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battery

So.. When you charge a macbook to 100%, it stops charging and runs the laptop from the power provided by the wall socket.

Batteries naturally discharge a few % here and there. When the laptop reaches around 90% it will start charging again.

You don't want it to charge all the time as that puts added stress on the battery, apple did this to limit charge cycles. If you want to "top off" the battery just unplug it from the wall until it hits around 90% and plug it back in, it should charge back up to 100%.
 
It's perfectly normal for a battery to stop charging between 93% and 99%. Read the CHARGING section of the following link. This should answer most, if not all, of your battery questions:
 
you are better off checking your battery health using iStats or yet better CoconutBattery. My battery recently exhibited similar behavior and the issue was that battery health was down to 98% (and then rapidly dropped to 88 in less than 3 weeks time).

I have replaced mine now. :(
 
Say you're using your laptop in your bedroom, on AC, battery charged to 100% and you want to take it to the kitchen.

so you do, and walk across the house and plug in again in the kitchen.

Do you really want the laptop to put wear on the battery by charging it that tiny percentage that was lost during that walk? Of course not, it would be silly.

This behavior protects the battery against excessive topping off charging. It also helps prevent the batteries from being inadvertently overvolted.
 
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