Testing the CMOS battery


ICIT2LOL

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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.
 

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    Asus P8Z77-V
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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.
 

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

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I am having a problem with my BIOS resetting every time I shut down
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,
CMOS battry.png


Best of luck,
Denis
 

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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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    OS
    Windows 11 Pro 23H2 (OS Build 22631.4169) Desktop (OS Build 22621.4317)
    Computer type
    Laptop
    Manufacturer/Model
    Asus Vivo notebook X712FA or Desktop Ivy Bridge build
    CPU
    i7 -10510U / Intel i5 3750K
    Motherboard
    Asus generic & Asus P8Z77-V
    Memory
    Samsung 16GB DDR4 2666 MHz & G-Skill 16GB DDR3 2134MHz
    Graphics Card(s)
    On board Intel CPU graphics & Nvidia GeForce GTX 1050Ti
    Sound Card
    Laptop onboard & Xonar DSX Card
    Monitor(s) Displays
    Generic & Samsung 27" SAM0C4C
    Hard Drives
    Samsung 970 Pro NMe & Samsung 870 EVO 500GB
    PSU
    N/A
    Case
    N/A
    Cooling
    Asus in built
    Keyboard
    Generic
    Mouse
    Logitec Wireless
    Internet Speed
    50Mbs max allowance - occasionally up to 75Mbs
    Browser
    Brave
    Antivirus
    ESET Ultimate Security on both
    Other Info
    Desktop running Windows11 Pro with unsupported hardware fix
  • At a glance

    Windows 11 Pro OS build 22000.376i53750K16GB DDR3 @ 2133MHzAsus GTX 650TI
    Operating System
    Windows 11 Pro OS build 22000.376
    Computer type
    PC/Desktop
    Manufacturer/Model
    Home build
    CPU
    i53750K
    Motherboard
    Asus P8Z77-V
    Memory
    16GB DDR3 @ 2133MHz
    Graphics card(s)
    Asus GTX 650TI
    Sound Card
    Asus Xonar DSX
    Monitor(s) Displays
    Samsung 4K
    Screen Resolution
    3840x2160
    Hard Drives
    Samsung EVO 970
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    Corsair HX1100
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    Coolermaster HAF -M
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    Liquid
    Keyboard
    Microsoft Sidewinder 6
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    Logitec
    Internet Speed
    50Mbs
    Browser
    Edge
    Antivirus
    Only Windows at the moment
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 ;-)
You mentioned the motherboard model. ;-)
 

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    Manufacturer/Model
    ASUS ROG Zephyrus M GM501GS
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    Core i7-8750H
    Motherboard
    Zephyrus M GM501GS
    Memory
    SK Hynix 32 GB (2 x 16 GB) HMA82GS6CJR8N-VK 16 GB DDR4-2666 DDR4 SDRAM
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    Realtek ALC294
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    AU Optronics B156HAN07.1 [15.6" LCD]
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    Samsung MZVKW512HMJP-00000 512 GB, PCI-E 3.0 x4
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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.
 

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I should have mentioned this is a tower desktop
John,

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

Denis
 

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

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    Computer type
    PC/Desktop
    Manufacturer/Model
    Stigg's Build
    CPU
    Intel Core i9-10900X
    Motherboard
    GIGABYTE X299X DESIGNARE 10G
    Memory
    Corsair 64 GB (4 x 16 GB) CMW64GX4M4C3000C15 Vengeance RGB Pro 3000Mhz DDR4
    Graphics Card(s)
    GIGABYTE GeForce GTX 1660 Super Mini ITX 6 GB OC
    Sound Card
    Realtek ALC1220
    Monitor(s) Displays
    Samsung 27" FHD LED FreeSync Gaming Monitor (LS27F350FHEXXY)
    Screen Resolution
    1920 x 1080
    Hard Drives
    Samsung 970 Pro Series 1TB M.2 2280 NVMe SSD
    Western Digital Red Pro WD8003FFBX-68B9AN0 8 TB, 7200 RPM, SATA-III
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    Corsair HX1200 1200W 80 Plus Platinum
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    Fractal Design Define 7 Black Solid Case
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    Noctua NH-D15 Chromax Black
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    Razer Ornata V2
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    Razer DeathAdder Essential
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    Manufacturer/Model
    ASUS ROG Zephyrus M GM501GS
    CPU
    Core i7-8750H
    Motherboard
    Zephyrus M GM501GS
    Memory
    SK Hynix 32 GB (2 x 16 GB) HMA82GS6CJR8N-VK 16 GB DDR4-2666 DDR4 SDRAM
    Graphics card(s)
    NVIDIA GeForce GTX 1070
    Sound Card
    Realtek ALC294
    Monitor(s) Displays
    AU Optronics B156HAN07.1 [15.6" LCD]
    Screen Resolution
    1920 x 1080
    Hard Drives
    Samsung MZVKW512HMJP-00000 512 GB, PCI-E 3.0 x4
    Samsung SSD 860 QVO 4TB 4 TB, SATA-III
    PSU
    N/A
    Case
    N/A
    Cooling
    N/A
    Keyboard
    PC/AT Enhanced PS2 Keyboard (101/102-Key)
    Mouse
    Razer DeathAdder Essential
    Internet Speed
    FTTN 100Mbps / 40Mbps
    Browser
    Mozilla Firefox
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    N/A
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    USB2.0 HD UVC Webcam

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