How To Replace The CMOS Battery In Your PC

How To Replace The CMOS Battery In Your PC

Most PC users don't think much about the CMOS battery until their computer shows signs of losing its BIOS settings on boot up. If you tend to upgrade rather than replace your PC, replacing the CMOS battery every couple of years makes sense.

Likewise, if you purchase a used PC, battery replacement is a good idea unless the PC is less than two years old. It's just one more preventive step you can take to prevent troubles in the future.

If you have never replaced a CMOS battery before, you can find step-by-step instructions below.

In most cases, frequent CMOS errors are a sign of a dead battery. The CMOS battery maintains your settings while your PC is powered off. You can easily replace the battery yourself.

Difficulty Level: medium
Time Required: 10 minutes

Instructions:

1. Boot your PC and enter its setup mode.

2. Write down all of the settings from the various BIOS menus. Click this link to learn more about this procedure.

3. Power off your PC.

4. Open the case of your computer

   Figures 1-2. Undoing the screws on your PC case.
   Figure 3. Opening the case of your PC.

5. Locate the battery on the motherboard.

   Figure 4. Battery location on the motherboard.

   The layouts of the components differ on different motherboards, so you'll have to consult your motherboard user manual for specifications about the battery and its location.

   This is a close-up view of the battery on the motherboard.

   Figure 5. Typical CMOS battery.

   The most common type of batteries used in modern PCs is coin-shaped lithium/manganese-dioxide battery that looks like a large watch battery.

6. Obtain a replacement battery from a local or online computer parts dealer.

7. Remove the old battery.

   Figure 6. Removing the old battery.

8. Replace it with the new one, as shown on the picture below.

   Figure 7. Replacing the battery.

9. Document the date of replacement for future reference.

10. Replace the case and power on the PC.

11. Enter the setup mode of your PC.

12. Reenter the settings you have written down from the various setup menus.

Tips:

1. Don't forget to observe proper anti-static precautions when working inside the case of your PC.

2. If you can't see your battery right away, try removing expansion cards or unplugging cables. The majority of newer motherboards use lithium batteries that look like large watch batteries.

If the battery is already dead and you receive messages saying "CMOS checksum error", skip Step 1 and Step 2.