VirgilBudBrigman wrote: ↑
May 17 2016 1:16am
Finished spot-welding 240 cells (20S12P from 5 separate 4S12P packs, LG HG2 cells, 3000mAh/ea, 20A continuous each, total of 2.6kwh). Used 0.2mm x 8mm pure nickel, carefully laid out to achieve approximately 160-170A ampacity.
JP Welder has not been perfect, but I got through it! I blew a trace and a mosfet, but I put that down to the several feet of 1GA welding wire I originally used to extend from the car to the table. Later replaced all the MOSFETS with same type but automotive grade (like another $1-2 total, why not!?). Also implemented the diode mod (VS100BGQ045) that Okashira recommended. Of course, I also stopped using the long wires (less resistance) and implemented other mods, like the cooling fan and 12GA romex wire from the bus-bar to the MOSFETS. The whole thing runs VERY cool now, used to get almost burning hot! (Only the tips of the electrodes get warm when doing rapid fire welds)
The biggest issue I had (and a scary one) was several dozen times I had blowouts (craters), which are quite scary! My material is pure nickel and I experimented with differing pressure, timings, angle, cleaning the electrodes constantly, etc. I'm thinking the copper electrode material of these is not ideal...there must be something better! Furthermore, the wires themselves are not flexible at all...so I'm glad to see others looking to rectify these issues.
Another issue was sticking, and some of the copper getting left in the weld. This happened for up to half of all the welds. I tried the press and rotate technique others spoke of...which helps some. The sticking seems to contribute to the breakdown of the electrode, and needing to un-screw, put in the drill and spin it smooth and round/pointy again. I also lowered the settings down until pulling hard would "just" not break free of the cell.
I used a single brand-new Rural King battery (same as Exide Edge for a little more than 1/2 the cost, my wife's car battery had just died so the timing was perfect! http://www.ruralking.com/battery-auto-a ... gm24f.html
) and it worked VERY well. Before the mods I was up to 2/3 or so on the dial. After the mods, I was down to under 1/3 on the dial. Don't assume that you will need two batteries, for a good battery and 0.2mm nickel, you probably need only one!
SUMMARY: This spot-welding business is not for the faint of heart. Ironically, it's also not for the careless! Biggest improvements (post-mods) would be better electrode material and more flexible welding cables. (Or go with Headways if they dramatically improve the chemistry and you can fit them!