Noozer wrote:
> Might be a dumb question, but the expensive part of a UPS is converting the
> AC to DC for storage, then back to AC for use.
>
> Why not put the UPS *after* the PSU... three (?) mini UPS's actually - 5v,
> 12v and 3.3v... and the -5v, etc if necessary. It could possibly even mount
> into a 5.25" drive bay.
>
> Sounds simple, doesn't it?
>
>

Some years back a friend and I started working on an uber-UPS which
would solve the runtime problem quite effectively by floating a
diode-isolated bank of series-connected 12V batteries across the
rectified primary DC of a computer's PS. We ran into concerns, not the
least of which was potential safety problems, and never got much past
the measuring and dreaming stage.

Given the weight and volume of even the small 6AH alarm gel batteries we
were intending to use it would not have been a lightweight solution (10
or 11 batteries) and the volume would have necessitated an external
battery enclosure in all except the most humongous AT tower cases of the
time but it would probably yield outstanding runtime. In modern
universal supplies the primary voltage is twice what we were assuming so
the number of batteries would have to be correspondingly doubled also.


--
John McGaw
[Knoxville, TN, USA]
http://johnmcgaw.com