Light powering - voltages?

[neo]

First of all, we are wondering how other teams are powering their light boxes. We've tried computer PSUs, but either there isnt enough voltage or enough amperage (we have 3 lights. .7A x 12). We've tried running straight from a battery, but the voltage diminishes and the camera notices. I rigged up a second plug to one of last year's batteries and plugged it into a charger while the battery powered the lights. This just tops off the battery at ~13.6v.

Second question is, does anyone know what FIRST is powering their lights with? If they are using a 120v to 12v converter and letting those light have a constant 12v, would it make a difference if other teams are running their lights at 13-14v?

thanks.