Diagnosing Computer UPS - Page 1
Forum section: electronics / projects

author: ee851
author_rank: Regular Contributor
timestamp: July 31, 2012, 05:27:10 pm
content: I suspected my PC's uninterruptable power supply wasn't working correctly. So I unplugged my PC and plugged in an incandescent light bulb. Sure enough, pulling the AC mains cut output power about a third of a second later. Should have run at least 15 to 17 minutes off the battery.I pulled out the 12V sealed lead acid battery. It measured 13V unloaded. is there another test I can do to see if it's the battery that needs replaced or if there's something else wrong with the UPS ? Brand is APC Back-UPS ES 725 Model BE725BB.www.apc.com

author: gxti
author_rank: Frequent Contributor
timestamp: July 31, 2012, 05:36:17 pm
content: I'm not a fan of APC's lower-tier supplies, if it doesn't say "Smart-UPS" then it's shoddy firmware not worth putting up with. I've switched to CyberPower's PFC-compatible line (pure sine output). But let's give APC the benefit of a doubt -- how long has your set of batteries been in service?

author: M. András
author_rank: Super Contributor
timestamp: July 31, 2012, 05:42:22 pm
content: check their site for manuals and service manuals for this model. they usually write problems+cause and solution for it. dont expect part by part replace guide

author: Technoguy3
author_rank: Contributor
timestamp: July 31, 2012, 05:57:07 pm
content: I haven't had good luck with the low-end APC UPSs either. I have had two fail even though the batteries appear to be in perfect working order.

author: HooRide
author_rank: Regular Contributor
timestamp: July 31, 2012, 06:00:07 pm
content: Quote from: Technoguy3 on July 31, 2012, 05:57:07 pmInteresting, I've never run into a malfunctioning APC UPS that wasn't fixed by replacing its batteries.

author: SeanB
author_rank: Super Contributor
timestamp: July 31, 2012, 06:39:16 pm
content: Shake the battery. If it rattles it is dead, and needs to be replaced. As well place a 12V halogen lamp across the disconnected battery ( 50W is best, but 20W is ok but will take longer) and see how long the lamp takes to dim, or the battery to drop below 11V. If it is dimming and drops below 11V in under 20 minutes then it is dying.I took mine and replaced with a much bigger battery outside the case, where it stays cool, and does not get cooked by the heat from the UPS. Just note most UPS batteries are not isolated from the mains internally, so the wiring and the external battery has to be protected in a box rated for the mains voltage. You need to use a minimum of 4mm cable to connect the battery to the wiring inside the UPS, preferably 2 4mm cables per terminal.

author: Nirios
author_rank: Regular Contributor
timestamp: July 31, 2012, 07:46:10 pm
content: Quote from: HooRide on July 31, 2012, 06:00:07 pmSame here. Every one I have come across the battery is usually so swollen I have to use a pry bar to get it out. IMO, the low end APC units seem to slow cook the batteries which in turn shortens their lifespans (usually to 1 day past the warranty).

author: nctnico
author_rank: Super Contributor
timestamp: July 31, 2012, 08:41:27 pm
content: Also the same here. The low end APC designs are pretty basic and rock solid. In my experience an UPS is causing more problems than it solves. You will need to replace the batteries at least every 3 years.

author: ee851
author_rank: Regular Contributor
timestamp: August 01, 2012, 02:52:41 pm
content: The UPS is eight to ten years old, still with the original 12V battery. The battery looks okay. Next, I will take the battery out and test it by discharging it with a 50W or bigger incandescent light bulb as SeanB suggested.

author: nctnico
author_rank: Super Contributor
timestamp: August 01, 2012, 03:05:54 pm
content: After 8 to 10 years the battery is dead for sure. Just replace the battery.

author: SeanB
author_rank: Super Contributor
timestamp: August 01, 2012, 03:11:49 pm
content: Yes, that old it is very unlikely to be still in good condition. Generally they last at best 6 years in a good UPS, in a poor one it might make it out of warranty.At least power mosfets have made small power inverters possible, I still have 2 ferroresonant units, one working and one not. The not working one had a faulty driver board, and this sent 40 2N 3773 transistors to a smoke filled grave one day. Some day it will be turned into 3 piles for recycling.......... 100kg of copper and steel inside for sure.

author: SoftwareSamurai
author_rank: Regular Contributor
timestamp: August 01, 2012, 07:30:35 pm
content: I've recently had an APC UPS die on me nearly the same way. It was only 3 years old or so. For me, the problem was that I suddenly started getting "Battery disconnected!" messages, followed a few seconds later by a "Battery reconnected!" message. Yanking the mains AC caused it to shut off within a few seconds with no load at all. Replacing the battery didn't fix it. And after emailing APC tech support, they confirmed the UPS itself was faulty. Unfortunately they also claimed it was out of warranty, so I was SOL. (FYI: Just about everyAPCUPS I've owned has died on me in some way or another. Draw your own conclusion.)

author: madires
author_rank: Super Contributor
timestamp: August 01, 2012, 08:28:11 pm
content: Can't complain about APC Smart-UPSs. There are used widely in small companies for securing several servers and run great for a lot of years. Only need a battery replacement from time to time. My one at home is >5 years old.BTW; You don't need to buy those expensive battery packs from APC. All packs are based on standard batteries. Simply get some Panasonics and you'll save 50%.