My late 2011 17" MBP was delivered with an 85W MagSafe adapter.
Under heavy stress (either CPU and/or GPU) the MBP has to draw additional power from the battery in order to keep everything running. Though I can't imagine this being particularly healthy for the battery (as it keeps starting to charge a tiny bit every chance it gets, and stops again when power consumption goes up), this seems to be 'expected behavior by design', if I'm to believe the various discussions on the internet.
What strikes me as odd though, is that the 85W adapter isn't actually delivering a full 85W when the MBP starts pulling additional juice from the battery. It stalls at about 77W, according to the DC In sensor. This doesn't seem right to me.. why leech power off the battery if the preferred supply has energy to spare?
So, in essence, my question boils down to this:
- Is anyone else seeing similar behavior?
- Does anyone measure higher throughput from the 85W adapter than 77W? (charging / leeching both maxes out at this rate more or less)
- Would the adapter be actually delivering 85W, and is the DC In sensor just plain wrong?