The CHARGE animation plays continuously while the Attack & Special Buttons are held together and stops immediately when either is released. If the last frame is reached and there is no loop, then that frame will display indefinitely. While charging the entity will recover MP according to its chargerate setting. Just for clarity, this animation has nothing to do with CHARGEATTACK.
Note that while the charge animation is valid for all types, the AI will not use it without being scripted do so. Also note that the charge animation itself does not directly control charging behavior. If you script a charge, you’ll need to make sure the charging entity property is set.
Charge Rate
chargerate <int>
#default
chargerate 2
Model header property. When charging, the entity adds {int} to MP ~twice a second.