.au and .eu spec = brochure says 100watts/220v, only available whlie ACC engaged.
in the US models, its 120v but also 100 watt
w.r.t the battery question, i guess that depends on where you are going, how often you intend to have the alternator running, do you / will you have something supplemental to charge with when not moving ( solar ? electric hookup ? ) and what you intend to hand off the back of that power socket(s) ? and for how long ? Many questions, but a safe bet would be 'yes', retain enough power to start your motor, and dont let the 'service' battery kill that. Put all your fridges and other electrics you intend to use when stationary on the service battery('s)