Solar battery chargers are much smaller than the big solar panel installations used to power homes. The required power is much less and only one panel may be needed to generate enough electric current to recharge a battery. These systems operate on direct current (DC) and therefore no inverter is needed to generate 120V/240V alternating current (AC). With fewer inefficiencies to overcome and less equipment required, a solar battery charger is cheap to install and easy to maintain.
Many rechargeable battery companies offer a solar power recharger for their products. It incorporates a solar cell, a charger controller and a holder for the different battery types. These units come with small solar panels which usually takes a couple of days in direct sunlight to recharge an AAA battery.
If you would like to create a more powerful solar battery recharger, look for a unit with a cigarette lighter connector. These have a charge controller that can be directly connected to a larger solar panel that also has an appropriate connector. The higher the power rating on the solar panel, the more current it will supply thus speeding up the recharging process. With a 20W solar panel, it may take only 3-4 hours to charge AA & AAA batteries; and 7-8 hours for C & D batteries.
These lithium-ion batteries hold more energy and take longer to charge. You'll need a 12 V car charger for appropriate for your phone or camera battery, a charge controller and a larger solar panel of at least 20W, higher if possible. The charge controller is placed between the solar panel and the phone or battery and will disconnect the electric current when the battery is fully recharged.
When a car isn't used for a long period of time, the battery slowly discharges. A solar cell is practical for helping to maintain the charge. Select a solar panel with a power rating as high as possible that will conveniently rest in the windshield or hang on the window. Look for one that can easily be plugged into the cigarette lighter. These panels usually use a trickle charger but since the capacity of the battery is so large, there is little worry of overcharging. No charge controller is necessary.
Large solar battery rechargers are great for RVs & boats. The open roof or deck is fully exposed to the sun all day and can charge multiple batteries. Be sure to use a charge controller with a Maximum Power Point Tracking (MMPT) circuit that's placed between the solar panels and the batteries. Its current capacity should be able to handle the maximum amount of current from all of the panels. The MMPT circuit will optimize the voltage and current produced by the solar panels to maximize the battery recharging.
Look for solar panels that are weather-tight and have a light-weight and strong aluminum frame. The mount should be compatible with the surface of your boat or RV.
Never charge regular alkaline batteries in a solar charger. The battery may rupture, leak and could possible explode. Also, for boat & RV systems, check with the battery manufacturer to see if explosive hydrogen gas is vented when charging. Extra ventilation may be required.
Solar battery chargers are more than just novelty devices. They provide a reassuring power source when you're away from the electric grid and in times of emergencies. "Free energy" is available, and a solar battery charger is an inexpensive way to tap into it.
What to look for:
Knowing how to build a solar battery charger is a great way to contribute to the eco-friendly movement, while also enjoying the benefits of an alternate source of energy.