What is a Typical Symptom of a CMOS Battery Failure?

You may not have heard of it, but a CMOS battery is one of the essential parts of a computer, and if this battery fails, it may cause several problems in your device. 

So how do you tell it may be time to replace your CMOS battery? Although there are many telltale signs, a typical symptom of a CMOS battery failure is having to reset the date and time whenever you turn on your computer

If you believe your device may be going through a CMOS battery failure, we’ll help you figure it out for sure. 

What is a CMOS Battery? 

Before diving into a CMOS battery, we must first understand BIOS. 


All your computer’s functions come down to how the inputs and outputs work together.  The BIOS, which stands for Basic Input Output System, manages the information between these inputs and outputs. 

In addition, it instructs your device on how to boot up its Operating system. It also enables your computer to communicate with peripherals such as your keyboard and mouse, allowing you to operate them. 

Furthermore, BIOS also stores basic information such as the time, date, and system configuration information. 

BIOS is the first thing to load when you start your computer. While you can install, uninstall, and update your operating system, BIOS is different as it was integrated into your device at the manufacturing time. Therefore, it is pre-programmed into the computer’s hardware. 


BIOS must remain operational at all times. So what powers it up when you shut down your computer? 

That’s where the CMOS battery comes in. CMOS (for Complementary Metal Oxide Semiconductor) provides power to the BIOS, which keeps it working. 

Remember how we said BIOS stores information? It does, but this data is not stored in the BIOS but the CMOS battery. CMOS contains the time, date, and configuration details used to start the computer. 

You can think of CMOS as a memory technology that stores the time, date, and configuration date BIOS needs to start a computer. 

Although CMOS batteries are present in desktop computers and laptops, they are more common in the latter as the former is seldom unplugged from the power source. 

Every time you start your computer, your CMOS battery charges itself so that it may power the BIOS when needed. 

Although significant, your device will still work without a CMOS battery. However, you’ll have to reset the date and time whenever you start up your device again since the operating system does keep the date and time on its own. 

What is a Typical Symptom of a CMOS Battery Failure?

Symptoms of CMOS Battery Failure 

The life of your CMOS battery depends on your device’s usage and environment. Generally, the battery may last anywhere from two to ten years. 

A dead or failed CMOS battery failure can cause several computer problems. Here are a few symptoms to watch out for. 

Incorrect Date and Time 

This is a typical symptom of a CMOS battery failure. 

As we discussed, the CMOS battery stores the time and date. From the moment you turn off your device to when you turn it back on again, CMOS tracks the difference between these two moments and calculates the correct time to display on your screen. 

If you observe your device displaying the wrong date and time, you may want to think about replacing your CMOS battery. 

Hardware Problems 

BIOS identifies and configures hardware and stores this information on the CMOS, enabling the computer to track the hardware drivers. 

If your CMOS battery is not functioning correctly, your device will not be able to identify some of the hardware due to the missing drivers. For example, you may face problems connecting to your printer for no apparent reason. 


Constant beeping is not a good sign and may indicate a hardware issue. Get your computer checked as soon as you can. A CMOS battery replacement may be due. 

Connectivity Issues 

In addition to hardware drivers, BIOS manages network drivers storing this information in CMOS. A dead or dying CMOS battery means your computer may not be able to connect to the Wi-Fi or internet. 

Errors While Booting 

You may encounter a reading error or a Checksum booting error while booting your device. A failing battery corrupts CMOS values such as date, time, and hardware settings. Because the computer can no longer verify these values, you’ll see errors when booting your computer. 

A dead CMOS battery may not necessarily mean your computer won’t boot. It depends on the motherboard. Some motherboards require a CMS, while others may boot without it. 

Random Shutdowns 

Another symptom of a failing CMOS battery is that your computer may randomly shut off without warning. 

This may happen because a hardware driver may stop working while your computer is in use, causing it to crash. 

In addition to irregularly shutting down, your device may be hard to start due to booting issues. This happens because some of the drivers are not working. 

Removing and Replacing Your CMOS Battery

Have you found out your CMOS battery needs to be replaced? Not a problem! You can easily remove and replace your battery by following the given steps. 

The process of replacing the CMOS battery from a laptop and a desktop are slightly different due to the size and other structural differences between the two types of devices. 

Your Laptop 

Before beginning your work, move to a hard and flat surface. This may help prevent electrostatic discharge and provide a stable workplace. 

If you have a conductive foam pad to work on, even better. 

 Keep some containers close by so you may easily collect all the screws without misplacing any. 

  1. Shut down your laptop and unplug it from the power source (both the charger and battery).
  2. Flip it over and undo all the screws. You may need either a Philips or a flathead screwdriver, depending on the make of your laptop.
  3. Your motherboard may immediately appear, or you may have to undo more screws after the first casing. It’s best to look up your laptop on the internet and find out where the motherboard is located so you may quickly get to it.
  4. Carefully remove the CMOS battery. The cell is easy to recognise. It’s a silver, shiny, round cell in the motherboard placed in a smallholding socket.
  5. Insert the new battery in the same place. Ensure the orientation is the same as the battery you’ve just removed.
  6. Screw the casing back on and replace the battery. 
  7. Reset the date and time.
  8. Reinstall the drivers. And you’re done! Wasn’t that easy? 

Your Desktop 

Once again, find a flat surface to work on and keep containers nearby to keep all the components in. Keeping these parts in one place will prevent you from losing them. Once ready, follow these steps to remove and install your new CMOS battery. 

  1. Ensure your computer is off and all the cables connecting to it are removed. Remember the order of the wires so you can put them back in the right place once you’ve installed the battery.
  2. By using a suitable screwdriver, remove the side panel of the CPU.
  3. Locate the motherboard; it may be visible after removing the panel.
  4. You’ll find the CMOS battery here. It looks similar to the battery used in laptops, a silver, shiny, round cell, except it’s bigger.
  5. Carefully remove the battery.
  6. Insert the new battery in the same place. Ensure the orientation is the same as the battery you’ve just removed.
  7. Slide the side panel back in and tightly screw it in place. 
  8. Reattach all the cables exactly how they were. 
  9. Reset the date and time.
  10. Reinstall the drivers. Your desktop computer now has a new CMOS battery. 

What Happens After 

Once you remove your CMOS battery, all your BIOS settings are cleared. When you turn on your computer again, the time you’ll see on your screen is when your device is powered off. 

Buying a New CMOS Battery 

Just like any other cell or battery, you can’t fix the CMOS battery either. So if your CMOS battery has failed, there is no other way except to buy a new one and replace the old one with it. 

The battery is relatively easy to find; just visit any local computer store in your area. The battery itself doesn’t cost too much either. You can even order it online from Amazon. 

Your Battery May Not Be the Problem 

How long the CMOS battery lasts depends on how much and how well you use your device. Remember, your battery should last you anywhere between two to ten years.

However, if your CMOS battery keeps dying or drains too fast, the battery or even the usage may not be the issue. In fact, the problem may be much more extensive and may indicate a faulty motherboard. 

It may also be possible that your computer’s motherboard may not be adequately grounded, causing the battery to drain too fast. 

Either way, if the lifespan of your CMOS battery is much shorter than expected, the problem may be in the motherboard. 


Now that you know the symptoms to look out for, you can replace your device’s CMOS battery without your computer suffering any long-term damage. Remember not to be nervous; follow the steps, and you’ll have a new battery in no time. 

Of course, if you think it right, we recommend seeking professional help, so everything goes smoothly. 

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