Homebrew battery tab welder

battery tab welder

[Phil Pemberton] has been building quite a few battery packs over the last year and decided he needed a better method than soldering. Soldering can often damage the end caps and cell seals. He decided to build a simple capacitance-discharge resistance welder to assemble the packs more efficiently. It doesn’t take many parts, but you’ll have to do some tuning to get it to work correctly.

Comments

  1. CDE says:

    So, where can I find some computer caps to try this out? I’d figure that I can use a computer psu to weld those laptop batteries together…

  2. doctord says:

    You can get them at Fair Radio Sales: http://www.fairradio.com/comput.htm

    Good luck!

  3. Tony says:

    Too bad the builder didn’t create a parts list with part numbers and sources along with a schematic. The circuit is simple, but a schematic would make it easier for folks to understand. The capacitors in the link from poster #2 don’t seem to be the same value as the builder used. I guess as long as you get close to the 600,000 mark using more caps, then you will be ok…???

  4. I’ve put a copy of the parts list in my blog – http://www.philpem.me.uk/blog/ – I’ve added the parts list to the page itself, too, along with a few possible sources for components.
    If anyone finds a source of 0.003 Ni200 or Ni201 nickel shim stock in the UK, please tell me!

  5. tony: As long as you get close to 600,000uF you’ll be fine. The Hobby Spot Welder I based mine on uses a 680,000uF capacitor. Any less than 600,000 and you’ll have problems.

  6. thanks phil! i’ve been trying to find a way to build new lion packs. does anyone know of a good source for getting new cells? i haven’t found anyone who will sell them to end users.

  7. CDE says:

    Jason, ebay, google (for the generic part number), and http://candlepowerforums.com/vb/ (ask around for a particular part)

    Or atleast, that’s the only place I remember that people talk about them alot.

  8. Tony says:

    Phil,

    Thanks so much for updating the webpage with the parts list and suppliers! That will really help out a lot of people wanting to build this. It seems like such a useful tool for so many uses. I fix and restore pinball machines and I am going to try and use this to repair spot welds on metal ramps and guides that use thin metals… Thanks again for providing the additional info!

  9. Jimbo says:

    Cool hack. But put it in a case! Its going to be a bad when your elbow shorts the caps.
    -James

  10. Andre says:

    Two things.
    1) The voltage on those capacitors isn’t high enough to warrant a case
    2) I’ve used a 1F “audio” capacitor but these are slightly overkill. 0.5F might work and be a little cheaper if you go for the budget option.

    I supplied the electrodes and wire- the outer pipe is silver soldered to the core to maximise conductivity (at 100+A it really does make a difference)

    -A

  11. zeropanic says:

    Is it me, or does that picture look as if it says $hit in a [can]?

  12. ryan says:

    that doesn’t look like a “t”, maybe it’s “shims in a can”

  13. nutwithawrench says:

    Just a tip;
    to make the electrodes, put copper rod in an electric drill, where the bit usually goes, and spin it on sandpaper, sharpening stone, the sidewalk, anything stronger than the copper!

    does anyone know if this welder can weld other metals? ie .006 copper?

  14. zeropanic: It actually says “Shim in a Can” on the tin. Shop-Aid makes it, McMaster-Carr distributes it.

    nutwithawrench: Nice idea. Problem is, the copper tends to bend when you do that.. Also, copper won’t weld at all IIRC – it’s too conductive, both to heat and electricity. That’s why the electrodes are made of copper – stops the heat building up on the electrodes, so they don’t stick to the battery tab.

  15. CDE says:

    Hey andre, so an 1f audio cap works? At what voltage?

    And I have a question. Can I charge one of those caps at 12v, (from a computer psu) and would it still work?

  16. cde: i’m running my caps at 9v, but you need all 600,000uF to manage that. if you’re using a lower capacitance you’ll need to use a higher voltage to get the same output power.
    every welder is different – get a bag of flat alkaline batteries and some nickel shim and have a play around. in a pinch, you might be able to use 0.003 stainless steel, but that’s got a really high resistance compared to most metals and isn’t really ideal for battery packs.

  17. Andre says:

    Hi,

    Yes, 12V should work. You can compensate for the increased capacitance by lowering the charge voltage.

