Do a search on this forum for BPRC (Battery-Powered, Remote-Control).
I've been running BPRC for over 4 years now, 3-rail engines and rolling stock on 2-rail code 148 Micro-Engineering, Atlas, and Signature Switch track/switches.
I started in 3-rail and didn't want to spend the $$$, time, and effort of converting/selling the 3-rail stuff to buy 2-rail stuff. I did however tear up the old 3-rail layout, replacing it with Mianne benchwork and 2-rail track a year and a half ago. I'm finally got my track like I wanted it and have been putting down minimum ground cover the past few weeks in hopes of bringing it to some form of life.
No changes to the rolling stock (except Kadee couplers) and removed the rollers on all passenger cars.
The real changes were made to the engines. Had to remove all the center rollers and electronics except the dc can motors. Installed a receiver, battery, and other necessary electronics (on/off switch, charging jack, LED lights) in the engines and purchased a couple of transmitters and battery chargers.
They run just as good if not better than before, but the current installs have no sound or smoke (yuck, don't like it anyway). I've converted MTH, Lionel, Atlas, 3rd Rail, Williams, and Weaver engines to BPRC (close to 20 now). I have an old Williams/Samhongsa brass N&W Class J 4-8-4 that weighs 14lbs and I never thought a 12v battery would be able to handle it but it runs great. I get 2 to 2.5 hours of run time and it takes about that long to recharge. All of my batteries are in the engine or the tenders (steam), but they could also be installed in a trailing boxcar with tether. I have 2 Williams/Samhongsa USRA 2-8-2 and 2 USRA 4-62 brass engines also converted to BPRC.
One of my best running engines is a MTH RailKing Imperial USRA 0-6-0, excellent slow speed for switching. Another excellent runner is a Lionel 4-8-2 Mountain.
The only engine I feel needs work on is a new Williams by Bachmann USRA 4-6-2, a bit jerky on startup but I think a washer on the drive shaft/gearing would fix it.
Here's another excellent runner, a Weaver 4-6-0 chassis (thanks Ed Rappe!) sporting a homemade boiler, pulling a 4-car train. 9.6v NiMh battery in the tender, excellent slow startups
In the 4+ years I have not a one single failure of any electronics. Batteries are good for hundreds of charging cycles.
Another plus...NO wiring to the layout! Don't have to clean track if I don't want, don't have to worry about a derailment and shorting out any components (I'm a firm believer that applying 18+ VAC to the rails and running trains that arc and spark, is a sure way to blow up some electronics). The ONLY issues I have had was when I forgot to throw a turnout the right way causing a derailment, my fault not that of the track or the electronics.
2-rail track can get pricey (especially turnouts) but you pay for what you get. All 20 or so of my turnouts are Signature Switch and I wouldn't have anything else (even tried to make some myself, failed).