Who owns a UPS (Uninterrupted Power Supply)?

  • Thread starter Thread starter RayLopez99
  • Start date Start date
The only advantage I see for building a UPS in or adding
appropriate external connections for all of the needed DC voltages
would be that things could be set up so no inverter was needed
when running from batteries. This wouldn't make much difference
for computers that approximately a fixed amount of power since
it would only save the inverter losses of about 20%.
Click to expand...

I have had thoughts along these lines.

Note that the actual improvement is a lot better than 20% as you also
save the losses in the power supply converting it back down.

Unfortunately, it's not going to work. The problem is that the
voltage from the pack will drop as it discharges while the computer
needs a very precise voltage.

Assuming 6 cells in the battery we have a full-charge voltage of about
12.75 (I'm looking at a graph). Trying to knock off .75 volts from
this isn't going to be easy as semiconductors generally impose about a
..7 volt drop.

This can be partially overcome by switching to IIRC germanium. The
voltage drop is only about .2 volts. Unfortunately, by the time 45%
of the power has been used the voltage will have dropped to the point
that the .2 volt drop is right at the limit, going any farther means
we can't maintain a 12v output.

The only fix I see is to use seven cells instead of the normal six.
This means we can't use any off-the-shelf batteries, the costs go up.
It will work, however. You will need a whole second power supply
circuit, though.
 
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