No Notification for Apple Pencil Low Battery?

I had thought that iOS 9.3.1 would provide a notification when the battery in the Apple Pencil is low. I had the pencil in my desk's drawer and was surprised that its battery was at 0% when I tried to use it today. I often use the drawer so the pencil connects to the iPad Pro each time when it's moved, but I never received a low battery notification. Is such a feature not provided or do I need to activate it somewhere? I use the pencil not very often so I don't check its battery regularly. I am not sure about Li-Po batteries but I know that the life of Li-Ion batteries becomes shorter when discharged fully. So it is pretty worrisome if the iOS does not warn when the Apple Pencil battery is low. Any suggestions? Thanks.