[twindman]

I think the furnace fan uses 10A or so. I figured it out when my batteries died at 8300 ft. The furnace seemed to be running about 3/4 of the time, so it used 7-8 amp per hour x 10 hours (8 pm to 6 am). I had also had lights on from about 5 until 10 pm, so I was dead by 5 am. On a side note, it is not fun to hook up the truck at 5 am to charge the batteries in your pajamas!