The 15 mins you mentioned first sounds abnormal for the Mavic 4 pro.
Your flight data will probably find the reason for it.
Can you give a little explanation for your new "carbon based batteries" ?
Welcome from the Hampton Roads area of Virginia, USA. We have a Member's Map in the Upper Right of the Title Bar. Click on "Members" and then Click on "Member's Map…" Check it out and you might find some new flying friends...
If you are a “scientist in the aircraft design and development sector” then you should know that hovering is not the most economical flight mode for a rotary wing aircraft. That is normally when moving (forward) at a constant speed so that the...
DJI's specs have always been realistic.
There may be another factor affecting your hover time.
If so, the explanation will probably be found in the recorded flight data from one of those flights.
Post the flight data and someone here will be...