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Everything in the trailer works on 12 volts, including the lights, furnace, vent fan, etc. The convertor will supply power for those when plugged into 110volts. The 110 volt outlets only work when plugged in. You need the charged battery to lift the top and also to supply power to the emergency brake switch. The black switch controls the 12 volt circuits, with exception of the fridge in 12 volt mode, and also the power to the lift depending on what position it is switched to. Up 12 volt, center off, down lift.
Go to the video manual to get a good run through of the trailer systems, etc. Lift maintenance is most important. http://www.hilotrailerforum.com/f49/...-youtube-1233/