Battery Prolonger is a simple applications, that informs you when is the best time to plug in/unplug your MacBook to/from a power adapter to prolong your battery life.  "Cadex Electronics CEO Isidor Buchmann told WIRED that ideally everyone would charge their batteries to 80 percent then let them drain to about 40 percent. This will prolong the life of your battery — in some cases by as much as four times."  http://www.wired.com/gadgetlab/2013/09/laptop-battery