What is CMOS Battery, Functions, Failure, Reset, Replacement

[CMOS Battery]

Today we are going to discuss all about the CMOS battery. I will try to give the answer to all frequently asked questions about CMOS Battery such as What is CMOS Battery, Functions, Failure, Reset, Replacement.

CMOS stands for Complementary Metal Oxide Semiconductor.

In our computers and laptops, a CMOS chip is placed to store BIOS settings. Basically, the CMOS chip is a nonvolatile memory. It is also called CMOS RAM. CMOS chip is used to store time, date, and other hardware settings.

Why CMOS chip is used in our computer?

Let's think about our conventional Watches. If we remove the battery from those Watches and insert it again after a few times it will show the wrong time. We need to set again the time on those Watches. So it is clear that if we want to see always the right time on our conventional Watch then we must keep always turn ON the Watch.

Our computers and laptops also show time. But if we turn off the computer and again it turns ON after a few times it will show the right time, how it is possible? It is possible to use a CMOS chip.

In our computer motherboard, an RTC(Real Time Clock), a CMOS Chip, and a battery is used for the real-time timing system. The RTC, CMOS chip always works even when we turn OFF our computer and gives us the real time when we turn ON the computer.

What is the CMOS Battery?

Basically, a CMOS Battery is a lithium cell battery that looks like a coin. As the battery is used to provide a power supply to the CMOS Chip that is why it is called a CMOS battery. Don't confuse it with its name. There is no CMOS technology is used in this battery. The CMOS battery is a simple lithium cell.

What is the Function of a CMOS Battery?

As I told you before, we need to keep always turn ON the CMOS chip. So the CMOS battery is used to provide the power supply to the CMOS chip even when the computer is OFF.

CMOS Battery Voltage

Generally, CMOS batteries are used in the range of 3V to 5V. Most of the cases 3V CMOS batteries are used. In some devices 5V CMOS battery is also used.

Is CMOS Battery Chargeable?

No, the CMOS battery is not chargeable. When the computer is ON, the CMOS chip takes the power supply from the motherboard. but when the computer is OFF, then the CMOS chip takes the power supply from the CMOS Battery.

There are some circuits are used in the motherboard to prevent charging of the CMOS Battery when the power supply is available. You may notice a Diode always connected with the CMOS battery.

The lifetime of CMOS Battery

In earlier days, the lifetime of CMOS batteries was 3 years, but nowadays the CMOS batteries are designed with a lifetime of a maximum of 10 years. The lifetime of the CMOS batteries varies with uses and working environment. CMOS battery may need to be replaced before 10 years.

How would I know my CMOS battery is damaged?

The following problems will be noticed when the CMOS Battery is failed,

1. Change in date and time, the computer will give an incorrect date and time.

2. If you set up the BIOS password then it will be reset.

3. Drivers do not work properly.

Read Also:

• Concepts of Semiconductor Memory in Digital Circuit. Internal structure of Semiconductor Memory.
• Difference between Microprocessor and Microcontroller and CPU
• The Actual Difference Between RAM and ROM explained in detail

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