SpeedFreak wrote:Are you just gonna slap the solar panel straight onto the chassis of that car?

Yes, the solar panel has a perfect length and width to sit directly on top of the unmodified chassis. the only problem i have is getting the motor to mount in because the screw holes have different spacing. but im thinking of changing motors anyways to maybe a hacker b20-15l which i think is more efficient and also lighter. However, this motor will also require a modified motor mount.

Brightwhite, your suggestion for the use of a rc10l3 was great, i can see that it has a very low friction drive train, and the chassis is easy to work with.

TonyB wrote:problem i have is getting the motor to mount in because the screw holes have different spacing.

I used the included motor mounting cross plate. Attached the crossplate to the motor using the 16mm spaced holes. Attached the plate to the car running one screw through the POD plate, Cross Plate into the Motor at a 19mm spaced hole. Using a Nut and 3mm Bolt attach one of the cross plate tabs to the POD.

brightwhite im going to have to make my own mounting plate in order to get the motor to mount properly.
Also i have a problem with the gears, i got a new motor and its only got a 2.3mm shaft, so i need to make an adaptper to convert the gear from 2.3mm to 1/8th which is the standard gear size.

I had problems locating pinions for 2mm and 2.3mm shafts. I did find that Venom makes 9T~20T pinions in .4 and .5 MOD which I think is 64 and 48P.

Because of the pinion problem I just went with the smallest Outrunner motor with 1/8" shaft. I found that the AXI 2204 and the 2208 motors would work, the 2204 has only a 9mm long shfat and the 2208 has a 12mm.

I Ended up getting the Orion Breeze which looks like the Axi 2004 but with an 12mm shaft and lower KV.

I bought spares of the Orion motors, but with my luck the post office lost the package.

Hey could you send me the link where you found the 2mm and 2.3mm gears from venom. i cant seem to find any and ive been searching for days.

Tower Hobbies 2.3mm and 2mm
http://www3.towerhobbies.com/cgi-bin/WT ... =CLC&V=VNR

List of places to find pinions
http://www.rcgroups.com/forums/showpost ... tcount=134

Hyperion Pinions
http://www.aircraft-world.com/shopexd.asp?id=2877

One more...Not Pinions but Top Speed Esitimator. I used this along with an excel spreadsheet that calculated resistance to predict my max speed based on my motor selection.

http://www.scriptasylum.com/rc_speed/_top_speed.html

Great thanks brightwhite.
I currently have a 64pitch spur, is that .4mod or .5mod?

i believe .4mod is 64p

hey thanks for those links they are great. im gonna order some pinions tonight, i need them asap, they are currently the limiting factor in my build.

im gonna have a mess around with that speed estimator, ill update you.

I played around with the MPPT today. Sunny and 52F or 11C today. Just under 55 days to my midwinter.

My panel was acting kinda wimpy with only about 12watts peak.

I did two back to back test MPPT and without then repeated.
According my data recorder the MPPT averaged 11.15watts and without average 9.68watts. A 15% in crease of total power delivered!

I didn't have my lovely assitant wife with me to record or stopwatch but from what I saw, the MPPT at least 50% more power for the 1st meter, and about 30% speed for the first 3m. After the car was up to speed it was hard to tell. When I turned the car the MPPT kept the speed constant while without the car bogged down and was slow comming off the corner.

The overall top speed went to without the MPPT by the slimist margin but I could tell there was a slight reduction in top speed.
Conclusion, The MPPT will give any solar r/c the holeshot corner after corner and racing is not about top speed it is about corner speed!

Tony I want to do a load test with the MPPT to catch it on the data recorder then do a comparison test without. How should I size the reistor? A few watts bigger than the panel's current peak wattage? Or Should I get a POT and increase the resistor value by hand?

If you have a 30 watt panel i suggest you get 2 x 2ohm, 10 watt resistors and connect them in parallel to give you an effective 1ohm @ 20 watts.

You can use larger Ohm resistors if you like but if the ohmage is too large you wont get all the power coming through from your panel because its only 10 volts or so.

