UPS alarm but batteries test good?

[Anonymous user]

This seems to happen to me a lot. The UPS starts alarming which tells me the batteries must need replacing, but when I take them out they test higher (12.9 volts each) than the new batteries I would be putting in (12.5 volts).

I've never understood this. And often, when I put new batteries in the UPS still doesn't work.

I have a wide variety of UPS boxes but they are all mostly different models of APC and they all seem to exhibit this same behavior.

Is it current I should be trying to measure and not voltage? And how can I know for sure that its the UPS failing and not the batteries?

Thanks for any guidance here.

[BillP · Accepted solution]

Hi Steve,

To help you out further let us start by gathering information with your UPS.

You have mentioned that the batteries needs to be replaced. May I ask what LED is currently lit up on your unit? Does it also produce or emit a tone or beep? If yes, can you explain the pattern that it makes?

Since you do have a spare battery, have you tried putting that one in? If yes, did it clear the fault? There are different things why would a UPS tell you that there is a bad battery, aside from the voltage the UPS also checks if the rate of discharge becomes too fast or quicker than before. It also checks by running a self-test if the battery could support the load, it does it by transferring to battery during the self-test.

Here is a kbase that would somehow explain the expected life span of a battery and the ways that you could do to take care of a battery - [What is the expected life of my APC UPS battery?|http://nam-en.apc.com/app/answers/detail/a_id/8301/kw/battery%20lifespan]