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- Posted on
- Re: UPS
- David Mahon
July 16, 2005, 3:50 pm
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Looking back through my mail archives (I ordered them online) I see I
replaced them in October last year. It's not like I just replaced them.
Hopefully the automatic shutdown is done to prevent further problems and
the temperature (70 degrees centigrade) is selected because of that.
What I don't know is if the shutdown of the unit also shuts down the
charging or if it just turns off the power outlets. If the charging
continues, the temperature may continue to rise (it certainly hadn't
fallen much, if at all (from 70 degrees C) in the three hours it had
been turned off before I found it, unplugged it, opened it, removed the
batteries and threw them into the garden.
When you do come to replace yours, look at:
http://www.upsbattery.co.uk/ (owned by the following)
rather than directly at APC - who charge 2-3 times more for the same
cells in their RBC6 kit. This could still have happened even if I'd paid
the 120 pounds directly to APC.
Anyway, as this is getting a bit off topic here, and to perhaps get any
further input, I'll crosspost to sci.electronics.misc,alt.comp.hardware
I bought Yuasa at a 1/3 of the price APC charged for their cells. When I
opened up my UPS to fit them, guess what APC had fitted at the factory.
Yep - the exact same Yuasa cells, the only difference being the letters
APC stamped on the grey plastic (along with all the regular Yuasa
I had a strange symptom of a UPS problem - the Carbon Monoxide detector
in my living room started indicating low levels (about 17ppm I think)
when it usually reads zero and there were no sources of it in the room
- the gas fire wasn't being used.
Then I noticed I was getting high temperatures inside the UPS, to a
pattern. It would run at its usual level (around +32C) for some hours,
then start rising over about half an hour, getting to about +50C, then
falling back again. I opened it up and found that the batteries were
bulging, and I had to lever them out with a crowbar!
I contacted APC who said that obviously the batteries were knackered,
but because of the swelling I should get a whole new UPS (yeah, right!
:-) I went to MDS (on the North Circular near Edmonton, I think) and
bought the new batteries there for about a third of the APC price. I
had to do a bit of work to fit the old bits to the new batteries - they
have some plastic plates and a set of leads and connectors that
presumably would come with them from APC, and the two batteries are
stuck together to form one unit. A bit of prising and resticking of
the plates and some gaffa tape to hold the batteries together did the
job, and they've been working fine since.
This is a Smart-UPS 1400 iNet by the way, and the original batteries
lasted 5 years (APC reckon 3 years is their design life). The
batteries I fitted were the same type of Yuasa that APC use,
The UPS top-up charges the battery from time to time, but also does
some "maintenance" of the battery if you are using the Powerchute
software - you can schedule self-tests and "calibration" runs, and I
had the latter being done monthly, which runs it down to the "low
battery" condition then recharges it, noting the energy needed to
discharge it, so it can calculate run-time remaining.
I think the failure mode was this: The batteries were worn out, and
the top-up charge was overcharging their (reduced) capacity and the
excess energy went to heat, raising the temperature and pressure,
causing the casing to soften and bulge. Then the pressure-limiting
vents let out some of the gasses (Hydrogen and Oxygen) and that's what
my CO detector was reading. This reduced the battery capacity even
more, and lead to a downward spiral. As more electrolyte was lost, the
peak temperature during the top-up charge would have risen further and
further, but I got to it before it reached the stage of thermal
shutdown, as David's did.
If David's unit is still overheating even with new batteries, there is
obviously another problem, and maybe a case for a new unit, but if only
the old batteries overheated, new ones should solve it. Mine has been
running with the MDS-supplied batteries for about 16 months now, with
no problems (so much for APC's suggestion to replace it! :-)
Oh, and the battery voltage has been showing 27.74V for some time
according to the logs, so I think the reading given above is perfectly
Why would you think that a CO detector would be triggered by other
gases? Isn't it more likely that someing in the UPS was actually
Suppose the problem is in the control electronics? Putting in new
batteries will just get them wrecked.
Jeremy C B Nicoll - my opinions are my own.
It depends on the technology used to detect CO. Some actually use an
artificial haemoglobin which darkens when it binds to CO, and this is
picked up with a light sensor.
Others use tin dioxide on a ceramic base with wires running through.
This causes it to be electrically charged and attracts both O2 and CO
which both affect the resistance - a low resistance corresponds to a
high level of CO. Other molecules can be attracted and cause false
readings, but typically these don't normally appear in high enough
concentrations to make any difference so it's a reasonable test.
Besides, if it does pick up an unusual gas in the atmosphere, wouldn't
you rather be safe than sorry?
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Please contribute to the beer fund and a tidier house:
On Sat, 16 Jul 2005, Bob Eager wrote:
Excellent. Thanks for the info, guys. I notice my UPS does a load run for
about 10 seconds once a week but this has had no effect on the quoted
runtime figure and the runtime has only changed (reduced) since we had
a 15 minutes powercut. I really should do a complete run-to-flat operation
to see how mich capacity the batteries really have.
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