Will Macbook Battery be Damaged by Continuous Charging?

your model does not require battery calibration. Also, it will not hurt as the mac stops charging when it reaches 100% and will not overcharge it. Is is a good idea to exercise the battery and let it drain to 20-40% a few times a month. http://www.apple.com/batteries/notebooks.html

From the linked article.

Portables with built-in batteries

Current Apple portable computer batteries are pre-calibrated and do not require the calibration procedure outlined in this article. These computers use batteries that should be replaced only by an Apple Authorized Service Provider.

MacBook

MacBook (13-inch, Late 2009) and later

MacBook Air

MacBook Air (all models)

MacBook Pro

MacBook Pro with Retina display (all models)

MacBook Pro (13-inch, Mid 2009) and later

MacBook Pro (15-inch, Mid 2009) and later

MacBook Pro (17-inch, Early 2009) and later

danieliwvernick wrote:

Ah, I didn't see that--so I won't calibrate it. But will leaving the Macbook continuously attached to AC charger do any damage at all to the battery?

Thanks for your help!

read my first response to you

From the link:

"Portables with built-in batteries

Current Apple portable computer batteries are pre-calibrated and do not require the calibration procedure outlined in this article. These computers use batteries that shouldbe replaced only by an Apple Authorized Service Provider.

MacBook

MacBook (13-inch, Late 2009) and later

MacBook Air

MacBook Air (all models)

MacBook Pro

• MacBook Pro with Retina display (all models)
• MacBook Pro (13-inch, Mid 2009) and later
• MacBook Pro (15-inch, Mid 2009) and later
• MacBook Pro (17-inch, Early 2009) and later"

You can let it go lower, but 20% is good enough.

Will Macbook Battery be Damaged by Continuous Charging?

NOPE!

In my experience, the battery may be damaged...I've had three laptop batteries go bad from three different manufacturers (none were Apple though) due to always being on the charger. The battery won't go bad as far as being overcharged since there is built-in circuitry that will prevent overcharging.

Having a battery go bad while always connected to the charger would be because of *battery* non-use because it's always on the charger and the battery is essentially not given the chance to charge/discharge. Today's batteries need to be actually used and not just let sit. Monthly charge cycles will keep the battery's electrons flowing and keep the battery healthy. Do a monthly charge cycle and it should be just fine.

Will continously charging it/leaving it attached to the AC Adapter damage the battery?

YES

Keep it plugged in when near a socket so you keep the charging cycles down on your LiPo (lithium polymer) cells / battery, but not plugged in all the time. When not being used for several hours, turn it off.

http://www.apple.com/batteries/notebooks.html

"Apple does not recommend leaving your portable plugged in all the time."

General rule to remember of Lithium batteries is:

Never drain them LOW & dont always/often store them HIGH

While cycle count is commonly seen to be the “miles” on your Lithium Ion pack cell in your Macbook, which they are, this distinction is not a fine line at all, and it is a big misconception to “count charge cycles”

*A person who has, for example, 300 charge cycles on their battery and is recharging at say 50-60% remaining of a 100% charge has better battery usage and care than another person who has 300 charge cycles at say 15% remaining on a 100% charge.

DoD (depth of discharge) is far more important on the wear and tear on your Macbook battery than any mere charge cycle count. *There is no set “mile” or wear from a charge cycle in general OR in specific. As such, contrary to popular conception, counting cycles is not conclusive whatsoever, rather the amount of deep DoD on an averaged scale of its use and charging conditions.

(as a very rough analogy would be 20,000 hard miles put on a car vs. 80,000 good miles being something similar)

*Contrary to some myths out there, there is protection circuitry in your Macbook and therefore you cannot overcharge it when plugged in and already fully charged

*However if you don’t plan on using it for a few hours, turn it OFF (plugged in or otherwise) ..*You don’t want your Macbook both always plugged in AND in sleep mode (When portable devices are charging and in the on or sleep position, the current that is drawn through the device is called the parasitic load and will alter the dynamics of charge cycle. Battery manufacturers advise against parasitic loading because it induces mini-cycles.)

