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Possible Duplicate:
Should I disconnect my MacBook Pro’s power cord when the battery is fully charged?

I'm wondering if it's reasonable to use a MacBook Pro Retina as a desktop replacement with power-cord plugged in all the time? Or does the battery suffers from this kind of use?

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marked as duplicate by Gerry, patrix, gentmatt, Michiel, Mark Nov 5 '12 at 13:48

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

Since your question seems to be just about wether or not is it OK to keep the power adapter plugged in, I feel it's been already asked and answered here and here. – Gerry Nov 5 '12 at 11:14
-1 for duplicate posting as @garry already pointed out – FLY Nov 5 '12 at 11:32
up vote 3 down vote accepted

Well, Apple does not recommend leaving your portable plugged in all the time, as for a lithium-based battery, it's important to keep the electrons in it moving occasionally. MacBook / Pro, though, are designed to deliver up to 1000 full charge and discharge cycles before it reaches 80% of its original capacity.

A charge cycle means using all of the battery’s power, but that doesn’t necessarily mean a single charge. For instance, you could listen to your iPod for a few hours one day, using half its power, and then recharge it fully. If you did the same thing the next day, it would count as one charge cycle, not two, so you may take several days to complete a cycle. Each time you complete a charge cycle, it diminishes battery capacity slightly.

Since 2009-2010 laptops carry a technology called Adaptive Charging which basically is a chip within the battery that talks to its cells monitoring everything from charge level to temperature. The chip relays this information to the computer, which uses an advanced algorithm to determine the optimal charging current. Adaptive Charging reduces the wear and tear on the battery giving it a lifespan of up to 5 years.

So, I'll actually won't worry that much about the battery. Just try not to keep it plugged all the time, and remember to do a full charge cycle at least once per month.

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There are a few aspects to this:

  1. Does it harm the battery if it's hooked to the charger all the time?
  2. Does it harm the battery if it's stored at full charge?
  3. Does it harm the battery if it's charged without being discharged?
  4. Why does Apple want my to discharge it regularly?

  1. Imagine what would happen if the battery is charged all the time the charger is plugged in. The battery would be overcharged leading to a dramatic fault. To see what happens check this one.

  2. Actually it does harm the battery, but not much. I still use my MBP Mid 2009 with it's first battery. I kept it at full charge most of the time, having only 121 charging cycles in three years and it's still at 93% of it's design capacity. You can look this up via ioreg -l | grep LegacyBattery on the command line.

  3. No, it doesn't. This is the main reason why lithium ion and lithium polymer batteries are used in modern equipment. (Beside the fact, that they offer a large current, but this is not that interesting for laptops, but for drills.) If you want further information about lithium batteries and their lifetime under special conditions which include being charged to 40% you might want to have a look at this.

  4. While discharging and recharging, a chip embedded in the battery measures the amount of charge the battery can still hold. There is no safety issue or reduced lifetime if you won't do that, but it makes the Battery menu item's information inaccurate.

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That’s ridiculous, any Apple device has protection against overcharging. No MacBook will explode. 4. is factually wrong. – idmean Aug 28 '15 at 15:43
@idmean Are you sure you understood the 4th point? It's not about overcharging or exploding devices. – Max Ried Aug 28 '15 at 16:01
Probably I partly misunderstood 4. But I also don’t think that this chip needs the battery uncharged to determine the amount of charge the battery can still hold. Do you have anything backing up that claim? – idmean Aug 28 '15 at 16:06

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