Can anyone suggest suitable modifications for using an old APC UPS (Back-UPS 500, BK500MC) with non-computer equipment? I am finding that the UPS apparently thinks it is connected to a computer that has shut down, so it shuts down too, and I have to press the alarm-off button to restart it. (This behavior is not documented in the UPS's instruction sheet.) How can I get this UPS to work reliably with equipment that draws only a light load or an intermittent load?

On 21/07/2014 15:00, wrote:
Can anyone suggest suitable modifications for using an old APC UPS (Back-UPS 500, BK500MC) with non-computer equipment? I am finding that the UPS apparently thinks it is connected to a computer that has shut down, so it shuts down too, and I have to press the alarm-off button to restart it. (This behavior is not documented in the UPS's instruction sheet.) How can I get this UPS to work reliably with equipment that draws only a light load or an intermittent load?

Easy but wasteful work-around is wire in a filament lamp in parallel

It certainly sounds like the UPS is defective. People routinely turn
off their computers without their UPS's complaining.

Sorry but I have no fix short of plugging in the smallest light bulb or
appliance that will fix the problem.

On 7/21/2014 7:00 AM, wrote:
Can anyone suggest suitable modifications for using an old APC UPS (Back-UPS 500, BK500MC) with non-computer equipment? I am finding that the UPS apparently thinks it is connected to a computer that has shut down, so it shuts down too, and I have to press the alarm-off button to restart it. (This behavior is not documented in the UPS's instruction sheet.) How can I get this UPS to work reliably with equipment that draws only a light load or an intermittent load?

On Monday, July 21, 2014 10:12:15 AM UTC-4, N_Cook wrote:
Easy but wasteful work-around is wire in a filament lamp in parallel

Curiously, my first attempt at that (with an LED lamp, about 13 watts) didn't succeed. The UPS still shuts down. Maybe it's not a heavy enough load. I'll continue experimenting.

I am thinking these may be the symptoms of a weak battery -- the UPS wants to shut down but can be induced to try again by pressing the test button. I'm going to continue checking. Another one of the same model does not seem to have the same quirk.

On Mon, 21 Jul 2014 07:00:03 -0700 (PDT), "
wrote:

Can anyone suggest suitable modifications for using an
old APC UPS (Back-UPS 500, BK500MC) with non-computer equipment?
I am finding that the UPS apparently thinks it is connected
to a computer that has shut down, so it shuts down too,
and I have to press the alarm-off button to restart it.
(This behavior is not documented in the UPS's instruction sheet.)
How can I get this UPS to work reliably with equipment that
draws only a light load or an intermittent load?

I have one of those in the office.
http://cdn3.volusion.com/olthw.fyqav/v/vspfiles/photos/BK500MC-4.jpg
I haven't observed any similar symptoms but can conduct a test if
necessary. Incidentally, that model was first produced in about 2000,
and has historically required a new battery every 6 years.

I can't tell what's happening from here, but my guess(tm) is that your
battery is not fully charged. Check with a voltmeter. I've seen the
charging circuitry die in such low end Back-UPS's.

If the battery is old, you might try testing it with a 12v 60 w
headlight to see how long it will run. A 12v 7A-hr battery will
deliver about 60 watt-hrs before it becomes dangerously discharged.
Therefore, the 12v headlight should run for about an hour with a new
battery. (Numbers are approximate).

Beyond that, I need specifics:
- How light a load are you presenting, in watts or VA?
- What are you measuring across the battery in DC volts when
in standby and when powering the light load?
- What happens to these numbers when you use a light bulb as a load?
- What is the buzzer doing?
- What is the fault light doing?
- How do you have the switches set?

Also, you might get a better answer from the APC forums:
http://forums.apc.com
http://forums.apc.com/community/general_discussions/products_general
My experience there hasn't been good, but perhaps you might get better
responses. Nothing found specific to the BK500MC, probably because
it's so old:
http://forums.apc.com/community/general_discussions/products_general/content?itemView=detail&query=BK500MC

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Thanks; I'll investigate further.

wrote in message
...
Thanks; I'll investigate further.



I once took my UPS on a camping holiday so I could charge my phone and
camera batteries every so often, but like yours it would not stay on with
such a light load.



Gareth.

I need to look back in QST Magazine. About 5 years ago there was a lot there about modifying UPSes to use with ham gear. That included bringing out the 12-volt battery terminals so you could use it as a 12-volt source, and also so you could charge the battery from a separate source.

On 7/23/2014 10:22 AM, Gareth Magennis wrote:
wrote in message
...
Thanks; I'll investigate further.



I once took my UPS on a camping holiday so I could charge my phone and
camera batteries every so often, but like yours it would not stay on with
such a light load.


They're disappointing for that use, because the battery has to supply
the magnetizing current for the transformer, so the lifetime isn't very
long. You'd be much better off with an LM317 running right off the gel
cells, or (if you're feeling fancy) a $2 eBay SMPS module.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net