After 5 years of flawless shutdowns, the gopro 7 finally started losing data when the battery died.  It either uses coulomb counting to time the shutdown & the coulomb counter slowly drifted over the years or a power management chip died.  It would no longer shut down properly or beep when the battery died.  Thus, a dummy battery was finally needed to have any hope of using the camera.

Right away, the battery board was DRMed against taking any power from the bench.  The power had to be directly soldered to the contacts.

PLA & scotch got it to connect to the camera.

Then, the camera obviously read a fuel gauge in the battery, since it always said 27% on the 1st boot.  That must have been the last charge state of the sacrificed battery.  After making a recording, it always said 100%, probably because the DRM had to be bypassed. 

The buck converter has to be within 20" for the voltage drop to be low enough to record 4k 30fps.  That drops .3V over a 22 gauge wire.  It seems to need 4.1V to record & handle up to 4.5V with no load.  4k 30fps seems to be the highest power user.  It seemed to burn 1.2A at 4.2V.

The next step is getting rid of the battery door & making new enclosures to keep the dummy battery in.

  Careful handling & swapping of batteries could probably get it to keep the current time.  It would be a pain to always transport with a novel enclosure to keep the battery in.  The gphoto.wrapper program could set the dates if they're invalid.