When I was in the middle of a mod I came across the shipped arc caster and noticed one thing... it doesn't use multiple ordnances, it has only one, but it still uses a charge, yet it doesn't have the NextCharge parameter anywhere... how does it work then? it has MaxPressedTime but what controls the variable strenght and range of the Arc Caster's ordnance?

It most likely has to do with the arc caster's ordnance, which is an "emitterordnance." Charging it up makes the ordnance do extra damage, chain from unit to unit, etc.