Hi,

The I-LapRC system at http://www.rclapcounter.com
connects to your laptop and gets its power from the USB port.

The same is true of the AMBrc, not sure about their newest with the LCD screen.

An inverter, if available, would be an option as well to power others.

The Orion (Pro LCS) is a practice timer for one car at a time only. If that fits what you are trying to do, it runs on batteries. It may also be available as the Alex Racing Hakarunjer (sp)

Craig