Testing the CMOS battery

I am having a problem with my BIOS resetting every time I shut down and am wondering if there is a way to check the CMOS battery voltage without removing it from the board. Any ideas really appreciated. I should add I have checked through my BIOS settings but have no idea just where to find the voltage if that is possible. The board is an Asus P8Z77-V model.

A sure sign of a bad CMOS battery is having to set time and date at each bootup. Having issues with the changes can be caused by not saving the ones that were done before the problem came up. Most BIOSes have a place to set the Default but still have to be Saved. Some OEMs include software for making changes, my Dells of Oct. and April have it.

If it was me, I'd just change it.
It's a lot easier than messing around testing it.
You need a CR2032.

ICIT2LOL said:

I am having a problem with my BIOS resetting every time I shut down

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In a laptop? I always thought that the main battery would keep sufficient power reaching the Bios even if the CMOs battery was degraded.

I suggest you go to the maker's support site and download a copy of the Service manual if they provide one.
As well as telling you how to change the CMOS battery, it will probably include a drawing of it so you can see whether you are just changing a simple standard battery or a special-to-type one [which might typically be a standard battery & fixed cabling within a moulding]. For example,



Best of luck,
Denis

Thanks for the replies to both of you it isn't that the time and date changes just the boot order and sometimes the RAM speed and XMP settings. Same thing happens when I swap drives too when running either Windows 10 or Windows 11.
Anyway I have ordered a new battery and will change it when I get it.
Again, thanks for the replies.
Oh and Denis mate I should have mentioned this is a tower desktop

ICIT2LOL said:

Thanks for the replies to both of you it isn't that the time and date changes just the boot order and sometimes the RAM speed and XMP settings. Same thing happens when I swap drives too when running either Windows 10 or Windows 11.
Anyway I have ordered a new battery and will change it when I get it.
Again, thanks for the replies.
Oh and Denis mate I should have mentioned this is a tower desktop

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You mentioned the motherboard model.

Asus P8Z77-V: motherboard from 2012.

If the CMOS battery is the original one, it has lasted longer than I'd expect.

In the US, I think I could get a 2032 at CVS (ubiquitous pharmacy chain). Overpriced there, maybe.

ICIT2LOL said:

I should have mentioned this is a tower desktop

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John,

I made the elementary mistake of reading your system specs.
I should have known better.

Denis

Well dang, the mobo in my system 2 is from 2011 with it's original CMOS battery. Gonna change mine too.

Scott said:

Well dang, the mobo in my system 2 is from 2011 with it's original CMOS battery. Gonna change mine too.

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If you keep the power on to your desktop computer / motherboard, the CMOS battery will obviously last much long.
But some people turn the power off between boots.
Either way, batteries are cheap and easily replaced.