[BrianG]

From what I've read in the past, charging at a high (~2C) rate increases the voltage at high current draws but gives up some runtime, while charging at a slower rate (~0.5C) reduces the votage under high current draw, but increases runtime. Someone please correct me if I'm mistaken, but this seems to hold true from personal experience. I usually compromise though; I charge a 3300mAh battery at 3-3.5A (~1C).