A: to protect the battery, Mac OS X power management take this measure. Generally speaking, when situations like sudden large amount CPU calculation or unstable voltage happen, if the laptop is still with battery, probably temporary battery power consumption may happen. In Windows, system power management would charge by AC power right away as the battery now is not full. Therefore, you may find that when connect with AC power, laptop battery is 100% full; but in Mac OS X, power management won’t charge at once, but wait until battery capacity is less than 95% and then it begins to charge. Compare these two styles, the previous one, Windows, could always keep the battery full, but as the times of charging and discharging increase, battery life would shorten quickly (at least the lithium battery belongs to the situation). That’s why salespeople would remind you to remove the battery when you not use the laptop; while the latter one Mac OS X, could not keep battery always 100%, but greatly reduce the charging times. Comparatively, this could protect battery better, so people could totally not worry about this; certainly, periodic battery checkout could help power management manage battery better, but no quite frequent, about once two months. Concrete operation: first discharge battery completely, not use external AC power, but supply power by battery, until the laptop runs out of power and go sleep; and then reconnect external power until charge full. Then discharge completely, simply speaking, just a complete charge/discharge period.