2-Truck Climax
Like most locomotives, this one came track powered and with no DCC. So step one was remove the trucks and retrofit them to take track power instead of battery power.
I replaced the rather inefficient stock smoke generator with a much more efficient one. The stock unit used a linear power regulator and I replaced that with a switching regulator - a difference of 30% versus 90% efficient in power conversion. I also preferred to replace the stock smoke unit with lower voltage Pico smoke generators.
All the wiring comes together in the firebox of the loco.
Normally the track power goes from the wheels right to the motor next to the wheels, embedded right in the powered trucks. I cut into that and wired motor power to the controller.
There is very little room inside the tender box on the Climax. I had to hunt down a 2-inch speaker, and there was just (barely) enough room for the wireless controller. The battery would need to be in a trailing car.
I scratch built this "tool car" using the chassis of discarded too-small tender. The only thing in here is the 9000mAhr lithium battery pack. The wood used to build this car was new when I started. A few layers of paint later, it is "old".