You’ve got options…

There are three ways to get electric lights at a show:

1. AC Electricity from a local source, like a light pole or garden receptacle. Sometimes you can beg electricity from a local merchant at a sidewalk show. This method is usually against municipal code, but can work. Some shows offer electricity if they have evening hours, Wells Street and Ann Arbor State Street both sell generated electric hookups for example. If this kind of light is available, you can use track lights with rotating heads, swing arm lights that fit into the top of ProPanels or clamp to poles, or any light that you can fix to a stable point. Make sure to run the cord above the ground to avoid electric shock and tripping hazards.
2. Generator — this is better than running batteries, but a generator is expensive, noisy, smelly and heavy. That said, Honda and Coleman both make a small, relatively quiet gas generator that will pump out about 1500 watts. If you can locate a generator away from your neighbors and the show allows it, this is an option. Many shows prohibit gasoline powered generators as the gas is a fire hazard. To run lights off a generator you simply plug an AC cord into the standard receptacle, start the engine, and flip a switch. You can get 3-6 hours from a tank of gas, depending on the generator. A small 1500-3500 watt generator will run from $600-1000. Home Depot carries the Coleman and some larger models with Subaru engines. Honda makes a super-quiet generator in three sizes.
3. Battery powered lights — generally powered by Marine Deep Cycle batteries. The bigger the better, and more than one. They are very heavy and bulky. You also need a micro-processor controlled charger to get the best charge into them overnight, as they will definitely need to be charged every day you do the show, and an inverter for each battery. I’ve heard of people running batteries in parallel (+) to (+) and (-) to (-) to increase battery life, but I believe that it is just as efficient to divide the load between two or more batteries — one battery per light bar, for example.

Some info on batteries:
Art Fair Insiders Discussion on battery lighting
http://www.batterystuff.com/tutorials_index.html

To get power from 12V batteries, you need to either use 12 volt DC lights, or an inverter that changes the voltage from 12 volt DC to 110 volt AC. These are basically a transformer, and they also have standard receptacles for plugging your AC lights into. Inverters come in small (300 watt – 450 watt) that will run off a cigarette lighter in a car and power a laptop or small radio, to large 1500 watt. The bigger the inverter, the more quickly it will drain power from the battery. The inverter also takes power to run, which decreases the amount of time you can run your lights.

To hook up the inverter to the battery, you run a thick cable from each of the two posts on the battery to the two corresponding posts on the inverter. The RED cable is the positive cable and is hooked up to the battery (+) terminal, and then to the inverter (+) terminal. The BLACK cable is hooked up to the inverter negative (-) terminal and then to the battery (-) terminal. The lights are then plugged into your inverter and the inverter, when switched on will power the lights. It’s probably better to run multiple batteries if you’re planning to run a lot of lights.

Fluorescent lights take less power than halogen lights for the same amount of lumens, but are less efficient as a point source of light. Halogen lamps run between 20 and 50 watts each; a fluorescent spiral bulb can be as low as 10 watts, running up to 22 watts or so, with the output of a 75 watt incandescent light bulb. Since halogen and incandescent bulbs generate heat when they “burn”, they drain more current from the battery.

I know that a battery system can work, as I have a friend who does it successfully and I’m working with a similar system for this weekend’s show. My system has two Deep Cycle batteries, about 200 CCA each, two 750W inverters and a 20A three stage charger. It’s not cheap however, requires space to truck it to the show, a dolly to get the batteries back and forth to your car, and charging each night. Batteries weigh 50 -75 pounds apiece, and the charger and inverters also take up space. The batteries definitely won’t mount on a Trimline.

For light bars, I use standard track lighting mounting to 1×2 oak trim. I have two tracks, one 9′ long with an 8′ track, and one 8′ long with a 4′ track. I have extenders that are bolted to the ends so that the track will go across the tent. The ends slip over the ends of the Propanels I use, and I have aluminum extenders that raise the tracks 8″ above the panels. The extenders allow the tracks to fit into my trailer, and adjust to different length configurations. You could also duct tape the light bars to the metal braces that ProPanels use, although I was leery of bringing 110V electric in contact with anything that might conduct into the tent. Same with attaching directly to the aluminum Trimline frame. The wood acts as an insulator, keeping the electrical away from the metal parts of the tent. These lights are AC, standard halogen fixtures, and work well off of rented AC or generator. I’m anxious to see how well they work with battery, and how much life I’ll get from them.

**UPDATE September 19**
Switched the lights over to 12V DC and eliminated the inverters. The inverter itself draws about 60 watts an hour, and each 120 Ah battery with 4 50W lights can be powered about 2.5 hours before the voltage drops below the usable point on the inverter. With DC, you can drain the battery further and run the lights longer, although the color temperature will change as the voltage drops. At my most recent show, I ran 9 lights from two 120 Ah batteries for over 6 hours each before one ran completely out of juice. The other was still going.

**UPDATE June 17 2010**

I’ve pretty eliminated the use of the 12V batteries and 12V lights at shows. I did buy a generator, however. I found a Homelite 2000W generator that is very similar to the gold standard Honda 2000. Home Depot was selling them for a whopping discount, about $350 as I recall. Using the generator instead of battery has a couple of advantages: no double sets of lights, and no heavy batteries and chargers to deal with at night.

There is only one show that I do now that needs lighting after dusk that does not already provide electricity — Crosby Gardens in Toledo. My spot is near the periphery, so I am able to string a 100′ 14A power cable out to the genny and keep the noise and smell down. I wouldn’t recommend using a generator in close quarters, however. Many times you can get free electric power in parks and on the street from light poles or garden lighting. The polite thing to do is scout around and ask permission to use the public electricity.