you said you bought a battery for the brakes....that battery only powers the brakes IF the breakaway is pulled. The brakes are powered by the tow vehicle, that's why the round 7 pin (one leg is brakes. The fridge should be gas or 120 volt A/C electric. The furnace and fridge also need 12 DC electric to power the controls. Your lighting is 12 volt DC also. I use Thetford original in the black tank and nothing in the grey tank just a flush when done. Please do not take this the wrong way but from reading your post you have a lot lot lot to learn before you go out the first time. Please read and do google searches learning how everything works before you go out and have major problems on the road. Good luck