Microwave Oven Transformer Spot Welder Part 1

Recently while I was at the solar cup event (which we placed 5th overall and 1st in Endurance) I talked with someone about their electric bike. He had used a hub motor from goldenmotors and built the battery himself from the cells inside laptop batteries. We talked for a while about it and I was surprised to find out it had a top speed of around 45 mph (but not on public roads) and a range of over 100 miles. I was really impressed and spent a lot of time researching about different motors, how to build different batteries. I even researched velomobiles, thinking it would be awesome to build a electric powered trike velomobile because of the comfort and range.

I decided to take it one step at a time though. I had already taken apart and salvaged parts from an old microwave so I had all of the parts I needed to build a spot welder. A spot welder is used to connect all of the 18650 cells together to form the larger packs needed to run vehicles.

I started trying to take the second transformer out by hacksawing it directly out of the transformer. I do not recommend this way. I ended up just cutting the weld on the transformer and prying and hammering out the coin coils.

I then used nail polish to cover the places on the primary that I had scratched off so that it would not short.

For my secondary, I did not have thick enough wire and so I made due with 6 strands of 14 gauge wire.

The main parts of the spot welder.