Capacitive Discharge Welder Anyone?

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Chris Stone

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Sep 13, 2015, 1:35:53 AM9/13/15
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For those that don't know what it is: http://www.batteryspace.com/prod-specs/5997.htm
TL;DR: Dump a metric ton of amps(legit units) from a BIG capacitor into a join between two pieces of metal in 2-3 milliseconds to weld them together.  

I want one so that I can safely weld battery tabs onto lithium ion battery cells to assemble them into packs, but I was having difficulty locating a good capacitor. 
I finally found a source, but they aren't cheap. It looks like it's going to cost between $200 and $300 to build this thing.

I can't justify that price by myself for the project I'm working on, is anyone else interested in getting this?




Craig Carmichael

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Sep 13, 2015, 3:07:42 AM9/13/15
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My memory says they shouldn't cost that much. Did you check digikey.ca, futureelectronics.com, ca.mouser.com, canada.newark.com ?

But also, here's much experience speaking:

I have soldered wires to battery cells, _mostly_ alkaline but a very few lithiums, for decades now without ever having had any problem whatsoever. I have 300 soldered NiMH "D" cells (3 x 100 AH 12V batteries) in my electric car alone.


I used #16 stranded wire - in a car stiff solid wire/bars eventually breaks the solder join with vehicle bumps and vibration. Always wrap any metal cells that have only plastic insulation with masking tape, cardboard, tarpaper, etc, because if they get hot the plastic melts through, the metal cans short, and then everything starts smoking and popping, and there's not one cell left afterward.

See Turquoise Energy News #87, 88 or 89 (?) where I solder together a new NiMH "sub-C" pack for two cordless drills, for more info. And somewhat earlier ones for the car batteries, and some even earlier ones to see what's left of battery packs that got too hot without the paper wrappings on the cells.

Craig

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Eric Davies

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Sep 13, 2015, 3:07:46 AM9/13/15
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On youtube, there is a brit guy walking you through the steps of making a supercapacitor at home.  Buying a supercapacitor might be faster though :-).

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Eric Davies

Chris Stone

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Sep 13, 2015, 12:59:47 PM9/13/15
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Craig: I did check, the specs on these things make them very unusual 1.5-3 farads at 20v (the shitty walmart special car audio ones do not hit their capacitance ratings)

Eric: Supercaps don't have the esr requirements for cap welding.


On Sunday, 13 September 2015 00:07:46 UTC-7, Eric Davies wrote:
On youtube, there is a brit guy walking you through the steps of making a supercapacitor at home.  Buying a supercapacitor might be faster though :-).
On Sat, Sep 12, 2015 at 10:35 PM, Chris Stone <> wrote:
For those that don't know what it is: http://www.batteryspace.com/prod-specs/5997.htm
TL;DR: Dump a metric ton of amps(legit units) from a BIG capacitor into a join between two pieces of metal in 2-3 milliseconds to weld them together.  

I want one so that I can safely weld battery tabs onto lithium ion battery cells to assemble them into packs, but I was having difficulty locating a good capacitor. 
I finally found a source, but they aren't cheap. It looks like it's going to cost between $200 and $300 to build this thing.

I can't justify that price by myself for the project I'm working on, is anyone else interested in getting this?




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bryanb

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Sep 14, 2015, 1:25:22 AM9/14/15
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I have a number of 1300 to 2000 uF 600vdc caps I could donate to the cause if you want to make this happen ...
Bryan

Craig Carmichael

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Sep 14, 2015, 3:28:59 AM9/14/15
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I can't find the cheap imitation tab welder I once made (I never
added a switch - touch and zap), but it seems to me I was burning
right through thin tabs with 24 or 30 x 4700uF from Queale, ie, .11
to .14 farads. (@25v) I think using the considerable number of
distributed "smaller" capacitors (connected to #8 wires) was an
advantage to get the sudden high current.

Craig

=====

>Craig: I did check, the specs on these things make them very unusual
>1.5-3 farads at 20v (the shitty walmart special car audio ones do
>not hit their capacitance ratings)
>
>Eric: Supercaps don't have the esr requirements for cap welding.
>
>On Sunday, 13 September 2015 00:07:46 UTC-7, Eric Davies wrote:
>
>On youtube, there is a brit guy walking you through the steps of
>making a supercapacitor at home. Buying a supercapacitor might be
>faster though :-).
>
>On Sat, Sep 12, 2015 at 10:35 PM, Chris Stone <> wrote:
>
>For those that don't know what it
>is: <http://www.batteryspace.com/prod-specs/5997.htm>http://www.batteryspace.com/prod-specs/5997.htm
>TL;DR: Dump a metric ton of amps(legit units) from a BIG capacitor
>into a join between two pieces of metal in 2-3 milliseconds to weld
>them together.
>
>I want one so that I can safely weld battery tabs onto lithium ion
>battery cells to assemble them into packs, but I was having
>difficulty locating a good capacitor.
>I finally found a source, but they aren't cheap. It looks like it's
>going to cost between $200 and $300 to build this thing.
>
>I can't justify that price by myself for the project I'm working on,
>is anyone else interested in getting this?
>
>
>
>
>--
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>
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>Eric Davies
>250 595-0639
>
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Chris Stone

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Sep 15, 2015, 5:29:21 PM9/15/15
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Bryan, those caps are too small (and too high voltage) for this project but thanks for offering

Eric, 0.1 Farad at 25v is only 31.25 watt seconds, even the lowest cap welders I see are rated for 100ws, with the better ones being adjustable up to well over 200.
I would love to see what you have though if you can locate it. 


>For more options, visit
><https://groups.google.com/d/optout>https://groups.google.com/d/optout.
>
>
>
>
>--
>
>Eric Davies
>250 595-0639
>
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>To unsubscribe from this group and stop receiving emails from it,
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bryanb

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Sep 16, 2015, 12:38:02 PM9/16/15
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Sorry ... I was thinking milli instead of micro ... dooh.
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