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From: Martin Brown on 30 May 2010 06:29
On 29/05/2010 23:49, John Tserkezis wrote:
> Robert Baer wrote:
>
>> As a "point" of reference, i have an old UPS by APC and replaced the
>> batery only once so far in the appx 15 years of "use".
>> Most of the time it just sits there - maybe on trickle charge, who knows.
>> But on rare occasion when the power goes out and i am online, it keeps
>> all running for a careful save and shutdown.
>
> :-)
>
> Just because you *can* do that, doesn't mean you *should* do that.

And it is at least worth the occasional visual inspection of the
batteries for obvious signs of swelling and distortion of the case.

> The recommendation is two years, to ensure the battery doesn't
> magically fail soon afterwards. In fact, in those conditions, they're
> probably almost guaranteed to last double or more of that.
>
> Problem is, "almost" doesn't cut it in a mission critical application,
> thus the two year replacement recommendation.

UK replacement is annual test and replace on fail or 5 years old
whichever happens sooner. Mine live in a fairly cool environment and
would still hold a decent charge when retired. I have seen some 8 year
old ex UPS cells that I took to the recycle centre in a bucket because I
was unsure if the plastic cases would hold out. They were very obviously
mangled shapes with big bulges but still not leaking.

> This is why some UPSs have an automatic scheduled "test", where they
> shut down the server but leave it powered on, go to battery backup,
> ensure it lasts pre-determined amount of time and power up again.
> Otherwise you have no way of knowing a battery has failed.

Exactly. No point in having an emergency back up that doesn't actually
work when you need it. Same applies to emergency lighting.
>
> I should qualify my quoted constraints assume normal domestic SLAs.
> Higher grade UPSs use higher grade batteries that can last many years
> longer before the recommended replacement.

Even so it makes sense to check them annually. You don't really want a
failed SLA spewing corrosive electrolyte over your UPS.

Regards,
Martin Brown

From: John Tserkezis on 30 May 2010 10:08
Martin Brown wrote:

> And it is at least worth the occasional visual inspection of the
> batteries for obvious signs of swelling and distortion of the case.

Unfortunately, that's not an effective enough test. Most fail at end
of life looking like new. So a visual test alone is not enough.

Some of the large commercial scale units perform an internal battery
test with a limited load, with the marketing blurb claiming it's good
enough to detect a dud battery even while the unit is live and running,
never having to go offline for the test.

> UK replacement is annual test and replace on fail or 5 years old
> whichever happens sooner. Mine live in a fairly cool environment and
> would still hold a decent charge when retired. I have seen some 8 year
> old ex UPS cells that I took to the recycle centre in a bucket because I
> was unsure if the plastic cases would hold out. They were very obviously
> mangled shapes with big bulges but still not leaking.

We were so poor, we had to used other's disposed of batteries as our
new ones.

We went so far as trying to recover open circuit SLA cells. We dumped
10-15+ volts into the things (single 2v cells!), till they took a
charge, then they somehow magically worked. For a while anyway.

That's on good quality (albeit old) cells. I've never really had any
luck reviving cheapies.

> Even so it makes sense to check them annually. You don't really want a
> failed SLA spewing corrosive electrolyte over your UPS.

True. I've seen batteries go short, overheat, dry out and become
basically useless. A real chore to get the buggers out because they had
warped so much.

No-one noticed because the power had never gone out in that time (many
years) till someone thought it would be a good idea to actually look at
it...
From: legg on 30 May 2010 14:09
On 28 May 2010 05:51:02 GMT, John Doe <jdoe(a)usenetlove.invalid> wrote:

>I would like to learn something about proper care of sealed lead
>acid (SLA) batteries. Is there any good authoritative science on
>how SLA batteries should be cared for? I am searching... I suppose
>battery makers/distributors would be one of the best sources of
>information about that?
>
>Specifically... I wonder why instructions that come with SLA
>batteries so strongly emphasize charging the battery immediately
>after use, without specifying how much use. Are they concerned
>that the battery might eventually self discharge too deeply? Or
>does it degrade an SLA battery to rest it in any state but fully
>charged?
>
>Thanks.

