"Point welding"?

Hi All,

How do you call the technique that attaches those extremely thin (0.01") tabs to the steel casing of rechargeable battery cells so that they can be soldered to wires or connectors?

Looking closely at the welded tabs, they have very small, point-like signs of having being fused.

Also... Any ideas for achieving this in a DIY fashion?

Spot welding -- it's just a very small spot.

The spot welder that I had the opportunity to work with used copper electrodes and put a controlled current through the electrodes. Because the underlying steel had a higher resistance than the copper, and because the electrodes tapered down, the current would heat the steel far more than the copper and weld everything nicely together (at least if everything was nice and clean before hand).

Dunno about the particulars for spot welding battery straps. It may well depend on melting the nickel plating, you'd almost certainly have to make sure that the strap material was compatible.

Hopefully someone who actually knows will be motivated by all my erroneous and/or vague statements to come and correct them...

Thanks Tim,

As obvious as it sounds *now*, I tried and tried but coulf not come up with SPOT welding!

...Off to Google again, do some more searching - now that I know what to look for.

Thanks aga>>

Try: "resistance spot welding battery pack" as a search term. Bring lots of cash when you go shopping...

DJ

I have never had a problem *soldering* leads to cells.

-- snip --

I saw those prices, too. It does make one want to DIY, at least if it can be done economically.

resistance welding

Soldering directly to many cells (lithium comes to mind) is a recipe for a rather spectacular destruction of the cell, involving lots of smoke. DAMHIKT. That's why they have those tabs spot-welded on.

Battery tab welding has been discussed on SEJW in the past and can be found archived thru google groups:

One discussion in 2002 ) led to this posting in the metalworking.com website dropbox: The author (MikeR) used a microwave transformer and timing circuit (using a GAL20V8 PAL chip), but didn=92t include a schematic.

A more recent discussion on SEJW (

) led to this link: uses an octal timer, solid state relay and modified transformer.

A DIY capacitance discharge (CD) welder is described here:

Other DIY microwave transformer spot welder videos: ?v=3DZ7M9_YEqF6o This one is a particularly nice build showing controls for pulse width and voltage (but no schematic): There is also a relatively new Yahoo discussion group =93batterytabwelding=94, but it has gotten only a few posts.

Commercially available Sunstone CD welder video: