I found a couple tutorials but they were confusing or sounded like way too much work. So I made my own.
You will need:
* 1 Deep-Cycle Marine Battery - these are meant to be run down and recharged repeatedly. Auto batteries will work but not as well and not as long so you're wasting your time and money. WallyWorld has these for less than $100 if you can turn in another battery (any type) and avoid the core charge.
* 1 Pair small auto headlights. It doesn't matter what type car they fit. I paid about $18 for a set of 2 new ones. You may find them cheaper or free.
* Wire. Take a look at the wiring coming off the headlights and use the same gauge. I used one package each of black and white because my booth is decorated in those colors. I needed enough wire to run them from the battery to each side of my 10x10 canopy I use for shows so I used 20 feet of each color for each light.
* Wire cutter/crimper
* Wire connectors that will fit the connectors on the headlights.
* Small battery clamps
I spent a grand total of $120 and I bought everything new except the wire tool. (If we hadn't moved 5 times in the past 8 years I could have spent far less - I know I have a boat battery SOMEwhere!)
Remember - DEEP-CYCLE Marine Battery - not an auto battery. I started looking into wheelchair/scooter batteries because they are smaller (and lighter) but went with what I knew would work.
Use one strand of each color to connect each headlight - black to black and white to white.
As with all wiring, be certain there is no bare metal showing at any of your connections. You want to light up your booth - NOT your booth frame! And you certainly don't want to electrocute anyone.
I used these lights for shows for about a year and did not notice much if any dimming after 5 hours of use. I recharge the battery with a trickle charger the day before a show.
Understand that these will light up your booth enough that you may need to attach shades to prevent your neighboring vendors from complaining. I sell Naughty Bits jewelry (and other things) which are made using just the *best* parts of recycled romance novels so my shoppers need to be able to read book-sized print and these lights make all the Sterling silver findings on that jewelry really sparkle too. The light also brings out the depth and color of the recycled record bowls I paint. (You can find my work at oddartist.com)
The battery weights about 40 or 50 pounds which I don't have an issue with so long as I can drive up to my booth to unload my display. If you can't carry that weight or if you have to hike a bit with it (think camping/BBQ) you may want a hand-truck or something to tote it with.