A 12 volt solar charger is surprisingly easy to build and will help you save money, reduce pollution and reduce dependence on foreign oil. This article will talk about the different kinds of solar battery chargers, which type is best and even how to build your own.
The simplest battery charger is just a power supply that sends electricity of the correct voltage to a battery. You can connect battery to the power supply until the battery is fully charged and then disconnect it. For a 12 volt battery, you can plug it into a 15-18 volt power supply and then when it is fully charged, disconnect it. Unfortunately, though, there is nothing to prevent you from overcharging the battery using such a simple system.
Overcharging a battery will decrease its life, sometimes significantly. You can damage a 12 volt battery if you overcharge it too much, sometimes to the point that it will no longer hold a charge. Using a charge controller will ensure that the correct voltage is used to charge the battery and that the battery is not overcharged. Since you are probably going to want to leave a 12 volt solar charger connected to the battery during the day when the sun is shining, you will want to use a proper charger controller to make sure that you don’t overcharge.
A Pulse Width Modulation (PWM) charge controller is the most common type for 12 volt batteries. Basically, it controls the voltage and amperage going to the battery by flipping a switch on and off very quickly. At the start, the switch is on more than it is off. Over time, as the battery gets more and more charged, the off time increases until when the battery is fully charged it is fully off and doesn’t send any more power to the battery. This kind of charge controller typically has a microprocessor chip to monitor and control the charging process. This type of charge controller can be left plugged into the battery all the time because it will only send power to the battery if the battery is less than fully charged. This “topping up” of the battery is called trickle charging Is very useful in situations where you have a battery that you don’t use all the time, but you want it to be fully charged when you need to use it. Again, for a 12 volt solar charger, this is probably what you want. This type of application is very common for 12 volt batteries in boats and RVs, for example.
That’s all there is to a 12 volt solar charger. The only thing that makes a 12 volt solar charger different from a 12 volt battery charger that you plug into the wall is the power source. In the case of a solar charger, the power comes from a solar panel instead of from the wall.
The standard type of solar cell that you see in solar panels on houses is about half a volt and three to four amps. In order to produce the 15-18 volts you will need to charge a 12 volt battery, you need to connect many cells. Small solar panels come in many different voltages. You much match the voltage of the solar panel to your charge controller. Each charge controller will have a voltage rating on it to tell you the correct voltage. Use a solar panel of 15-18 volts if you aren’t using a charge controller. If you are using a charge controller, though, remember to use whatever voltage the charge controller requires.
The wiring of the solar panel to the charge controller depends on the controller. If the charge controller connection uses a particular type of connector, your best bet is to solder this type of connector onto the solar panel. Put whatever kind of connector is on your battery onto the solar panel if you aren’t using a charge controller. For most larger 12 volt batteries, spring loaded clamps are best. If you don’t want to solder you can twist the wires together and apply electrical tape, but this type of soldering is very easy so don’t be afraid to solder. You can get a decent soldering iron and solder pretty cheap at Radio Shack. Twist the wires on either side together, apply the soldering iron to the wires and then touch the solder to the wires until it melts. The two things to be careful of are not burning yourself on and heating the wires, not the solder itself. You want the heated wires to melt the solder.
That’s really all there is to it! A diy solar charger is pretty easy to build. First, you need a 12 volt battery. Then get a charge controller that matches the voltage of the battery. Next build or buy a solar panel that outputs the correct voltage for the charge controller. Last, connect the solar panel to the charge controller and the charge controller to the battery. After that, you get free power forever! You are saving money since you won’t have to pay for electricity to charge the battery any more, you are reducing pollution and not adding to greenhouse gasses, and you are helping the country by reducing dependence on foreign oil.