I don't use Lipo batteries. I use old-fashioned rechargeable gel cells (lead-acid) as used in alarm systems, back-up computer power supplies and exit lights. They are the gel equivalent, in charging and performance, of automotive wet cells.
I don't do much switching on my little railroad; I just watch the trains go through the scenes. I'm sure that all of you will agree that most MU consists of Diesels have at least one unpowered B unit, most freight trains have a boxcar, and most passenger trains have a baggage car. That's where my batteries are installed. These cars feed power to the locomotives via flexible tether wires. I rotate several of them in and out of my train sets, when they run down.
I have a recharging track, where the switcher spots the battery cars, and the little workers plug in a two conductor lead with a coaxial connector, as found on wall-warts, that recharges the batteries. The charger is mounted under the table. It's only turned on when I'm in the room, or close by. Simple.
