Updated version of my DIY Spot Weld using Super Cap. Now it is battery operated. :-)
500 FARAD / 2.7V Super Capacitor (Bought from Alixpress around USD5)
Protection Board for Super Cap (Bought from Alixpress around USD4)
2 pcs 1 Ohms / 5W resistor (or 1pc 2 ohms 10W resistor)
1 pc Red LED
1 pc 50 ohms 1/4W resistor (though I used 20ohms as I have no 50ohms on stock)
I added LED indicator, as it takes a while to charge the capacitor. When it started to glow, the voltage on the Capacitor is reaching 2Volts already, when it glows brighter, it is ready for spot weld. After series of usage, LED will turn dim and a sign to take a rest and wait to glow again. :-)
2 ohms Resistor is added to limit the charging current to less than 2Amps only. It would take around 5 minutes to fully charged the capacitor.
PS: It takes practice to get the right timing of spot weld, as this has not pulsing circuit for simplicity sake. Up to you to modify it.
After you finished using it, disconnect it from the battery and short circuit the terminals so the energy stored from the capacitor will be discharged on the resistor.