John R Pierce wrote:
> On 07/01/11 4:05 AM, Timothy Murphy wrote:
>> It seems to me that it should be possible
>> to have a simple, torch-battery operated
>
> assuming 'torch' in this context means what us yank's call a flashlight,
> and that a 'torch battery' is a C or D cell, lets see how much juice we
> could get out of a reasonable setup..
>
> According to HP's 'quick specs', the Microserver has a 150W supply, that
> nominally draws 0.63 A (from 115VAC) or 0.35 A rom 220VAC, about 75 watts.
In fact, my MicroServer has never exceeded 45 watts,
and usually runs at about 30 watts.
I'm not sure what sort of current a computer uses when shutting down?
> According to wikipedia, an alkaline D cell is typically rated at 1.2 amp
> hours at 1.5 volts. Most inexpensive AC inverters run on 12V
> (automobile power), so we'd need 8 of them to get 1.2AH at 12V or about
> 14 watt*hours... My calculations seem to suggest you'd get maybe 9
> minutes total from those 8 batteries with an 80% efficient AC inverter
> at 75 watts. And then of course, you'd be throwing those 8 D cells
> away and replacing them with new ones.
Actually, I would only want the batteries to last long enough
to shut down the computer cleanly, which I think takes about 30 seconds.
And we can get quite large 12 volt batteries pretty cheaply
this side of the pond.
Nb I didn't say, or mean to say, that I wanted to _make_ a "flashlight UPS".
My electronic skill is close to zero.
I was simply expressing surprise that no-one had done it.
I've been completely convinced that a UPS is what I need,
and am trying to source the APC UPS-BE350G, which was recommended.
--
Timothy Murphy
e-mail: gayleard /at/ eircom.net
tel: +353-86-2336090, +353-1-2842366
s-mail: School of Mathematics, Trinity College, Dublin 2, Ireland
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