Date: Fri, 06 Mar 1998 20:40:59 -0800 From: Mike Smith <mike@smith.net.au> To: shimon@simon-shapiro.org Cc: Chuck Robey <chuckr@glue.umd.edu>, Terry Lambert <tlambert@primenet.com>, dmlb@ragnet.demon.co.uk, wilko@yedi.iaf.nl, julian@whistle.com, chat@FreeBSD.ORG, lada@ws2301.gud.siemens.at, Karl Denninger <karl@mcs.net> Subject: Re: Old farts blathering (was Re: SCSI Bus redundancy... ) Message-ID: <199803070440.UAA02245@dingo.cdrom.com> In-Reply-To: Your message of "Fri, 06 Mar 1998 20:34:07 PST." <XFMail.980306203407.shimon@simon-shapiro.org>
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> > On 07-Mar-98 Mike Smith wrote: > > > > Where I come from we shoot people like this before they get started. > > The last time I had to put up with this, the geezer in question was > > busy trying to explain how resistors were more vulnerable to static > > electricity than capacitors. > > I see from the below, you have very little trouble joining in :-) So it seems. I think us young farts have a controbution to make too. > >> >From R/C car racing, a sub-c NiCd battery will put out 60 AMp for about > >> >3.5 > >> minutes. > > > > That's 3.5Ah, which is substantially beyond the capacity of a "sub-c" > > NiCd cell (usually around 1.1Ah until quite recently). In reality, > > that sort of discharge rate will cause electrolyte depletion and > > self-regulation after a few seconds, although even then in older cells > > there's room for the sucker to pop on you. > > I thought so too. First, the cells are nominally 1,700MaH, then the > chargers are really tricky, then the batteries have the life expectancy of > an NHRA funny car engine, then they get hot enough during a run that you > cannot solder the tabs, they must be welded, or the pack will fall apart, > then the cells must be one particular Sanyo model. If not, all that you > said happens. Quite amazing. Hmm, I prefer the Varta 2.2Ah cells actually. The Sanyo ones have lots of "these are great" legends floating around, but the "really tricky" charger you're describing is basically just a box with a DC regulator and an energy polariser crystal, and I still never saw them create energy from nowhere. But I 'fess that most of the little driving I did was off-road, where capacity per weight matters more than peak output. I used to think those weenies in the shopping centre carparks on weekends were just that. (Hmm, I guess over here you can't do that sort of thing in that sort of carpark, what with 7-day shopping and all.) > > DC-is-better-than-AC is a comfortable myth with a grounding in FUD and > > a fertile ground in the not-so-well-informed minds of Telco engineers. > > Yup. We are back to Edison-vs.Tesla all over again :-) That seems to be about it. Edison got the telcos and Tesla the utilities. > > You have to be outrageously stingy to produce rotten DC these days, or > > just obsessed with doing it the hard way. (Of course, PC manufacturers > > are typically outrageously stingy...) > > Yup. The WDT board I am polishing the driver for alarms for low-voltage on > a new, EXPENSIVE, rackmount CPU box. No, the WDT is not broken, but the 5V > is really 4.73. You are right, you have to try hard to mess up... Have you tried adjusting the output on the supply? Like I said, PC manufacturers are pretty stingy; it was probably factory-set at about 35C and 90% RH with no more than a few minutes runtime. We used to make a habit of readjusting supplies in the (expensive) rackmount CPU cases we bought, particularly for systems destined for (ant)arctic environments where the air-on temperature with the gear unattended could be expected to run below 10C on a regular basis. They were generally quite stable, just wrong when they arrived. -- \\ Sometimes you're ahead, \\ Mike Smith \\ sometimes you're behind. \\ mike@smith.net.au \\ The race is long, and in the \\ msmith@freebsd.org \\ end it's only with yourself. \\ msmith@cdrom.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-chat" in the body of the message
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