Batteries - What do you use

It helps being an engineer for doing many mods to RV's/vehicles etc. You can do wonders with batteries, inverters, relays, switches, fuses, dedicated wiring circiuts, etc, a little knowledge and a lot of commonsense and you won't even need need a lot of money to accompolish most any goals. However, there are lots of places that will do it for you but bring a boatload of money and often plenty of time for them to do it and very specific written list of your wanted mods and get quotes. Time and material is like handing an open signed checkbook or wallet to many of these places. There are some very honest ones too but it's just spinning the barrel and seeing if anything comes out the end! Yoo late if it does!