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The panel I bought at SunDanceSolar is a little stronger than the stock battery (1.2 Volts @ 130 mAh). The Battery in my Zip Zap is 1.2 Volts @ 100mAh.
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I'm still not sure it would work. Two of them wired in series might. This way, you have higher voltage to push that current to the motor. The problem is that the circuit gets very power hungry under load. This load increases dramatically when the motor first starts to turn. A current of well over 100mA is required to begin the motor turning. Once you are rolling the current requirements are much less. The solution? Double the VDC, or double the running current. And, in truth, both should be done to maintain high power levels at all loads. Forget the specs of the stock battery. Solar applications are very different from battery applications. Allowing for the same specs for solar that the battery provides simply won't work. Two of your cells might do it, it may take three. This, of course, pushes up the weight factor of the solar cells which in turn increases the start up load. You end up in an endless cycle that will produce a stalemate. The answer is to provide the maximum power per weight. No matter how you slice it, this translates into very expensive solar cells. The idea is to measure the motor load under stall conditions. That is, hold the forward control while you have the car against an immovable object. You will find that the current consuption is extremely high under these conditions. I think Namuna has some figures on this somewhere on this forum. And, also keep in mind this is very dependant on which motor you use as well. This is the starting point for your required current. Now, factor in the required VDC to pump this current to the motor under load and you have a working solar car. Of course, there are other considerations. A buffer capacitor would be needed to keep the car moving when clouds come over or if you accidently run into a shady spot. This is an easy one though and is the least of the problems incurred here.