If only it was that easy. They don't appear to have a separate plug for battery as the main input (which is permanently joined to the transformer) appears to be the only input socket.Kev, get a second bike battery and put them in series, that will give you 24volts, problem solved.
Cheers dude I've got solar panel and optimates, etcThat's good news kev twice the voltage half the current, I'll soon have the opportunity to get hold of some 12v battery's from work. I'll put two to one side for you. All you're need is a good 12v or 24v charger