[time-nuts] [OT] Re: Power Back-up

Dave Baxter dave at uk-ar.co.uk
Mon Aug 10 14:24:39 UTC 2009


Hi...

The other (little known) "Feature" of some of the later UPS's, is that
once fully charged, and if shut down the right way, you can often power
them up "Off Line" as a portable source of AC power if you so need.  On
a light load, they run for quite a long time!  OK, so the run time can
be short if heavily loaded, and you often have to tolerate the nagging
beeper, but the facility is there on many of them.

For others, the dodge used to be, pull the incoming AC lead, and after
they have taken on the load, shut them down from the front panel.  Then
they will usually let you power up things again if needed, with the
incoming AC line still missing!. 

Sadly, if you try to use higher capacity batteries, that is, "many
times" higher (cabling in say 80AH batteries instead of the original
17AH types!) their internal chargers can't cope, and flag the batteries
as bad all the time, even if they are the same "type" (AGM, Jelly etc)
as the originals.

(Some of the small desktop units, have pitiful chargers, literally just
a trickle at best...)

Also with second hand UPS's, as many of them are fan cooled when running
Off Battery, and there is often little to no air filtering, remove the
cover (after all the usual precautions) from time to time and blow out
all the dust bunnies and dead bugs etc, & also check the fan is OK.

I currently have one APC1400 device running things at home, cheap via
eBlag with sick batteries (replaced of course) and I also have an eye on
a rack mount 1kW unit here at the office, that is currently complaining
of bad batteries.  It's not the newest, and we've changed the batteries
several times in the past, but the IT peeps will probably just want to
swap it for a new one now, as they do.  Problem is, that'll probably
happen next week, when I'm not here.  Expressing an interest now could
cost me.  Waiting for it to gather dust after it's redundant, then
offering to "dispose" of it for free, costs less.  :-)

The nice (if that's the right thing to say) thing about the APC range,
is that the built in native UPS support code in Windows (certainly in
Win2k) was developed with the help of, or by APC, and has options to run
other programs just before things are finally shut down.  That is mainly
meant for notification etc, but can be good for a host of things, such
as remote shutdown of "other devices" also living off the same UPS...
The not so nice thing, is the custom cable needed for the older serial
port equipped "SmartUPS" devices.  The lead details are on the web if
you search.  If not just ask, I'm sure I have it on record somewhere...

As for reliability.  One we have here on a print server, an old SmartUPS
400, on it's "nth" set of batteries, and is coming up for it's 20th
birthday soon!  It just keeps on going.  We only ever had one permanent
hardware failure in the past, and I suspect that had something to do
with the big dent in the side of the case it acquired at the time!

Despite all the warnings, the batteries are usually generic types and
easily sourcable, just not with the "approved" logo, and pre-wired as a
ready to go pack.  The secret is to identify the originals before you
throw them of course, then get like for like (characterised for Float,
or Cyclic use accordingly) just that often nowadays, for the same
physical size, you get a few extra A/H for your money.  (Google is your
friend in this respect!)

Also, keep your UPS cool.  Heat kills batteries.

Lastly, as in most UPS's (except the small desktop units) there are
often more than one battery in the set, often a pair, sometimes 3 or 4
(or more in the very big units.)  Try and identify the "bad" one, then
keep the others for other needs.  Solar charged lights in an outhouse,
etc.  They can often have quite a lot of life left in them, for such
retirement uses.   Don't try to replace just one of a set in a UPS,
you'll only have trouble!...   The only exception of course, is in the
case of a genuine "Must do" emergency..

Regards to All.

Dave B.


> -----Original Message-----
> Message: 3
> Date: Mon, 10 Aug 2009 09:21:09 +0200
> From: Magnus Danielson <magnus at rubidium.dyndns.org>
> Subject: Re: [time-nuts] Power Back-up
> To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> Message-ID: <4A7FCA65.5010005 at rubidium.dyndns.org>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
> Joseph Gray wrote:
> > Over the years, I have gotten several APC Smart UPS for next to
> > nothing. In every case, all they needed were new batteries. Unless
> > they are physically damaged or a circuit board is toasted, they seem
> > to work fine. The attitude seems to be "The battery died, throw out
> > the UPS and buy a new one."
> 
> That's how I got UPSes. The first once caused me much trouble, until 
> I've learned that it needs working batteries to even power up 
> properly, 
> since the relay that breaks the line in needs power from the 
> battery to 
> engage... dead batteries => dead UPS. That relay is needed in 
> order for 
> the invertable AC/DC converter to not try to feed the devices on the 
> feed-side of the UPS on power failure, so it is not illogical, just a 
> feature of the design.
> 
> Getting new batteries for the UPS have solved my problems since I 
> learned that lesson. Have another big one which needs new batteries 
> awaiting my attention.
> 
> Cheers,
> Magnus



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