It may be that the laptop’s battery is not capable of supplying enough power to run the computer as well as the screen and may need to be replaced.
If you have Win 10 installed in the laptop, try creating a [https://www.windowscentral.com/generate-battery-report-windows-10|Win 10 battery report] to check the status of the battery.
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What is the exact model number of your laptop, as there are several Elitebook 840 variants?
Hi,
It may be that the laptop’s battery is not capable of supplying enough power to run the computer as well as the screen and may need to be replaced.
If you have Win 10 installed in the laptop, try creating a [https://www.windowscentral.com/generate-battery-report-windows-10|Win 10 battery report] to check the status of the battery.