Check the Yuasa website for VRLA operation and maintenance
recommendations:

http://www.yuasabatteries.com/literature.php
http://www.yuasabatteries.com/pdfs/TechMan.pdf

There used to be some good stuff from Exide, but I've lost links to
the electronic format manuals.

RL
From: Cydrome Leader on 3 Jun 2010 13:23
In sci.electronics.basics John Tserkezis <jt(a)techniciansyndrome.org.invalid> wrote:
> Martin Brown wrote:
>
>> And it is at least worth the occasional visual inspection of the
>> batteries for obvious signs of swelling and distortion of the case.
>
> Unfortunately, that's not an effective enough test. Most fail at end
> of life looking like new. So a visual test alone is not enough.
>
> Some of the large commercial scale units perform an internal battery
> test with a limited load, with the marketing blurb claiming it's good
> enough to detect a dud battery even while the unit is live and running,
> never having to go offline for the test.

I've chatted with and watched quite a few large (tens to hundreds of kVA)
UPS maintenance techs.

the standard procedure seems to be a visual check, retighten all
connectors, measure voltage across all batteries, then again with the UPS
in test mode where there is a real load across the batteries.

They can usually spot a bad battery before it would cause problems.

larger UPSes have redundant strings of batteries so even with a dud you
can still operate.
From: terryS on 9 Jun 2010 16:43
On Jun 3, 3:23 pm, Cydrome Leader <prese...(a)MUNGEpanix.com> wrote:
> In sci.electronics.basics John Tserkezis <j...(a)techniciansyndrome.org.invalid> wrote:
>
> > Martin Brown wrote:
>
> >> And it is at least worth the occasional visual inspection of the
> >> batteries for obvious signs of swelling and distortion of the case.
>
> > Unfortunately, that's not an effective enough test.  Most fail at end
> > of life looking like new.  So a visual test alone is not enough.
>
> > Some of the large commercial scale units perform an internal battery
> > test with a limited load, with the marketing blurb claiming it's good
> > enough to detect a dud battery even while the unit is live and running,
> > never having to go offline for the test.
>
> I've chatted with and watched quite a few large (tens to hundreds of kVA)
> UPS maintenance techs.
>
> the standard procedure seems to be a visual check, retighten all
> connectors, measure voltage across all batteries, then again with the UPS
> in test mode where there is a real load across the batteries.
>
> They can usually spot a bad battery before it would cause problems.
>
> larger UPSes have redundant strings of batteries so even with a dud you
> can still operate.

The telephone industry has been using vented lead acid batteries for
decades; and has very precuise instructions for charging and then
maintaining the 'maintenance' or float voltage. Also checking for
discrepancies between individual cells.

Mostly telecomm. batteries are 'floated' so that they are sitting
there neither charging or discharging ready for instant use if/when
the power fails.

So while most auto and similar batteries will charge at anything up to
a voltage of 2.33 volts per cell (that's 14 volts for a so called, six
cell, 12 volt auto battery) and be completely discharged at just
below 2.00 volts per cell ( 11.9 volts for auto) the
telecommunications batteries are carefully floated at ether 2.15 volts
or 2.17 volts per cell, dependent on which administration e.g. ATT or
UK Telecomms. and whether the battery cells are Lead-Calcium or Lead
Antimony construction.

As said; you can ruin a battery by overcharging it (have seen them
boiled dry) and or leaving them in a discharged state for long periods
of time. Heat is also a factor, under the hood of a motor vehicle in
hot climate being one of the worst environments. In some parts of the
Middle East auto batteries sometimes last only a couple of years;
whereas in a cool climate with light use our Nissan pickup battery is
already 8 years old and may not have to be replaced yet, even next
winter!

UPS batteries are also floated; but when they are needed they are
probably discharged aggressively for relatively short periods of time
to operate inverters etc.
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