Did some work with a few "Real Capacitors" ..... I got a good deal on a dozen 36,000uF 35V (45V Surge) Mallory electrolytics on eBay. Results were mixed; I can see that there is potential using lower capacity at higher volts, but for now I prefer the reliability and consistency of the Tab Welder II.
I paralleled the twelve capacitors for a total of 432,000uF... Nearly half a farad. I gotta admit that the ESR (Equivalent Series Resistance) on these 'real' electronics capacitors beat the heck out of the ESR of even the better car audio Caps.
The capacitors were hooked up in parallel using some flattened and drilled 1/4 inch flexible copper tubing (like for evaporative cooler water supply lines) for the bus bars A bit of work to prepare, but it is cheap, easy to find, and will handle the voltage and current just fine.
LEGAL WEASEL WORDS:
You will, of course, insulate all of the exposed metal, (except for the very tips of the electrodes), with electrical tape, heat shrink, self vulcanizing rubber tape or something safe, and submit it to Underwriters Laboratories for safety approval before you plug it in and try to use it, won't you?
If you short it out, anywhere other than the electrode tips on semi-resistant material (steel, nickel etc.) you will get a big spark, and possibly a major meltdown, fire, death and destruction.
Just because I don't show something or write about it or am completely ignorant about it myself, doesn't mean it should be ignored.
Lithium batteries especially are inherently hazardous. Understand the chemical and electrical characteristics of them before you even touch one, much less try to weld one, charge one or use one in any device not specifically designed for the specific battery. They can blow up, burn, stink, release poisonous gasses, fluids, particulates and solids. If you swallow one, it will probably kill you in several unpleasant ways. Do not stick them in any other bodily orifice.
Nickel Metal Hydride, Nickel Cadmium, Alkaline, Silver Oxide, Carbon Zinc, Zinc Air, and Lead Acid batteries are only slightly less dangerous in general. Don't abuse them either.
It is very likely that I forgot something important; So unless you absolutely know what you are doing around electricity, electrical components, hot and sharp tools, ask an expert licensed electrician and/or electrical engineer. Make sure that all your wiring is up to code, and get it inspected by your local code and zoning authorities. If disaster befalls you from following the previous and following instructions, don't call a lawyer and try to sue me. I spent the last of my money on parts for this thing and on batteries. I'm broke, and there will be nothing for you or your lawyer.
Using a variable 0-30V @ 3A bench power supply to charge the capacitors. Basically the same SCR and foot control as used on the earlier projects beyond the PS and caps being different. Here are some of the results:
Here are the basic results of varying numbers of capacitors and voltage:
With all 12 capacitors at 25 to 30V it is just too hot for normal battery
tabbing, but not quite enough for for doing copper or aluminum to copper
aluminum or steel.
With nine of the capacitors (324,000uF) at anywhere between 12 to 20 V works pretty well for tabbing Nickel to steel can batteries; not much good for anything else though. Same with seven caps at 13-15V.
Using six capacitors (216,000uF) at 14-16 V battery tabbing is just about right. With six caps at 30-32V, it is a little too hot for battery tabbing, but will tack a variety of other materials. But often the plain copper electrode will leave a big hunk of its tip behind.... Seems like above 25 volts, even with just 200,000uF of 'real' capacitors, the plain copper electrodes aren't very good, and it is time to step up to using chrome copper or other alloys as used for "professional' spot weld electrodes. I haven't tried any yet, but I'll order some in the not too distant future, and let you know if it works any better.
The 3A maximum current on my 0-30V bench supply is OK for testing purposes, and doing small projects, but if you are going to do any kind of 'production' You will want something with higher current.
UPDATE 2-7-08:Just a heads up:
Please don't try to contact me for more information. Everything I know about this is covered on these pages. For more ideas and information go to: http://endless-sphere.com/forums/viewtopic.php?f=2&t=2633&hilit=welder The guys over there have expanded on my design and tried different approaches. Maybe you can find out what you want to know over there.
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