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APC battery backup not working sometimes

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Peabody

Jan 1, 1970
0
This is an APC Model BE550G UPS. It's just a few months old, but
has developed an intermittent problem that I'd like to fix if I
can. I know if I send it back to APC it will just happen to be
working then, and I will have accomplished nothing.

The problem is that sometimes when the UPS switches into backup
mode, no power gets to the plugged-in devices. It's apparent the
UPS thinks it's supplying backup power (4 beeps every 30 seconds,
just like the manual says), but it isn't. The battery shows as
fully charged, with 27 minutes of run time available. And when it
works, it works fine. So it's not the battery.

I first noticed this during powerup of the UPS. At first,
everything is on mains AC. Then it switches into backup mode as a
test for a few seconds, then reverts back to mains AC. What I
noticed was that my modem would turn on at first, but then turn
back off when the UPS went into test backup mode, then turn on
again at the end of the test period. Sometimes. Most days, but
not every day.

Then of course I tried a full test - unplugging the UPS from the
mains, and all the devices shut down instead of continuing to run
under backup power. But all of this is intermittent. Sometimes
when I do the test, it works fine.

I called support, and they had me reset the sensitivity of the UPS,
and of course it started working then. But I strongly suspect this
has nothing to do with sensitivity - after all, it's hard not to
notice the mains dropping out completely.

Logically, what this seems like to me is that everything is working
ok, but the relay which switches over to supplying backup power to
the devices has bad contacts that don't always make contact. I can
hear the relay click when it goes into backup, and again when it
reverts to mains, and I can hear that whether the backup power gets
through or not.

Well, I just wondered if anyone here has any experience with this
kind of thing, and might offer some advice on what to try. I have
already opened it up and made sure all the internal cable contacts
are good, even tightened a couple just to be sure, but that didn't
help.

Any advice would be appreciated.
 
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Peabody

Jan 1, 1970
0
Jeff Liebermann says...
Well, if you're ambitious, open the box and look inside.
If the relay is an open frame type (fairly common), you
should be able to inspect the contacts. If the relay
has a cover, it can usually be removed to reveal the
contacts. My guess(tm) is that you'll find pitted
contacts or a mangled relay armature.

Thanks very much for your reply, Jeff.

The relay is a PCB style DPDT:

Goodsky
EMI-SH-212DCF
12V coil
8 amp contact rating at 250V

I found the datasheet for this series relay, but not the
exact "DCF" part, at:

http://www.goodsky.com.tw/en

searching on the part number EMI-2P over on the left.

But, I haven't been able to find anything equivalent at
Mouser.

The relay is encased in plastic, so I doubt I can get
inside, but I haven't desoldered it yet.

I found 10 with a similar number for sale on Ebay for $79,
but no singles.

This is a really dinky little relay to be rated at 8 amps,
which is probably why it is failing.

If I could find a replacement relay, it would probably cost
less to buy that than to ship the UPS back to APC - it
weighs a ton.

Of course while it would be nice, it wouldn't absolutely
have to physically fit - I could bridge from the PCB holes
to the relay with wire - but the coil and the rating would
have to be right, as well as the speed I assume.

Well, let me know if any solutions come to mind. Thanks
again for your help.
 
P

Peabody

Jan 1, 1970
0
Peabody says...
But, I haven't been able to find anything equivalent at
Mouser.

Ok, I may have lied.

On page 1896 of the pdf catalog, I find:

Omron G2RL series
8 amp rating, same size and pinout

Omron part: G2RL-24-DC12

Mouser part: 653-G2RL-24-DC12

Looks like this should work. The only question would be if
there is a speed issue - how fast it switches.
 
P

Peabody

Jan 1, 1970
0
Jeff Liebermann says...
http://www.digikey.com/product-detail/en/RT424012/PB967-ND/1095291

Watch out for the contact material and switching speed.
The original is 12msec max operate and 8msec max
release. The first (and cheapest) one in the list is
8msec and 6msec respectively, which should be faster
than the original. However, the contacts are AgSnO2
which is better than AgCdO contacts of the original.

Well, that one is silver/nickel per the data sheet. The
AgSnO2 version would be RT423012, which DigiKey doesn't
stock.

But this one:
http://www.digikey.com/product-detail/en/RTE25012/RTE25012-ND/14276
74

is silver/nickel with gold plating - per the datasheet.
Would that be worth a couple extra bucks?
 
P

Peabody

Jan 1, 1970
0
Jeff Liebermann says...
1

I ordered this one today from Digikey. Came to $5.27 with
shipping. It should be here Saturday or Monday, and I'll do
the switch-out and see what happens.


I guess there's always the possibility that the problem will
turn out to be something else, but the fact that the problem
is intermittent, and that the UPS behaves normally in all
other respects, makes it seem likely that the relay contacts
are responsible. But, you know, it's only $5 either way.

I really appreciate your help with this.
 
P

Peabody

Jan 1, 1970
0
Peabody says...
Jeff Liebermann says...

http://www.digikey.com/product-detail/en/RT424012/PB967-ND/1095291

I ordered this one today from Digikey. Came to $5.27 with
shipping. It should be here Saturday or Monday, and I'll do
the switch-out and see what happens.


I guess there's always the possibility that the problem will
turn out to be something else, but the fact that the problem
is intermittent, and that the UPS behaves normally in all
other respects, makes it seem likely that the relay contacts
are responsible. But, you know, it's only $5 either way.

I really appreciate your help with this.

The relay arrived this morning, and I've installed it, and everything
works fine so far. Of course I don't know for sure that the relay was
the problem because it was an intermittent problem to begin with. But
I've gone through about a dozen tests with the new one and it hasn't
failed to work. So I'd say this looks promising.

I have to keep the old relay in case I ever need to send the unit in
under warranty. So I won't be taking it apart. But, it does rattle
when I shake it, which I think is not a good sign.

Anyway, time will tell. Thanks again for your help.

By the way, I assume the lead-free solder they're using now has a
higher melting point than the 60/40 I use - it was a bear to get the
thing unsoldered with my 30W iron. Ended up having to add some of my
solder to the pins, then braid it off, two or three times before it all
wicked up and the holes opened up.

And Digikey is amazing. I ordered late Thursday afternoon, and it
arrived in the mail Saturday morning, all for $2.20 postage. Hard to
beat that.
 
P

Peabody

Jan 1, 1970
0
Jeff Liebermann says...
Congrats, so far.
It might be a spring. Some DPDT relays have two
springs, one of which might have come loose. With a
spring missing, the tension on the normally closed
contacts will be reduced, possibly causing the symptoms.

Well I'm going to declare victory and withdraw from the
field of battle.

It's been a week now, and the UPS has passed the boot test
every morning without fail. And as luck would have it, in
our 100-degree weather there have been two short-term power
outages (two that I know of because I was at the computer
each time) and the UPS switched into backup mode perfectly
each time.

So it appears the problem definitely was the relay, and my
replacement operation was successful. And all for less than
the cost of shipping the UPS back to APC. Plus, if
something goes wrong in the future, I'll know what to do.

Thanks very much for your help, Jeff.
 
W

Wolfgang Allinger

Jan 1, 1970
0
Well I'm going to declare victory and withdraw from the
field of battle.

It's been a week now, and the UPS has passed the boot test
every morning without fail.
[...]
So it appears the problem definitely was the relay, and my
replacement operation was successful.
[...]
Thanks very much for your help, Jeff.

THX for the feeback.


Saludos (an alle Vernünftigen, Rest sh. sig)
Wolfgang
 
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