Brightwhite, make sure your solar panel is already warm before you set the mppt.

Because as your solar panel heats up, your solar panels maximum power point voltage will change drop, and the mppt will then be regulating with an incorrect reference, and you wont be getting as much power as you could be getting.

By the looks of it, your car is using naked solar cells. Naked cells have are very light, thus, have very small heat capacity and their temperatures can vary steeply with fluctuations in sunlight. Best to set the mppt with race conditions.

Over here our races only go for 100 meters, and usually take around 16 - 20 seconds to complete. We set the mppt before the race because the mpp (maximum power point wont fluctuate much in 16 seconds). However, if the races were to go for any longer than 30 seconds like i mentioned above.

Heres a pic of our track and some cars.

Tony, I'm having problems finding the resistors under 1ohm or 10ohm in the wattage i need.

Could I just use some 5, 6, 10, 15 watt light bulbs as a resistor load?


Also, I read somewhere that silicon cells should be allowed to be exposed to sunlight for at least 5 min before a load is attached. It was to allow the crystals to align and increase performance. If that was the case, should I build a light box to zapp my un used cells to find that extra 1%. Then along with zapping, I have NiMH/ NiCD battery zapper that can zap batteries from 0~90V (unknow capacity). Could that be used to help push the limits of the cell. The results are positive with batteries by "electropolishing" the medium to limit areas where the battery may self leak. I thought it could be helpful along with the light box to mend and align the crystal lattice

Hi brightwight,

you could just use a 0.5 - 1 ohm 5 - 10 watt resistor of any type.

If you cant find that, just use a long thin wire. maybe a 22-28 gauge wire around 1 meter long.
(same as the wire you get on your mobile phone chargers)

I was looking through my R/C junk and found some discharge trays that have 12 .47 10W resistor each so I can be in business.

Hi, I came across this thread and found it pretty interesting. I am entering a solar rc competition at work for fun and found some of the information on this thread very useful. I was wondering how your projects came out. I think that I saw brightwhite's on instructables. How did yours come out Tony? I am curious how your motor choice paired up with your smaller solar panel. I am working within a 14 inch x 24 inch size restriction so I can only get about 14 3x6 panels for a total of 7.7v at 3.6 amps peak. The panels I am considering are here: http://www.quadmodsusa.com/solarcells.html I am working on selecting a motor and speed control. I was also given 4 AA rechargable batteries to use and I am trying to figure out how to work them into the mix. I could just use them to power my receiver and servos and let the solar run the motor. At this point I haven't figured out a way to use the batteries in parallel with the solar to run the motor although that would probably be ideal. We are not allowed to use arrays of caps like you did Tony but that looked really cool. I am open to suggestions and I am interested to learn more about your results. Thanks, Chris

Hew SolarGuy,

The solar cells from the link are the same solar cells that I used. They have great output and light weight but are very very fragile. The 3x6 cells are only 8g each and are made from a single crystal drawn from a vat of sillicon much like pulling a film of soap when blowing bubbles. In the case of the silicone, the film crystalizes once a distance from vat. This is a cheaper and faster process than creating a massive silicon crystal and then cutting waffers to make the cells from.

For the 4AA batteries you will need 3 cells in series for each AA battery in series. The panel will need to be sperated by a diode to prevent the panel from discharging the battery in low light conditions. The average working voltage of a NiMH or NiCD battery is 1.2V, the peak voltage is 1.45. The O.C voltage of three solar cells in series would be 1.65 well within the tolerance of the batteries since the extra .2V would never be reached if the solar car is in use or the cells are not fully charged. Depending on the quality of the batteries and the load from the motor, the acutal voltage of the battery under load will be 1.3 to 1.4V on a charged battery.

On your car, 12 cells should be enough to keep everything going and adding the 13th or 14th cell in series may also be helpful in keeping the battery voltage closer to the max power point of the solar cells under load. I would not recomend letting the 14cell panel overchage the batteries by prolonged exposure of no load. Once the batteries are peaked, cover or disconnect the batteries when the car is not in use.