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I built a spot welder that is powered by a car battery. The battery is 12V and 100amps. But unfortunately, it is a little bit too powerful, because it burns through the nickel strips and also through the battery really quickly most of the time.
So I would like to know what is the easiest way to reduce the power/voltage of the battery just a little bit? Will a voltage divider work in that instance? I added the picture of the spot welder.
It is really simple, no buttons nor switches:
I once worked for a firm (RADCO in Toledo, Ohio) that built and refurbished resistance welding equipment. The voltage at the tips was less than 2 volts, but the current was very high. I recall one of the transformer's secondary rating was about 1.6 volts and 100,000 amps!
Forget about using a battery, friend.
Edit, just noticed how old OP is, sorry.
Using a surplus car audio "stiffening" capacitor of 1 farad or even 0.5 F (500,000 uF) and using a known value resistor to slowly charge the capacitor over a few seconds (maybe 10 ohm, 20 W?) You can use a voltmeter on the capacitor to monitor charge on the capacitor, when the charge reaches say 6 V, stop charging and try a weld on a piece of sample nickel first.
Adjust your charging time to vary the charge in the capacitor and thus how many joules are out into the weld.
In auto body collision when we weld new panels onto a car we sometimes use pieces of scrap metal from the old damaged pieces to do a destructive test on new welds to make sure the spot welder is set properly.
Many other ways to weld batteries, good luck.
For the record, No, a resistor divider is not suitable for this kind of high-current application. When 100A flows through any resistor you can buy, it will instantly vaporize into stardust. The power (Watts) = resistance multiplied by current squared; and the temperature rise is closely related to power dissipation. Even with a 0.01Ohm shunt resistor, 100A requires dumping 100W of power out of the resistor.
A better strategy is to use either a transformer or a lower voltage source.
This is going to be pretty much a link-only answer, and behind a paywall at that, but Digital Machinist magazine had a 2-part article last year on building a spot welder using a car battery as the source.
It uses a bunch of parallel semiconductors (MOSFETs or IGBTs, don't remember which) to control the power. Looks like a series inductor to control the current ramp as well.