Keeping batteries connected to a charger ensures that periodic "top-ups" do very minor but continuous damage to individual cells, hence Apples recommendation above: “Apple does not recommend leaving your portable plugged in all the time”, …this is because “Li-ion degrades fastest at high state-of-charge”.

This is also the same reason new Apple notebooks are packaged with 50% charges and not 100%.

LiPo (lithium polymer, same as in your Macbook) batteries do not need conditioning. However...

A lot of battery experts call the use of Lithium cells the "80% Rule" ...meaning use 80% of the charge or so, then recharge them for longer overall life.

Never let your Macbook go into shutdown and safe mode from loss of power, you can corrupt files that way, and the batteries do not like it.

The only quantified abuse seen to Lithium cells are instances when often the cells are repeatedly drained very low…. key word being "often"

Contrary to what some might say, Lithium batteries have an "ideal" break in period. First ten cycles or so, don't discharge down past 40% of the battery's capacity. Same way you don’t take a new car out and speed and rev the engine hard first 100 or so miles.

Proper treatment is still important. Just because LiPo batteries don’t need conditioning in general, does NOT mean they dont have an ideal use / recharge environment. Anything can be abused even if it doesn’t need conditioning.

From Apple on batteries:

http://support.apple.com/kb/HT1446

http://www.apple.com/batteries/

Storing your MacBook

If you are going to store your MacBook away for an extended period of time, keep it in a cool location (room temperature roughly 22° C or about 72° F). Make certain you have at least a 50% charge on the internal battery of your Macbook if you plan on storing it away for a few months; recharge your battery to 50% or so every six months roughly if being stored away. If you live in a humid environment, keep your Macbook stored in its zippered case to prevent infiltration of humidity on the internals of your Macbook which could lead to corrosion.

Considerations:

Your battery is subject to chemical aging even if not in use. A Lithium battery is aging as soon as its made, regardless.

In a perfect (although impractical) situation, your lithium battery is best idealized swinging back and forth between 20 and 85% SOC (state of charge) roughly.

Further still how you discharge the battery is far more important than how it is either charged or stored short term, and more important long term that cycle counts.

Ultimately counting charge cycles is of little importance. Abuse in discharging (foremost), charging, and storing the battery and how it affects battery chemistry is important and not the ‘odometer’ reading, or cycle counts on the battery.

Everything boils down to battery chemistry long term, and not an arbitrary number, or cycle count.

Keep your macbook plugged in when near a socket since in the near end of long-term life, this is beneficial to the battery.

Peace 😊

some usefull, partially "ok, interesting" information on same

Gaming: In cases of heavy and frequent use in gaming it is recommended, if possible, to keep your Mac plugged in since these frequent fast and deep discharges of the battery are not ideal for battery longevity.

If you were to always keep your macbook battery floating between 20% and 80% charge roughly, then you’d have no other considerations to make about your battery and its care,… except for long-term storage.

Natural changes of capacity in lithium batteries happens when they undergo cathode degradation at roughly 20% per year where Ion exchange becomes less efficient. Mostly low draining (deep DOD) and to a much lesser degree high standing charge rates accelerate this process. Unnatural capacity for lithium battery charges changes, and chemistry changes in a lithium battery when often pushed or pulled to extremes

In a lithium battery, deep discharges alter the chemistry of the anode ➕ to take up lithium ions and slowly damages the batteries capacity for the cathode ➖ to transport lithium ions to the anode when charging, thereby reducing max charge levels in mAh. In short, radical swings of power to lithium cells disrupts the chemical ecosystem of the battery to hold charges correctly which likewise impedes the perfect transfer of lithium ions both in charging and discharging. In charging your lithium battery, lithium ions are “pushed uphill” (hard) to the anode, and discharged “downhill” (easy) to the cathode when on battery power. Deep discharges, damages this “upward” electrolyte chemistry for the battery to maintain a healthy charge and discharge balance relative to its age and cycles.

Optimally, in terms of a healthy lithium battery and its condition, it is most happy at 50% between extremes, which is why low-power-drain processors such as the Haswell are ideal on lithium battery health since a partially charged battery with a low-drain processor has, in general, much more usage in hours

Battery calibration, battery memory, battery overcharging, battery training, …all these concepts are mostly holdovers from much older battery technology, and on older Apple portable Macbooks ranging from early nicads, NiMh and otherwise; and these practices do not apply to your lithium battery and its smart controllers.

