Low power mode during an activity?

With the Forerunner 235 when the battery got below a certain percentage (10% I think) during an activity the screen would be blacked out in part to conserve power. I noticed today during a long run the 5S+ battery was low and then boom... powered off.No warning.

I was running on a trail so I am not exactly sure when it turned off but I did see beforehand it was around 6% and the screen was "normal".

Is there a setting somewhere to set the watch to go into a low power mode or to conserve screen battery drain?

I couldn't find one so far. I would be happy to sacrifice screen display (unless button pressed) and to have lower accuracy GPS when the battery is low so at least it records to the end of an activity. Not sure if it's a configuration or a "new idea" for developers :confused: