I was out on the web looking at different DIY battery spot welders that people have built. Most are built using repurposed microwave oven transformers and quick switches. Some were successful and all pretty much have single pulse to weld. Some were just too powerful. I did however find one that utilized a 12 car battery and and arduino board to control the power of the weld. It happens to be a DIY but you can also buy one prebuilt for you if you don't want to do that your self. As with me, I opted to just buy one already built. This sucker can be totally portable but normally uses a 12v 1amp power for the arduino and a Car Battery for the main power to weld with. It includes a place to connect up a micro switch so you can hit your switch and once you hit the switch it will not continue to weld. The board is a dual pulse board and will allow for 1 to 20 milli second pulses. The first pulse is 1/8th the power of the second. That is automatic. It is setup up to do these welds by hand but you could build a box to allow you to put constant pressure on your welds so each is consistent.
I plan on building a box to give constant pressure so I get real constant welds. I have some I want to connect together for testing and some for my RC stuff. Now that I don't have to worry about those micro wave transformers I can get on with welding. I have a series of 4 CALB cells for my 12 volt pack. Its light enough to carry and I can lug it with me if I need to weld out in the field.
Finally, a DIY welder you can build or buy to do good spot welding of the tabs instead of soldering and making a mess. I hope to build a power wall with some cells and if the cells I am testing are good I will see if I can buy enough for a pack for my EV and enough for two for my house. Built it myself and it they re LiFePO4 chemistry. The safe Chemistry.
