Trivial capacitor based battery tab welding machine - Page 1
Forum section: electronics / beginners

author: Unknown
author_rank: Unknown
timestamp: April 23, 2014, 11:48:08 pm
content: another research I was doing was about welding tabs to a li-ion battery. Soldering seems to be difficult due to dangers of over-heating. Remember when I was kid was discharging capacitors, low charge ones and two metal thingies were sticking together from the spark energy.Wonder if that would be possible with a high 100F capacitor to stick a nickel tab to the battery.Found another thread here and tons of videos with over-engineered devices and tools.for me the idea is to load the capacitor and the booom (hopefully not my head)

author: calexanian
author_rank: Super Contributor
timestamp: April 24, 2014, 01:53:15 am
content: Typically capacitor discharge welders for battery tabs use a step down transformer to generate high current and switch on the high voltage side. It's very common. Just you tube videos of battery tab welders. I built my own out of a big variac and a harbor freight spot welder with a foot pedal to close the jaws and some bending of some micro welder electrode rods.

author: Rerouter
author_rank: Super Contributor
timestamp: April 24, 2014, 02:12:28 am
content: Most of them rely on voltage rather than capacitance to make the massive currents necessary, on i worked on a few months back had a voltage control know and a trigger button on a lead, it charged up the capacitor bank with a SCR rectifier, so that it would stop charging once past set point, then when you hit the trigger circuit, some active device would shunt the capacitor array across the 2 leads

author: GeoffS
author_rank: Unknown
timestamp: April 24, 2014, 02:18:29 am
content: A couple of DIY designs for capacitive discharge weldershttps://ultrakeet.com.au/write-ups/cdWelderhttp://frikkieg.blogspot.com.au/

author: Rerouter
author_rank: Super Contributor
timestamp: April 24, 2014, 10:04:27 am
content: I would strongly recommend even a crude trigger circuit, so you can get things in place, nice and firm and then hit to weld, i would not want dangerous voltages constantly on the wires, and tapping to zap will burn the surface more than weld,

author: SArepairman
author_rank: Frequent Contributor
timestamp: April 24, 2014, 07:21:14 pm
content: Ah you guys gave me the idea to modify my home made optional isolation variac box to be modified with a switch that disconnects mains and connects the mains input through additional connectors on the front panel so I can hook up a capacitor and use it as a spot welder. good idea?what voltage/capacity capacitor did you use for yoour variac spot welder?could I use a 10000uF capacitor charged to 170V discharged through a variac?how good of a pulse circuit do you need? I'd prefer a low tech momentary contact switch solution.

author: ion
author_rank: Regular Contributor
timestamp: April 24, 2014, 09:57:09 pm
content: Well, you can't get much simpler than this:http://ledhacks.com/power/battery_tab_welder.htmJust make sure to somehow disconnect the power supply before you trigger the SCR. IIRC there's a note somewhere on that site that leaving it connected eventually caused the power supply to fail.

author: calexanian
author_rank: Super Contributor
timestamp: May 15, 2014, 05:30:26 am
content: The more I use my home made AC welder the more I like it. I use a 10 amp variac with it, typically at about 60 to 70 volts for nickel strip of the sort used for battery ribbon and its happy. I have it rigged up to a foot pedal that closes the jaws and hits a switch and applies power. Very handy for all sorts of things. I use it primarily for my vacuum tube hobby stuff but i find myself using it for all manner of other things around the shop.