Welding Tips and Tricks

With all the welding equipment I have, there must be some way I can rig up something to allow rebuilding battery packs for my cordless tools. I end up with multiple drills because a kit with a tool, battery and a charger costs just a bit more than a replacement battery itself. I want to standardize on Milwaukee for my cordless tools, but want to rebuild battery packs to save some money.

I have tried various methods and using a time variable delay relay to control the "on" time of a 220VAC spot welder works. Instead of tongs I use woven ground wire and hand held ground copper rods as the electrodes, but the welds are inconsistent and I wouldn't trust this method to make battery packs that are reliable.

Granted by now I am spending more time than this is worth, but I'm intrigued by this problem and want to solve it. Does anyone have any ideas or experience on how to get consistent spot welds on rechargeable battery tabs?

Yeah.

Go to Battery Depot, and order "tagged" batteries in your size and A/h. They come with the connectors already attached for the same money you're spending to try it the hard way.

If you insist on doing it the hard way, set up for solder. Prep the battery and the tab for solder, cut a little tab of rosin-core, mash it flat, and put it between the battery and tab. Then, it only takes a fraction of a second of heat to make the joint, and hopefully not damage the battery.

Steve S

Batteries Plus rebuilds packs at a fair price - why not have them weld the tabs for you? I've inquired about their welding rig, and it's a pretty specialized piece of gear designed to fuse the tabs without damaging the batteries. It's a form of inverter spot welder.

Welcome to the forum tmeinc.

Thanks for the input. I have continued to fiddle with this and am now making very satisfactory spot welds. The tabs I have welded on old nicad batteries are secure and when I peel them off the battery the failures look like the failures on the old factory battery tabs I removed when I started this. The back sides of the welds look like they got about as hot as the factory welds. Here is my latest set-up. There are some tricks I needed to learn, but

220 volt Harbor Freight spot welder with heavy woven car ground strap instead of tongs.
Hand sharpened 1/8" tungsten tig rods for electrodes.
Hand held electrodes for the spot welding process, and hand force to hold good contact among the electrode, tab and battery.
Time delay relay set at .25 second step pulse driving a 40 amp double pole relay. This controls the 220vac to the welder, not the actual welding current.
Foot pedal to start the time delay relay and initiate the weld.

I'm ready to order new battery cells and build a few replacement battery packs, and will post again when I have completed welding and tried the finished product. Along the way I expect to add spring loading to the electrode holders but have not worked out a suitable configuration yet.