It is on! I am going to build R/C car. I just graduated and earned my degree, I have some spare time to play with toys. My first solar R/C was built to the French Solar R/C Cup rules and I would say my car was phenominal for speed, handeling and acceleration. But I am not content. The size of the solar car makes it very much a sail in high winds. My car has gotten air several times and broke some cells. Also, the car does not have a battery. I know the Solar Cup wants to focus on proving solar works without backup systems. I want to focus on having a smaller working system that uses solar just at much as maximizing efficency for 1 hour of endurance racing. My goal was to have a 1/10 to 1/8 sized car so that it will look at place on a r/c track.

So after some thinking I decided to make a car based on some simple rules.
No Min weight limit.
Max Solar Array: 1000cm^2
Max Battery Weight: 100g battery alone or 125g with onboard battery protection/charger modual.

I will continue the old design of using foam for the chassis and attaching Assoicated style pan car parts to it. This design has shown me great handling along with durabilty form crashes. The solar cells are no longer 3x6" becuase they were very fragile on my car as I did not case the cells in glass. I went with 2x3" sized cells to reduce the size of the cells for the smaller panel size so that my voltage will be higher (13V) I will back each cell with 1.5mm foam sheet before gluing to the top of the car. This should keep the cells from flexing as much and allow for easier replacement of damaged cells. I plan on doing another www.instructable.com again but with better detail in the steps so that anyone can make a fast solar car. So now that UPS has arrived with my parts, and cells the build is on!!!

This sounds like an awesome project.

I might sponsor you and send you a low power FATMAX mppt for use on your new car. The FATMAX handles up to 200watts, ill give you one that's up to 40 watts but half the weight.

What cells and voltage are you using?? i think its better to go higher voltage, the let the tracker reduce the voltage and boost the current, to match your battery charge voltage, and you panel will always be on its maximum power point. The FATMAX is a automatic continuous tracking mppt.

i'll be using Evergreen solar cells. The cells are 3x6, but they were lazer cut to be 3x2. Each cell should put out 1.2A at .5, .55V oc. No luck on getting any triple or double junction cells.

Since my panel will only be 15w, i do not think a 200w version will be needed. The battery is a 1300mah 11.1V LiPO rated at 25C which should help with charging. I'll have to wire the LiPO to a PC board that balances and prevents over and under discharge of the cells.

I am worried about the diode and the voltage drop. My array will be a nice 5 x 5 cell array for a total of 25cells. I know I am cutting it close on voltage, but if need be I'll add 2 or 3 more cells and just use painters tape to mask off a little of each cell to have an effective 1000cm^2 panel. I would hate to cheat my self.

Ill send you a Low Power FATMAX, 40 watts, it will work from anything above 8 volts. You don't need a diode for the fatmax whilst charging batteries, unlike the smaller Easymax.

hi, i m building a rc solar powered car too..
my choice of rc car is 1:10 but i havent buy it yet.
i m planning to use a 12V 180mA laminated solar panel to charge a 12V 1.2Ahbattery.
the charge controller is controlled using microcontroller
but i afraid the solar panel does not have enough current to charge the battery or it have to charge for long time to fully charged. do i need a buck converter to connect the motor between the battery? coz the rc car uses a 9.6V rating..
i m quite confuse..

Nah you dont need a BUCK converter.
Your panel voltage will drop to match the 9.6v battery.

If your planning to use a 12v battery, you can just just connect it straight in, without a BUCK, as a fully charged 9.6v battery usually exceeds 12volts anyways, and then later the voltage drops to 9.6volts.