Solar panels vary in the amount of volt – the power of the power – and their enhancers – the current of the charge – which is derived from them. Two 10 watt panels may vary by several volts, and a certain amount of amplifiers. This affects how your system battery is charging.
We’re going to keep this simple. There are not many things worse than mathematics.
When it comes to solar panels, there watts, amps and volts.
Watts are a measure of the ability of a solar panel.
Amps is also referred to as “current”, and is a measure for the charging rate.
V is also referred to as “electrical potential” and is a measure of the force for the flow of charge.
Watts Amps Volts multiplied by (if you remember your high school physics). So a 10 Watt panel is twice as powerful as a 5 watt panel.
Now to complicate things a bit, you should know that several solar cell chemistry will produce slightly different voltages. For example, a 10 watt solar panels using CIGS technology (such as panels Brunton) working at 16.5V, while the Power Film amorphous cells to create panels that have an open circuit voltage of 15.6V.
Which is better?
Well, remember that Watts is Amps multiplied by volts, it is logical that there is a 10 watt panel provides more Amps, will the solar panel will charge a battery pack to be the fastest.
Most solar panels are designed for use in so-called ’12 Volt systems, “while” 12 V “is actually a better term. 12 Volt is used because this is the nominal voltage of the car battery, and is a simple multiple of 120V alternating current which you can find in your home. A lead-acid battery like the one in your car, includes six cells requires 2 volts each. A 12V battery is actually slightly more than 13V when fully charged and somewhere around 10.5V when actually empty.
Lithium batteries have followed this convention as they were the latecomer to the scene.
Charging the battery is a bit like transferring water from one container to another. As long as the charger has a higher voltage than the battery is charging, charge will flow between them and the battery is charged. That is why solar panels are designed to 15-18V, so a 12V battery is good charging. Charge Controllers are used to ensure that the panels do not overcharge the batteries when they are full (in the transfer example, this would be like closing a valve on the hose once the second bucket is full).
Since lithium batteries are everywhere in small electronics, personal solar chargers are designed around them. This is why the USB format has become the standard for charging small electronics – the 3.7V lithium cell costs 5V USB. Lithium batteries in small electronics also comes with its own built-in controller that stops them be charged when they are full.
Source: http://ezinearticles.com/?Solar-Tutorial—Amps-and-Volts&id=3451368 by Graham Morfitt