TL;DR / What?
Unequip armor removes all shield and battery charge, and charge from anything that holds a chargeWhy ?
Needing to manage power in modular armor is a moot point because you can build multiple of them and swap them around.It should be viable to swap armors to swap layouts quickly (eg one for combat, one for running) but not be viable to swap armors to have a full charge again.
Currently if you unequip just the battery it will discharge, indicating that the devs do not want us to be able to hold a ton of charged batteries in our inventory to swap into armor.