Calibrate Your Battery
Laptop batteries like the MacBook battery can hold a charge for a certain amount of time depending on manufacturing, age and use. A first step to knowing how long it takes to charge your battery is accurately calibrating the battery.
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With your battery in the computer, plug in the power adapter until the light ring or LED on the power adapter plug is green--the onscreen meter in the menu bar will show the battery is fully charged. Let the battery rest fully charged with the power adapter plugged in for 2 hours. Disconnect the power adapter with the computer running and run the computer off battery power until the "low battery warning" message appears on the screen. Save all work and leave the computer running until it goes to sleep (automatically when the battery is too low). Turn off the computer for 5 hours, then connect the power adapter until it is fully charged again. A microchip in the battery that monitors its use will now be calibrated.
Charging Your Battery
Your MacBook battery is lithium ion. These batteries are charged by two methods--fast charge and trickle charge. When your battery is completely run down, the charger will use a fast charge voltage and amperage to bring your battery up to about 80 percent full capacity in about 2 hours. After two hours, the charging voltage and amperage gradually decrease until your battery is 100 percent charged. This second stage is known as trickle charging, and takes about an additional 2 hours.
Battery life decreases slightly after each charge cycle--the amount of use required to drain 100 percent of the battery's power. You can recharge the battery at any time during use; it doesn't have to be fully dishcarged to warrant topping off the power.
According to the Apple website, if the battery is at about 50 percent power, it should take about 1 hour to reach 80 percent full power, with an additional 2 hours to reach full power on trickle charge. If you charge the battery at 80 percent full power, it will take 2 hours to reach full power. A battery at 25 percent full power should take about 1 1/2 hours to reach 80 percent full power, with an additional 2 hours to full charge.
Older batteries that have gone through more charge cycles may take slightly longer to reach the same power levels as new batteries.