My purpose is extending the battery lifespan of my rMBP battery. I only use it at home. I know it needs some modification in OS X or Battery firmware and it's not an easy thing to do, and no one has done it yet. Any possibility for this? According to battery university keeping SoC between 20% and 80% is best for maximizing the lifespan of all kinds of batteries and car makers do this for electric cars' batteries, so why not to do this for laptops? for example imagine when the battery SoC reaches to 60% or 80% the light on magsafe turns green and charging stops.