Hi forum.  I often photograph moving vehicles and it's common for us to take off and head in one direction for an entire battery.  I have been surprised more than once with our Inspire initiating "battery low, returning to home" at what seems an earlier than normal battery percentage, like 45%, when we've had the RTH set in the app to activate at 15 or 20%.  I'm developing a theory that perhaps the Inspire knows how far it is from its home point and how much battery it will take to get there, although I've never heard or read anything to that effect.  Any thoughts?  Luckily we're nearly always on two controllers so my camera operator has eyes on the screen and cancels otherwise could be a big surprise or worse.  Just curious if anyone else has experienced this and if there's a way to turn it off.  Thank you.

It's on Page 13 of the User Manual...
Low Battery RTH
The low battery level failsafe is triggered when the DJI Intelligent Flight Battery is depleted to a point that may affect the safe return of the aircraft. Users are advised to return home or land the aircraft immediately when these warnings are shown. DJI Pilot app will advise user to return the aircraft to the Home Point when low battery warning is triggered. Aircraft will automatically return to the Home Point if no action is taken after 10 seconds countdown. User can cancel the RTH by pressing once on the RTH button. The thresholds for these warnings are automatically determined based on the current aircraft altitude and its distance from the Home Point.
Aircraft will land automatically if the current battery level can only support the aircraft to land to the ground from the current altitude. User can use the remote controller to control the aircraft’s orientation during the landing process.