Conversion of UP NW2 to radio control battery power

I finally had the components together to convert my first locomotive to battery power. As I mentioned in a previous post, I decided to go with AirWire for the decoder and remote control. The AirWire catalog includes a series of decoders that are specifically designed for several USA Train models, so I thought starting with my UP NW2 from USA Trains would be a good idea.

For battery power I decided to go with Makita 18V batteries. I wanted to get a couple of big 5.0Ah batteries and I started looking online to compare prices. I ended up finding a tool set at Home Depot that was about 50% off, so for the price of what I was expecting to pay for two batteries and a charger, I also got a couple of new power tools. Both of which I've already put to use over the weekend.

The battery will not ride on the locomotive but in a trailing battery car. I'm using one of my BN boxcars as it has nice wide doors so I can easily slip the battery in and out. Eventually I'll need another battery car so I can run two locomotive simultaneously.

UP NW2 and BN boxcar in the shop ready for some major work.

The decoder kit includes two new circuit boards and a very detailed installation guide.

This is the main circuit board which receives and decodes the radio signal and controls the motors and lights.

Super fast double charger!

I'm connecting the batteries using a replacement Makita battery terminal.

View of the shop during disassembly.

View inside the hood prior to conversion. I had not been under the hood of my NW2 yet so I was surprised how many more wires there were compared to my U25B.

Disassembly was a bit more difficult than I was expecting. The screws were very tight and I ended up stripping a couple of them that were a big pain to remove. But things got easier once I got everything disassembled, as I was then just following the step-by-step instructions in the manual. My NW2 has some slight differences from the one AirWire used for their instruction manual, so I did have to improvise a little bit at times. Also, as I was using an external battery I had to come up with a solution for how to run wires from the hood circuit board out the back of the locomotive.

Once all the wires were hooked up I needed to conduct a power test to make sure everything was operational. I connected the battery, turned on the power switch, and there was a small pop and a cloud of smoke. I immediately disconnected the power as something was terribly wrong. My first thought is that I had just fried the circuit board. But fortunately the source of the smoke was the power cable. I had reused a plug that had been removed from the locomotive as it wasn't needed anymore, and upon close inspection I realized that the red/black wires on this plug were the reverse of what I needed, so I had accidentally crossed the polarity of the battery. The wires attached to that plug were also a smaller gauge, probably smaller than I should have been using, and so that thin wire is what had overheated and caused the plastic coating to burn off.

I removed the damaged section, got a different plug with a heavier gauge wire and checked twice to make sure the polarity was correct, and reattached it. I nervously hooked the power back up and this time was rewarded with a green power light and a happy little beep. I ran through the various tests and everything was working as expected. I was very fortunate that the wire had served as a circuit breaker and the board was unharmed.

Circuit board has been mounted and wires are reconnected, prior to hooking up the power.

I was planning to drill a hole at the back of the locomotive to run the power cable out. But then I noticed there were two small holes hidden under a step below the cab door, so I used them for the two wires.

I wanted to do an actual track test before closing up the locomotive, so I took it outside and got a gondola out of the garage to temporarily hold the battery. It was so exciting to see it zip around the track while I was testing out my new remote. After I was satisfied with the performance, I finished closing up the locomotive and reattaching the decorative pieces.

Then it was on to the battery car. Not much to do here compared to the locomotive, as I just need to decide how to hold the battery and run the power cable out the front end of the car. I was not able to complete it today as I'm waiting for some supplies to arrive, and hopefully I'll get it done next weekend.

Out for a test run, with the battery just sitting in an open hopper

The battery will sit in the middle of the box car so it can be accessed from the center doors. I need to create a cradle to hold the battery in place so it doesn't slide around while the train is in motion. I wasn't able to complete that step today as I'm still waiting for the materials to arrive.

A close-up showing the power cord coming out underneath the car floor. I thought this looked a lot nicer than a hole in the end of the car body.