If you have read the Basic information about solar you now understand what solar can do for you, and you may now be thinking you would like to add solar to your set up, or perhaps if you already have solar you may be considering increasing how much solar you have.

The intention of the following information is to help you understand the terms, and some of the key points about solar, so you can understand what people are talking about. Helps when dealing with salesmen. This certainly not intended to give you enough knowledge to build your own system.

First of all lets understand some of the key words people use when talking about solar, lets look at them one by one:

Volts, commonly abbreviated to V, and expressed like 12V or 12 Volts. The volt is a measure of what is called the electrical potential. It is a bit like how strong the electricity, or how big a gap it could jump. The higher the voltage, the more dangerous it is.

Amps, abbreviated to A, and expressed as 10A or 10 Amps, are a measure of how much electricity is moving, referred to as current. Again a bit like the volume of electricity flowing through whatever is being measured.  Often electrical items are rated by how many amps they can handle.

Watts, are a measure of power. Watts are typically used to indicate how much power something can produce.

How do they all connect together, they key formula to remember is Watts = Volts * Amps.

Sorry to get technical on you, but it is important to have a basic understanding of these terms. Dont worry if you feel a little lost at this point, I hope it will all become clear as we work through a solar system.

First the Solar Panels, their purpose is to convert some of the energy in sun light (typically up to about 20% of it) into electricity (you already knew this). The manufacturer of the panel would have built it to suit a particular voltage system, and will have rated it to produce a certain amount of power (Watts).

When we talk about how much solar we have we talk in number of panels, and the theoretical wattage they can produce. For example Fred might have two 120 watt panels, giving a total of 240 watts. The more watts we have the more powerful the systems is, and the faster it should be able to charge the battery it is connected to.

Panels can be connected in many ways, but we will leave that to the experts.

Now as I mentioned in the last thread, the panels are connected to a charger, chargers come in a couple of main types PWM is the older style, and MPPT are the newer ones, but both work perfectly well.

Chargers also come in different voltages, typically 12, 24, or 48 volts. Most RVs use 12V systems, with a few of the larger systems using 24V. You need a charger that matches the voltage of your battery.

Chargers also come in many sizes, rated by how much current they can handle. Most caravan systems are built using basic 30 amp chargers.

For the purpose of the following example we will assume that the system is built with a 12 volt battery.

In Freds example earlier he has two 120 watt panels on the roof, but he is finding his battery is not charging enough, so he has decided to add more panel, but first he needs to work out how much more panel his charger can handle. BTW, he should have analysed his power use, and battery situation first, but we will deal with that in another thread.

He checks his charger and finds it is a Brand X MPPT solar charger rated at 30A, the important thing here is the amps, because that defines the capacity of his charger, the maximum amount of current it can deal with.

Hmm, Fred is confused, his panels are in watts, but his charger does not say anything about watts!

After a bit of head scratching he remembers that Watts = Volts times Amps, and he knows it is a 12V system, and his charger can handle 30 amps, so he works out the total number of watts of solar he can have is 360 (12V * 30A = 360W), he then subtracts the 240 watts he already has, and now he knows he can fit another 120W of solar panel with the current charger.

Before you know it Fred is on the phone to his friendly caravan dealer, asking how much to have another 120w panels fitted. He remembers reading somewhere that panels now cost about a dollar a watt, so factoring in a bit for fitting, he knows roughly how much he expects to spend. 

I think I have loaded you up with enough detail for one thread.

A bit of detail on solar panels for those who are interested.

How do they do this? (feel free to ignore this section)

The manufacturer of the solar panel starts with a sheet of silicon which they treat chemically to turn it into a giant diode (lets electrons travel through it in one direction, and then not come back), then when the sun hits the front of the panel, this excites the electrons, and some of them go through the diode. This creates a situation where one side has too many electrons, and the other does not have enough, thus the electrons want to get back to even things up. This is called an electrical potential, and is measured in volts. Thus when the sun is shining the panel is just like a battery with a positive and negative connection (one connected to the front, the other connected to the back). When it is connected to something it will be a source of electricity just like a battery.

The bigger the panel, the more electrons can flow through and the more flow the panel can generate in the circuit it is connected to, this is measured in amps.

So the manufacturer will rate the number of Volts, and Amps the panel can generate, and from this they can work out the number of Watts the panel can be rated at.