The Airstream has dual electrical systems, 12 VDC and 120 VAC. On my '72 all of the lights are 12V
. All of the venilation fans are 12V
. The furnace blower is 12V
, as well as the on board water pump. My 'fridge was replaced by previous owners, and is a 120 VAC model. You may have a propane/12 VDC /120 VAC model, or some variation. My TV and microwave oven are 120 VAC only.
The battery is used to power the 12 volt
side of things when you are not connected to "shore power" as we like to call it, when you are in transit, or if you are camping at a site without 120 VAC power.