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.