I recently purchased two remote control cars for my nephews from a dollar store. The cars came with three rechargeable AA batteries and also a cheap AC charger that connects to the car, but unfortunately grew hot when plugged in (a classic wall wart). So I’m giving them the cars with a solar panel and withholding the AC chargers. The best part is how easy it was to make it all work as I piggy-backed on the car’s built-in charging circuit.

In this case, I was lucky as the car’s AC charger was the same size as our panel, 3.5mm x 1.3mm. If it didn’t fit, it is quite easy to connect the panel to the circuit box and the circuit box to one of our 4 standard sized universal adapters.

There is a blocking diode in the circuit box, so using the circuit box will prevent charge from flowing backwards out of the battery. I’m giving this to youngsters so I wanted to make it as simple as possible and left it out.

On a bright day, I put 3 flat, rechargeable batteries in the car and connected the car to the panels. I pointed the panel at the sun for an hour and then ran the car for 15 minutes. Success.

A single 6 Volt, 1.5 Watt panel would charge all three batteries (700mah) in about 4.6 hours of direct sun.