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I'm working 95% of my time with AC power and Thunderbolt Display. Since macbook pro retina's battery are no longer easily switchable I'm concerned about it's life and would like to maximize it. Before macbook retina I used to charge the battery to 50%, then after removing it I used the macbook without battery on AC power. But it's no longer possible.

I googled a little but didn't find a clear guidance about how to use your macbook mainly connected to AC power and not doing damage to your battery.

From what I know :

  • Full discharges should be avoided.
  • Keeping you battery charged to its maximum for too long time is also bad.
  • Try to keep charging cycles as low as possible. It's battery life (macbook pro retina battery is expected to keep 80% of its charge after 1000 charging cycles).

I try to disconnect AC power once a week until battery indicator goes down to approximatively 75% and then I connect back the AC to charge it to 100%. I don't know if it's the best steps to maximize the battery life but I think it's much better then to keep it all the time connected to the AC power.

What do you think. How to preserve battery life working on AC power ?

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4 Answers 4

up vote 5 down vote accepted

It's best to follow the guidance of Apple: http://www.apple.com/batteries/notebooks.html

Standard Maintenance

For proper maintenance of a lithium-based battery, it’s important to keep the electrons in it moving occasionally. Apple does not recommend leaving your portable plugged in all the time. An ideal use would be a commuter who uses her notebook on the train, then plugs it in at the office to charge. This keeps the battery juices flowing. If on the other hand, you use a desktop computer at work, and save a notebook for infrequent travel, Apple recommends charging and discharging its battery at least once per month. Need a reminder? Add an event to your desktop’s iCal. When your battery no longer holds sufficient charge to meet your needs, you may choose to replace it. If your notebook came with a built-in battery, you should have the battery replaced only by an Apple Authorized Service Provider.

Long-Term Storage

If you don’t plan on using your notebook for more than six months, Apple recommends that you store the battery with a 50% charge. If you store a battery when it’s fully discharged, it could fall into a deep discharge state, which renders it incapable of holding any charge. Conversely, if you store it fully charged for an extended period of time, the battery may experience some loss of battery capacity, meaning it will have a shorter life. Be sure to store your notebook and battery at the proper temperature. (See “Notebook Temperate Zone.”)

Basically what it says is use your Macbook in whichever way is comfortable to you. If you prefer to use it plugged into AC at all times, just make sure to disconnect it at least once per month and let it discharge to make sure the electrons moving around inside it.

Cycles are based on a cumulative basis. If you choose to let it go down to 50% twice, that's one cycle. If you chose to let it go down to 75% four times, that's still one cycle. The cycles will go with normal usage and you'll be much happier if you don't worry about it too much. The hardware is designed to last much of the life of the unit since the switch from Li-on batteries.

Contrary to your post, Apple DOES NOT recommend running laptops with removable batteries on AC without the battery: http://support.apple.com/kb/HT2332

Please check out this link from a less official, but still helpful source: http://forums.macrumors.com/showpost.php?p=9875442&postcount=23

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However they don't say if it should be full discharge or just a partial one. –  Thomas Jaskula Aug 20 '12 at 20:50
It doesn't matter. Even if you drop it down to 80%, your still moving the electrons around. It's not like an HDD or a tape where not going to full empty will not touch that part of the item: discharging is discharging and it will help keep battery condition even if you run it for 30 minutes. AppleCare support, however, recommends that if you leave your Mac plugged in most of the time, unplug it every 2 or 3 days and run on battery down to somewhere around 50%, then plug it back in. That keeps the electrons moving at the best pace. –  Bo Shubinsky Aug 20 '12 at 20:52
Thanks for your help. Just curious if you have any link to AppleCare support recommnadation about unpluging it every 2 or 3 day ? –  Thomas Jaskula Aug 21 '12 at 8:39
AppleCare doesn't put support up on the internet (otherwise, there'd be no reason to pay for it). You can certainly call them if you have AppleCare and ask. –  Bo Shubinsky Aug 21 '12 at 14:43

I asked Apple themselves and they told me that charge the Computer to 100% and then get it down as close as possible to 0% without it shutting down and then charge it back up and dont keep it plugged in, also you can close your laptop hence putting in sleep mode and not needing to shut it down.

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A recent article on Wired suggested that you should unplug the charger once it gets to 80%, then use it until it gets to about 40%, then plug it in again and charge it until 80%, etc.

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However, this article is not on Apple notebooks (which can make some difference for the topic discussed). –  yurkennis Jul 3 '14 at 19:28

Guys I have a macbook pro retina display as well, and the funniest and awesomest thing happened to me. Once while I was charging a huge spark came out of the wall. I quickly removed the charger and shut down my computer! when I reopened it, I checked the coconut battery and the Istat and it was at 100% percent of its battery Health!!! I was shocked! I checked the macbook pro's battery capacity and it was 6600! and my showed 6764 and that time! That was a week ago now my battery health capacity is 6612!

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What is lstat? I've seen some variation in full charge capacity between models, but your tale of an increasing value seems rare. I'd have your circuitry checked and the Mac if FCC continues to increase. –  bmike Jul 24 '13 at 11:31

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