If your computer is losing its time or date settings, or you are receiving a message CMOS Read Error, CMOS Checksum Error, or CMOS Battery Failure, the CMOS battery needs to be replaced. To do this, follow the steps below.
Locate your CMOS battery
Caution: When inside your computer, make sure you are aware of ESD and its dangers.
Open the computer case and find the battery on the computer motherboard. Verify that it is accessible and can be removed. Today, most computers use a coin cell CMOS battery, like the CR2032 battery shown in the picture.
Tip: Some CMOS batteries may be held down by a metal clip or bar. This clip just holds the battery in place and the battery can still be removed by sliding it out from under the clip. Do not bend this clip to get the battery out, as a bent clip can result in the battery not staying in the battery socket.
If you cannot locate your CMOS battery, refer to your motherboard documentation or contact your computer manufacturer for additional assistance in locating it. If you no longer have the documentation for your motherboard, it's quite likely you can find it online.
Note: With some computers, you may need to disconnect cables, remove drives, or remove other parts of the computer to get full access to the CMOS battery.
Obtain battery information
Unfortunately, most manufacturers do not list the exact type and model of your CMOS battery. Once you have located the battery, we recommend that you write down its specifications (voltage, chemistry, wiring). If possible, remove the battery and take it to a retail location.
Tip: For most computers, the model or part number for this battery is CR2032.
If your computer is using a coin cell battery, removing the battery is relatively simple. Use your fingers to grab on the edge of the battery and pull it up and out of the socket holding it in place. Some motherboards have a clip holding the battery down. If your computer's motherboard has this clip, you may need to use one hand to move the clip up and the other hand to pull the battery out.
Caution: When inside your computer, make sure you are aware of ESD and all its potential dangers.
Unfortunately, not all CMOS batteries are removable. Some manufacturers only allow a replacement battery to be added. If your computer does not have a coin cell battery, refer to your documentation or contact your computer manufacturer for further assistance.
If your computer's motherboard does not have a removable battery, you need to set a jumper on the motherboard to install the new battery.
Insert the new battery
After purchasing a new battery, remove the old battery and replace it with the new battery or insert the new battery into the secondary battery socket on the motherboard.
Enter CMOS values
Once the battery has been replaced, turn on the computer and reset the CMOS values to the defaults. After the values have all been entered, make sure to save the settings before exiting. Many CMOS setups allow you to press a key (such as F10) to save values and exit all in one action.
If you continue to receive the error after following all the steps above, this is a sign of a more serious issue. The most likely causes are a bad power supply or bad motherboard. You may need to look into replacing the power supply or the motherboard to resolve the issue. At this point we would recommend taking your computer to a computer repair shop to have them diagnose the issue.