DIY Portable Solar Power Supply

I put together a basic portable solar power supply from a 20 watt solar panel, and 4 12v Batteries from Amazon. I thought I would turn summer camping out of the back of the Durango into summer glamping out of the back of the Durango. Hence the husky tool box battery housing, to make it portable.

The solar power supply also allows me to recharge headlamps, GPS units, range finders, cellphones, a laptop, and power lighting and speakers without worrying about depleting the car battery. In an emergency situation it could possibly be used to aid the starter battery of the Durango, or any other vehicle. It should make hunting season a little more enjoyable.

The 28 Amp solar system cost me just under 140 dollars, but in all fairness I already had wire on hand, as well as a 200 watt inverter I wasn’t using. Assuming you have to buy an inverter, it is still a small usable system you could build for less than 160 dollars. It would also be possible, to start with 2 batteries, and increase the number of batteries as funds permit, but 28 amps seemed like a good starting point. Other cheaper car batteries could probably be found if you look for a deal, or get something used.

Parts List:

Initial ‘Basic’ System Setup
I connected the solar cell to the charger
I connected the 4 batteries in parallel for a 12v system at 28AH
I wired a rocker switch for a solar charger cutoff, mounted it to the box
I connected the solar charger lead to the cutoff rocker switch
I wired another rocker switch from the battery bank, to the inverter and 12v output terminals

Power Output and Consumption
The battery bank initially was 28 amp hours at 12 volts, or 336 watts. Assuming we never deplete batteries to less than a 50% charge for battery health, we have 168 watts. Assuming a safer consumption to no less than 60%, we have 134.4 watts available.

A cell phone charger uses around 3-10 watts, a laptop charger uses about 45 watts, and an LED flood lamp uses about 10 watts. In theory, all those items could run for about 2 hours, before depleting 1/2 the battery bank.

Realistically, aside from the 10w LED lighting, most objects require very little time to fully recharge. Once recharged, the cellphone gets at least a full day or two if lightly used with wifi and bluetooth off. The laptop gives me about 3.75 to 4 hours on a full battery charge, which actually takes half and hour, or less, to charge.

Recharging The System
That amount of power consumed in the example usage above should only require less than 4 hours of full sun to recharge completely, because the solar charger outputs a 3 Amp charge rate at 12 volts, or 36 watts per hour. In 3.75 hours the system should produce the 134.4 watts required to replace the consumed power.

Upgrades
While the solar charger will handle overcharging, its inconvenient to monitor the battery bank for power. I have added a combo battery Amperage and Voltage meter for $13.80. I’ve included it in the links above. I also added a 10w LED flood lamp to the system, to light a camping area or back of a vehicle for another $9.79. I’ve also included links to that in the parts list above. I wired a 3rd switch for the 10w LED light, and bumped up the bank with a donated 12v 8amp hour battery.