How to calculate motor current draw?

[suicideneil]

So, I was looking at various new batteries to replace my exploded one (the other is for sale on feebay as I need a matching pair), and I noticed that alot of packs had a discharge rate of 30-50mah. This I was dimmly aware of, but my question is - How do I find out how much current my motor is trying to draw from the batteries?

I personally run the HvMaxx 6.5 on 14.4v, the motor has a rating of 375watts.