Chaos Witch Power Charge

Firstly, the description for charges and what they do is not descriptive enough.

Google says "grant a substantial 50% increased critical strike chance per charge for spells"

I notice when I'm gaining power charges by using Profane Ritual, I'm casting spells like Chaos Bolt and Essence Drain, but it is not consuming my power charges.

I'm assuming if I have 3 stacks of power charges it increases my crit chance by 150% and they cannot be consumed, instead its a buff for the duration.