Lego train sets can vary according to the number of pieces in the build, the intricacy and difficulty of the build, whether it includes the “Power Functions” motor and availability.

A Qi coil in the bottom of the train car and one in a specially designed section of track got the power flowing, but getting them lined up proved a bit finicky.

LEGO’s Power Functions elements mostly consist of DC motors and the hardware to be driven by those motors like gears and wheels. They also include battery packs, usually a bunch of AA cells in a ...