# Solar R/C Car



## trailranger (Feb 9, 2006)

Just thought I would let all the electric roadies see my new project car.

This car is completely solar powered and drives in excess of 22mph(34kph). I built the car to the Solar R/C Cup rules.

Since Solar R/C Cup is not held in the U.S. I thought by posting my car others would be interested in competing Summer 2009 in the U.S. This would be a relatively cheap project for any High School, College or individual to take on. It took only 10 hours of build time for my car and my budget was under $400 for everything including the Castle ESC and Spektrum RX.

Video of my Car: More Video at my YouTube Channel 
http://www.youtube.com/watch?v=1GGUpOY7Li8

Vieo of 2006 Solar R/C Cup.
http://www.youtube.com/watch?v=WmVhK7cn8RQ


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## trailranger (Feb 9, 2006)

This is a photo of some Solar R/C cars like mine.


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## trailranger (Feb 9, 2006)

My car after first crash. I was doing sometesting and a strong gust of wind took the car airborne and flipped it over. The upper two cells were smashed when they landed on some gravel and others were slightly chipped. I did catch the flight on camera, and posted in on youtube.


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## trailranger (Feb 9, 2006)

http://www.instructables.com/id/Building_a_Solar_Powered_RC_car


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## jgullo53 (Jun 26, 2008)

if u could make them smaller, they would look cooler, but those dont look that bad! lots of time and effort im sure!!! looks good!


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## jgullo53 (Jun 26, 2008)

maxxgullo said:


> if u could make them smaller, they would look cooler, but those dont look that bad! lots of time and effort im sure!!! looks good!


i mean as in more to car scale that is, not just a flat top, like a whole body made of Solar Panels!!!! haha


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## Railroader (Jan 2, 2008)

This is a cool idea. What is your source for the solar cells?


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## trailranger (Feb 9, 2006)

I used Evergreen Solar cells made by the new Cheaper Ribbon Technology from Ebay Member Fred480V

New Toys to play with.

I just got a Maximum Power Point Tracker this last week, aka EasyMax III MPPT from Competition Electrioncs! To briefly explain the function of a MPPT is a Current Limiter with a Electronic Torque convertor. Solar panels have a narrow range which they will function at 100%. If the motor is not pulling enough amps, the solar panel is under ultilized, if the motor pulls too many amps the voltage will drop drastically and the total wattage is less

The MPPT first acts as a man in the middle and sets a barrier for the maximum load seen by the Solar Panel. In my case that would be 3amps on a summer day and 2 amps on a winters day. But all I need to do is hook up a calibration resistor and push the one-touch set button to automatically find the Power Point.

The motor is capible of pulling more than 3amps on take of, and if MPPT was not present the load would exceed max power point and the panel voltage would drop soo low the ESC and Radio would power off and I would loose control of the car untill the RX and ESC resetted. With R/C cars using batteries, normally excesssive amp loads do not bother the ESC or RX during brief hard accelerations. With Solar Panels the total power is very-very limited.

The second function of the MPPT is torque conversion by Voltage Conversion. When the MPPT sees that the motor is needing a load of 6amps, it will convert the Panel's power of 8.4V at 3A to a lower voltage but higher amps such as 4.2V at 6A. There is a normal 5% loss for the conversion. In terms of motors two things make the motor spin: KV and KT. KV is useless unless there is enough KT to spin the loaded motor. Since KT is based on AMPS and at low Speed more torqure is needed, it would be better to have more amps and less voltage than More voltage at the same power. The MPPT give the motor the AMPS needed for torque and increases the voltage once the car begins to move and less and less amps are needed to advance the motor.


I used my Eagle Tree Data recorder to measure the performance. Today being close to midwinter I did not have alot of sun to work with but the car still drives and looks good driving.

With just the Solar Panel the car averaged 9.68watts for driving manuvers of figure 8 and hard stops and go's. The car would studder for the first 10 feet from a standing start and studder a little comming of a corner.

With the CE MPPT installed the car average 11.15watts or 15% more power during the operation! The studdering disappeared, and the car was at least 50% faster for the first 3 feet of a standing start and about 30% faster for the first 10feet from a standing start or comming off a corner. Top Speeds were nearly the same, but the MPPT showed a marginal decrease of topspeed caused from the 5% loss in voltage conversion.


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## trailranger (Feb 9, 2006)

maxxgullo said:


> i mean as in more to car scale that is, not just a flat top, like a whole body made of Solar Panels!!!! haha


What is not to scale?










Looks to be 1/5 the size and shape of the Missouri Rolla Solar Car


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