In a well assembled car kit given suitable lighting conditions the solar cell supplies more than enough electricity to spin the wheels and propel the car.
A 100W bulb held closely to (but not touching) the collector side of the cell will power the car. Overhead projectors produce a strong enough light to test functioning of solar cell and motor connections. Again be carefull not to overheat the cell on the hot lamp.
Optimum performance is always achieved under natural lighting conditions when the cell can 'see' as much of the sky as possible (speeds attained outside will be higher than speeds on a window sill for example).
Diffuse sunlight from a cloudy sky will normally provide enough energy for the car to run. Remember that the Plugging into the Sun® cell is designed to respond to light scattered by cloud cover as well as sunshine.
If the model is released in bright direct sunlight and on a reasonably smooth surface you may have to run to keep up!
