Have you thought about using a motorbike battery and an inverter? We're converting an old caravan for our community radio station to use as an OB vehicle. We're running the whole thing - mixing desk, CD players, recorders, laptop, etc from several car batteries, trickle charged by solar cells and running through inverters. Mains power will only be used to charge batteries when required and, when it's available, to run optional equipment with higher current drain. A recording engineer friend runs his DAT recorder from a motorbilke battery when recording in the field (often literally!).
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