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I've worked with models made by Unitek and Hughes. The basic idea is to charge some capacitance and then discharge it into a spot. The units I've worked with were simply wonderful - they made nice, clean bonds and could attach dissimilar metals easily. The really fancy newer models cost many thousands, and have things like dual (or more?) pulse capability. First pulse cleans the weld area, second pulse actually does the bonding. The welders I used were rated in watt-seconds, IIRC, and a 250 watt-second unit can weld just about anything I can imagine I'd want to using this technology. The weld power supply is about the size of a case of bottled beer.
This kind of welding is ideal for battery packs. The electrode configuration is side-by-side, and the weld current doesn't pass through the battery cell - only the surface of the case where you weld a tab onto it. The finished weld isn't even noticably warm, so it's very safe in that respect. A 125 watt-second unit could weld battery packs all day long without straining.
I've been keeping an eye out for a while for used units, but they still command pretty high prices. I slap myself for never having opened one up and checking out how it's built. I can probably build one.
So anyone here know the details? Capacitors I've got. Do the caps discharge into a pulse transformer, or straight out to the weld head? IIRC, the weld voltage is pretty low - maybe less than a volt, certainly less than 3 volts. That would require a hell of a switching device, but not if the caps were at a higher voltage and dumped into a transformer.
Please tell me one of you has been under the hood of one of these wonderful machines and can provide the skinny on them. Thanks.
-Mark
This kind of welding is ideal for battery packs. The electrode configuration is side-by-side, and the weld current doesn't pass through the battery cell - only the surface of the case where you weld a tab onto it. The finished weld isn't even noticably warm, so it's very safe in that respect. A 125 watt-second unit could weld battery packs all day long without straining.
I've been keeping an eye out for a while for used units, but they still command pretty high prices. I slap myself for never having opened one up and checking out how it's built. I can probably build one.
So anyone here know the details? Capacitors I've got. Do the caps discharge into a pulse transformer, or straight out to the weld head? IIRC, the weld voltage is pretty low - maybe less than a volt, certainly less than 3 volts. That would require a hell of a switching device, but not if the caps were at a higher voltage and dumped into a transformer.
Please tell me one of you has been under the hood of one of these wonderful machines and can provide the skinny on them. Thanks.
-Mark
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