We were looking for a simple, inexpensive, but efficient way to keep our cell phone charged when outside. Whether you are using your GPS while camping, playing music while tailgating, or out hunting Pokemon (watch our video), your phone may be burning through it's battery. By plugging its car charger straight into a solar panel, you can easily keep the party going.
We didn't want to complicate the system or make it expensive by adding batteries, so this will only work when the solar panel is in the sunlight. Likewise, we didn't want to make the system so small it couldn't keep up with your power use, so we used a 10 Watt (W) 12 volt (V) solar panel. Smaller solar panels are available, but they may not output enough current to charge your battery.
By connecting a cigarette socket to the solar panel, you can easily use your existing car charger to send the correct 5V to charge the phone. A 10W solar panel can output up to 2 amps at 5V, that's plenty to keep you going all day long.
12V 10W solar panel - $39
Cigarette outlet - $3
18AWG wire - 2 wires - $0.54/ft (5' used)
Step 1: Connect Wire to Solar Panel
If your solar panel does not already have wire attached, you need to open the junction box (j-box) and connect 2 wires to the back. It should be labeled as + (plus) and - (minus). Generally red is used for + and black for -. The solar panel may have a way to crimp or solder right onto the terminals, or you may need to crimp lugs onto your wire to screw down.
Step 2: Wire the Cigarette Socket
Most cigarette sockets that I have used have a flat terminal to slide on a spade female disconnect. Crimp a disconnect on each wire. If the disconnect does not have insulation on it, we recommend you use heat shrink to prevent accidental shorting of the wires.
The middle terminal is the positive (+), connect the red wire to it. The outside terminal is the negative (-), connect the black wire to it.
Step 3: Test the Socket
Bring your solar panel outside in the sun. With your volt meter, measure the output of the socket. Put the red probe inside to the metal circle on the bottom, and put the black probe on the outer metal ring.
If you measure a negative number, like -20V, the system is wired backwards. Figure out if you wired it wrong on the solar panel or on the socket. If you measure a positive number, like 20V, you are done!
Step 4: Go Outside and Play.
You just need to plug your car charger into the socket, and your phone will start to charge. If you want to make it a bit more portable, you can attach it to a backpack or messenger bag to wear around.