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I have an APC Back-UPS 550 that is showing a replace battery alarm (alternating red/green flashing LED with constant tone). The battery registers 12.7 volts on a multimeter when disconnected from the unit. This makes me question whether the battery is actually bad. Is there another test I can do to ensure the battery needs to be replaced before spending money on a new one?

zenzic
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Is there another test I can do to ensure the battery needs to be replaced before spending money on a new one?

Plug the UPS into utility power, plug your equipment into the UPS, then unplug the UPS from utility power. Does it carry the load? For how long? I'm no electrical engineer, but I'm guessing the voltage output while not under load isn't a very good test of whether or not the battery needs to be replaced.

Addendum:

The alarm indicates that the battery needs to be replaced. The UPS will not hold a load when on battery. You're wondering if it's not actually the battery that needs to be replaced because the battery reads 12.7v while not under load.

If it were me I'd tent to trust the alarm. What else could be the problem with it? Is it an internal malfunction that is erroneously causing the replace battery alarm to go off? What if the battery is good but it's a problem with the circuitry, the motherboard, etc., etc.? What would you actually do about that? What other test could you perform on the battery other than a load test? What's your course of action if the battery actually is good? Does it even matter? The UPS won't hold a load.

joeqwerty
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  • No, of course it doesn't carry the load. It's alarming and nothing works at all. I'm no electrical engineer either and that's why I'm asking for help. Everything I've read, and what little I know about batteries says that a voltage test is a good confirmation that the battery is ok. If that is true and the UPS itself is at fault, I'd rather not waste money on a battery that won't solve my problem, so I was asking if there's another way to test the battery. – zenzic Sep 01 '22 at 22:35
  • My course of action would obviously be to replace the UPS rather than wasting money on a battery that will not solve my problem. – zenzic Sep 01 '22 at 22:48
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    I get where you're coming from... you don't want to spend the money on a new battery if the problem is something else, but 99.9999999% of the time, a replace battery indicator means the battery needs to be replaced... regardless of what voltage it reads while not under load. – joeqwerty Sep 01 '22 at 22:53
  • Take your concerns of the cost of the replacement to your battery vendor. If they want your business, they could offer easy returns, or a repair service. – John Mahowald Sep 05 '22 at 17:22