Solar Powered Shed

Nothing says civilization like electricity! I definitely wanted to have some type of electricity in my shed, but it is really cost prohibitive to place underground wires from the house and what if I want to relocate the shed? Extension cords are only a temporary fix and are easily damaged with tractors and snow blowers running around. Since I really don't need that much power (maybe a few lights, charge a battery, or run something off an inverter for an hour or two). I opted for a completely self-contained, solar powered 12-volt system. I built this system for a little over $200 dollars, and is pretty easy to do for someone of a moderate "handyman" skill level.

Items you will need for this are as follows:
1) 15 Watt Solar Panel with Charge Controller (I went with "Sunforce" brand bought on Amazon for about $100)
2) Deep Cycle Marine Battery (I got mine at Tractor Supply for about $80, it has 105 Amp hour capacity)
3) 18 gauge, two strand lamp wire
4) 4 crimp on terminals
5) 12 volt outlets (used to turn a single cigarette lighter into four outlets)
6) 30 amp fuse and holder
7) A couple light fixtures (just buy standard 120 volt stuff at home depot, works fine for 12 volt applications)
8) A couple 12 volt compact fluorescent bulbs (These are used for RV lighting typically)
9) Optional: A couple 12 volt battery clips to make an ad hoc charger for 12 volt batteries

The first thing to do is to situate the solar panel. Obviously, you want to put this where it is going to get a good deal of sun. I put mine on the side wall of the shed and just drilled a small hole for the wire. This is not really optimal placement. In order to optimize the efficiency of the solar panel you want to point it due south and angle it similar to your latitude (+15% in winter and -15% in summer). However, I think a 15 watt panel is more than enough power for me so I just mounted it flat on the wall. This looks less "tacky" than having a solar panel sticking off the roof and also it is unlikely to get covered with snow since it is completely vertical. I am willing to exchange this for a decrease in output, but you should adjust this based on your particular needs.
The battery itself is a 105 amp hour deep cycle battery. I built a heavy duty shelf in the corner of the shed to keep it out of the way. This battery has plenty of capacity for my particular needs. I used 18 ga. lamp wire to connect everything. It is easy and cheap. I put a couple crimp-on terminals from the controller to the battery. Coming off of the battery I have two systems. One connects to a block of 12 volt "cigarette lighter" plugs, the other runs two CFL light bulbs. Don't forget to put a fuse in here! If something shorts out, you will take out your entire system! Don't skimp on a 2 dollar fuse!

For the light bulbs, I just used standard receptacles for basic home lighting. I opted for the "pull chain" type fixture with an outlet built in. These were purpose built for 120 volt AC systems, but they work fine for 12 volt DC. I ran the positive wire to the center of the bulb fixture, with the negative on the threads. That seems to work fine. The light bulbs themselves are 12 volt DC and designed for RVs. They put out about as much light as a 60 watt standard tungsten filament bulb and are more than enough to comfortably light this shed.
Next regarding wiring, well I drew a little diagram to give you the idea. I am not going to go into the basics of wire stripping and all that: if you have gotten this far, I hope you already know how to do this and have some reasonable electrical tools (stripper, voltmeter, etc.) . The purpose of a "charge controller" is to shut the power off from the solar cell once the battery is full. This prevents over charging. However, I am not certain that with such a low amperage solar panel I even need this. (I think it puts out about an amp in full sun) plus I think it sucks some of the power out of the system. However, since it came in the kit, I put it on.
As a bonus, I had an old 12 volt AC extension cord, that I cut the end off of and crimped on two battery clamps. This easily plugs into the outlet on the light fixture to charge my lawn tractor battery. CAREFUL! Have a voltmeter handy to be certain you have the correct polarity!
All in all this system works great. The light bulbs pull about two amps or so that means I could run them for about 52 straight hours without sun before the battery ran down. I have never come close to running the battery down, but if I did it would take about two weeks to fully charge up and that is if it was particularly sunny!
You should also note, even though this battery is a "deep cycle" it will last much longer if the cycles are short (let's say 20% discharge or less). So for your own system, you need to gauge how many amp hours you plan on using daily and plan your battery capacity accordingly. If you plan on running an air conditioner: you are going to need a much, much larger system! However, if you just want to run a couple lights for an hour or two; or use an inverter to charge your power drill battery; this will work fine in my opinion.
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