Calibrating the battery on older Apple portable Macbooks with removable batteries.

http://support.apple.com/kb/PH14087

There is no calibration of current Apple portable Macbooks with built-in batteries.

http://support.apple.com/kb/ht1490

There is no battery calibration with current Apple portable Macbooks with built-in batteries. Lithium batteries have essentially a 0-‘memory’, and all such calibration involve the estimations fed to the system controller on the SOC (state of charge) of the battery over long periods of time as the battery degrades. The software based battery controller knows the battery's characteristics, or SOC and adjusts itself. This is why there is both no need and purpose to periodically deeply drain your macbook battery, since it doesn’t affect the characteristics of the battery, and further still deep discharges are something you should not do on purpose to any lithium battery.

From BASF: How Lithium Batteries work

https://www.youtube.com/watch?v=2PjyJhe7Q1g

How its made, Lithium batteries

https://www.youtube.com/watch?v=HJrNCjVS0gk

Bad discharging or battery use conditions:

Heat (due to environmental conditions or due to rapid discharges from heavy use = gaming / video editing)

Rapid discharging of the battery frequently causes chemical changes over time in the battery leading to decreased capacity and resistance of current flow.

The very worst use of your battery is often draining the battery very low, and worse still letting it remain in such a state.

*Most long-term rapid damage to the battery occurs from discharging it with high loading (gaming) conditions but paramount is avoiding deep and frequent low DOD (depths of discharge) in use.

Undesirable charging or charged conditions:

High perpetual SOC (state of charge), where the battery is always or very often connected to charge

Parasitic loading where the battery is both usually on and charging or worse both always charging and in sleep mode, since this induces mini-cycling of the battery.

Bad general handling conditions:

Temperature use conditions when either too hot (95F and above) or too cold (50F and below)

Storing your battery away with a low charge (40% and less) long-term.

Considerations:

Your battery is subject to chemical aging even if not in use. A Lithium battery is aging as soon as its made, regardless.

In a perfect (although impractical) situation, your lithium battery is best idealized swinging back and forth between 20 and 85% SOC (state of charge) roughly.

Further still how you discharge the battery is far more important than how it is either charged or stored short term.

Ultimately counting charge cycles is of little to no importance. Abuse in discharging (foremost), charging, and storing the battery and how it affects battery chemistry is important and not the ‘odometer’ reading, or cycle counts on the battery.

Everything boils down to battery chemistry long term, and not an arbitrary number, or cycle count.

Keep your macbook plugged in when near a socket since in the near end of long-term life, this is beneficial to the battery.

danieliwvernick wrote:

Would it be more benefical to the battery to run it down to like 5%, instead of 40%, a few times a month?

No, it would be more harmful.

What do you mean by a monthly charge cycle?

But on this link (http://www.apple.com/batteries/notebooks.html) it says "Apple does not recommend leaving your portable plugged in all the time."

Correct,

A: batteries should BOTH not be drained low AND not "always on charge" those 2 things are not contradictory

however deep discharges is far far worse by far on any lithium battery

B: Meaning if left on charge very often, near 100% draining the battery down to 20% to cycle anode to cathode ION exchange ("exercising the battery some" )

In a perfect (although impractical) situation, your lithium battery is best idealized swinging back and forth between 20 and 85% SOC (state of charge) roughly.

General rule to remember of Lithium batteries is:

Never drain them LOW & dont always/often store them HIGH

I keep my MBA 'docked' to my Thunderbolt display which requires the power adapter to be continuously connected or the screen mirroring disconnects. The Thunderbolt monitor itself has the MBA power cable integrated and is used to power / connect the MBA.

Will it be necessary to undock the MBA once a month (or more often?) and allow the battery to discharge to ~40% in order to preserve battery health? While the circuitry may prevent overcharging I am still concerned with never discharging the battery. AM I wrong to be concerned?

Please excuse my ignorance - I am new to the Apple Support Community.