Thanks for that info, Andy. I've bookmarked the site.
I noticed a standard delivery charge of £7.97 in that "More Information" page which would nearly double the price on a single battery order. However, since the standard delivery charge is only a penny more for the PL75-12 battery, I'm assuming this delivery charge is per order based on weight (a 70AH 12v battery will be approximately ten times heavier than a
7AH 12v one) so I'm guessing you only paid the same delivery charge on that set of four PL17-12s (assuming you opted for standard delivery).A delivery charge of just under 8 quid spread over 4 batteries is pretty cheap as far as delivery charges go (even more so for a set of ten such batteries) but I suspect I just might be able to cut a better deal with my local Alarm Supplies company's proprietor who used to be in the same computer club I used to frequent way back in the mid 80s. Mind you, iirc, I paid 22 quid or so for a pair about 15 years back so maybe not but it's still worth checking out.
Annoyingly, the "Technical Specification" not only fails to specify the AH discharge rate, it also neglects to specify the maximum discharge current ratings. The 7AH alarm batteries had an 80A rating which is comfortably in excess of maximum demand on a 1500W/2KVA sine-wave inverter UPS with a 48v battery pack.
I calculated the per AH cost of each battery. For those PL7s it was £1.43, dropping to £1.33 for the PL12, then down to £1.23 for PL17 and PL26 batteries before climbing up to a hefty £1.87 for the PL45. Clearly, it pays to use paralleled banks if more than 33AH's worth of battery is needed.
When I do finally get hold of an inverter genset to put me back in the market for a set of UPS batteries, I think I just might go for the PL12-12s as a compromise between capital investment cost and improved autonomy. That extra 60% spend is likely to buy me a doubling or more of autonomy thanks to Peukert's Law.
Even a cheap Aldi/Lidl 1.2KVA inverter genset should be enough, at a pinch, to power a couple of PCs (the NAS box and my desktop PC), the VM SH2 an 8 port Gbit switch, a TV set, the CH/HW pump and all the lights (including a couple of fluorescents and the loft aerial distribution amp. Basically, just "The Essentials"[1]. :-)
Obviously, a 2 or 3KVA inverter genset would be better but I think those
1KVA (continuous, 1.2KVA peak) Aldi/Lidl gensets at 150 quid or less would make a nice start, even if I do have to take care not to light the whole house up like Christmas tree in the cold depths of winter.At a first guestimate, the IT kit looks like it'll be a total of 300 watt's worth, leaving some 700W. The CH/HW pump and the Potterton controller and the 3 port zone valve (say 100W max) should leave some
600W or so of capacity for the lights and the living room TV set.Including a 100W incandescent lamp in the bathroom, four 35W tungsten halogen downlighters in the shower room, a "58W" 5ft tube in the office and a "40W" 4ft quickstart fluorescent lamp in the basement (52 actual watts), I estimate a maximum lighting load of just 400W, leaving in excess of 200W to power the main TV set in the living room so it looks like even a mere 1KVA inverter genset should be able to power the essentials *and* light the whole house up like a Christmas tree to make our neighbours envious.
BTW, I monitored the power used by the BackUPS500 after shutting the NAS box down and disconnecting it to move it onto my workbench to disconnect the now redundant 3TB HDD and update the N4F firmware. After some 12 hours or more, the initial battery recharging consumption of circa 12 watts eventually tailed right off to a mere 2.2 to 2.5 watts, averaging some 2.3 watts versus the 2.7 watts I'd mentioned previously.
Disconnecting the 3TB Hitachi Cool-Spin drive ,rather surprisingly, only saved a mere 3 watts at best. I had anticipated something like a 5 to 7 watt saving when taking the power consumption of the drive being reflected onto the mains through the additional losses in the 145W PSU.
Now that I've completed the maintenance and testing of the NAS box on the workbench, I've restored it to its rightful place and the overall consumption (NAS box and UPS) is hovering just below the 50W mark which represents a small but welcome reduction.
[1] Of course, if I'm looking to protect against outages much longer than 4 hours, I might need a 2 or 3 KVA rated genset to include the fridge and freezer. The fridge looks doable on a lightly loaded 1.2KVA inverter genset (a 60 or 70W compressor load afaicr when I last tested with a plug- in energy monitor a year or two back, so maybe a surge load of 350W max).If I *really* need to know what the startup surge is, I can repeat the test with my trusty Metrawatt analogue wattmeter which, unlike those plug- in energy monitors with their digital displays, can give an unambiguous indication of a brief peak power surge (provided I remember to switch to the 25A and 100v range combination - it's normally kept plugged in and set to the 1A and 100v range combination (100W scale) to monitor IT kit on the workbench).
If we ever do see an extended outage, with careful management, I might even be able to keep the freezer going by leaving it un-powered for at least 12 hours before selecting a time in the day when all the lights, the CH, TV set and desktop PC are shut down before plugging it into the handiest UPS protected socket and let the UPS handle the surge. The SmartUPS2000 can cope with the massive degaussing surge of a 19 inch CRT colour monitor which bodes well for this strategy to keep the freezer contents safe (it's also another good reason to choose PL12s - they should have a higher maximum current rating than the PL7s).