btw, you don't have to have even multiples either. I often charge at anywhere from 1.2 to 1.5 C on my RX packs (on a 500mah pack, anywhere from 600-750ma). Gets you done a litte faster than an hour, but less abuse on the packs.

As you can see, the rates aren't "fixed", the key is to avoid overheating or over charging the batteries.

"C" stands for Capacity.