Always follow the Original Manufacture Guidelines for Maintaining the Batteries. I learned this the hard way.
I always heard about deep cycling your batteries and my experience with this is, DO NOT DEEP CYCLE your batteries, just do what the Original Manufacture says in the maintenance guide. Here is a link from DJI to follow the proper procedure for anything related to this drone and batteries.
https://www.dji.com/support/product/phantom-4-pro-v2
