Who needs battery tab welding?
In the last few years, a lot of electric bike batteries & telsa cars if I’m not mistaken use 18650 sized lipo cells. 18650 cells weigh about 50g each and can hold anywhere up to and maybe a bit north of 13Wh per cell. Many consider them the best available source of power for Ebikes and use them exclusively now. Since you have to make packs using dozens or even hundreds of cells, they need to joined together. There are 3 ways I can think of to join them, soldering, tab welding or through compression with springs or other contacts. I’m tempted to add my 2 cents to the ongoing debate over solder vs. welding of cells. I will simply say welding has been adopted by the industry, for whatever reason be it economic or safety or other, and since I want to produce industry quality packs, I’ve chosen to weld packs. I have successfully soldered packs in the past so I know it does work but I’m not expert enough to provide any proof that one is better than the other. It would involve measuring the amount of heat produced and transferred to the battery chemicals and seeing if it affects life or capacity. I will say that done improperly, both welding & considering can both lead to cell rupture so be careful. Don’t add more heat than needed regardless of how you join batteries together.
What kind of welding is battery welding?
When you hear the term battery welding, what people are referring to is resistance welding. Thin strips (tabs) are placed on top of the battery, current is passed through the tab and battery shell causing a small spot to melt and join together permanently. This is the same type of welding that is used to assemble cars, and many many other things, but on a much smaller scale.
There are two kinds of resistance welding machines that I have built and tested. The first uses a modified microwave transformer to reduce the line voltage and increase current to generate the weld. The second stores power in capacitors and then quickly discharges that power through the work to create the weld.
Microwave Transformer based Welder