How to Build a Solar Battery Charger for Household Applications

Learning how to build a solar battery charger is an easy introduction to solar power generation. The free energy provided by the sun can be harnessed by inexpensive solar cells and stored in batteries for later use. These solar collectors are practical for charging batteries used in electronic gadgets, cell phones, car batteries and even larger RV and boat power storage systems.

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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.

Solar Charger for AA, AAA, C, D Batteries

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.

Solar Charger for Cell Phone & Camera 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.

Solar Charger for 12 V Car Batteries

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.

Solar Chargers for RV & Boat Power Storage Systems

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.

Safety First

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:

  • Trickle charger - These provide a constant charge whether the battery is fully charged or not. These should only be used for where the unit will be disconnected after a few days (i.e. AA/AAA, cell phone and car batteries). Leaving these continuously connected may boil the electrolyte or damage the plates within the battery.

  • Float charger - These have circuitry that will stop the charging once the battery has reached its maximum storage capacity. You never need to worry about 'over-charging' the battery.

  • Charge indicators - Most units have Light Emitting Diodes (LEDs) that indicate if the unit is charging or if the batteries are fully charged.

  • Weather-proofing - Not all solar battery rechargers are weather-tight, especially for small appliances. Check if the model is rated for outdoor use.

  • Size - The larger the solar cells, the more electrical power is produced. Buy a unit that will provide enough power that's still easy to handle and store.

  • Car battery charger - Look for units that come with a connector that can easily plug into the cigarette lighter.

  • Flexible versus solid solar cells - Flexible solar foil are convenient and easy to handle but produce less electricity than their solid counterparts. Determine if the practicality of a flexible unit more than justifies the lower power generation.

  • Mounting hardware - Larger units for boats & RVs need to be attached to the deck or roof so they can maximize the daylight hours. Look for units with light-weight, yet strong aluminum frames with mounting flanges that are compatible with the surface of your boat or RV.

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.