I've never had an uninterruptible power supply and think of buying one. What not-so-obvious things should I not do to the UPS so that it lives longer?

I don't mean some obvious abuse like dropping/exposing to direct heat/exposing to wrong voltage. I mean less obvious things like its not acceptable to leave an acid battery UPS unplugged for long time after it has been used because some chemical processes start in half-discharged batteries and render the batteries unusable. What other misuses should I know about?

7 Answers 7


If you know you have wonky power (flicker flicker) adjust the sensitivity of the UPS so it doesn't trip for every little flicker. My apartment unit is next to the elevator. I killed a set of batteries in 8 months this way.


The SLA (sealed lead acid) batteries in UPSes shouldn't be left in a discharged state. If they are, sulfates will build up on the plates and their capacity will be reduced. This isn't normally a problem in UPSes, since they're always plugged in and after a power outage will charge the batteries back up when the power comes on. But if you somehow decided to unplug a UPS after the batteries were drained and then left it sitting unplugged for a week, you'd probably notice the battery discharging sooner next time.

  • APC suggests that if you stop using a UPS, you should disconnect the batteries - and that said batteries will last a long time.
    – Mei
    Oct 31, 2011 at 15:46

Dont overload it. If it has a nice status screen to see the load on it try to keep it below about 60%

By discharging it faster will wear out the the battery faster

Heat, humidity are also bad for it.


While in college I was moving some servers from one room to another. They all where on a really old UPS which apparently had less protection circuitry then current UPS equipment. I started by disconnecting all the servers from the UPS and moving those. Then without shutting down the UPS I unplugged it from the wall. Sparks started shooting out of the UPS and it literally started bouncing.

The electronics teacher had a plausible sounding explanation about why something like this would happen given the design of the UPS, but I don't remember enough details to explain it here.

So the moral of the story is this.

  • When there is no load, always turn off the UPS before disconnecting the power.
  • Generally sound advice for all electronic equipment Jun 22, 2009 at 9:08

According to the answers to my question over here, it's a bad idea to have a power strip touch it either upstream or downstream.


Don't plug a UPS into another UPS (i.e. Daisychaining them).

There's a good discussion on why not to here, or from APC themselves here.

  • 1
    I have a great story about that .... a 6 UPS dasiychain. We had to turn them off to move equipment. Then no one could figure out which one we needed to turn on first ... That was a great day. Jun 22, 2009 at 10:34
  • 1
    You're not likely to have one, but I have heard stories of people running a ferroresonant (Sola) transformer through a UPS and literally blowing it up.
    – dmoisan
    Jul 6, 2009 at 17:12

Your main concern should be heat. Don't cover it with a bunch of stuff. Keep the vents clear, and allow airflow.

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