[Alan Anderson]

You can power the OI from a robot battery. Measure the output from the wall-wart power supply to determine its polarity. Wire a similar plug to an Anderson battery connector, matching the polarity. If you're not comfortable exceeding the "spec" supply voltage, use six D-size alkaline cells in series, or a high-capacity 9.6v NiCd rechargable battery pack.

I've considered using cordless drill battery packs as a portable OI supply, with a built-in slot on the operator console to accept one. (The ones I've been toying with are many years old, from the days when they were used to power FRC robots, and don't last very long.)