Spot welders

Discussion in 'General Electronics Chat' started by R!f@@, Feb 8, 2013.

  1. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
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    It's been bugging me for quite sometime now.
    Since I see this done on batteries and cells terminals. Typically on Li-ons I get from battery packs.

    I wanna now how it's done without destroying the cell. You tube got jack. I did a search and all I get is useless junks.

    Any one got any real info on this ?

    May be any DIY project on doing this on coin cells as such.
     
  2. PackratKing

    Well-Known Member

    Jul 13, 2008
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    I would like to know that myself.
    For all NiCad cells, as in power tool packs... I first determine that they will take and hold a decent charge, and then solder the bands or even wires to them...

    Soldering ain't too shabby. I use my 350 watt Weller gun, " Oatey " brand of lead-free plumbing solder and their flux.

    I get the Weller really hot... and with flux on the battery and the solder, it takes about half second to tack a wire on the batt without heating the battery too much. and afterwards brush off the flux left behind with a toothbrush and denatured alcohol.
    I have yet to have one fail for bad solder... Though I haven't tried that method on a button or wafer cell yet due to the heat issue. Shall update if any luck.

    I would like to know if they use some kind of capacitor-discharge spotwelder, tho' it seems the HV pulse alone would retard the battery...

    I sometimes overlook the fact you're out there in the middle of the ocean, and d/n know what all supplies you have immediate access to...:D
     
  3. R!f@@

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    I am in the middle of the ocean and I have to buy most parts off ebay and they take sometimes a month or two to reach.

    I think it's capacitor discharge spot welding.
     
  4. Mad Professor

    Active Member

    Apr 15, 2009
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    From what I have seen on the internet it is done by "Capacitor Discharge Welding".

    Just doing a Google or YouTube search on "Capacitor Discharge Welding" finds lots of hits.
     
  5. chuckey

    Well-Known Member

    Jun 4, 2007
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    I am about to do this, The secret is that copper electrode do not stick to other metals. Normal spot welding relies on the high resistivity of the metals and a timer to switch the current off and clamping the metals together by the welding tips. Industrial capacitor welding, sort of does the current and time at the same time. I reckon it will need 100A for 1 sec (work out the cap size!!) I have use the classic 50,000MF at 50 V to clear the internal shorts from NiCad cells and the probe makes a small flash mark ~.5mm diam, not enough to weld a proper strap, unless its a grasshoppers watch strap.
    Frank
     
  6. #12

    Expert

    Nov 30, 2010
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    I solder most of 'em, as per PackratKing. A diamond coated fingernail file will break up any plating material that might be in the way. I'm ignorant about current and time for a spot welder. I have heard people speak about welding their thermocouple back together with a capacitor discharge. Trial and error, mostly error. Two skinny wires to make a connection with each other is a tiny job compared to spot welding a couple of steel sheets together. The clamping spot welders I have seen don't use capacitors, but a low voltage winding like a big Weller soldering gun. Those worked from a 120 VAC American wall outlet. Probably less than 1800 watts.

    Watching and expecting to learn something here.
     
  7. BillO

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    Nov 24, 2008
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    You didn't find this?
     
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  8. spankey666

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  9. BillO

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    Nov 24, 2008
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    Nice picture on your wall!:D
     
  10. spankey666

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    Nov 30, 2011
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    are you referring to my wife ? or the electroplated images ??? :rolleyes::D
     
  11. BillO

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    Nov 24, 2008
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    You wife, eh? Nice!
     
  12. R!f@@

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    Spankey & Bill0, ain't that the same thing.

    Do I need to buy the plans or what ?
     
  13. thatoneguy

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    Feb 19, 2009
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    What is that power supply you are using to charge the caps?
     
  14. strantor

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    Oct 3, 2010
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  15. spankey666

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    Nov 30, 2011
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    its just a small bench power supply.

    Rif@@ for welding copper the out put just needs to be DC so a simple ne555 inverter circuit can be used to charge the caps. alas this doesnt work well for aluminium as the output needs to be a massive burst of high frequency ac to get a good weld.
     
  16. BillO

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  17. R!f@@

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    I don't get it yet.

    some people uses single pulse and other dual or even three. What gives?
     
  18. BillO

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    Nov 24, 2008
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    Not sure, but I think two smaller pulses will give a better and cleaner weld than one big one.
     
  19. Mad Professor

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    Apr 15, 2009
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    Last edited: Feb 23, 2013
  20. THE_RB

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    Feb 11, 2008
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    What's the logic behind that Bill? I've used industrial spot welders and normally they make one pulse, large enough total energy and time to bring the target to above melt point so the two metals fuse together.

    I'm no expert but to me it seems if using smaller pulses there won't be enough time on any single pulse to bring the metals to melt, and time between pulses allows heat to spread out in the metals so by the time it's welded you have needed more energy and the metals have more localised heating causing more warp, more chance of burning fingers etc when handling.
     
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