CMOS Battery- Full Form, Functions, and Replacement

CMOS battery provides power to the motherboard chip for updating real-time clock and retain other BIOS settings and configurations.

In this article, we will know about its full form, functions, replacement process, and some other important considerations relating to this technology.

So, let’s get started.

What is CMOS Battery? (CMOS Battery Definition)

CMOS battery is the part of the motherboard that is installed for the basic hardware settings like BIOS, date, time, and other configurations. The system loses all this information’s in off power mode.

So to retain the stored setting’s, CMOS battery provides power to its chip. People generally think that this battery provides power to the computer system. But the actual function is to provide the same to chip only.

Specifically speaking, this battery is generally used by:

Digital Logic Circuits
Microcontrollers.
Microprocessors.
SRAM- Static RAM.

CMOS chip requires very less power to increment the time parameters. It is also known as ‘backup power’ for motherboard.

CMOS Battery Full Form (Long Form of CMOS)

The full form of CMOS battery is Complementary Metal- Oxide Semiconductor battery. It is non-volatile battery to power up the chip.

What is the Function of CMOS Battery?

The major function of the CMOS battery is to keep a real-time clock. This battery operates with the CMOS chip even when the computer system is off. The primary parameter of this battery is to keep the parameter values stored.

The Second major function of CMOS in computer is to power the BIOS firmware either in laptop or computer.

The circuit of chip updates the time on-increment basis with the power of its battery. So, in the CMOS backup battery function, the parameter will be the same at the time of the booting up of the computer.

What is the purpose of CMOS Battery?

The CMOS Battery purpose is to prevent the loss of data in the event of a failure of the external power source.

A computer won’t work correctly or even start up at all if it doesn’t have this battery.

The on-board battery powers the CMOS, which is a physical component of the motherboard. It is a memory chip that stores configuration information.

Why to Remove Battery?

There are many reasons to replace a CMOS battery. Some are as follows:

You need to change battery if your computer is losing its settings for time and date.

Some error or alert messages shows battery is bad now. Like,

CMOS Read error
CMOS Battery failure
Checksum error
System Battery voltage is low.

These errors or issues show that you need to replace the battery as soon as possible.

So, if you want to know about the process of replacing the battery. Then, follow the steps in the next answer.

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How to Replace CMOS Battery?

The foremost step is to locate the CMOS battery in your system. Without knowing its location, the whole process is meaningless.

So, let’s get started with it.

Open the computer case.
Now find the battery attached to a motherboard.
The major consideration in this step is to verify the accessibility of the battery and to check is it removable or not.
In case, you cannot find the location of the battery then refer to the documentation of the motherboard or contact the computer manufacturer.

The second step is to obtain battery information. In this step, you need to put some extra efforts.

Most of the manufacturers do not put exact information of CMOS battery like its model and type. So in order to replace the battery, you need to write down the specifications like voltage, chemistry, wiring to know about it in detail.

Third step is to remove the battery.

How to Remove a CMOS Battery?

There are two types of CMOS batteries, so the method of removing both is different. The first type is of coin cell battery, which is comparatively simple to remove. Just grab the edge of the battery using your fingers and pull it out of the socket.

On the other hand, the second type is of the clip holding battery. In this case, you need to move the clip using one hand and pull it out using your other hand.

Note: You need to consider one more thing that all batteries are not removable. So, you need to replace it from the manufacturer only. The other option is to set a jumper on the motherboard for the installation of a new battery.

How to Insert New Battery?

After removing the old battery and buying the new one. You just need to put this new one in the second socket available on the motherboard.

After inserting a new battery, turn on your computer and reset CMOS values on defaults. The important consideration in this step is to securely save the settings. You can press F10 for this and exit from it. Giving a look at a different perspective, some computers continue to give error messages even after the replacement of a battery.

So, this shows that the motherboard has some other major issue and you have to take it to the computer repairer or get the new one from the manufacturer.

How long it takes to Remove CMOS Battery?

The process of removing the battery is very simple, it just requires certain steps to follow. So, the duration of changing or replacing the battery cannot be estimated as it depends upon your knowledge and skills.

If you have basic knowledge of electronics and have worked with batteries and all. Then, it will take only 15-30 seconds to replace it. On the contrarily, it can take much time for the newbie in this.

What is the Lifespan of CMOS Battery?

CMOS batteries are very effective and don’t give a trouble for up to 3 years generally. Thus, the average lifespan of this battery is 3-4 years.

What is the Cost of CMOS Battery?

The Range of CMOS battery varies from $10- $20, depending upon the purpose and manufacturer you are opting.

How long does a CMOS Battery Last?

The CMOS Battery function lasts for 5 – 6 years. The more usage of your computer, the longer duration of the CMOS Battery.

What happens when CMOS Battery Dies?

The dead battery shows the same signs and reasons to remove CMOS battery as mentioned above. The basic symptom is that your computer will lose hardware settings, which will cause day- to- day problems.

General FAQs

Can a computer run without CMOS?

The CMOS batteries are not attached to provide power supply to the computer system. The purpose is to provide power to CMOS chip only for storing the hardware settings/information.

Can CMOS battery cause a black screen?

Yes, this battery retains the hardware settings. So, when it dies the information or settings are also losing. It may result in blank or black screen until you replace the battery.

Does a CMOS battery recharge?

Most of the CMOS batteries are not rechargeable. It contains lithium button cells. But if you want a rechargeable one, then some manufacturers install the specific rechargeable version in it. You can find so.

How to detect CMOS battery failure?

There are some signs and computer systems shows pop-ups or notifications showing that battery is dying. Some of those signs are:
1. Invalid Configuration pop-up appears on your screen.
2. Run setup appears.
3. Clock Error, system loses time configuration.
4. Pop-up appears, press f1 to continue.
5. After pressing F1, invalid drive specifications appear on your screen.

What is the Function of CMOS Battery in Motherboard?

CMOS being the physical part of the motherboard supplies power to it.

What is CMOS Battery in Computer

To retain and maintain the real time clock RTC (system clock), and to power the memory chip that contains the system configuration file, a computer uses a Complementary Metal- Oxide Semiconductor battery.