Micro Welder Unit

[Chris]

[nakros]

Chris,

. He has schematics and such and describes the process. Were you looking for something large like this (he mentions using this machine to weld with 5/32" rods), or something smaller? Perhaps this plan could be scaled down, if need be?

Hope this helps!

Greg;

[Chris]

Hey Greg,

That's a pretty awesome site; in fact something I may build once I have my shop But I'm actually looking for something very small in size.

I'm going to be rebuilding a number of battery packs around home for various reasons and soldering the batteries together is bad in so many ways. The best way to make battery packs is to use a "micro welder" and weld the "solder tabs" on to the batteries.

This is a quick and instant weld not even requiring any solder or flux. No mess. It's also the fastest and most secure way to assemble one's battery packs. You can throw a pack together in minutes vs hours with a soldering iron. You also eliminate the chance of destroying your battery pack with too much heat before its even finished.

Bottom line I picture something that would probably be nothing more then one or two large capacitors, low voltage. They would discharge the instant I touched them to the surface of the piece and poof instant weld.

It really would be for instantanious contact ...not for doing a bead or anything larger then pin point welds.

What are the electrodes made of in a spot weld unit? Those electrodes are probably what I need to get my hands on.

Hell you could probably use a big CAR Battery to do this ...12v is probably the perfect voltage and they can push 200+ amps. I just need to know what electrode material is required. Also what material are those "solder tabs"? Are they silver, Nickle ...or some alloy? I need to get my hands on a number of them as well or a ribon of it that I can just cut into tabs.

Anyone have some larger capacitors (lots of uF but low voltage) that they'd be willing to send my way for this little project?

[nakros]

[Bob Boyce]

[Chris]

[bonehead]

[Etownlax]

The Site above explains how to weld with 3 car batteries... it said if you were a really good welder you might be able to get it with just 2 batteries...

Just worth a thought.

-Randy

[nakros]

Chris,

I don't know if you are still interested, but here is another link to a I came across it while looking for a way to weld tabs onto battery packs. My cordless drill batteries have been taking less and less of a charge, so I'm planning on replacing the cells with NiMH, instead of NiCAD. We'll see how it works out.

Greg;

[WiLi]

Dear Chris,

some time ago I had my NiCad battery pack refurbished in a supermarket. The man there does it somehow like the MisterMinutes, on the fly.

He used a double spot welder.
That is in principal a big transformer from a TV or the like with a VERY thick secondary winding. It needs only one or a few turns, because the voltage needed is very low. Only the Amperage needed is very high. (For these tiny batteries I expect necessary current of 50 to 100 Amp. Professional spot welders for heavy metal work do have something like upwards from 2000 A, they are switched from primary side by a mechanical clock that starts with a minimum current)

His welder had a lever somehow like in the stand of an electric drill. By pressing down, the contacts to the primary side of the transformer where closed. I am not sure wether there was an automatic switch off. Welding time is in the range of 1/4 sec.

So a heavy copper pipe hammered flat or the like could serve well for such a winding. Maybe even a car battery copper cable directly wound to the trafo would do if the old secondary windings where removed, this would have the advantage that you need no heavy contacts for extension: you could use the cable unto the welding tips.

Welding contacts are always copper, since other material would heat up too much. They must be maintained in a blank state.

Important for spot welding is not only good contact (blank metal is always mandatory) but also pressure on the welding tips.
Also they must be as close apart as possible for low resistive paths.

When the welding takes place, the heat from the current produces a small "pond" of liquid metal between the welded parts. The pressure is needed to squeeze the liquid metal sideways out so that only uncontaminated metal builds the newly welded contact zone.

Metals that can easily be spot welded:
stainless steel (best)
galvanized steel
Nickel
Zinc
black steel


Difficult metals:
Aluminum
Copper
Brass
Bronce

It may be worth a try to put a thin layer of stainless steel between the parts if you have to weld the difficult metals.

Be aware that although the secondary winding is of extreme low resistance, it will have an opening voltage (shut off voltage) in the range of thousands of Volts. Not very desirable to hold contacts with bare fingers.


Have fun!

WiLi

[juanito]

[Etownlax]

[Chris]

[ElectroGasMan]

[BEMET]

The spot welder electrodes should not be used to "clamp" the metal together. They should only touch. If the two pieces of metal do not touch without pressure where you want the spot weld bend or grind them so that they do. Clamping the metals together with the electrodes causes the electrodes to stick in the spot weld and sometimes throw sparks and blow a hole in the metal.