A single solar panel unit can keep a car battery topped off or even recharge a dead battery. Some solar auto battery chargers are designed to keep a battery at full power at all times. This type of solar panel battery charger is especially useful on vehicles that are seldom used, but it can also prolong the life of any auto battery. Apply a higher power solar automotive battery charger to a dead or weak car battery to recharge it. Once the recharge is complete, remove the charger to prevent overcharge or damage to the car battery.

A solar car battery charger designed for constant use will not exceed a 14 volt charge, nor will it produce enough amperes to damage your car battery. The higher power models come with a volt meter. When the readout approaches 14 volts, remove the solar powered battery charger.

Here are a few points that answer some common questions:

1. Solar power chargers are generally not as fast as other types.

2. Most models are weatherproof and durable. Even low quality solar chargers will last at least 3 years, and high quality units can last up to 25 and still deliver the power.

3. Solar chargers require little maintenance; they usually require a periodic cleaning.

Action Steps
The best contacts and resources to help you get it done

Shop legitimate sources for solar car battery chargers

Innovative experimentation continues, but manufacturing a basic, portable solar battery charger is relatively simple. Pay special attention to the company you are buying from to ensure you get a solar power battery charger made with quality parts and that does what it is supposed to do.

I recommend: The Solar Maintainer from BatteryStuff.com is a good way to go for a nice, cheap constant-use model. They also have some high power models, and will even place special orders for their customers. BatteryMart.com is another safe way to go.

Have realistic expectations of your solar car battery charger

Don't expect to boost up a dead battery in a matter of moments. A 15 watt solar auto battery charger will produce 1 amp-hour when placed in direct sunlight. Overcast conditions can further slow things down. Since solar battery chargers are not always expedient, and because high power models can potentially damage a car battery, the low power constant-use solar battery chargers are used most frequently. In the case of battery maintenance and storage, speed is not of the essence. In terms of recharging, a portable solar battery charger is useful, but not a cure-all.

I recommend: Keep up on this changing industry by viewing products from companies like Silicon Solar Inc. and 21st Century Goods.

Build your own solar powered battery charger

If you're feeling adventurous, try building your own solar battery charger. Pay close attention to your personal safety and avoid damage to your car battery. Check the amp-hour rating from the manufacturer so you can be sure you don't charge the battery too fast.

I recommend: The directions for building a solar AA battery charger on the Instructables website is a tame place to start. The exercise is useful and serves as a tutorial on basic concepts. A second article on the same site introduces you to possibilities for car applications. This includes includes a charge controller, which prevents overcharge and discharge. National Solar Supply is a great source for charge controllers and other components.

Tips & Tactics

Helpful advice for making the most of this Guide

• •  Put solar panels in series to achieve higher voltage ratings. For instance, 2 12 V chargers in series can fully charge a 24 V battery.
• •  Some solar battery chargers include inverters that change a 12VDC to 110VAC, for instance. Keep in mind that inverters eat up a lot of power, lowering the efficiency of your charger. Avoid them if you can.