For my high school engineering course I have to make a project that involves solar panels. I have chosen to convert an RC car to recharge the battery while driving with solar panels, because I realize it wouldn't be possible to fully power the car with solar. Now I need help on the circuit. The car has a 6 volt 700 mAh Nickel Cadmium battery, meaning it is five 1.2V cells in series. This battery of course powers the DC motor - of which I do not know the power consumption etc. Now my question is how exactly I should make the circuit to charge the battery while in use. I have already purchased three 2V, 240mA solar panels, which I planned to place in series to meet the voltage of the battery and thus be able to fully charge it.
My plan is to place wiring from the negative terminal of the battery to the negative terminal of the solar cell array (the 3 in series), and from the positive terminal to the positive terminal, this would be parallel. Would I need to place a diode in between either of the poles? And would this diode mean I need a greater voltage than the 6 volt of the battery? Also, is this a dangerous thing to do, should I use charge controller such as http://www.maximintegrated.com/datasheet/index.mvp/id/1666.
Also, if I do this, would I be charging the battery while it is being discharged, or does the current from the solar panels go straight to the DC motor, with additional current being pulled from the battery?