On Thu, Mar 2, 2023 at 9:42 PM Tim via users
<users(a)lists.fedoraproject.org> wrote:
I have a UPS sitting next to me, right now, in pieces, which (half)
died in a most peculiar manner:
A burning smell was eventually traced to it. There's no visible signs
of burning, and no schematic available for the model, that I can find.
A rather acrid smell, not one I'm used to with component failure, I'm
beginning to suspect a large AC transformer.
While running off the mains its output is a (too) low voltage, but
still high enough for most switch-mode power supplies to run normally
(i.e. the computer and monitor). It has some kind of AC voltage
regulation built into it to deal with under and over-voltage. The
AC supply was normal, at the time.
But running off its battery it produces the full 240 volts it's
supposed to.
If you read about normal UPSes they are not normally designed to run
100% duty cycle (ie on battery for days, or fixing up a low voltage
for days). So if you run yours at say 40% load it will probably
survive under the higher duty cycle, but if you run it close to 100%
load and it gets into cleaning up low voltages the UPS electronics may
not survive long (ie if fixing the voltages for hours/days).
So if they end up running in that state for long periods of time
(either because of adding bigger batteries--my UPS came with 12AH
batterys but now has external 35AH ones) and/or extended low voltages
various components may burn out.
There is also a setting on at least some UPSes that you can change so
that it does not regulate the lower voltages (wider acceptable voltage
range) and accepts those voltages as ok. I have done that with both of
my UPSes because the default setting prevents the UPSes from charging
when on a small generator, and would if the voltages was low but still
good enough cause the UPS to keep fixing the slightly low voltages and
possibly burn out.