On the battery mode, the blank screen appears while the system is running

This is an odd case that he is trying to find a solution for Basic information about the system then the details to follow.

One of my clients is still using the Laptop. The Laptop is a Dell Precision 3510 with an i7 processor and 16 gigs of memory. it has a Windows 10 Pro 1809 version.

This issue has been, tested with the latest updates from May 2019 for version 1809 and up to current updates for version 1809. This also includes the Dell drivers and firmware available from Dell and the manufactures of the parts.

Now to Discuss the issue.
When the laptop is powered on with the power cord plugged into the unit, everything works fine properly with no issues.

He can see everything on the LCD Screen and/or external monitor.
He can run different tests on the unit to make sure everything is in working order.
He can even run the Dell ePSA hardware diagnostic test and get green checkmarks of passing the test.

The log reports even show it passes. When he pulls the power cord from the unit and counts to five the screen goes blank with the unit still running.

He can hear it running. See the lights lit on the power button and the indicator lights for the power and hard drive. Neither LCD Screen nor external monitors display any images.

He has to plug the power cord back in and hard boot the laptop to get the display to return an image.

If he tries to boot the laptop with battery only, he sees it power on, Dell splash screen appear as well as the Windows splash screen then it goes blank with the same deal as above.

He has talked to Dell Support on this issue and they have had me go through several different tests to figure out what is wrong.

As long as he has a power cord, it passes. When in battery mode the test does not run or provide a log file for errors.

They have replaced several parts saying that was the cause of the issue. Motherboard, Battery, Power cord, the different cables, memory and LCD screen. Even went as far as replacing the hard drive. No one item fixes the issue.

Turned off all power-saving mode settings for the battery as well.
With all of this work in parts and time, a new laptop has been built or could have been bought. The catch is the unit is just (barely) 2 years old.

What he has found has corrected the issue is hardware replacement of the following items: Motherboard, Battery, cables, and LCD screen.

I have read several forums where others have had issues with Windows Black Screen but they do not describe my issue in them.

Therefore, I want to see what your thoughts are. For the record, the Windows 10 image can be our custom image.

Thanks in advance for sharing your experience.