How I made my Lionel trains remote-controlled and battery-powered!
This practice amongst model railroaders is also called dead-railing. The tracks are not powered at all, instead, the trains are battery-powered. It is more common in larger-scale model railroads, due to the size it requires. It specifically makes sense with Garden railroads, since their tracks are exposed to the outside elements
For this project I used Lionel O-scale trains and tracks. The track that I made is an about 4 feet by 8 feet loop. It is portable, and can be used both indoors and outside. The tracks can also be powered, so it can also be used with traditional trains that require track power.

The train engines I am using for this project are Lionel EMD NW2 Diesel switchers, from early -50’s, and early -70’s.
These Lionel engines have the famous Pullmor AC motors. Those motors can also be run with DC power, which we need, since we are using DC battery power.
The 1970 MPC-era NW2 switcher has enough room inside the shell to contain the battery and other needed parts, but the post-war switcher doesn’t have the room, unless I choose a much smaller battery. So, I decided to convert a caboose to a power-unit, which can be used with either engine.

The caboose I have available for the project is a Lionel 6257 caboose from early 50’s. Size-wise it was still a bit crowded for to fit all the stuff, and I didn’t want to alter the original shell, so I designed a custom shell, that fits on the original frame.
For battery power, I chose a 14.8V 2200mAh rechargeable LiPo battery. It might be overkill, but I wanted plenty of pulling power, and longer running time, and the 4-cell battery still is small enough to fit.

For the remote control I used a wireless led-strip dimmer kit. The receiver unit is small enough, and the sender has on/off and its dimmer control functions as speed control in this case.
It doesn’t have reverse control, but if the train engine has the Lionel electronic direction unit, the direction can still be controlled with the remote.

Other parts needed for the project are a 6A circuit breaker and a diode, both in order to protect the receiver unit from electrical shorts, power switches, wiring, and optionally, led lamps, or other type of lamps. I use an automotive resettable breaker, but it seems to react too slowly, so it would be better to use a poly-switch breaker.
The circuitry is quite simple, just have to be careful with polarity, and not forgetting the diode at the controller output.

I added switches to the locomotives, for switching between power from the track, and battery power.
I salvaged the switches from some old remote-control cars. One switch is for the battery power, and one is for switching between rail- and battery power.
You should be able to find all the electronic components online, at fairly low prices.

You also need some method of keeping it all together. Fortunately, I have a 3D printer, which I used to make cradles and holders for the various parts (scroll trough the slide show below).
After testing the self-powered train, I can tell it has plenty of power. At full speed, it won’t stay on the track in curves, and it pulls 9 cars very easy at lower power.
This short YouTube video is a slide show, and has some additional images and video, showing how I built my dead-rail train (pardon my heavy accent…)