I have a battery disconnect on my 1000 watt inverter. It only uses power when I decide to use it.
That said, batteries need to be sized for required usage.
I thought You were asking for a quick way to get your TV etc working. I think the simplest way is to get an inverter, hook it to your batteries in the RV or vehicle and run the power to the equipment. May be several ways to do that. One being to plug the RV into the inverter, turning off everything that runs on electric (including the conveter, fridge, water heater etc) other than the TV etc. I don't really know how well the newer TV's function on the cheaper inverters.