On Fri, 27 Jul 2018 10:00:32 +0100, Dave Liquorice wrote:

On Fri, 27 Jul 2018 09:10:25 +0100, Tim Watts wrote:

Who makes good domestic UPSes these days? Looking for about 500VA (need
to put a power meter in to be sure) and 30 mins runtime.

Most small UPS's are designed with an up time of about 10 minutes at
full load, ie long enough to see if the power comes back ina minute or
two and long enough for things to shutdown nicely if it doesn't. So your
looking at a 1500 VA unit.

Also be aware that UPS's are far more sensitive to overload than the
mains. Switching on a CRT monitor did't bother the mains but the UPS
would instantly shutdown.

Switching on a 19 inch CRT colour monitor whilst powering a 300W load (a
desktop and server box fed via an Upsonic600 - I'm not *that* stupid!)
didn't disturb my venerable SmartUPS2000 in the slightest despite the
brief 20 or so amps degaussing transient "CLANG!!!" from the monitor. :-)


But it's more about which make and possibly series are any good?

Now that I've got at my APC Smart UPS 700 to stop it cooking batteries
it "just works". It did before but would kill a set of batteries in 3 to
4 years. Charge rate far too high for the temperature of the batteries.
In March 2014 I fitted a fan, reduced the charge rate and replaced the
batteries., That set of batteries are still working fine. The cheapo PC
slot exhaust fan has just needed to be replaced but that's only a fiver
versus £50 ish for a new set of batteries...

Battery cooking is a well known trait of APC UPS's, so unless you
willing to dive in and mod your new UPS or can find real evidence that a
given model doesn't cook the batteries I'd avoid APC.

The more recent (less than 20 years old) APC SmartUPS series can be
configured via their serial/USB interface to float charge at less than
the default[1] 2.3v per cell setting, allowing you to chose a less
corrosive 2.25v per cell (13.5v per 12v SLA) setting. I'm not sure, but I
think even that ancient SmartUPS2000 of mine originally had such
provision (I could look at but I could not touch any of the settings for
some undetermined reason).

Luckily the VR4 pot allowed me to adjust the 55.5v setting (it had
drifted up from my original 55.2v setting) down to 54.0v to save a
recently acquired set of four 7AH SLAs bought cheap from my local Alarm
company (I know the proprietor from our computer club days) from a
premature demise.

The original capacity spec was for 17AH SLAs but I was recommissioning
this UPS on the cheap to test the PGI 1200 B2 Parkside inverter genset's
immunity from the leading current induced overvolting defect common to
standard generators that use the raw output from a single phase 50Hz
alternator driven at a notionally steadyish 3,000rpm with AVR control of
the rotor field winding magnetisation current[2].

A significant downside with that SmartUPS700 is the 20 watts standby
consumption *after* its battery pack has fully recharged and drawing mere
micro-amps of charging current. At 15p a unit, that's about 26 quid a
year. I retired it in favour of a BackUPS500 (quasi-sine wave 500VA/350W
rated single 7AH SLA unit with a 2.7W standby consumption) which floats
its battery at 13.49v in standby but raises this to 14v when plugged in
and switched off - no wonder the battery lasts so long! It's only ever
plugged in and switched off for a few hours after a battery change in
order to quickly put a refreshing charge back into the battery. :-)

[1] This rather corrosive float charging voltage is chosen as the default
merely to claim an extra 5 to 10% or so autonomy out of a brand new set
of batteries (for the first 12 to 18 months at least) by way of 'Bragging
Rights'.

It's not just APC who are guilty of this, all the manufacturers use this
trick (at least in the case of SoHo kit). You'd do well to RTFM and
adjust the float voltage down to the 2.25v per cell mark. It might
curtail the autonomy by 5 or 10% over that of a not yet fried battery
pack but it'll pay dividends some 3 or 4 years down the line when you can
expect to see at least another two or three years of life out of your
'consumable'.

[2] Your old fashioned emergency/work/leisure petrol generator is
becoming more and more of a liability than an asset with modern lighting
and other electronic loads now being far more prevalent than in those
long distant days of incandescent lighting and electronic valved (vacuum
tubed) radios and monochrome TV sets and suchlike.

It doesn't surprise me too much to see the likes of Lidl selling 1KW
rated inverter gensets for a mere 99 or 129 quid each (the later PGI 1200
B2 and its predecessor, the PGI 1200 A1 respectively).

Having recently tried three examples of Aldi's 2000W Workzone inverter
gensets (at 290 quid a pop - about a 100 quid or so cheaper than other
similar commodity inverter gensets), I can honestly say that these are
absolutely ****e and not worth wasting any time or money on.

--
Johnny B Good