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.

My first attempt to remove the secondary.

This is the way I recommend removing the secondary.

I then used a screwdriver to pry the transformer apart.

Once the weld breaks on the top, it is easy to break the one on the bottom by just prying the transformer open.

I then tried using a piece of wood to hit out the coils.

 

I wasn't able to hit out the coils with the wood so I left the transformer in the sun to warm up. It was then easier to take out, both with the wood and the screwdriver prying out the coil.

I just removed the center coil and the shunts.

I just pulled the coil o

Since I had already sort of cut one side off, I had to push a screwdriver through the transform in order to get the leverage I needed to remove the coil. I ended up just pulling the good end of the transformer up and over the center post of the transformer in order to get it out.

You can see the screwdriver in this picture.

Placing the wood on the screwdriver and hitting.

Here is were I decided to just hit the transformer out.

The finished transformer.

I put nail polish on the places I saw nicks.

The wire I used since I did not have anything thicker.

I cut them to a length of about a meter (or a yard).

I cut two lengths from each color.

Test fit.