Yep. You charge the system as a synonym for adding refrigerant. The "charge" in the system is the total mass of refrigerants. You can "meter" in a charge using pressure and temperature, or you can "weigh" in a charge on an empty system using a scale on your source.
Incidentally, what does it mean to "charge" them?
Charge like a battery? Or charge as in refill them, like you would with freon?
Yep. You charge the system as a synonym for adding refrigerant. The "charge" in the system is the total mass of refrigerants. You can "meter" in a charge using pressure and temperature, or you can "weigh" in a charge on an empty system using a scale on your source.