Shields and Energy Turrets charge with some energy generator.
ARMORS and Gun Turrets from THIS Mod Dont recharge, instead, the first time you place on the vehicle grid they are charged to full capacity through Scripts/Code, they work until the energy is depleted, then you need to remove from the grid and craft again.
The logic is:
Armor - You place some steel plates over the tank, they get damaged, you remove and repair. Thats why the recipe has Repair Kits.
Gun Turrets - You place a Turret fully loaded on the tank, the turret shoots all bullets, you remove and reload. Thats why the recipe has Ammo.
But the game dont store the energy on equipments when you move or remove from the grid, because of this, you CANT move the Armors or Turrets after placing then, doing so, the equipment will lose all charge and will need to be Repaired/Reloaded by crafting again.
The ONLY exception is the 2 Nano Repaired Armors, they start empty and slowly "repair" itself using a lot of time and energy. Will also lose the charge if moved.
The mechanics of Shields/Armor are quite simple, when you get hit, you lose Shield/Armor until is depleted, after that, you start losing Health. That is true for every shield in the game. But is not exactly extra health, shields dont have any resistance, for exemple, tanks have very high resistance to impact, running over rocks will deal low or zero damage to the tank, but will deal full damage against shields.