On Mon, 16 Jun 2014 12:16:23 +0100, Martin Brown
wrote:

On 13/06/2014 13:14, Johny B Good wrote:

I've run out of suitable SLAs for the UPS and don't care too much for
the extortionate pricing of replacements so it's sat in the basement
in bypass. The "Protected Sockets" are no longer 'protected'.

Keep an eye out for suitable replacements from RapidOnline when they are
doing a good deal or one of the other non ripoff merchants.

Avoid any that say "wheelchair" battery as they are typically cunningly
rebadged heavy duty deep discharge cells sold at 3x the normal price!

Deep cycle is what I'm after but not at 3x the 'normal' price (not
even at 'normal' prices after taking a gander at the Rapidonline
website).

If you can match voltage, dimensions and Ah capacity you should be OK.

No problems on size or AH capacities other than finding a matched set
of four 12v batteries. Since I didn't get the battery case half with
this UPS, I've used externally connected batteries. Initially a set of
36AH car batteries I blagged for 60 quid the lot which I stood on the
lower shelf of the angle iron shelving unit in the basement upon which
the UPS is perched.

I've supplemented this with sets of four 12v7AH SLAs and even a set
of four 12v 25AH SLAs mounted on a sheet of MDF hanging from bolts
underneath the top shelf and over the car batteries below.

As I said, the car batteries were the first to go bad and were
weighed in when I tried yet another set of car batteries which are now
sat there disconnected. The 25AH, along with the 7AH batteries
eventually went bad a few years later and the UPS is disconnected
until I can find another set of 25AH SLAs for 40 to 60 quid the set at
a major Radioham rally or flea market.

My best bet may be to set my sights a little lower and use the 7 or 8
AH batteries. It can be rather galling to think that whatever capacity
of SLA battery you choose, you'd be doing well to get 4 or 5 years
life out of the investment before you have to 'splash the cash' once
more.

The maintence costs in battery replacements alone, never mind the 35W
maintainance consumption of a SmartUPS2000, is rather high to achieve
autonomy periods measured in hours rather than minutes.

The obvious solution to hours long autonomy by using a petrol genset
is only workable with the more expensive inverter type of genset. An
ordinary 2.8KVA generator will grossly overvolt if it sees even a
modest leading current load. A 4.7uF PF correction cap was enough to
send the nominal 230v north of 270 volts and there's nearly 9uF's
worth in the mains input circuit of the SmartUPS2000 alone, before we
even consider that due to the protected loads themselves - no wonder
the poor UPS kept cycling endlessly between mains and battery power
when it was supplied by the genset!
--
J B Good