Why you want to distinguish between more or less power of energy.
Once you charge it will remain charged up till consumed . VK is compatible with serums and it uses own wisdom to provide energy to users as per need or request.
While in charging water or other items the intensity of energy remains same as after first charging and there is no need to charge them again.
While in direct request we can boost the intensity of energies every 10 minutes for the same healing request.