On Mon, 20 Nov 2017 07:33:20 +0000, Andy Burns wrote:

Johnny B Good wrote:

JOOI, What did you reset the charging voltage to on that APC SmartUPS?
Presumably it would have originally been set to 27.6v. Did you throttle
it all the way back to 27.0v?

I knocked mine down one click in the PROG mode to 54.05V according to
multimeter, and the internal data log agrees with that, however this is
constant regardless of temperature.

Most APC UPSes arrive from the factory with CSB (now Hitachi) batteries,
the datasheet for NP17-12 specifies all their characteristics at 25°C,
with a nominal charge voltage of 2.25 to 2.35V per cell, mine sits in a
cupboard where the UPS has an external temperature probe and measures
the temperature outside the case as 19°C and inside the case as 31°C.

Technically, I think the voltage ought to be dropped by 3mV per degree
above 25°C, and given that mine seems to sit between 31 and 34°C maybe
I'll knock it down another couple of clicks.

BTW, I've never seen APC batteries so badly cooked as that.

Did you see my photo? Quite a hump, though not from my own UPS I hasten
to add, currently using Tayna/Powerline batteries which seem to be doing
fine after 2 years.

I've long since retired the SmartUPS700 simply because of its
unconscionably high maintenance consumption of 20W (virtually none of
which goes into keeping the battery pack charged).

Yes, they are on the inefficient side ... but I've had a couple of power
cuts in recent months and the smug feeling when you see that every other
WiFi signal in the street has gone off is worth it :-)

We've only suffered one major outage of supply back in the mid 80s just
after I'd acquired my very first UPS (a 2nd hand Emerson 30 - 450VA 300W
quasi-sinewave jobby using a pair of NP7 SLAs).

The power went off about 7pm on a Wednesday (Radioham club night) just
as I was about to set off. Luckily, the UPS was plugged into the mains
and backing up my desktop PC so I was able to shut down the PC (or it may
already have been shut down, I forget which) and relocate both the UPS
and a lamp stand (with a 13W CFL fitted) onto the half landing to
illuminate the hallway and first floor landing.

I daren't shut that UPS off since it couldn't do a 'black start'. I
later found out, when I returned from the club meeting about 3 hours
later, that the children had sat on the loo seat lid in the half landing
toilet to finish their school homework by electric light.

The power was back on by the time I got home. Apparently it had only
lasted about 3 hours or so before the supply was restored - apparently,
an underground joint that had been damaged by roadworks which allowed
water ingress over the preceding days which had caused a few random
glitches before it finally tripped the supply off at the local substation.

Since that one and only memorable outage event, we've only experienced
the odd half second or so dropout maybe only once or twice a year. The
last one happened about 6 months back and was just long enough to reset
unprotected computers, including those that were cunningly disguised as
domestic TV sets, little more than a full second or so's worth.

The almost total absence of power outages by the time I needed a new set
of batteries for my basement SmartUPS2000 (feeding protected sockets
around the house) made me pause to reconsider a less costly UPS solution
than using an expensively large capacity battery to give me hours and
hours of run timen means I'm now looking to getting an inverter type of
genset in the 2 to 3KVA range so I can make do with a cheaper bunch of
NP7s in place of the originally specified 18AH battery pack or a set of
50AH car batteries all of which are likely to be in need of replacing in
less than 5 years of service (maybe 10 if the voltage reduction to 54v
float charging proves an effective solution to the problem of short
battery life).

I've already discovered the hard way that the classic emergency genset
just won't cut it due to the the capacitive loading of the SmartUPS2000
mains input network which totally screws up the AVR of such generators
causing them to drastically overvolt whilst the UPS is in pass-through
mode[1]. As soon as the UPS switches to battery power the genset voltage
drops from some 275v or so back to its set voltage of 230 and the UPS
senses this and goes back into pass through to trigger yet another
overvolting cycle and a flip back to battery power ad infinitum.

The only type of emergency gensets that are immune to this problem are
the inverter types which are considerably more expensive to buy although
a little cheaper to run if an eco-throttle feature is incorporated (the
cheapest ones don't). The consequence of which has lead me to
procrastinate over the decision to recommission the basement UPS.

