Potential Battery fault

[EFLYNN]

Batterry test ing

Sometimes the result is battery normal and sometimes the result is Replace battery.

Tested using HP support assistant and diagnostics EUFI.

When ac adaspter is disconnected the result is always Battery normal.

The battery stops charging at 78%

I am confused - please clarify

EFFLYNN

[ZBoost_Ultra]

@EFLYNN

The UEFI diagnostic program is more accurate than the Support Assistant, I'd recommend to update HP UEFI diagnostics. 
 v10.8.1.0 - https://ftp.hp.com/pub/softpaq/sp161501-162000/sp161700.exe

With the latest version, attempt the test again. 

Should you continue to face the problem, perform a CMOS reset- https://support.hp.com/us-en/document/ish_11469889-11469938-16

Update your BIOS - https://support.hp.com/us-en/document/ish_3894564-1633733-16

CAUTION: Ensure that you have a stable device and power connection before attempting the BIOS update.

Perform the battery tests after these updates. If the problems persist despite the updates, review the battery test details.
Compare the Designed Charge Capacity with the Full Charge Capacity value. That will help you understand if your battery has a problem or otherwise.

Hope this helps!