I vaguely remember the dram and camera clock rates being reduced when the battery SoC went under 40% in the nexus 5, and then when users complained of early shutdowns when using the camera with HDR mode, an update changed it to 60%.

I think I even commented on the bugreport that it would be best to do the frequency scaling based on interrupts from the voltage regulators on board, but that piping all the necessary drivers/events to do that with low enough latency to not cause an under-voltage reset was far more work than was feasible.

Thats also why 60fps video dropped frames at the start of the video if you were recording video with less than 60% battery.

Anyone care to dig out the relevant commit...?