How to stop a UPS beeping when it's using its battery normally? (APC Back-UPS BX650LI-MS)

Question

I'm in a country where power outages are a daily occurrence, and 12 hours of power in a day is a good day.

I've got a UPS (a APC Back-UPS BX650 model) and it works fine. Its capacity (12V 7Ah = 84 Wh) could easily keep my modem and wireless router going for the whole period there's no power (if I can find a solution to another problem...), and since my other computing-related devices I run through it are pretty energy efficient, it could keep them going for a valuable extra hour or more comfortably.

There's just one problem - its infernal beeping. It's clearly designed assuming that users are running power-hungry desktop PCs or servers in an environment where a power outage is a rare emergency, not a fact of daily life. Any time it is using the battery, it beeps loudly four times every 30 seconds, and doesn't stop until it's turned off, or the power comes back on. This is extremely distracting. In my case, it's like Homer Simpson's "Everything is okay" alarm - it's beeping at me to tell me it's doing the thing I bought it to do.

I've looked for ways to stop the beeping and found I'm certainly not the only person with this problem:

• Some models have a USB port to allow such settings to be changed. Mine doesn't and I don't think there's any model that does which is available on sale in this country.
• Some models have a "mute" button. Mine doesn't and again I'm not found any model available in this country that does.
• The diagram in the instructions mentions nothing that seems relevant (on/off button, LED status light, battery connector, input power cord, outlets, fuse).
• Some users unable to do the above have opened up their UPS and de-soldered the buzzer. This is the extreme 'nuclear option': the buzzer is the only indication on this model of several genuine problems I'd need to respond to, like overheating or overload.

Is there any alternative? Any other means e.g. a physical way to stop the buzzer sounding when the UPS is simply doing its job and supplying battery power?

For example, is there any way to find a diagram of the circuitry of this model such that I could add a rudimentary on/off switch to the connection to the buzzer without breaking anything? Or could I replace the buzzer with something like an LED with the same resistance to flash instead of buzz, still telling me about genuine emergencies but without buzzing? Or maybe there's a wire or connection leading in to the buzzer or buzzer controller that is only related to this specific battery-in-use warning that could be safely severed...

Answer 1

You do this at your own risk. Mains voltages may be present. If you have any doubts, get a competent person to do this. You may want to make sure someone trained in CPR is present.

You could use the same method as shown in the desoldering-the-buzzer article: identifying the buzzer is the same (search for images of piezo buzzer if you want to be sure what it looks like), and they add a switch.

Disconnect the mains lead and battery before touching anything else and make sure it cannot accidentally reconnect.

You could use a SPDT switch to change between the buzzer and an LED (with a series resistor) so that you have a choice of indicator. Without knowing the voltage that the buzzer operates at, I cannot give a value for the resistor. LED resistor calculators are available online, e.g. ledcalc.com/.