Back-UPS ES-500 emitted continuous tone during operation, and has since seemed to die by stages

[Anonymous user]

I've had an ES-500 for a number of years, but this week it seems to have died.

Perhaps a week ago, it was in normal operation with 5 devices plugged into it: A laptop, a wifi/router, a small network switch, and 2 raspberry pis (small, low power computers). Not a heavy load. And then it started emitting a loud continuous tone, which only stopped when it was turned off via the power button.

This has happened a few times since then, and each time, the tone has gotten weaker. Most recently, I could barely hear it through a closed door, and when I turned it off and on again, it then sounded like a little faint warble.

During these events, the devices plugged into the battery backup side were not receiving power, even though the UPS was still receiving mains current. (I find this pretty frustrating! If the battery dies, shouldn't the UPS continue supplying power, uninterrupted?)

At this point, when I turn it on and no load is on the battery backup side, it soon begins making erratic little clicking or chirping sounds. I think this is the sound of a tone generator that is only receiving a trickle of power.

• Is this something that can be fixed by replacing the battery?
• Can I test the battery in some way?
• Is there a logic or power board I need to replace?

[Anonymous user]

You might check the serial number of the UPS. The first four numbers after the first two letters indicate year and week of manufacture. The loud continuous tone usually indicates a battery failure or overload condition. If the battery is more than 3-5 years old, it's likely worn out. APC supplied batteries also come with a serial number, in the same format as that of the UPS.

You could use a DC voltmeter to test the battery. However, this doesn't test it under any sort of meaningful load and it could fool you into thinking it's still good. You'd want to see at least 12.4 volts from a battery fresh out of a unit that was plugged into the wall and charging, maybe a bit more.

These particular models don't require a good battery to operate, though they will protest continuously with the the tone you heard. A battery that has failed with an internal short could possibly drag down the charging circuit's output and cause the internal logic to operate improperly. You could disconnect the battery and see if operations return to "normal".

Neither APC nor Schneider Electric considers these things to be repairable, so they don't supply any parts. For something as low end as an ES-500, you'd be better off replacing it anyway, if it turned out to be broken.

[Anonymous user · Accepted solution]

Thanks for the info! This one looks to have been made in 2005, although it hasn't been in use for all that time. At least 5 years, though.

I'll check the battery, and will see if disconnecting it at least allows me to use the battery backup side as extra surge protector slots in the meantime. And I guess I'll be making use of the trade-up program.