Build your own CD battery tab welder for about $100.00+-

[Jeremy Harris]

I'd go for a capacitor with a genuine capacity of around 2F, the only thing to watch is that some car audio capacitors have a real value of capacitance that is less than the claimed value. It's pretty easy to check the value by charging the capacitor up to a known voltage and then discharging it in to a big resistor of known value. You can time how long it takes to discharge and calculate the true capacitance easily enough.

As to whether or not a CD welder will weld A123 cells then the answer is yes, as that's how the Killacycle A123 battery packs are welded up. There's a video on YouTube showing this, somewhere.

Jeremy

 

[The Mighty Volt]

I'd go for a capacitor with a genuine capacity of around 2F, the only thing to watch is that some car audio capacitors have a real value of capacitance that is less than the claimed value. It's pretty easy to check the value by charging the capacitor up to a known voltage and then discharging it in to a big resistor of known value. You can time how long it takes to discharge and calculate the true capacitance easily enough.

As to whether or not a CD welder will weld A123 cells then the answer is yes, as that's how the Killacycle A123 battery packs are welded up. There's a video on YouTube showing this, somewhere.

Jeremy

Thanks Jeremy!

 

[chemosavi]

Some tid-bits on welders after going down this road for awhile now. I stick weird metal stuff together all day, everyday for a living so I write this in hope of someone offering more insight into whatever I have already garnered from this experience.

Welders owned in addition to 2 tigs, 2 migs:
Sunstone/Orion Jewelry welder (capacitive discharge) 230Ws. Fusion/Pulsed spot/resistance.Cost = 4k
DIY 2 transformer 115v AC spot/cross-wire/tab welder with foot control/timer/relay. Cost$100 for timer and relay.

The DIY AC welder is more powerful than the Orion. (MOTs from salvaged microwaves) With the time control and the ability to disconnect one transformer it can do basically everything the other can except fusion weld( also not so well known as stud weld). I have made a variety of guns and pincers to do various things. Size of cable to gun is very important and must be BIG, like 1awg and short. Orion is limited to 10AWG by the manufacturer.

I need more power to spot weld and fuse larger diameters so I priced the Sunstone 1000ws machine. 8.6k. Too much so I'm going to get a stud welder for 2k and foot switch it to also do resistance spot welding which is very close to battery tab welding.

For me with very moderate but very practical knowledge of electricity the diy road to a CD welder is long and the 2 thousand dollar investment is hopefully a working solution. Operating under the theory that a stud gun is basically a precise way to hold a stick of metal while it gets electrified and vaporized while it gets jammed into another piece of metal. Something imprecisely but practically done with a pair of pliers and a switch (which is the way it's done with the Orion Jewelry welder).

If someone has modified a CD stud welder as I intend to do I would love to hear about it. Thanks

Side note: The Sunstone guys are really nice folks and the welders they sell are very precise so I don't want to tarnish their reputation in any way, just offer the budget minded an alternative. I have asked them to clarify what the difference is between their cd welder and a cd stud gun and am waiting for a response.

 

[The Mighty Volt]

Just a thought: what charging method did every one here use for their capacitors {this applies to people who used "Audio" caps}.........I used a resistor that came with mine, but there is also a method involving a bulb.

 

[Jeremy Harris]

There's no need for any charging resistor, the capacitor will be just fine charging directly from the power supply.

The box you have contains a charge switching relay, so it will click when you press the fire button and this will also stop the welder from shorting the power supply out during the weld. As soon as you release the fire button the capacitor will start to charge, so it's best to ensure that the weld is complete and the electrodes pulled off before you release the button.

You'll find that as the capacitor initially charges after each weld it will put the power supply into current limiting, as it pulls maximum current for a few seconds at the start of the charge cycle. This should be OK.

Jeremy

 

[The Mighty Volt]

There's no need for any charging resistor, the capacitor will be just fine charging directly from the power supply.