Needless to say, the NAS box was undisturbed by that recent 1 second
dropout, being as it was, the only item of IT kit that was still
protected by an APC BackUPS500 UPS which is now recovering from a
27minutes and 40 seconds autonomy test on the 50W NAS box load (booted
into a Knoppix Live CD session to get the power management operational
without risking the integrity of the file system). ISTR that the last
such test was over three years ago when I fitted the current 7AH SLA and
got something like 33 minutes or so runtime before the UPS quit.

This time, I restored the power shortly after hearing the mournful beeps
change to a continuous beeeep, indicating critically low battery voltage
and imminent loss of power in anywhere from seconds to minutes, depending
on the loading. It's possible I may have had another 3 or 4 minutes left
but I was happy to cut the test short after seeing over 27 minutes
runtime, about twice as long as I was hoping for considering how long the
battery had been installed in an APC UPS. I suspect what contributes to a
longer than typical APC battery life in this case is the fact that the
maintenance power consumption is a mere 2.7W once the battery pack is
fully charged up.

I've had to repair both these UPSes (failed 7812 regulator chip in the
BackUPS500's battery charging circuit and a broken mains voltage
switching relay coil connection pin in the SmartUPS2000). Rather
fortuitously, I'd discovered a Russian website with downloadable circuit
diagrams and service manuals for most of the older APC UPSes just a few
years earlier (over a decade ago now) and I ransacked the lot (several
dozen afaicr, including several variants of the SmartUPS2000 and
BackUPS500 models).

[1] The problem with augmenting a UPS with a cheap 'n' cheerful emergency
generator set isn't due to "The Dirtiness" of such mains voltage sources,
it's all to do with the overvolting effect from even modest amounts of
capacitive reactance across the generator's output terminals.

The UPS isn't bothered by harmonic distortions of the genset's waveform
measured in tens of percent or even of a modest 2 or 3 percent departure
from the nominal 50 or 60 Hz frequency of supply. The issue is solely to
do with a defect of all such rotary magnetic machinery when connected to
a modest value of capacitance, a defect that's been put to good use when
people have used large HP rated single phase squirrel cage induction
motors as genset heads in their DIY genset projects where several dozen
microfarads' worth of capacitive loading is used to magnify the effect of
residual magnetism into full blown excitation to saturation of the rotor
core to create a genset that needs to run at slightly higher rpms than
the 1500 required to generate a 50Hz ac voltage output with a
conventional generator head(the reverse of what happens when used as a
motor).

What I discovered when experimenting with trying to filter the 5KHz or
so slot ripple frequency on a 2.8KVA genset in the mistaken belief that
this was possibly one source of "Dirtiness" that was upsetting the UPS,
was that a mere 4.7uF (a 20W fluorescent light fitting PF correction
capacitor) was all it took to send the voltage north of the 270v mark.

The SmartUPS2000 has a pair of this size of cap effectively in parallel
across its mains input only when in pass-through mode, disconnecting them
when running on battery, hence the endless switching between genset
supply and the battery powered inverter supply. It's not the "Dirtiness"
of the emergency genset supply, it's the overvolting effect of even
modest amounts of capacitive loading that does all the harm.

Hell! As sine-waves go, the mains waveform as displayed on an
oscilloscope is a far from pretty sight. As I've already mentioned, the
inverter gensets are free of this overvolting effect so are the only
practical solution to this specific problem. Mind you, since most house
lighting is now comprised of LED lamps which mostly utilise a wattless
volt dropper in the form of a mains voltage capacitor, the demand for
inverter gensets just to provide emergency lighting power alone must be
going up, hence those 1.2KVA inverter gensets now being sold by the likes
of Aldi and Liddle.

The demand for an emergency genset that *won't* instantly fry all the
house lights will lead to a decline in production of the classic cheap
'n' cheerful genset and hence to cost savings in mass production runs of
the ever more popular inverter based emergency genset reflected in the
more competitive pricing already appearing in the small suitcase sized
end of the market.

The last time I saw the Parkside gensets on sale in Lidl a few months
ago, they were priced at a mere 150 quid each. I'd have bought one just
to test but they'd either sold out or else didn't get delivered to any of
my local stores, possibly on account of a last minute recall for which I
couldn't track down any stories to corroborate what one Lidl shop
assistant had intimated to me. Hopefully, I'll get my chance to sample
one of these suitcase sized inverter gensets in the not too distant
future to try out for myself. I might yet invest in another battery pack
for my basement UPS after all (a small 7AH one - I'm not made of money!).

--
Johnny B Good