Battery Care?

On my new Macbook Pro 15" Retina: anything special I need to know about battery care to maximize the battery life? Should I let it charge, then discharge, all the time? Is there a problem with keeping it plugged in even when full? Etc.? Thanks!

Please check out the "Battery" link in my signature.

- Nick

Great, thanks Nick!

That answered all my questions but one: after it hits 100%, should I keep it plugged in, or run on battery? Thanks.

mattymac said:

That answered all my questions but one: after it hits 100%, should I keep it plugged in, or run on battery? Thanks.

Click to expand...

Leaving it plugged in is fine. This is what I do all the time with my Apple laptop computers. Usually 1-2x/month I run the battery down to 50%…then plug it back in. If you only plugged the computer in to charge it…and then only used the computer on battery power otherwise. You would be accumulating "battery charge cycles" way too quickly and unnecessarily.

If you are near an electrical outlet…your choice...keep it plugged in or not. If not near an electrical outlet…then use it on battery power.

- Nick

Ok thanks.

As you read that thread that Nick pointed to, make special note of Post #13. Pendlewitch got it all right in that post. The chemistry of modern batteries used in the MBP line is not what used to be in the older batteries and does not need the deep cycles that Ni-Cad batteries needed. In fact, LiIon batteries like in the MBP prefer fewer deep cycles. But they do start to decay slightly at about 2 years after manufacture, no matter how gently treated they may be. But that decay is very slight at first. According to coconutBattery, my battery was manufactured March 16, 2011, making it 1688 days (4.6 years) old. It has a design capacity of 8450mAh, but presently has a max charge of 8026mAh, about 94.8% of design. But in the time I've only used the equivalent of 62 load cycles because the MBP is on external power almost all of the time. I do use the battery when I am traveling or when I move from my office to the coffee table to control my Apple TV with it. As you can see, even with very gentle use I've lost over 5% of capacity, so batteries eventually decay, even if you treat them gently like I have.

The reason you'll see Apple recommending one deep discharge each month is that that discharge will calibrate their battery management indicator for you. It's not for the battery, it's for that software. I don't bother and the error in the indicator is practically zero. So I would say you can safely ignore Apple's advice on that part. If the indicator of charge or time remaining becomes erratic, then you can charge it up full, then discharge it deeply to do that recalibration. Otherwise, leave it plugged in if you can.