The box you have contains a charge switching relay, so it will click when you press the fire button and this will also stop the welder from shorting the power supply out during the weld. As soon as you release the fire button the capacitor will start to charge, so it's best to ensure that the weld is complete and the electrodes pulled off before you release the button.

You'll find that as the capacitor initially charges after each weld it will put the power supply into current limiting, as it pulls maximum current for a few seconds at the start of the charge cycle. This should be OK.

Jeremy

Thanks Jeremy, I had a lot of fun with it this evening, and it really does speed up the entire process in comparison to solder etc.

 

[Chillboy]

If you need a good capacitor with specs you can trust, check out Harrison Labs.
http://store.hlabs.com/pk4/store.pl?section=3

 

[The Mighty Volt]

If you need a good capacitor with specs you can trust, check out Harrison Labs.
http://store.hlabs.com/pk4/store.pl?section=3

can you vouch for these people? I just used an audio cap that was rated 2F and came out at 0.23F when tested

 

[Chillboy]

I had an 800W amp and 1F cap in my stereo days and the amp was ultra efficient at >15A max draw.
Reviews at the time was these caps stand up over time. A lot will loose thier peak voltage quickly too even though they work well when new.
You might find one on ebay under harrison labs or hlabs.
I know it's getting pricey but would this work better than a capacitor? http://store.hlabs.com/pk4/store.pl?section=5
You might find a Jacobs Accuvolt unit on Ebay cheaper.

 

[Jeremy Harris]

I know it's getting pricey but would this work better than a capacitor? http://store.hlabs.com/pk4/store.pl?section=5
You might find a Jacobs Accuvolt unit on Ebay cheaper.

Unfortunately, one of these power supplies won't help, as the weld current needed runs at a few thousand amps. Those capacitors mentioned previously might just do, if they really are rated properly and have a low ESR (there don't seem to be any stated ratings on that web site, which rings alarm bells for me.........).

Personally, I'd want to see a vendor giving firm statements, such as "capacitance 2F +/- 10%, maximum voltage 20VDC, ESR 0.003 ohms maximum at 1kHz" or similar. Vague assertions that they are "low ESR" or work with systems "up to 20V" doesn't cut it with me.

For one of these welders we need a capacitor with a true capacitance of around 2F or so, and a true ESR of as low a value as we can get. We don't need the car audio bullshit glossy stuff, nor do we need the fancy (but totally pointless) displays that are added to appeal to the boy racer crowd.

Big power supply capacitors are a good bet, if you can find some. I'm running 20 paralleled 97,000uF 20V power supply capacitors in my welder and they work fine. Given that size is a fairly good indicator of capacitance value, it's worth noting that each of my 0.097F capacitors is 3" in diameter and about 6" tall (so maybe half the size of some car audio capacitors notionally rated at a couple of Farads). 20 of them give me a true 1.94F but make a pretty big box full, maybe 8 to 10 times the size of a 2F car audio capacitor. The other advantage of these power supply capacitors is their low ESR. Each one is rated at 0.012 ohms, so the total ESR for my pack of 20 in parallel is only 0.0006 ohms, much lower than a typical car audio capacitor.

The down side with using big power supply capacitors is finding them at a good price. The list price for the ones I have was around £35 (~$50) each (so around £700 (~$1000) for the lot), but I got lucky with a job lot on eBay.

Jeremy

 

[liveforphysics]

I had an 800W amp and 1F cap in my stereo days and the amp was ultra efficient at >15A max draw.

800w at 12v means pulling 66.6amps. The cap isn't a magic source of power.
You had a ~150-160w setup.

Reviews at the time was these caps stand up over time. A lot will loose thier peak voltage quickly too even though they work well when new.
You might find one on ebay under harrison labs or hlabs.

I think what you're trying to say here is the ESR increases. Peak voltage on a cap means the voltage that when exceeded, the cap is at risk of dielectric break-down and explosion similar to a bomb.

I know it's getting pricey but would this work better than a capacitor? http://store.hlabs.com/pk4/store.pl?section=5
You might find a Jacobs Accuvolt unit on Ebay cheaper.