    I say its better to have too much storage than too little :)

    -A

  18. Mike harris says:

    just a note of caution, to everyone, If you do this “PLEASE” be very careful to start out small, if your trying to weld Li-Ion cells!!! they are very dangerous and if you breach the can while welding you will create a mini blowtorch. and it will burn just about anything in its path, including your fingers! also FYI, this will not weld copper, you can but you need to use a different electrode. you will need to use a tungsten or molylibnium(sp?) Electrode to be able to weld copper. also I recomend that you use the Nickel .003-.005 thick for welding cells together, remember the wider the tab the more current will travel without overheating. I work in the Battery Industry, and I just want people to be very cautious even trying to weld Li-Ion cells. I DO NOT reccomend it at all.

  19. mike harris:
    thanks for your suggestions and warnings. like i said – start low, then work up. you only tend to do breach the can if you do something stupid, like jumping straight to 20V and ending up pumping 100 joules (watt-hours) over a <3mm section of nickel. that’s why i tested with alkalines – they’re not too bad if the can gets breached.
    “start low, then work up”.
    i’ve successfully welded to a lithium ion cell. can’t remember what voltage i used (about 6V IIRC), but it worked pretty well, even though there were the remains of some weldtabs already on the cell.

  20. Paul Meiners says:

    Search for “240,000 uf electrolytic caps” on Ebay, item 5821442863. Seller has quite a few Philips ’97 for excellent price. Searched google for over a day, was ready to buy at rediculious prices.

    Ebay

    http://cgi.ebay.com/240-000-uF-electrolytic-caps_W0QQitemZ5821442863QQcategoryZ48708QQrdZ1QQcmdZViewItem

  21. Amos says:

    To bad that ebay seller refused to shipping to my “overseas” country of Canada.

  22. amos says:

    I wish that I could remove the above comment I made about the ebay seller. The employee offered to go out of his way to sell me the caps. I feel like jerk because of the overseas crack.

  23. Paul Meiners says:

    The seller is a nice guy, I can understand you frustration trying to locate caps. Our Customs agency requires nonsense forms to ship to Canada, can’t blame him for not wanting to get involved. Some of the regular Ebay sellers are charging high prices for much older caps 1982

    I almost have all the parts, the case is going to cost more than the Ebay purchased Sorensen 20v 12amp PS ($54.00).
    As a mod to Philip’s unit, I going to place an SCR on each set of two parallel capacitors (8 total), so I can use simple switches to add capacitor banks. Just so happens the SCR I got off Ebay fit the screw thread of the caps, which will be be a easy SCR mount. Just using short wires and crimp lug between the caps, I’m not spending another day locating copper bus bars, again probably costing more than the power supply.

    I am adding an SCR to turn off the feed from the power supply, as the SCR to the “workload” is triggered. Figuring ,if I vary the PS volt/amps, the welding power will not be influenced by the power supply feed, for consistency, especially at higher volts/amps settings.

  24. Paul Meiners says:

    The seller is a nice guy, I can understand you frustration trying to locate caps. Our Customs agency requires nonsense forms to ship to Canada, can’t blame him for not wanting to get involved. Some of the regular Ebay sellers are charging high prices for much older caps 1982

    I almost have all the parts, the case is going to cost more than the Ebay purchased Sorensen 20v 12amp PS ($54.00).
    As a mod to Philip’s unit, I going to place an SCR on each set of two parallel capacitors (8 total), so I can use simple switches to add capacitor banks. Just so happens the SCR I got off Ebay fit the screw thread of the caps, which will be be a easy SCR mount. Just using short wires and crimp lug between the caps, I’m not spending another day locating copper bus bars, again probably costing more than the power supply.

    I am adding an SCR to turn off the feed from the power supply, as the SCR to the “workload” is triggered. Figuring ,if I vary the PS volt/amps, the welding power will not be influenced by the power supply feed, for consistency, especially at higher volts/amps settings.

  25. Don Shuen says:

    Hi Paul, Do you have a circuit diagram to share? I want to build one but I can’t figure it out from Phil’s picture.

  26. Rod says:

    The set voltage on a one farad car audio capacitor unit is 14.5 v for .004 inch stainless steel shim stock. The single capacitor eliminates the connection problems and normally has mounting brackets. Ebay has these monster one farad caps selling for around 40 to 50 dollars.Complete plans are there also. Solid electrical service ground wire makes good electrodes.

  27. eg says:

    The capacitors are not hard to find.

    Charging it up is expensive part.

    youtube has some videos on ‘Capacitor discharge welding machines’

  28. Fritz says:

    I just finished my 600Ws Capacitor spot welder with pulse width control check it out: http://www.youtube.com/watch?v=yabesdeGKJo

  29. Fritz says:

    Check out my tab welder with pulse width control http://www.youtube.com/watch?v=yabesdeGKJo

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