On Fri, 27 Jul 2018 10:20:12 +0100, Andy Burns wrote:

Dave Liquorice wrote:

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.

I replaced the batteries in my SU2200 three years ago, and they've held
up since, I did check it wasn't overvolting them.

Looking at the UPS internal (43°C) and external (32°C) temperatures for
the last few weeks, I suspect it doesn't de-rate the charge voltage for
temperature as it's been locked at 54.05V

Yuasa seem to suggest decreasing float voltage by 3mV for every degree
above 20°C

In my case (literally I suppose!), that's never been an issue with my
ancient SmartUPS2000 since I'd acquired it 2nd hand at a radioham rally
about twenty years ago sans the battery box it would normally have been
clipped onto the top of. As a consequence, I've always used an external
battery pack in an environment (my basement) where the ambient rarely
exceeds 20 deg C (and rarely drops lower than 8 deg C).

Despite this lack of battery exposure to extremes of temperature, I've
still suffered indecently short lives out of what the UPS manufacturers
glibly refer to as a 'Consumable'. 'Consumable' my arse! However, for
many years I'd had the float voltage set to 55.2v (which had drifted up
to 55.5v by the time I decided to sacrifice another set of 'consumables'
to APC's altar just recently) in the mistaken belief that this was the
optimal float voltage setting for a 48v battery pack.

I'd been obliged to decommission it for lack of serviceable batteries
some two or three years back. Shortly after which, I discovered that not
only was 2.3v per cell destructive of the two sets of cheap 36AH SLI
batteries (6 months of an unremitting 13.8v float charging regime being
sufficient to ruin your typical car battery), it didn't do any favours
for the typical SLA batteries specified for UPS duty either, which rather
put me off the whole idea of trying to gain hours and hours worth of
autonomy using a bloody expensive 100+ AH battery bank.

My previous experience with the alternative of backing up the UPS with a
cheap petrol genset had been a rather frustrating one since the
significant capacitive loading from the UPS (9.4μF across the mains
input) had sent my 2.8KVA 'Aldi special' genset into a massive overvolting
spree, ending only when the UPS gave up on bucking the excess "Mains
Supply" voltage and switching to battery power. I don't think I need
paint you a more detailed picture - I'm sure you can figure out the rest
of the story just from that description alone.

When Lidl put their Parkside PGI 1200 B2 1KW inverter genset on offer
just over two months ago, at a mere 99 quid it was an irresistible
opportunity not to be missed by which to verify that it would at long
last be possible to backup my UPS with a petrol generator that *wasn't*
doomed to overvolt when supplying emergency power.

This did prove to be the case although I only got some 30 seconds run
time before the genset cut out with an overload due to a loose alternator
plug connection to its inverter module. This, however, was more than
enough time to see me returning to Lidl for an exchange unit which
wouldn't start until I disconnected the low oil sensor switch.

Not knowing this was a common stock fault with a stuck float switch at
the time (I was worried it might have been a temperamental oil *pressure*
switch) I returned this unit (after running a more extensive UPS
compatibility test) for yet another exchange but the store was, by that
time, out of stock. I got hold of the current one a week later from
another store when I was by then, now wise to these two stock (and easily
corrected) 'faults'.

So now at long last, I *can* provide emergency power backup with
autonomy measured in hours and days rather than mere hours from 500
quid's worth or more of 'consumable' batteries alone.

Advice to anyone contemplating such an upgrade to their existing UPS
emergency supply, the trick is to avoid not only the ordinary emergency
generators but also that piece of ****e Workzone inverter genset,
currently being peddled by Aldi, and choose only modern "Suitcase"
inverter genset types for this task.

With modern LED lit homes, even those humble 1KW rated Parkside inverter
gensets are likely all you'll need to keep not only *all* the lights on
but power the CH/DHW circulator pump, zone valve(s) and controller, a
couple of desktop machines, a UHD Smart TV, an ethernet switch or two and
your modem router (and a DECT phone base station and a few USB chargers
to keep your tablets and phones charged up).

A 1000W (cont.)/1200W (30s surge) rated inverter genset is probably a
bit too marginal to include your typical fridge and freezer compressor
starting loads even using manual power management scheduling - a chest
freezer can go for 24 hours or more without power without risk of
spoilage provided you're not delving into it more than two or three times
a day. If you can schedule a 'fast freeze' run to drop the temperature
below normal, it'll probably last for 48 hours or more before you need to
repeat the cycle.

The fridge, otoh, assuming our larder fridge (Whirlpool) is typical of
the breed, is going to be harder to manage this way with its 4 or 5 hour
thermostatically controlled cycle and 1000 or so watts startup surge
(67W/130VA running), so an effective solution would appear to be to use
it like an old fashioned 'Ice Box' where you source your supply of ice
from the freezer and leave the fridge unplugged for the duration.

The discouraging surge loading test result with the fridge rather put me
off repeating the exercise for our Elcold chest freezer so I don't have
any similar figures. In view of the "Use the fridge like an old fashioned
Ice Box" option, fed with ice from the freezer, I now regret that
omission.

It's just possible that its surge loading may not have been quite so bad
so I might have a go at grabbing this data in the not too distant future
with the analogue watt meter and a digital movie camera to record the
startup readings as I'd had to do with the fridge.

Of course, it you use a modern fridge freezer with a VFD compressor,
this eliminates the hefty startup surge of the traditional sealed
induction motor and compressor, replacing it with a more efficient and
steady 30 or 40 watt continuous load - problem solved! :-)

--
Johnny B Good