When the lights went out today I noticed my UPS battery didn't work. I checked the monitor and this is what I see:

enter image description here

As you can see it says the battery has 90% but when I pull the plug, it doesn't work.

Is there a way I can fix this or find out if the problem is battery or UPS?

This is my UPS model I bought this FEB 2012, so it's about 1yr8mo. I only noticed the problem now because it's only now there's been power interruption.

  • 4
    Have you looked at the manual for a troubleshooting guide? They may tell you when to change the battery. Perhaps some information on the UPS would help us help you. – uSlackr Oct 10 '13 at 12:47
  • @uSlackr the manual only suggest that I charge the UPS for 6 hours which I will try later. – IMB Oct 10 '13 at 13:06
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    Perhaps your equipment load exceeds the output of the UPS. Try unplugging your equipment and plugging in something like a table lamp. See if, and how long, it runs on the UPS. – HABO Oct 10 '13 at 13:17
  • @IMB I would contact the company and see if the unit its still under warranty. Your battery has clearly been used if it has lost 10% capacity in only a year. – Ramhound Oct 10 '13 at 13:36
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    When testing a UPS do not unplug the UPS from the wall socket. That would also disconnect ground, and eliminates a safety feature to prevent shock. Instead connect the UPS to a power strip and that to the wall outlet. Use the switch on the power strip (which will maintain the ground connection) to simulate power loss. – sawdust Oct 10 '13 at 19:17

UPSes (particularly inexpensive ones, but many expensive ones are as bad) are notorious for having terrible charging behavior that kills batteries.

To address the comments that you might be overloading it, plug in a small load like a desk lamp. If it still doesn't work, the battery is toast.

You can replace the battery, and it will probably work for a while. Odds are, in another 18 months (or less) the new battery will also be toast. The more I use the things, the less I like them, for exactly this reason. They are very expensive to own when you have to feed them new batteries every year or two.

  • I have to agree with your conclusion. In this particular case the UPS isn't even under a 25% load, which means, he could triple the load in theory and his UPS wouldn't have a problem. – Ramhound Oct 10 '13 at 13:54

What you see in ViewPower is not reliable information. These cheap UPS doesn't have reliable internal monitoring of battery status and it is basically based on battery voltage, rather than having the circuit that can test battery capacity via charging and discharging currents and voltage drop delta.

To sum up:

  1. If you've experienced power interruption and the ups turned off immediately than 99% is that you have the battery issue (which is good :) )
  2. It is not unusual that you get the UPS that is fitted with battery that is unused for couple of months, which drastically reduce the battery life span
  3. I've just checked the FSP specification where they stated that "Battery/ Typical Recharge Time 4-6 hours recover to 90% capacity", which seems to be on the safe side for 12V/4.5Ah battery
  4. I have experienced multiple time that due to some UPS problems or bad design, switching speed is rather low and sometimes over 6ms (slow micro switch relays and/or undersized capacitors), which can lead that UPS shut down without having the time to switch on battery power.

What I can recommend you, is finding a good battery and try it with the UPS. If it still have the similar issues, than you can try to send UPS to service center for repair or replacement


Something I have noticed--virtually every bad battery I have replaced has been swollen to some degree. Have a look at it.

I don't really think the readout is wrong, just misleading. The battery is at 90% charge--but that says nothing about it's capacity. As it ages the capacity goes down.

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