I know that the new battery technology used in the newer MB's such as the new rMBP don't deteriorate if it's on AC power. However, it's still better to keep the number of cycles to a minimum as that is how the battery deteriorates. So my question is this: if I have say 75% charge left and plug in the adapter, how do I make it so that the battery does not charge? I just want to be on AC power for a couple of hours and when I leave with my laptop again, I want to use the 75% that I had prior. Essentially, how do I go about setting charge thresholds or anything similar?