Hey Beef, I could talk for hours on this one. We wired an 80 foot barn recently for lights with nothing more than a 55 watt panel, some golf cart batteries and a $70 inverter. It has 5 compact flourescent spotlights inside, a small light over the door inside, and another outside. The little lihts are 12 volt, so they can be turned on straight from the batteries without an inverter. This might be all you need if you just want a light for a few minutes here and there, skip the inverter, go with a smaller battery and smaller panel. The most efficient lighting for something like this is a 12 volt LED strip. Sometimes you can find them at truck stops on the freeway for just a few dollars, or at an RV place. My favorite place for them is super bright led's dot com, listed below.
If you have an old car battery, or better yet a deep cycle 12 volt battery, just shop for a small panel, maybe 40 or 50 watts. A 50 watt panel will put out 2.8 amps in direct sun. There is a rule of thumb that as long as your panels amperage is not more than 2% of the battery's amp hour capacity, you don't need a charge controller. You will need a diode however. A diode is nothing more than an electrical check valve, allowing the solar panel to charge the battery during the day, but not allowing the battery to discharge through the panel at night. Most panels today come with them already installed. A car battery could typically have anywhere from 50 to 90 amp hours of storage, so a small panel would work fine. Just hook the positive of the panel to the positve of the battery, and the negative of panel and battery together, and you'll be charging. Now you can hook your lights up to the battery. Our installation uses mechanical timer switches for the small 12 volt lights. It is very important they not be left on all the time, they would run the battery down to nothing, and in a few days the battery would be toast. Inverters have low voltage disconnects built in, they shut off when a battery gets down to about 1/3 charge anyway. When we go into the barn, we just wind the timer switch up for a few minutes, then we can turn on bigger lights if we want. Then we reverse the process when we are leaving.
A good quality led strip from the website might cost you 10 to 15 dollars, but light up a work area on a table, but only use 2 watts. Another fun thing to do is use a small inverter to run led Christmas lights, they typically use 2 watts per string, so 2 or 3 of them is no biggie for an hour or two during a party. If you decide to put more horsepower in your little shed, look for Trojan T-105 batteries at any golf cart place in the phone book. They are 6 volts each, so you need at least 2, but they hold 220 amp hours, you can hook up to 80 watts of solar to one pair without any charge controller. Then with a 750 watt inverter for about $70, you can run drills, spot lights, small power tools like an electric weed wip or similar contraption. The one to steer away from is refrigeration. Seems like everyone I talk to that wants to do this considers putting a small fridge in their shed or barn before long. That reefer needs to be running 24/7, and it will take 5 times the solar power they have to keep up with it. Lighting is almost never a problem. I'll put some sources below. Good luck, and have fun, Rudydoo
The Complete Battery Book, by Richard Perez, library
Home Power Magazine
Midwest Renewable Energy Association
Solar Energy International