A DC/DC converter is not helpful for this application.

 

[chemosavi]

Help needed, safety issues of great concern. Please correct if wrong.......

The DIY CD welders discussed in this thread use low voltage power supplies (under 20V) hooked up to larger capacitors (over 1,000,000uF) to make welds.

Smaller CD stud welders generally use 66,000uF caps with adjustable voltages from 35V to 200V. I'm assuming they use more voltage to make up for the use of less farads in the caps.

This would translate to EXTREME DANGER were someone to start messing around with a stud gun to make welds. Especially resistance spot welds. CORRECT? Thanks.

 

[Chillboy]

Thanks for clarifying, should have checked instead of memory but yes the 800.1 d-class amp I ran at 4ohm for way less output with loads of headroom on a Dynaudio13 for about 200W at 20A not 15 even. If you want a stereo on your ebike they take up to 46V input jk Very barebones in design. I was using this as testiment to quality not suggesting the cap had much to do with it (other than helping with that headroom). http://www.hlabs.com/technical/amplifiers/page3.html

I did think the "dc converter" was full of smaller caps though to discharge just as fast. I have a similar system running coil packs in my car and I have to change the large MSD plug wires every second season when they break down, so they def. produce a good amt. of steady current.
But not nearly what single cap large cap does I guess. Just trying to help.

Email HLabs and ask the ESR on their caps.

 

[Jeremy Harris]

Help needed, safety issues of great concern. Please correct if wrong.......

The DIY CD welders discussed in this thread use low voltage power supplies (under 20V) hooked up to larger capacitors (over 1,000,000uF) to make welds.

Smaller CD stud welders generally use 66,000uF caps with adjustable voltages from 35V to 200V. I'm assuming they use more voltage to make up for the use of less farads in the caps.

This would translate to EXTREME DANGER were someone to start messing around with a stud gun to make welds. Especially resistance spot welds. CORRECT? Thanks.

There are advantages in going to a higher voltage, lower capacitance set up, as big, low ESR capacitors can be expensive and weld energy available is proportional to the square of the voltage that the capacitor is charged to, but only linearly proportional to the size of the capacitor (doubling the capacitor value doubles the weld energy, doubling the voltage quadruples the weld energy). The potential downside is safety, as you've highlighted, so what many such systems do is discharge the smaller, higher voltage, capacitor into a big pulse transformer. This transforms the high voltage, relatively low current, pulse into a low voltage, high current one at the weld electrodes. For most of us, this is out of reach as a DIY project, as the transformer isn't an off-the-shelf part. Some have made welders by rewinding big transformer cores, like those found in old, pre-inverter, microwave ovens, but it's a fair bit of work just to save a bit of money on a big capacitor.

Jeremy

 

[The Mighty Volt]

Wow! Tonne of new information in this thread today!

Jeremy is correct: the audio caps are basically useless......wrapped in fancy tin foil with a fancy display so some youngster with a fake burberry cap can impress his mates as he squeezes 12 horsepower from his 1000cc Citroen Saxo. All the while deafening small animals with the noise from his exhaust.

They simply dont suit us. Unless you want to weld your pack with Wilkinson Sword blades.

 

[Chillboy]

ESR on the HLab caps is .004 ohms at +/- 20% operating temp to 95C
http://www.hlabs.com/manuals/CAPS/index.html

 

[The Mighty Volt]

ESR on the HLab caps is .004 ohms at +/- 20% operating temp to 95C
http://www.hlabs.com/manuals/CAPS/index.html

Fair play to you then.

Now...is that good or bad?

Jeremy will know the answer......

 

[Chillboy]

ESR on the HLab caps is .004 ohms at +/- 20% operating temp to 95C
http://www.hlabs.com/manuals/CAPS/index.html

Fair play to you then.

Now...is that good or bad?

Jeremy will know the answer......

