I think it’ll be useful to have some kind of a warning when the battery drops to a certain level.
It can be a minimal popup which won’t be distracting enough when watching stuffs.
Would be also better if a time remaining can be added in the popup based on the percentage left and current brightness mode.
As reference, my old projector gives a warning at the top when the battery drops to 15% and another one when it’s 5%. It’s very useful because I know when to plug it and won’t be surprised when the projector suddenly dies