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HP Desktop PCs - Removing and replacing the CMOS battery

If your PC displays errors about the clock or CMOS when starting the PC, the CMOS battery on the system probably needs to be replaced. Replace the battery using these instructions.

Warning:

The edges of metal panels can cut skin. Be careful not to slide skin along any interior metal edge of the computer.

CAUTION:

This product contains components that can be damaged by electrostatic discharge (ESD). To reduce the chance of ESD damage, work over a non-carpeted floor, use a static dissipative work surface (such as a conductive foam pad), and wear an ESD wrist strap connected to a grounded surface.

Find the CMOS reset instructions specific to your computer model number

CMOS reset instructions are specific to the system board installed on your computer. Find your computer model number, and then use it to get the reset steps (if available) on the HP Customer Support website. If steps specific to your system board are not available, use the generic CMOS reset steps.

  1. Locate the model number for your computer. This number is typically found on a label on the computer or on the box that it shipped in. Go to Find product and serial numbers for HP PCs, printers, and accessories for additional options.

    Note:

    The general or series name on your computer is not specific enough for identifying the correct computer specifications.

    Computer label with the product and model numbers highlighted

  2. Go to the HP Customer Support website, and then use the model number to navigate to the product page for your computer.

  3. Select Setup & User Guides, and then select either Maintenance and Service Guide or Hardware Reference Guide.

  4. Click RTC battery or CMOS battery, if a link is available, to find the steps to replace the CMOS.

  5. Go to Reset the CMOS using motherboard specifications to replace the CMOS using the specific replacement steps for your system board.

    Note:

    If specific CMOS replacement steps are not available for your system board, see Replace the CMOS battery using generic steps.

Replace the CMOS using instructions specific to your computer (recommended)

Use the CMOS battery or RTC battery steps from the Maintenance and Service Guide or Hardware Replacement Guide to replace the CMOS battery.

  1. Turn off the computer, and then disconnect the AC adapter from the desktop.

  2. Press the power button 10 times to fully discharge electricity from the system.

  3. Open the computer to access the system board.

  4. Follow the CMOS replacement steps for your computer model. See Find the CMOS reset instructions specific to your computer model number.

  5. Reassemble the computer.

  6. Reconnect the AC adapter to the computer.

  7. Press and hold the power button for 20 seconds.

  8. Release the power button and the system boots.

A message displays confirmation that the CMOS is reset. The message on your computer might vary.

Replace the CMOS battery using generic steps

If specific CMOS replacement steps are not available for your system board, replace the CMOS battery using these generic steps.

  1. Turn off the computer, and then disconnect the AC adapter from the desktop.

  2. Press the power button 10 times to fully discharge electricity from the system.

  3. Open the computer to access the system board.

  4. Remove or disconnect the CMOS battery from the system board.

    Example of CMOS battery types

  5. Confirm that all sources of electricity are removed or disconnected from the computer, including the CMOS battery.

  6. Press the power button for a minimum of 60 seconds to drain all power from the computer and reset the CMOS values on the system board.

  7. Reinstall the CMOS battery, and then reassemble the computer.

  8. Reconnect the AC adapter to the computer.

  9. Press and hold the power button for 20 seconds.

  10. Release the power button and the system boots.

    A message displays confirmation that the CMOS is reset. The message on your computer might vary.

  11. Confirm the that Time in BIOS is set to 00:00. If not, perform the procedure again, but hold the power button for 120 seconds at Step 6.

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