This (former) car audio guys 4cyl (2.5L) Sentra makes 391whp too (known as a Sunny where they drive Citreons). JK I know what he means but you can't jugde all caps by the no name ones on Ebay, esp. with their intended purpose...
My understanding is obviously ltd but from what I'm reading that lower voltage with more discharge is safer then
Kaption makes a 6F cap...but I also get that this is intended to be $100ish project.

 

[The Mighty Volt]

At this point I would happily part with the money. I just want the welder up and running.

I saw some of the home-made welders and when they fire their capacitor leads JUMP.

Do you have a CD Welder yourself Chillboy?

 

[Chillboy]

No I'm way too new to play with this, but I have a cheap Cammy pack that I want triangulated in the future.
So maybe by next season I'd try something like this.
Just trying to help you guys out. Maybe someone will help with my battery for a reasonable charge later if it works out

 

[The Mighty Volt]

No I'm way too new to play with this, but I have a cheap Cammy pack that I want triangulated in the future.
So maybe by next season I'd try something like this.
Just trying to help you guys out. Maybe someone will help with my battery for a reasonable charge later if it works out

Okay thanks for your help. I will wait to see what Jeremy says about the ECR rating of those Caps, and then maybe I will take it further. Thanks and good luck.

 

[chemosavi]

Not a great battery tab welder but a nice resistance spotter. Timer control with solid state relay. Two MOT's @115V in parallel and 4AWG in series. Pedal on bottom activates spot jaws. Also extra hand held pincers in two flavors. Wire cage in lower right is .045 wire welded with this and Orion Master jeweler plus. Found what appears to be a nice capacitive discharge welder called the HotSpot II @250ws for around $995.00 USD. That's quite a bit less than others with less power for those who don't wish to go down the DIY route. Many thanks Jeremy for your considered and thorough reply.

Back to the stud welder, if I understand you correctly, the danger is not that great since the transformer changes the high voltage to high current, same as my DIY AC spot welder here. I still cannot understand why Sunstone charges $8,600.00 for almost the same thing as a $1750.00 stud gun unless it's because it has finer digital adjustments and dual pulse. Granted, bigger caps but if the stud gun uses a transformer to get to the same place??????

 

[Jeremy Harris]

ESR on the HLab caps is .004 ohms at +/- 20% operating temp to 95C
http://www.hlabs.com/manuals/CAPS/index.html

Fair play to you then.

Now...is that good or bad?

Jeremy will know the answer......

That ESR is OK, pretty good in fact. Peak current into a dead short, when charged to 15 volts, would be 3750 amps. Realistically, given that the weld joint, cables etc will have some resistance, the weld current should be greater than 1500 amps peak, which should be OK.

The biggest capacitor they do seems to be 1.5F, which is on the small side. Ideally you need at least 2F to get good welds, so maybe two of these wired in parallel would be a good solution. This would have the added advantage of halving that already good ESR, so doubling the peak weld current, as well as allowing more weld energy to be supplied.

Jeremy

 

[Jeremy Harris]

I saw some of the home-made welders and when they fire their capacitor leads JUMP.

Mine does that, in fact anything nearby that's ferrous and not bolted down jumps, too.............

Jeremy

 

[The Mighty Volt]

ESR on the HLab caps is .004 ohms at +/- 20% operating temp to 95C
http://www.hlabs.com/manuals/CAPS/index.html

Fair play to you then.

Now...is that good or bad?

Jeremy will know the answer......

That ESR is OK, pretty good in fact. Peak current into a dead short, when charged to 15 volts, would be 3750 amps. Realistically, given that the weld joint, cables etc will have some resistance, the weld current should be greater than 1500 amps peak, which should be OK.

The biggest capacitor they do seems to be 1.5F, which is on the small side. Ideally you need at least 2F to get good welds, so maybe two of these wired in parallel would be a good solution. This would have the added advantage of halving that already good ESR, so doubling the peak weld current, as well as allowing more weld energy to be supplied.


Jeremy

Oh, is that how it works? Maybe that is worth a try then!