Instructions How to Replace a CMOS Battery


Instructions How to Replace a CMOS BatteryTypically a CMOS battery will need replacement every 3 to 5 years. You will often notice when your CMOS battery needs replacement if Windows displays an incorrect date and time on the Windows taskbar clock. Incorrect date and time can lead to problems such as a server’s security certificate showing as not yet valid, thus making it difficult to access certain web pages. You may also receive other messages or errors like CMOS BATTERY STATE LOW, CMOS CHECKSUM FAILURE, CMOS SYSTEM OPTIONS NOT SET and CMOS TIME AND DATE NOT SET. These step by step instructions explain how to replace a CMOS battery in most PCs. This procedure will require that you remove your PCs side panel to gain access to the motherboard where the CMOS battery is located.

1. Power-off: Shutdown Windows, power off your PC, and unplug your computer from the outlet for safety. Detach all other cables and wires so that you can move your PC to a suitable workspace.

An Anti-Static Wrist Strap

An anti-static wrist strap is highly recommended.

2. Move your PC to a Suitable Workspace: Depending on your PC model, you may need to rotate your computer’s case (possibly setting it on its side) to gain easy access to the motherboard’s CMOS battery. So in this step take some time to find a location with enough room to work. Additionally, you’ll want to select a workspace to help prevent accidental static discharge while replacing the battery. A good choice is a non-metallic desk or table, like a wood or laminate surface to work on. Keep in mind too, that carpet floors are known to readily transfer static electricity. So if possible try to avoid working in an area with carpeted floors. It’s always good to invest in an anti-static wrist strap to help avoid damaging your computer.


3. Gain access to your motherboard: Open your computer case side panel to gain access to the motherboard. Some PC cases have quick access latches or a combination of screws and latches.

4. Ground yourself to avoid static discharge: Attach your anti-static wrist strap and place the grounding clamp to a metal part of the case. If you plan on doing this without a wrist strap you can touch a metal part of your PC case while you work.

Grounding by touching a metal part of the case to avoid static discharge during CMOS battery replacement

5. Locate the CMOS battery: As the image below illustrates, you will need to locate the CMOS battery on your PC’s motherboard. Battery types include Lithium battery (as shown in the pictures here, a coin-shaped model CR2032), NVRAM (Non-Volatile RAM) and Nickel-cadmium (NiCd). Be sure that you replace the battery with the same type/voltage to avoid potential issues.

CMOS battery located on the motherboard of the PC

6. Remove the old CMOS battery: Release the CMOS battery tab by pushing it away from the battery. The tab should just move slightly and allow the spring underneath to push the battery upward so that it can be removed. Depending on your model this can be a little tricky. If you are using a tool to pry the battery use caution not to touch any surrounding part of the motherboard.

Showing the CMOS battery tab

7. Insert your new CMOS battery: Inserting your new battery is usually a lot easier than removing it. Be sure to keep the positive side up and facing you. For example, the model shown here is a lithium CR2032 battery. It has the positive plus sign + flat side up and visible from above. Simply apply some light pressure and it should snap securely in place.

8. Put things back together: Replace your PC case side panel, reconnect cables and power cord.

9. Power on / start your PC: Power-on your PC and start your computer as normal.

10. Set current time/date: Replacing your CMOS battery will reset your computer’s time and date. Make sure you manually set your Windows time and date so that it’s current. This can be accomplished through the Windows taskbar. You can verify if you BIOS are updated as well on the next startup. For some systems, you simply need to press the Delete / Del key to enter BIOS setup. Below is an example of the BIOS setup for this computer now displaying the correct time after I manually set Windows date and time on the desktop taskbar. So everything appears to be in order.

BIOS current date and time after CMOS battery replacement