Will replacing a CMOS battery reset the UEFI (bios) settings to default?

Topic

New Reply

Wondering if replacing a CMOS battery on an Asus motherboard will reset the UEFI bios settings.  (assuming, that things are off and power supply is unplugged)

Mike

Reply | Quote

Replies

Generally not. The settings are meant to survive the loss of power.

The battery is really to run the RTC (clock) so when you turn the PC on it remembers the time.

There should be a CMOS reset jumper on the board. Time to search…

cheers, Paul

Reply | Quote

This is very much ‘generally’. Some motherboards rely on the CMOS battery to remember settings and some don’t. It’s not a hassle to put the settings back if you do lose them, though, so don’t let this stop you from replacing the CMOS battery if you need a new one.

Reply | Quote

Specifics aside, perhaps take ownership of the situation and write the settings down, or take photos on a phone or camera,  or see if your board is one from which you can save the current screen to an image on USB (look at the bottom or right side of the screen for instructions.. and save each screen as it only does the one you’re on).

That way if it does lose settings or corrupt something subtly so you have to restore defaults anyway (which does happen, unfortunately) you have that situation in hand. Of course the machine might not boot so you might need to print the images if you haven’t a second machine and they aren’t on a phone / camera..

In accordance with PaulT’s post I dealt with Asus boards back in 2016-2018 and found removing the battery stops the clock and will just produce a message to the effect that the battery has failed at next POST- it takes a lot longer with the battery removed to lose the settings (30 seconds plus to be sure they’re gone if the battery was in good condition, less if it’s already failing); moving the CMOS clear jumper actually removes battery power and drains the reserve which otherwise permits a relatively safe battery change (or a slightly imperfect battery connection..) BUT as that reserve is in one small component which does little for the day to day running it can be downsized or omitted at the design stage with only a minor affect on failures, so the actual situation depends on your board model and the time/temperature profile of its operation.

So in summary, note the settings, best be quick, make sure you have the right replacement on hand and make sure you have noted the bitlocker recovery key, if bitlocker is enabled.

1 user thanked author for this post.

windbg

Reply | Quote

You absolutely should assume any “user setting” in the BIOS Setup Menu you made will be reset. So write them down before you remove the battery. Note many motherboards let you save those settings to a file you can use to restore after a reset. Look around in your user guide.

Note the purpose of the CMOS battery is to keep power on the CMOS circuit whenever the computer is unplugged from the wall. And the CMOS circuit is used to keep user settings, such as Date and Time. Note the RTC (real time clock) is NOT the same thing as the Date and Time – however the Date and Time depend on the RTC.

Note the CMOS is meant to be reset <span style=”text-decoration: underline;”>easily</span>. If the designers want it to be hard, they would have, and could have easily used a different type circuit instead of CMOS. Perhaps an EEPROM, for example.

Some motherboards do have a small storage capacitor to hold those CMOS settings for a <span style=”text-decoration: underline;”>short</span> time just to accommodate battery changes. But do NOT assume your motherboard does. And I do mean “short” so have your plan of action sorted out to get in there, remove the old and insert the new promptly.

Last, just as a reminder, do make sure the PSU is unplugged from the wall and you touch bare metal of the case interior BEFORE reaching in to remove or replace the battery to discharge any static in your body. Do not touch the new battery with your bare fingers. Skin oils promote corrosion and attract dust. I put a clean sock over my hand.

While the case is open, make sure the interior is clean of heat trapping dust, clean if necessary. After replacing the battery, inspect everything to make sure all power and data connections are tight and secure. Connect power and boot directly into the BIOS Setup Menu. Check/set your Date and Time, if necessary, and any other user settings you may have made (like drive boot order). Then <span style=”text-decoration: underline;”>Save and Exit</span> to [hopefully] boot normally.

And, as always, make sure you have current copies of any data file you don’t want lost BEFORE thinking of starting this battery replacement.

Bill (AFE7Ret)
Freedom isn't free!

Reply | Quote

I just replaced the cmos / bios battery in my old Dell 380, shut it down, unplugged the power , quickly changed the battery, re-booted,  … I selected F12 when it showed boot up options and I selected F1 (continue)   it booted to my normal settings .. .. it did not lose the BIOS settings, it didn’t revert to default settings,  .. 08/01/2025

1 user thanked author for this post.

SueW

Reply | Quote

As was mentioned earlier, take pictures of your settings with your phone. I did that before replacing my battery on my Asus P8Z77-V PRO  and it was a good thing that I did because I had to go back and reset everything.

Don't take yourself so seriously, no one else does
All W10 Pro at 22H2,(2 Desktops, 1 Laptop).

Reply | Quote

If you replace the battery while the system is turned on you won’t have any issues.

cheers, Paul

Reply | Quote

If you try a hot swap you might want to tag the cell on a bit of tape so you can hang onto it- There is potential for real damage as (especially with the holders where the battery is flat to the board) the battery doesn’t always release in quite the way you’d expect, liberating the cell to bounce off you onto the motherboard surface,  which even if its a glancing blow could connect points which the manufacturer never envisaged would or should be connected…

To be honest you have to ask the question was the machine built by an OEM (Dell, HP etc) or by someone else. It’s usual to ensure the machine remains functional if the battery fails. Small OEMs are stuck with installing Windows in the default conditions most times, large ones have access to tools enabling the defaults loaded upon loss of the settings to be pre-set. End users and “best mates” are generally the ones who set it all up fine but don’t think to do a confirmation check as to what happens if the settings are lost, as they’re only building one machine.

1 user thanked author for this post.

wavy

Reply | Quote

Some BIOS/UEFI s have a save settings option. Most likely you will need to be booted to use so make sure to note boot info.

Just because you don't know where you are going doesn't mean any road will get you there.

Reply | Quote

hi..my laptop can turn on after replace the cmos battery but i need to unattach and reattch the cmos battery if i want to turn on the laptop again.

can i know why this happens?

Reply | Quote

Your laptop is broken?
The battery is in upside down?
Make sure you reset the BIOS to defaults after replacing the battery.

cheers, Paul

Reply | Quote

hi paul. i had done reset the bios and it is successful. i am really grateful for that.

but the laptop still cannot startup. i still need to remove and reattach the cmos battery then the laptop can startup.

 

do you have suggestion for me?

Reply | Quote

What happens if you leave the battery out? If that works I would leave it that way as it saves fiddling with the laptop every time you want to use it.

cheers, Paul

Reply | Quote

do you possibly have the BBC Code to reset the bios on my surface laptop 4 model1953  I would greatly appreciate any help you can give me

Reply | Quote

You should talk to MS for that. This thread is about MSI motherboards and batteries.

cheers, Paul

Reply | Quote

imho, unless you are very fast(light speed), the process should be:

(assure unplugged)

change battery.
clear CMOS.
Plug in and boot to BIOS.
press F5 or whatever to get default settings.
F10 or whatever to SAVE AND reboot to BIOS.(there may be 2 or 3 restarts for ME etc)
make your necessary settings.
F10 or whatever to save and reboot.
Boot to windows.
I see each of these steps as essential.

1 user thanked author for this post.

PKCano

Reply | Quote