FWIW: mmf was pronounced "Mickey-mike" so I suppose you might say that 1 Mickey-mike = 1 puff John Ferrell W8CCW "Extremism in defense of liberty is no vice, and moderation in pursuit of justice is no virtue." -Barry Goldwater "You don't get harmony when everybody sings the same note." -Doug Floyd ----- Original Message ----- From: "Al Shinn" To: Sent: Sunday, July 26, 2009 3:04 PM Subject: Re: [EE] disposable cameras > Hey, lighten up!!, we are talking about a disposable camera here (see > the Subject). The cap fits INSIDE the camera, it's the size of my > pinkie! When was the last time you saw a 100 megaFarad cap, eh? - they > probably have them lying around at Livermore lab. > and no, not milliFarads either - microFarads . So I'm an old f@rt! So go > ahead, kick me around a bit. By the way, thanks for the correction > (update), I'll try to be more careful in the future, (but the intent was > to help folks repair batteries, not win a spelling bee). You could have > left it at a simple units convention correction without getting nasty. > Of course then you wouldn't have had all the fun of calculating how many > fission bomb equivalents there are in a disposable camera. > > This is a common practice for restoring NiCds. I have merely suggested a > common source for a tool to restore NiCds - no need to be nasty. > By the way - it did work for me on a dead 9V Makita battery pack and > some other stuff. And yes, you probably don't want to use this on a > button cell. > And yes, you can get by with less voltage, but >100V is common - I had > thought that 300V would be OK cause the cap is EVER so much smaller than > my house. > And yes, it's true, you can use <100V but if you don't want to take the > battery pack apart, I would guess that you need quite a bit more than > the terminal voltage if only one cell is shorted. > > I wonder though if someone who can't even spell ridiculous (you spelled > it "rediculous" should be listened to at all about anything that he is > ridiculing :-) I AM kidding here - wouldn't even have seen it, but my > spell checker found it. > > PLEASE forgive any gramme errors or misspellings on my part! > -- > > Looking forward, > Al Shinn > > > >That's obviously absurd! > > 1/2 (300V)**2 * 100MF = 4.5TJ = about 1 kiloton of TNT equivalent, or a > large fleet of B-52s fully loaded with conventional bombs, or about 1/15 > the > energy that leveled Hiroshima in 1945. > > Assuming you really meant millifarads instead of megafarads (additionally > assuming "fd" was supposed to mean Farads), that's 4.5KJ unleashed on the > battery in a fraction of a second. That's still rediculous when you > consider that's enough energy to launch a normal 5 pound clay brick 300 > feet > into the air. > > Don't try this at home folks. This is messed up advice on a number of > fronts and could get you seriously hurt. This guy can't even get basic > units right, so anything else he says is best disregarded. You don't want > the equivalent of a 5 pound brick falling 300 feet onto your battery, and > you don't want to be nearby if you did try it. > > Even with a lower capacitance, there is no need for 300V. A NiCd cell is > only 1.2V. The point is to produce a short current pulse to blow out the > little whiskers, or dendrites, while minimizing any other damage. It > doesn't take 10s of amps to do this. Ideally the damaging high voltage is > gone just as the dendrites fuse open. That's tricky to arrange since the > amount and strength of the dendrites is unknown. It's best to start at > 5-10V on 1mF and work your way to higher energies until the dendrites > blow. > Increase the energy by 2x each time, but 15-20V is max. Use a higher > capacitance if you get that far and they're still not blown. If 20V and > 10mF doesn't work there is little point trying to salvage the battery. > > > > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist