Topic: Will replacing a CMOS battery reset the UEFI (bios) settings to default? @ AskWoody

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 easily. 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 short 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 Save and Exit 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.