If you install the switch, just follow the normal shutdown procedure, then to the switch off to disconnect. If you disconnect batteries before hand and the alt is producing power, (or if you're using it cut power from the start button, turn your switch off last so it's good to go) the power will not go to the batteries, it will flow through the electrical system and could cause damage to wiring or other componets. Best to shut acceessory switch off, shutdown the motor, then disconnect using the switch. At least you wouldn't have to worry about somebody jackin your truck from walmart, unless their're good, then we will watch your truck in the Worlds wildest police chases!! Lol. Hope not.