From: John McCormac <jmcc at hackwatch.com>
To: ilug at linux.ie <ilug at linux.ie>
Date: 30 June 2000 15:39
Subject: Re: [ILUG] UPS for home use?
>Conor Daly wrote:
>>>> It's only a first guess off the top of my head. Probably should have
>> included the health warning though. It's all from my Motor Mechanic days
>> where things work in a voltage range of about 9 - 15 volts and use up to
>> 80amp battery drains at times!
>>Just to outline an important point that has been missed here - the UPS
>uses the battery supply (DC) to provide a mains like AC supply to the
Yeah, but I figured, "Why go from DC to AC and back to DC again?" Of
course, the use of an inverter to produce AC within the tolerance limits for
the mains supply *does* allow the PC's PSU to properly regulate the supply
to the PC components but there is an energy cost in using an inverter to
generate AC and the PSU to generate DC again (though trafos are very
efficient >90%) so losses in the conversion will affect the runtime
available from the UPS.
There wouldn't be much gain in component specification though since most of
the power path would be low voltage and thus high current while the high
voltage bit would be mainly the trafo and rectifier for the charging side
and the trafo (presumably) for stepping up the low voltage AC that would be
generated by the inverter (I presume)
Swings and roundabouts I guess...
One could probably build a decent home-made UPS with a lot of work and for
more money that you could buy it but you'd have the satisfaction of a job
well (poorly?) done...
Ph +353 1 8326146
conor.daly at oceanfree.net
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