from motor to wheel that allows the use of all the power produced by the panel.
Consider a car running at exactly this power matched position: · an increase in light level means that more current is available from the panel at a very slightly higher voltage. The very small voltage increase will cause a very slight increase in car speed and air drag. However the majority of the extra current available has not been used. To use this extra available current we need either to increase the motor RPM which requires more voltage which we do not have or to increase the motor load by changing the drive ratio ie. a higher ratio.
If we do not change the gear ratio there will be more power available from the panel than is being used. This “available” extra power that is not being used is effectively wasted. If this extra power was used the car would go faster. · A decrease in light level or increase in load such as a head wind or climbing the hill will mean the motor will not have sufficient current available from the panel to provide the power required to drive the car.
The panel voltage will 35 drop causing the available power to drop. The car will then slow down or stop depending on the magnitude of load increase or light reduction. The car will remain in this condition until the panel output increases or the load is reduced. Changing drive ratio ie. a lower ratio will reduce the motor load and restore balance. This description above is for a motor connected directly to a solar panel.