A computer may sometimes show error messages related to time and date options or other errors like 'no operating system or new CPU is installed'. All these are indications that it is time to change the battery of the motherboard i.e. the CMOS battery of the system. The depletion of this battery happens and hence it must be replaced ideally every five years. The replacement process has to be carefully followed to avoid any inadvertent problems. Saving the BIOS data prior to the battery change and configuration of the same, after the installation of the new CMOS battery, must also be done properly.

Replacing the battery of your motherboard (CMOS battery)

Symptoms

If your computer is experiencing problems with the date and time or you see the following error messages:

• bios cmos checksum error defaults loaded
• bios cmos battery low cmos wrong memory size
• no operating system
• CPU overclocking failed
• New CPU has been installed

These problems may be due to the fact that your CMOS battery is depleted and it's time to replace it.

Replacement sequence

It is recommended that you change the CMOS battery every 5 years.

Saving the BIOS data

Open the BIOS screen and note all the information on a piece of paper. It's important that you don't make any modifications. Once completed this document will be useful to check out if all the parameters are correctly inserted after replacing the battery.

Identify the CMOS battery

The CMOS battery is thin round button-like object. It can sometimes be hidden by extension cards or connectors. On older PCs it may have a cylindrical shape.
The most widely used battery model is the CR2032:

• Where :
  • CR- lithium battery
  • 20 - 20mm diameter
  • 32- Thickness 32* 0.1 mm
• This type of battery is easily found and fairly cheap to purchase

How to locate it:

• Turn off your PC
• Remove the power cable attached to your system unit and remove the casing.
• Discharge your system unit from static electricity by touching it with a metallic object.

Removing the discharged battery

• First of all, be sure that your System unit is laid down horizontally.
• The positive pole of the battery should be visible.
• Remove the battery, but avoid forcing it and any contact with other parts of your motherboard (refer to the manual provide with your motherboard).
• Go to your local retailer any buy a battery of the same model or something equivalent.

Installing the new battery

Be sure that the battery is placed correctly (firmly) in the slot allocated

Verify the BIOS data and resetting the clock

Once the operation complete, it is important to configure the BIOS settings:

• Start your PC.
• Enter the BIOS.
• Modify the date.
• Check the parameters are the same as the ones noted in step 1
  • Perform any modifications required if not
• Save and quit BIOS.

Note that

• For more information: Motherboard
• CMOS checksum error default loaded
• CMOS Battery Low/Wrong CMOS Memory Size

See also

Knowledge communities.

• Forum
• Hardware forum
• BIOS forum
• Word forum

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