I'm guessing you didn't look at my diagram.
You must CERTAINLY want a switch between the battery and the board and the track!!! What happens without a switch if you put power on the track? OOPS! Also, if you don't have a switch between the LC+ board and the battery, the locomotive is always on, that's probably not a great option either! Look at the left hand side of the diagram, that's the wiring in the engine. You only need to switch the center rail power, it's pretty clear which lead that is, it comes in on a separate connector with red & black wires. The red is the center rail.
As I described, I though fairly clearly, I used an existing switch on the engine to switch the center rail power to the electronics between the battery and the track. That gives me dual-power capability, I can run on battery or track power. So I have a standard LC+ locomotive that will run on battery as an option.
If you don't have a spare switch (the chuff on/off switch seemed like a good choice to me), you'll have to install one. It should be a SPDT switch if you want the dual-power option.
