Using a UPS with non-computer equipment

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 plugg> 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?

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.

I have one of those in the office. 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: 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:

Thanks; I'll investigate further.