I don't have a bank (fired them) and the battery from the bus runs the food cart when we don't need it in the bus. I don't have any 12vDC in the bus right now. I already know what batteries we will be using.
I don't have much in the bank since I recently had to replace the two 8-D's that start the bus, but the previous one's lasted about 7 years, so I guess I can't complain. I use two Die Hard Deep-Cycle Series 31 I believe for the 12 volt system for the cabin interior. They were a little pricey, but where they are located under the bus is a PITA to get to, so I wanted the maintenace free one's I could just check every once in a while for good connection. These are the ones that are hooked to my solar panels on the roof.