Small Solar System how-to

Many of the tools and devices recomended on this website require power. Many use rechargeable batteries, which is great until the power has been out for a few days. Generators are nice to have, but gas isn't unlimited, and the noise of a generator in an otherwise silent neighborhood may attract unwanted attention.

A small solar setup is a very simple, relatively inexpensive solution that can generate plenty of power to recharge batteries for your phones, flashlights, radios, etc. At current prices a 100 watt system can be built for about $200. Here's how.

First, our small solar system contains only four main components:
1. A photovoltaic panel. There's a bunch of different ways the chips are made out of silicone; poly, mono, etc. We don't really need to care about that. All we care is that it outputs a high number of watts, has a decent warranty and is of decent quality, and is the right voltage.
2. A battery. This serves as a way to store unused energy for later and allows you to keep using power when clouds briefly interupt your power production.
3. A charge controller. It's not really a good idea to just wire your panel to your battery - eventually you would over-charge and destroy your battery. The charge controller sits between the panel and the battery and manages everything.
4. A DC-AC inverter. If your electronics can be run off 12 volts DC, then great. But most stuff wants 120V AC.

In my case I bought this kit: Renogy 12v 100w Panel and Charge Controller for $180. They also have one for $20 less that doesn't include mounting hardware. I think I'd skip the hardware, in retrospect. Both these kits come with cabling to attach your panel to the charge controller. So now you have a panel, charge, controller and cabling.

Next part is the battery. Battery capacity is normally measured in Amp Hours at a specific load. I prefer to think in terms of watts; so a 100 Amp Hour 12V car battery should yield 1,200 watts of power (watts = amps x volts). But most lead-acid batteries shouldn't be depleted beyond 50%, so you really only have about 600 watts of potential energy storage. But that's a lot when it comes to charging radios and other small batteries.

Our problem is that lead acid car batteries are expensive. They also shouldn't be left lying around, unused. That will kill a new battery in relatively short order. But your car (or cars) have batteries in them that are regularly discharged and recharged. They also have a nice waterproof enclosure attached, which is a great place to park you charging electronics, and the whole thing can be locked up. Why remove that battery for use in an emergency when you can just use it where it is?

Lastly, we need a power inverter. You may already have one for use in your car's cigarette lighter. If so, you've probably also discovered that your cigarete lighter port can only output about 150 watts of power, even if you have a much larger inverter. That's because the wire used to hook up those cigarete lighter ports is usually a pretty small gauge and there's a appropriately sized fuse inline somewhere. Draw too much power, blow the fuse.

If you want, you can add a larger inverter to your system. It can be quite a bit larger than your panel in terms of it's maximum output. But a couple hundred watts should be all you need. I have one of these that I got several years ago for use in Africa. It's worked well. But I think if I was buying again I'd get this model, which also has some USB ports.

Now you need to wire all these components together. I'll try to post a picture of my setup shortly, as well as a schematic. Be sure to use wire that's heavy enough for the highest draw you anticipate. If you have a 200 watt inverter, and you are going to attach it to your car battery with 10 feet of wire, it needs to be at least 12 gauge wire. You can use wire gauge charts to determine this. Also, be sure to wire in a fuse of the right size wire attached to the positive terminal of the battery. You don't want to burn up your car and electronics in the middle of a disaster.

You can wire everything together and attach your charge controller, AC inverter, and other hardware onto a board. Then you can have a simple, plug and play, system to start collecting energy from the sun and charging your electronics.