Articles - Battery Power: J) Battery Power and Layout Planning
04/29/2018
So, let's assume that you have one or more engines equipped with the S-CAB battery power system. How will they function on a layout? If you already have an existing, wired layout, there is nothing that you need to do. Your S-CAB, battery-powered engines will run just fine on your layout. If you have the BPS wired to the locomotive's pick-ups, it will be automatically charging the batteries for as long as the layout is powered. A number of people who have fully-functional existing layouts generally converted some of the more "stubborn" locomotives to battery power, such as short wheelbase diesels or steam engines such as 0-4-0 and 0-6-0. Especially if they are used as slow-moving yard switchers that tend to stall on turnout frogs, these are great candidates.
If you are getting ready to build your layout or have already started, but you haven't made it to the wiring phase yet, you might want to entertain going "dead rail". Not having any wiring to do is a big time saver. However, you will need to consider these three things.

First, how are you going to recharge the engines' batteries? You might want to have a piece of track in a yard that is connected to a 12-volt power supply. At the end of the operating session, you could run the engine to that piece of track and let it charge overnight (it typically takes 8 hours to fully charge the battery).

Second, you may need to consider future visiting equipment. If you want to have friends bring over their equipment, you will need to think about how they have their locomotives equipped. Note that the reverse situation, you taking your S-CAB-equipped engine over to your friend's layout, is not a problem at all. The engine will run just fine on a DC-, DCC-, or even AC-powered layout.

Third, are you planning any automated signalling on your layout? If so, you will need some sort of detection system other than current-drain to detect the presence of a battery-powered train on a section of track.
Some people choose to wire only the main line of the layout. That way the engines are recharging while they are running, but you can skip wiring turnout and crossing frogs, reverse loops, turntables, and sidings.

I am currently building a large diorama layout that has absolutely no track wiring in it at all. Completely dead rail!