"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?

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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?

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On Tue, 12 May 2009 12:35:34 -0300, Bruno wrote:

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...

--
www.wescottdesign.com

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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 again!

wrote:

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

http://sunstoneengineering.com/site/pages/sales/#dpcap_2007

DJ

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On Tue, 12 May 2009 15:38:18 -0600, IdaSpode wrote:

-- snip --

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

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Battery tab welding has been discussed on SEJW in the past and can be found archived thru google groups: http://tinyurl.com/prpef6

One discussion in 2002 (http://tinyurl.com/ok8ul9 ) led to this posting in the metalworking.com website dropbox: http://www.metalworking.com/dropbox/_2002_retired_files/BatteryTabWelder.pdf The author (MikeR) used a microwave transformer and timing circuit (using a GAL20V8 PAL chip), but didnt include a schematic.

A more recent discussion on SEJW ( http://tinyurl.com/pxwybb ) led to this link: http://www.5bears.com/welder.htm It uses an octal timer, solid state relay and modified transformer.

A DIY capacitance discharge (CD) welder is described here: http://www.philpem.me.uk/elec/welder / Schematic:

http://www.philpem.me.uk/elec/welder/images/schematic.png Discussion: http://www.rcgroups.com/forums/showthread.php?t=763308

Other DIY microwave transformer spot welder videos:
http://www.youtube.com/watch?v=9spgDiU3_nw&NR=1

http://www.youtube.com/watch?v=Z7M9_YEqF6o

This one is a particularly nice build showing controls for pulse width and voltage (but no schematic):
http://www.youtube.com/watch?v=yabesdeGKJo

There is also a relatively new Yahoo discussion group batterytabwelding, but it has gotten only a few posts.

Commercially available Sunstone CD welder video:
http://www.youtube.com/watch?v=mWhWix72jJo

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

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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.

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resistance welding

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