When you disconnect your computer’s power supply from the wall, it jumps in to save your BIOS or UEFI settings in your motherboard’s CMOS-RAM (Complementary Metal-Oxide-Semiconductor). But even the most reliable battery only has a certain lifespan. Over time, a CMOS battery’s performance can degrade and, in the worst case, can up the ghost before your motherboard is ready to say goodbye.
If that happens, the CMOS memory chip can no longer hold your BIOS settings between power cycles, resulting in a full BIOS reset. Gross. To counteract this, it’s helpful to check the CMOS battery periodically. And the good news is you don’t need highly specialized equipment to do it.
A simple method is to disconnect the PC from main power overnight. The next morning, if your computer does not require you to reset the date and time, and the operating system starts without any obstacles, then the battery is probably still flawless.
But if the date and time have to be reset every time the computer is started, or if the BIOS settings have been reset to the default settings, it is probably time for a battery change.
Further reading: The best gaming motherboards for Intel and AMD
The replacement itself is usually pretty simple. Finding the CMOS battery on your motherboard is half the battle: It looks like a small silver disc and is usually positioned next to the main PCIe slot.
With a light press on the retaining clip, the battery can be removed and replaced. Most newer motherboards use a CR2032 battery, which can be bought for just a few dollars. But there is also the possibility that your board uses a different type, so you should definitely check this beforehand.
Buy an Energizer cr2032 battery on amazon
With laptops, on the other hand, replacement can be more complex, especially with the newer models. Often the battery is well hidden or even positioned on the lower side of the motherboard, which is usually difficult to reach. Take the laptop to a repair center for a CMOS replacement in that case.
Some laptop models, especially slim devices, 2-in-1 models, ultrabooks, premium laptops, and MacBooks, do not have a CMOS battery on the mainboard at all. Instead, they use the main battery to power the CMOS memory. Alternatively, as in the case of MacBooks, they rely on a small capacitor supported by the main battery to store the date, time and other BIOS settings.
Although the CMOS battery is an inconspicuous component, it still plays an important role in the smooth operation of your computer. Check it out if your PC starts acting weird
This article was translated from German to English and originally appeared on pcwelt.de.
FAQs
You can also check the voltage of the CMOS battery in the System Information window. To do this, scroll down to the “Battery” section and you should see the “CMOS Battery Voltage” field. This field will show the voltage of the CMOS battery. If the voltage is lower than 3.0V, then it is time to replace the battery.
How to know if a CMOS battery is low? ›
Typical Symptoms Of a CMOS Battery Failure
- The Time And Date Keeps Resetting To Its Default. ...
- Drivers Not Responding And Various Hardware Failures. ...
- Keyboard Acting Weird. ...
- Checksum Error. ...
- Random Shutdowns And Booting Issues. ...
- Constant Beeping Noise And No Internet Connection. ...
- Step1: Shut Down Your PC And Unplug It.
Generally, the BIOS/CMOS battery is placed fairly prominently on the motherboard for easy access, but sometimes it gets hidden by other components or heatsinks, so it may take some effort to find. Once you find the battery, swapping it out should be fairly straightforward.
Does removing CMOS battery reset BIOS? ›
The BIOS is also used to identify and configure hardware in the computer. For no boot or no display issues, clearing CMOS may help recover the boards because that restores the BIOS default settings.
Can a PC run without a CMOS battery? ›
Your motherboard and computer will be able to boot just fine even without a CMOS battery present. The only issue is all your BIOS settings will be reset and the time and date will be inaccurate. You will also be unable to save BIOS settings.
How often do you need to change CMOS battery on motherboard? ›
If your PC frequently displays an error message about the BIOS settings being cleared, there's a high chance your CMOS battery has been depleted. CMOS coin cells typically have a lifespan of three to five years, so even the best gaming motherboards will need their CMOS batteries replaced after a few years.
What to do before replacing a CMOS battery? ›
Before replacing the battery, make sure that all external devices are disconnected, and that the computer is turned completely off (including the power switch) and unplugged. Let the computer sit for a few minutes to fully discharge, and be sure to ground yourself before touching the motherboard.
Can you change the CMOS battery without losing settings? ›
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.
How do I reset my motherboard without CMOS battery? ›
Press and hold the power button on your computer for about 10-15 seconds to discharge any remaining power stored in the capacitors. By discharging the power, the CMOS memory will reset, thereby resetting your BIOS.
How do you know when the CMOS battery needs to be replaced? ›
The most common symptom of CMOS battery failure is incorrect or slow system date and time in the BIOS, loss of BIOS settings when the computer is powered off, time-of-day clock stopped error message and so on. If the CMOS battery is out of charge, the BIOS settings will be lost when the computer is powered off.
Correct option is D. Hardware settings, including the current date and time reverts to default values.
How do I reset the BIOS? ›
How to reset the BIOS from the BIOS interface
- Turn on the computer.
- Tap the F2 key several times until Entering Setup appears.
- Reset the BIOS to factory defaults. ...
- Press the Esc key and select Save and exit or Exit.
- Press the Enter key to save all changes and exit the BIOS setup screen.
Depending how much you use your computer and whether or not you have the power supply switch turned on or off when you shut your computer down, CMOS batteries can last from 3-10 years. However, just like any other consumable item, they need to be replaced at some point.
How to check battery health on BIOS? ›
You may notice other symptoms, such as your laptop suddenly shutting down, even though it indicates some charge remaining, or the charge level abruptly falling. To check your battery health, restart your laptop and press "F2" repeatedly to enter the BIOS. Select "General", then "Battery Information".
Do CMOS batteries run out? ›
If you don't charge a laptop for years, will the CMOS battery die? Yep, it discharges very slowly, but it does discharge. That's why if you turn the power off on an old computer and then boot it up again, after turning the power on, the time and date may be reset to factory defaults because that CMOS battery is dead.
Does the CMOS battery recharge? ›
CMOS battery
This cell battery has an estimated life of three years when power supply unit (PSU) is unplugged or when the PSU power switch is turned off. This battery type, unlike the lithium-ion battery, is not rechargeable and trying to do so may result in an explosion.
