What is CMOS battery, and how to reset and replace it?

What is CMOS Battery?

The CMOS battery is a small memory to store configuration details and BIOS settings needed to initialize system. The configuration details are date/time, disk drive, etc. It is located in a small area in Motherboard and looks like a coin. It is traditionally called CMOS RAM. It is also referred as Non-Volatile BIOS memory. The CMOS battery is a RTC(Real Time Clock) because it is responsible for showing the correct date and time. CMOS stands for Complementary Metal Oxide Semiconductor.

What is BIOS?

BIOS is a Small program, which lookup CMOS battery for system boot information. BIOS is responsible for successfully booting the system.

How long it lasts?

The CMOS battery is powered to hold information for up to 3 years even if you left the system unpowered. If you use the system regularly, it may get extended up to  5  years. The CMOS battery is not rechargeable if you try to recharge it may cause an explosion.

What happens when CMOS battery fails

1.    Shows wrong DATE and TIME
2.    The Mouse will not work properly
3.    Booting errors
4.    Network connection issues
5.    Device drivers fail(ex: Printer driver)

The CMOS battery is very important during the system startup because It stores the information required to start the system. So it is important to check the CMOS battery when the boot fails. If the CMOS Battery fails, you will notice a change in date and time in your system. The system time will reset to old time and you may face problem in booting your system. Sometimes system boot may fail.

How to check CMOS is working properly?

Every time you boot, Check whether the system date and time are showing properly. If the time displayed is old and not real time. Its time to replace the battery.

Resetting CMOS battery

If you face any boot error, try resetting the CMOS battery.
1.    Remove the battery.
2.    Wait for 5 to 10 minutes.
3.    Insert it again.
4.    Battery got reset.

How to replace the battery?

Replacing CMOS battery is a simple DIY. It requires no expertise in computer. If you are completely new to the computer, I recommend seeking help from a technician.

1.    Open CPU side cover by using a screwdriver.
2.    Spot the coin like CMOS battery around the motherboard.
3.    You can see it held by the battery holder
4.    Remove and replace with a new battery. That's it!!

See Also: How to replace CMOS battery?

Where to buy CMOS battery?

The CMOS battery is available in most of the online stores like Amazon and Flipkart. They offer in bulk number like 10nos per order. Also, check availability in nearby electronic shops.

Buy here at amazon