How to replace the motherboard CMOS battery

Published by JP Novak on March 14, 2022 and last updated on March 27, 2023

I had recently purchased a cheap Acer Veriton ES2730G desktop computer on eBay. Everything was working fine except that there was a CMOS error every time I removed and reconnected the power supply unit (PSU) cable.

The solution was to replace the CMOS battery and I am going to describe, step by step, how I did it in this tutorial.

I didn’t pay a lot of attention to the startup error message the first time I switched on the computer but I realised that the date and time were incorrect. I updated them in the BIOS and everything seemed to be fine. But I noticed the CMOS error message the next day after switching on the computer and I realised that the date and time were incorrect once again when I entered the BIOS setup.

The explanation was simple: the CMOS battery was dead and the settings values were lost every time I unplugged the power cable. The CMOS battery is used when the computer is unplugged to provide constant power to the CMOS chip storing these values. The battery will last years but it’s lifetime can be reduced if the computer is unplugged during a lot of time or if it is stored in a cold place.

The solution was an easy one too: to replace the CMOS battery with a new one.

Be sure to understand what you are doing and if you don’t feel sure about reproducing these steps, ask someone with good computer skills to help you. As always, the author and the website decline any responsibilities about the consequences of trying to reproduce these steps.

Be aware that static electricity can damage computer components. The charges may build up on your body when you walk on carpeted floors or if you wear woolen clothes for instance. You can easily neutralize these static charges by touching any conductive material not isolated from the ground (any metallic furniture or appliance will do) before opening the computer case.

The steps described in this tutorial require:

• a Phillips Cruciform screwdriver to open the computer case.
• a flat screwdriver to remove the battery.
• a coin-sized CR2032 cell battery (Buy it on Amazon).

1) The first step consisted in opening the computer case. As always, be sure to switch off and unplug your computer before doing it. I didn’t include the details here but you can see how to do it in in the steps 1) to 3) of this tutorial.

2) The CMOS battery was visible and easily accessible without having to remove the metal panel with the disk drives.

It was kept in place by a metal clip on the left side and two small plastic clips on the right side in this photo.

3) I used a flat screwdriver to slightly push the metal clip and unlock the battery:

I didn’t have to apply much force, the battery was released on the first try.

4) The button battery model was a CR2032 (Buy it on Amazon) that is commonly used on motherboards. I removed it with my fingers and I replaced it by a new one:

5) I locked the new battery under the metal clip by pressing lightly with a finger:

I didn’t have to apply much pressure, I heard a small “click” as the metal clip closed to lock the new battery in place.

6) The next steps were to close the computer case, to reconnect the cables, to turn on the computer and to enter the BIOS Setup one more time to adjust the date and time:

And to save the changes:

After replacing the CMOS battery the startup error message didn’t appear anymore, the PC did not forget the BIOS settings and everything worked correctly.

This page is part of a series of tutorials about upgrading the components of a second hand PC in order to give it a second life.

Conclusion:

Replacing the CMOS battery is a very simple task. Be sure to check the battery model (it is typically a coin-sized CR2032 cell battery) and to proceed with care while using the screwdriver to avoid damaging the motherboard components.

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