The LED lights Above the screen as in the attached pictures show you the state of the battery. When all are lit up it is fully charged. Frankly, in using my mavic 2 Pro 4 or 5 or 6 times I've never run out of smart controller battery.
See my post at:
https://mavicpilots.com/threads/proposals-for-suitable-bag-or-backpack.137979/post-1560707
I see posts by people showing these bulky overprotected carrying cases. The case I use has shown in the picture has been all over the...