The Apple Pencil 2 doesn't have a physical charge indicator or LED light. You check its current battery life on the iPad Pro to which it’s paired.
Swipe down from the iPad's top bezel to call up the Notification Center.
Swipe right to see the Widgets screen.
View the Batteries section.
If you don't see the Batteries section, tap Edit at the bottom of the Widgets area and tap the green “+” button next to Batteries to add it as an active widget.
(This how-to is based on my experiences and info on Apple's support pages — where the images sometimes come from.)