julian0706

So I've been trying to make a solar powered RC car but the car battery itself is having issues being charged by the solar panel. Even with the regulation of a charge controller, the battery will not charge to its optimal voltage. The battery, the charged controller(PWM), and the solar panels(12V-130mA) are all connected together by alligator clips and the charged controller picks up the battery and emits a light indicator showing the type of battery it is. All the parts are put outside together and the light indicator of the charge controls goes off, signifying that the battery is charging. After 3 hours of charging the battery is unplugged and tested in the car and then only seconds to a minute of charge is performed every time I do this method. Then I use a multi-meter to check the voltage of the battery and it is slightly over the maximum capacity the battery should hold, which is 7.4V and the multi-meter shows it has 8V. So it doesn't make sense how the battery doesn't even power the car for more than a minute when it is over the capacity, which should be more than enough to drive the car for an hour or more. What should I do?

Big Alice

At 130ma it's going to take a long time to fully charge a battery of any real size. That's a trickle charge rate. 3 hrs at 130ma is like buying a dollar's worth of gas in your car. Not going to last long. How many ma does the battery hold? You can figure out how long it will take to fully charge if you know the charge rate (130ma) and the battery volume.

julian0706

The battery is an Li-polymer 7.4v, and 850mAh, and 6.30Wh battery. How do i figure out the charge rate and the battery's volume?

Big Alice

Battery volume is 850mah. Charge rate is 130mah. Divide the charge rate into the volume. Should need a little over 6 1/2 hrs to charge fully. 130 mah is pretty much an overnight charge rate.

Big Alice

If you're trying to run an electric car on a 850 ma battery, you're never going to get more than a couple minutes of run time anyway. Depends on how much the car weighs and how big the motor is and the surface you're running on. Your battery is way too small. Of course a bigger battery will take longer to charge at 130ma. You'd have to charge several days to fill a car size battery. About 38.5 hrs for a 5000ma car battery.

julian0706

Hey Big Alice, I am referring back to you about the solar powered RC car problem and would like to tell you what ive done so far after. I have tried to to first use the original charger for the RC battery and charge it for 20 min through regular charge and then using the 130ma solar panel to charge for approximately 7 hours. Then we run the battery and compare each time to the amount of time it takes for the battery to be drained.

julian0706

Hey Big Alice, I wanted to ask you a question because after charging the battery with the solar panel and regulating it with the charged controller, I've gotten less run time on the car and I have a theory that the charged controller could possibly be draining the battery slowly while the solar panel charges it. The solar panel isn't strong enough to charge the battery while its being drained so that could be why my tests could be coming back with less and less time. So I charged the battery without the charged controller one time, and the results were off the chart, the battery ended up lasting almost double the amount of time it did with the charge controller regulating the voltage. So is it possible that the charge controller could be draining the battery slightly from the light indicators that are lit up to signify when the battery is being charged?

Big Alice

How many volts does your solar panel put out.? 130ma is a pretty small volume and the leds would certainly use a part of that. You have a pretty cool idea going there. I hope you get it figured out.

julian0706

My solar panel puts out 12V, and yes, I thought that the leds would use some of the volts somehow. Thank you for your support, you have been helping me out a lot.