kony wrote:
> On Mon, 01 Oct 2007 02:58:01 -0700, meow2222@care2.com
> wrote:
> >kony wrote:

> >> >If they only need power the pc for 10 seconds, and are forever on
> >> >trickle charge, when in use theyre always going to be fully charged,
> >> >under load, and with no charging source running. That gives a much
> >> >narrower voltage window. Whether its narrow enough is another
> >> >question, as you say.
> >> >
> >>
> >>
> >> I would expect it to take a bare minimum of sub-C sized
> >> NiCad, if not larger, to maintain the high current required
> >> without dipping too far under a stable voltage range.
> >> That's at least 17 cells for the 3 major rails,
> >
> >I make it 10 at nominal voltage, but with the high load current you
> >might be closer.
>
> I was speaking of the cells for the 5V and 3.3V rails in
> addition to the 12V.

Tap those off the 12v pack, no need to duplicate.


> >> it probably
> >> wouldn't fit in a 5 1/4" drive bay,
> >
> >I see no probem in getting it in a standard CDROM enclosure.
> >Sub-C batteries, dropper for charging, and a little detection
> >electronics would fit in half the size.
>
> With Sub-C, yes that would be possible but I was thinking
> along the lines of it being fairly expensive just to get a
> few dozen seconds of runtime (if that), it would be better
> to have larger than Sub-C and then discharge the cells less
> to decrease the voltage drop, plus the larger cells
> typically have a lower impedance as well.

IIRC radio control enthusiasts use NiCd D cells to run 60A motors,
and half that would be enough for a PC.


> There should
> probably be some cutoff circuit for when they fall below a
> certain threshold as having the system write to disk when
> instable could be even worse than just abruptly shutting off
> in some cases.
>
>
> >Cost depends entirely on sales volume. Eliminating both the mains
> >psu and the invertor are causes for a real price drop, but real world
> >cost depends as much on business and market factors.
>
> Yes, the cost has almost nothing to do with parts
> elimination, only market demand for volume of the product.
> You could probably buy a whole CDROM drive and gut it, that
> costing less money than it would cost for an empty
> electronics enclosure of the right dimensions, for example.
>
>
> >> It might be most
> >> worthwhile when size or weight were the most critical
> >> factors,
> >
> >true, but if it contains much less stuff and costs less it could
> >potentially take over market dominance from the current plugin jobs.
>
> I can't see that happening, I wouldn't expect it to run for
> over a minute if that long, contrasted with 15 minutes for a
> device that can power more than just the computer. Remember
> that often people might be actively using the system and may
> want the monitor to work, or an inkjet printer or
> modem/router/etc. depending on the circumstances.

Maybe so, though I assumed most folk just wanted to avoid losing
data on sudden power down. Even if its 50/50 that would still give
such a mini-ups half the potential UPS market - but perhaps theyre
bought mainly for other jobs.


> There's
> enough of a price disparity between SLA and NiCad that it
> wouldn't end up significantly less expensive but would have
> significantly shorter runtime (and versatility since it
> lacks any 110-220 VAC output).
>
> These other devices could also have their own individual
> battery packs but then the cost continues to rise.
>
> Also we haven't even considered the little odds and ends to
> implement this, like the wiring harnesses, connectors, etc,
> requiring the primary AC-DC PSU to input to this battery
> pack

I think we may have been talking at cross purposes then. I was
proposing doing away with all that, just trickle charging the battery
pack from the PC's molex connector. Would need nothing more
than a basic bottom price linear regulator. Same molex serves the
PC with power during the mini-ups's brief run. I dont know what the
continuous current rating of those molexes is, but if the UPS only
powers the system for 20 seconds its not going to be a problem.


> for a switchover circuit or else a more crude and lossy
> isolation would have to be used.
>
>
>
> >
> >One could possibly be daring and go with an SLA battery in a
> >plastic liner on the basis that by the time its rotted through the
> >ups
> >case the pc will be 10 years old and of little value anyway. A mini
> >SLA would be cheaper than NiCds.
> >
> >Using NiFe would enable even smaller cells.
> >
> >
> >> though Li-Ion cells might be even better for that
> >> if the budget stretched to cover a more sophisticated
> >> charging circuit. Enough Li-Ion cells & current capability
> >> might fit in a 5 1/4" bay space.
> >
> >If you up the price its range of application dwindles, and small
> >sales
> >volume equals high price - just not the way to go imho.
> >
>
>
> I think we'd already reached that point when the
> conversation about an internal battery began. It's not as
> though the tech to make it happen didn't exist, it's that
> nobody perceives a large enough market for it to make it
> practical.

You think so? I dont know, but I'd be mildly surprised if a large PC
mfr didnt think there was any mileage in offering a mini built in UPS
as an optional extra. Theres certainly a market for UPSes.


> There may well be such a device that already
> exists but that it's priced itself into obscurity already.
> I vaguely really I saw some power supplies somewhere that
> were half-height internally (I mean std. ATX form factor)
> and had a layer of Ni-Cad batteries under the PCB. The main
> problem with that today is the ever increasing current
> requirements of modern systems, there's just not enough
> empty space in decent ATX PSU for this today.


NT