I'm looking for the easiest way to switch which of three all in one solar units is powering a particular 110 appliance. This is a high draw item that could drain one of the three down to nothing so I want to either automatically or manually be able to flip a switch to change its power source. Plugging and unplugging it directly from the device doesn't work because of how these things fit in the space of my bus - hard to reach to keep plugging/unplugging. The units I'm using to power this can't be chained together. Is there any device that exists for this purpose? Thanks.