Question Cmos Battery Question

Jul 12, 2021
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Hey all!

I just changed my CMOS battery cause my computer is already 6 year old and I thought It might have ran out of power soon.
After I changed the battery the bios was reset, but the date and time WERE NOT.
Is this normal or should I be worried? I changed the battery after waiting 15 seconds.
Just wondering if I did everything correctly :D
 

Ralston18

Titan
Moderator
What time and date appeared?

Did you manually set the initial time and date or allow the host computer to go to some website source to get/synchronize the time and date?

If manual, be sure to "OK", "SAVE", or "Yes" the change to make the change permanent.

Or if allowing the system to go to website for time and date (synchronized) be sure that the source website is current and maintained.

FYI:

https://www.businessinsider.com/how-to-change-time-on-windows-10

Read the entire link before making any changes.
 
Jul 12, 2021
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I think my internet cable wasnt plugged in when I booted, but the time shown was correct. I found that really weird o_O The bios reset tho
 

ex_bubblehead

Champion
Moderator
There's typically a small electrolytic capacitor in circuit that keeps the clock running for the few seconds it takes to change the battery. This can also keep the CMOS from resetting if you're quick enough with the changeout.
 
I think my internet cable wasnt plugged in when I booted, but the time shown was correct. I found that really weird o_O The bios reset tho
I think it can depend on the RTC (Real Time Clock) circuit in your motherboard. It might take a lot longer than 15sec's for it to lose it's setting with just a battery pull and not shorting the pins.

It's both typical and practical as it helps maintain time continuity following resets after power loss should the CMOS battery be dead. That's important when the PC is used for something like unattended data logging application.
 
Last edited:
Jul 12, 2021
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I think it can depend on the RTC (Real Time Clock) circuit in your motherboard. It might take a lot longer than 15sec's for it to lose it's setting with just a battery pull and not shorting the pins.

It's both typical and practical as it helps maintain time continuity following resets after power loss should the CMOS battery be dead. That's important when the PC is used for something like unattended data logging application.
Ohh this explains alot ! Thank you :)
 

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