Originally Posted by kavadni
DC-DC step up circuitry disguised - mounted in a Power Cap.
Sssh this is very secret stuff.
Using a Maximum Power Point Tracker (MPPT) that has a built in DC-DC step/up or down converter will give the most performance.
My Solar R/C Car uses a MPPT and it is well worth 3 seconds a lap over just strait solar panel connection. This technology could be applied to regular R/C Cars.
It may be a complicated thing to explain, but I will try.
Solar Panels have a very narrow Maximum Power Point. The maximum power point is pretty much this. Any load less than that point and the solar panels are not being fully used. Any load higher than that point voltage drop will be so great that the actual power is less. The Maximum Power piont could be also called a point of diminishing returns for total power output. Batteries also have a Maximup Power Point. This is why some batteries are rated 10C, 20C and even 28C. When the load becomes so great the battery simply fails to produce as much total power as with a lighter load. The higher the MPP, the better the punch is for a battery.
My solar panel in 100% insolation (100% sunlight) can produce 9.9V without a load and a maximum dead short load of 3.6A. The problem is that at 3.6A my voltage is only 3V or about 10watts total power. This radical reduction in voltage and power normally happens when I give the car hard acceleration and my radio and esc will then turn off from lack of voltage.
According to test, my MPP for my solar panel is 3amps and the voltage is 8.4V producing 25 watts. 25 watts is 250% more power than 10watts at a dead short. With out the use of a MPPT, I have to gently apply throttle to the car to keep the amps under 3 or the car will stall and the Radio System will turn off from not enough voltage.
With a MPPT I can apply full throttle and no matter how great the load, the MPPT will always keep the load seen by the solar panel at 3amps. The added bonus to the MPPT is DC-DC conversion. The MPPT senses the increased load and coverts my 8.4V @ 3A into 2V @ 12A during the hard start to get the car to accelerate faster than without the MPPT. As the load decreases the MPPT is constantly bringing the voltage up to increase the motor speed.
Some of the older brushed ESC's had a simple version of a MPPT. The manufactures called this traction/punch control. Back in the day when batteries were only 1500 to 1800 preventing wasted current was a sure way to be the fastest and last man going at the end of a race. The punch control didn't use complicated algorithms to solve where the MPPT was, it just use a dial potentiometer to adjust the max current. The punch control was pretty much set by trail and error by the racer. On my MPPT I just hook some resistors and push the set button. After about 2 seconds, the power source is mapped and the MPPT point is chosen. Now days punch control is really only used when traction is an issue, not because batteries will dump. Two weeks ago, I entered a 500lap run-till it stops enduro. I I used punch control to limit wasted current and yes it worked as I and one other racer were able to complete over 400 laps before our 4-cell 4600's dumped.