When you see that your computer is not properly booting up, or maybe it shows an incorrect time and date every time you try to log in, there is a probability that your CMOS battery might be depleted. It may sound complicated; however, replacing your CMOS battery may be a simple affair. Nevertheless, it is important to first understand what a CMOS battery is and it’s role. Before we head on to CMOS, everyone needs to understand the meaning of a BIOS (Binary Input/Output System) of a computer.
A piece of firmware that is integrated into your computer is referred to as BIOS. It performs important and simple functions on your computer, particularly while booting. The input device on your computers, like the mouse and keyboard, are initialized by it. Moreover, it performs a POST (Power-On Self-Test) that checks the computer‘s hardware before proceeding to boot into the Operating System. Also, it sets up CMOS that forms the non-volatile memory of the BIOS. This means it retains information even after your computer is powered off.
CMOS is abbreviated as Complementary Metal Oxide Semiconductor. In a nutshell, CMOS stores information like date and time, as well as the hardware configuration of your system. Your CMOS battery is responsible for keeping the BIOS and CMOS powered on even after the computer is unplugged. The reason is that the CMOS keeps track of the time and date in real-time. Moreover, the system settings and hardware configuration must be accelerated when the computer boots. When the CMOS battery runs out, your computer loses every information, and the BIOS reverts to it’s default settings.
Most BIOS batteries last for around 2 to 10 years. There is a broad range as there are various factors influencing this. Whenever your computer is not used, the CMOS battery is not used. The CMOS battery in laptops might also charge itself whenever it is plugged in. However, this does not mean that your CMOS battery will be discharged in a few weeks when you do not plug in your computer. Maximum CMOS batteries last for at least two years, even if you never plug that into your computer. Removing your CMOS battery is pretty simple, but locating them may be difficult, particularly for beginner PC builders. Here we will show to identify and then remove them. Let us first see why you need to remove your CMOS battery.
When is there a need to replace your CMOS Battery?
When your CMOS battery has been discharged, your computer will begin to act abnormally. Below mentioned are some tell-tale signs:
Input device starts malfunctioning: As the BIOS is responsible for managing devices like the mouse and keyboard while booting, they might malfunction if your CMOS battery has been discharged. Your mouse cursor might become inaccurate, or there may be a delay in their movement. The mouse and keyboard can also stop working altogether, as the BIOS acts as the intermediary.
Incorrect time or date: The most common sign that the CMOS battery is discharged is the incorrect time and date on your computer. The time and date, usually, will be set to somewhere back in the past.
Power Off/On issues: While there may be plenty of reasons why your computer is not at all booting, one might be a failing CMOS battery. Your computer, alternatively, also can stop responding to the power off button.
Missing driver: It is likely that the recently installed drivers may disappear on the account of a failed CMOS battery. Most likely, these drivers will be related to the output/input devices connected to your computer.
An error message/ beeping sound: Error messages associated with CMOS and a constant beeping sound may also indicate a failing CMOS battery. These error messages consist of a CMOS checksum error, system battery voltage is low, CMOS battery failure, and CMOS read error.
How to remove CMOS Battery
To remove a CMOS Battery is a relatively simple process even though you have not handled the components of your computer before. You just need to press one small metallic lever that pops it out. Novice PC builders, however, might have issues locating the CMOS. This is because the motherboard will vary as per the manufacturer. Below we have mentioned the steps to remove the CMOS battery. You just need to follow them one after another. But before you start, follow the steps for discharging your motherboard:-
- First, turn the system off, and remove the power cable from the wall outlet or power outlet.
- You need to press your power button around 4-5 times to discharge any capacitors available on your motherboard.
Follow the below steps to remove the CMOS battery.
Removing the side panel
First, by removing the side panel, we need to access the motherboard. To remove the side panel, follow the steps mentioned below:
- On it’s side or back, remove all the screws. Most motherboards have one removable side panel on the left side of your CPU case.
- You just need to slide the panel out gently of the CPU case.
- Next, you can see the graphics card, the Power Supply Unit (PSU), RAM, and the processor.
Locating the CMOS Battery
The physical structure of a CMOS battery is similar to that of a watch battery, cylindrical and flat, the same as a coin. To locate it, you need to analyze your motherboard for a component that specifically appears like a silver coin. Once you have located your battery, we recommend you write down the specifications, such as wiring, chemistry, and voltage.
For ATX Boards
Check out the RAM slots (DIMM slots) or the PCIe express for large to medium motherboards because these chips are generally located around these areas. There is only one flat-circular looking component on the motherboard, so it is difficult to miss. Check the sign on top of your battery once you have located it. It must have a + sign. Always remember that if you insert your CMOS battery incorrectly, it won’t work. So, the BIOS will keep resetting each time you turn your computer off.
For Mini-ITX
For the smaller boards like the mini-ITX, you need to check the board for one colored insulating plastic wrap. The plastic wraps your CMOS battery. This colored plastic may be blue, red, yellow, black, or any insulating plastic. If you see any issues while trying to locate the CMOS battery, you can always refer to your motherboard’s user manual.
Removing the CMOS Battery
Follow the steps correspondingly based on the size of your motherboard.
For ATX motherboard
Larger motherboards have a separate slot for the CMOS battery. To remove the CMOS, follow these steps:-
- You can remove the CMOS battery simply by pressing the lock available on the CMOS battery slot available on your motherboard.
- Once you push it to the side, the battery will pop out easily.
If you face trouble while using the lock, it is a viable option to use a tiny thin pin to remove the CMOS battery. However, you must ensure that the pin is non-conductive, such as a toothpick.
For M-ITX or Mini ITX
A wire is attached to your CMOS battery on a smaller motherboard. Simply detach the cable connecting the CMOS battery to your motherboard. Before disconnecting the cable, you need to check it’s head to view how it is connected to the motherboard. This is being done so that you can reinsert the CMOS battery again back into your motherboard.
Wrapping up
It is not difficult to understand a CMOS battery. From the above section, it is quite evident that replacing a CMOS battery is like a breeze. Moreover, knowledge regarding the other vital PC components may also prove beneficial. While reinserting the CMOS battery, you need to ensure that the +(positive) sign on the battery is facing up. Insert the CMOS battery now into the CMOS slot by pressing it gently. If it is secured properly, you will hear a click.
Experiencing difficulties with your Device, check out our “How To” page on how to resolve some of these issues.
