Ok, here what I want: I want to run a secondary battery that is always connected to my primary battery while the truck is starting and running(charging) but isolated when the truck is off. I want to be able to use the secondary battery to jump start the primary battery if it is dead. The diagram below is what I came up with and it looks to me like it should work and the only parts I need are the cables and a solenoid. The "+12 volts switched ignition" connection will be made at a point that is hot through start and remains hot in run and the "manual switch in cab" will be a toggle switch that gets it's power from the secondary(isolated) battery to energize the solenoid for jump starting myself. So, will it work?