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The Solar Powered Camper

Since we're staying on site to keep an eye on things during house construction, we set up a solar battery charger to charge the camper's battery that is used for water pumping and lights. We also use a small inverter to produce 110 volts AC in order to power the laptops and charge batteries for phones, cameras, cordless drills etc. As I write this my laptop is powered entirely by the sun! It's not very efficient to convert the 12-14 volts DC from the solar panel and battery up to 110 volts AC with the inverter, and then convert it back down to DC with the laptop's power supply. But it's easy and it works.

The first photo below shows our 75 watt Siemens solar panel, and the second photo shows the charge controller that protects the battery from overcharging. The meters indicate a battery voltage of 12.5 volts with a charge rate of 4 amps, which means it's delivering 50 watts of power to the battery and/or inverter. We'd like to deliver 75 watts from a 75-watt solar panel, but the panel itself may not produce a full 75 watts except under ideal conditions, and we lose some power in the 75-foot wire run from the panel back to the charge controller. We could reduce these losses somewhat by using thicker wire and by reducing the distance from the panel to the battery, and by using a more sophisticated charge controller that can maximize the amount of power produced by the panel, but the system is already delivering more energy than we are using on a daily basis - at least on a sunny day.