Found some capacitors I want to make a spot welder

[999zip999]

I have these capacitors the two little ones are for starting motors and the two big ones marantz 71 volt 56, 000 uf.
The question can I use them for spot welding batteries with copper. Maybe a control board and a foot pedal.
And two handles.
I don't even know if they work maybe someone can tell me how to charge them and discharge them safely

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[docw009]

I believe the super-cap welders are using two 3000 farad capacitors, If your capacitor is 56000 uf, that is .056 farads.

 

[DogDipstick]

use supercaps nowadays. Outdo a big ol cap easily cheap. Those old caps dont last forever Without the skill and expensive hv rated and isolated oscilliscope with its 1000$ of probes this might be non predict ableresults.

71Vn rated cap? theone is 250vAC.... but the 70v? you are gonna have to step it down with a linear transformer if youwant to use 120v AC single phase from the wall.

Those are motor starting caps.

 

[999zip999]

Wow thanks guys that's an opener.
Get one of you suggest a good working hobby spot welder ? As you tell I'm kind of cheap but I don't want to break in 6 months.

 

[DaLanMan]

I have always loved watching capacitors shrink.

The first 25000uf cap I saw was about the size of a full keg.

In HS one of the nitwits got a 32000uf cap and hid it in his coat with a wire going down his sleeve so a pencil.. poke POP

You we can put enough capacitance to spot weld a ships hoist in place in a small day pack (it was in the news a few years ago that exactly that was done)

I am old...

 

[999zip999]

I guess this is the one you're talking about. I wonder if I use it for a tack welder on sterling silver if I use two silver welding rods. Of proper size. Sometimes it's nice to position something and tack it. Silver heats up and expands a lot sometimes you just want to get it to stick in the place then apply your right temperature silver solder. As it is 1450, 1400, 1350, 1250. The lower temperature are dirtier so you always want to use your higher temperature solders if you can. Oh silver melts around 1650

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[gromike]

I would assume the spot welder you linked won't do all that many welds until it fails.

 

[999zip999]

So many cheap spot welders it's mind boggling. It like when they tried to make a reasonably priced RC balance charger if they go over 6s you have to go real expensive for them to keep working. All the ones the people on here bought and in love with never last. Is it true that certain things just can't be made cheap. How about affordable ?

 

[DaLanMan]

I am using the vevor one. I modded it a bit, did the microwave transformer, replaced the interior wiring with better stuff and added a plug in for a hand held extension.

Unit was iirc like 120ish bucks? I bought a hand held unit for it for about 15-20, and the wire was left over from other things, but probably about 40 bucks. Microwave was given to me by a guy at the berkeley recycling place because he wanted me to show him the spotwelder when I was done. but I think he said it was 10 bucks to buy. so I am into this under 200 and I have made something like 40 12v batt boxes (21 cels) and a dozen ebike batts built from scratch, and have ripped a few apart to change out single cels, it is SOOO not as good as the 1200 unit I have seen at a place... but I am really a hundreds of dollars kind of shop, not a thousands. I could swing the money, but that is a lot to justify it being just more reliable.

 

[docw009]

I wasted enough money on spot welders to have bought a nice Kweld, but there was no reliable sellers in late 2021 when I wanted one. Two integrated units with internal Lipo pouch cells got weak after initial use, and I threw them out. I've been using a $20 unit with a 3S Lipo RC Drone battery to build my packs. Many thousands of welds with it,

.
It can do .15 mm nickel routinely, which is enough for me. I don't really like having the RC lipo around. I drain it to 30% SOC and keep it outside when not welding. A supercap model would be a lot safer, if it works,

 

[DaLanMan]

I have looked at the kweld numerous times, and know if I buy one the wife is gonna kill me.

I hemmed and hawed, knowing that to build a battery I was not gonna solder it, and had my doubts about the cheap units I had seen, then in a fit of irritation I got the vevor unit...

Then I found out about the kweld. It is still in my thought process for when this unit dies.

So far though, it has continued to impress me.... I mean not that it is great, I just learned to live with it's limitations. However what I have read about them vs my luck thus far has been kind of awesome. The first hour I played with it, could not get a decent connection. Called a buddy that used a spot welder at work. He swung by and kicked me off of it, he wanders inside like 10 minutes later, grabs a beer and says "brother, I hope that girl was at least cheap" Long and short, it is *not* a great spot welder, but he figured out that if you keep the leads clean, and mind the gap, set the pressure yourself, and then the foot trigger, it will make an attachment, but he also was using pure nickel, he could not get the nickel covered steel to work consistently. I ordered a copper/nickel alloy and same exact process, just turn down the power to 70 and bobs yer uncle. just have to be careful and remember the allow is *not* strong, and work hardens easily. so if you bend it too much you will break a chunk off.

 

[gromike]

Yeah, I went through two cheap spot welders and then bought a Kweld. The nice thing about the Kweld is it adjusts the energy in the weld logically and repeatable. Makes the welding the easiest part of battery building. Would of probably been smarter to get a Kweld first, but I guess you got to smoke a few before you find the welder that works for you.

 

[DaLanMan]

Oh, brother, believe me, if I had to do it over again... i probably would have jumped without digging deep enough, If I had the patience to... hey what is the shiny thing over there?

If I had ran across the kweld info before I bought the vevor, I totally would have used the kweld, much more my personality, I like to get in and say I had a part of the process... unless it is in a professional setting in which case I buy nothing without complete package and repair support. Always better to be able to blame someone else when you get a call at o'dark thirty on a sunday morning that something has gone teats up... But in my normal life... Yeah, I was the kid that took everything apart to see how it worked. I was taught the hard way to only take *my* things apart.