Will MacBook Pro battery stay at 100% when on charger or eventually start to drop?

Question

Level 1

21 points

Will MacBook Pro battery stay at 100% when on charger or eventually start to drop?

When a MacBook Pro remains connected to the charger, will the battery stay at 100% (or whatever level it was when the charger was connected) or will it eventually start to drop?

I seem to recall having read articles stating that the battery eventually starts to lose charge even while connected to the charger, but some Apple Store personnel have said the level shouldn't decline at all as long as the charger is connected.

I am sure that the level used to drop when on the charger with older Macs -- at least it always did on my old MacBook (i.e., drop to 95%, then begin recharging again). The question is whether that's no longer the case because of battery modifications that have been made since. I use a mid-2012 MBP running Mavericks.

Thanks.

MacBook Pro, OS X Mavericks (10.9.5)

Posted on Sep 4, 2015 3:00 PM

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Answer 1

Kappy

Level 10

361,753 points

Sep 4, 2015 3:06 PM in response to dymar

The charger shuts off once the battery is fully charged, so over enough time the battery level may begin to drop slightly until reaching around 93% when the charger will turn on again.

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Answer 2

Lanny

Level 6

13,183 points

Sep 4, 2015 4:11 PM in response to Kappy

I've never seen that happen, and have used various Mac laptops for almost 14 years.

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Answer 3

Sep 4, 2015 5:54 PM in response to Lanny

Happens all the time on my 2015 15" MBP and my 2012 13" MBP. It's normal.

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Answer 4

Kappy

Level 10

361,753 points

Sep 4, 2015 6:08 PM in response to Lanny

Never seen what, Lanny?

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Answer 5

Lanny

Level 6

13,183 points

Sep 4, 2015 6:48 PM in response to Kappy

I've never seen it drop below 100% when fully charged and connected to AC power.

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Answer 6

Sep 4, 2015 6:53 PM in response to Lanny

More recent MacBook Pros have the ability to do high-stress computation that would normally be too power intensive, by "borrowing" from battery power. This unusual feature means the battery charge can indeed go down with the power adapter attached, and nominally providing "all" the power for the MacBook Pro.

Users doing Video editing may see this. I am not sure more casual users (web surfing and email) would see it very often.

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Answer 7

Cunnla

Level 6

8,257 points

Sep 4, 2015 6:56 PM in response to Lanny

My Macbook Pro 13 mid-2012 when left plugged in slowly drops to about 95 percent before recharging to 100. Right now it's at 99 percent. I always thought this was usual, as Kappy says.

Mostly just doing Web browsing and iTunes music.

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Answer 8

Lanny

Level 6

13,183 points

Sep 4, 2015 6:58 PM in response to Cunnla

I can't really comment, since I've never observed this behavior.

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Answer 9

dymar Author

Level 1

21 points

Sep 4, 2015 7:56 PM in response to Lanny

Hmmm . . . I guess this is what they call a controversy.

When this -- i.e., the battery level remaining at 100% indefinitely while on the charger -- first happened on my mid-2012 MBP I brought it in to the Apple Store. Tests run there at the Genius Bar did in fact show a problem with the battery. The machine was sent out and returned with a new battery.

Now that I'm experiencing the same behavior I guess I will return to the A.S. and attempt to find out definitively whether this condition is normal or abnormal.

I can say without a doubt that when I had my considerably older MacBook, it was normal for the battery level to drop to 93-95% (while on the charger) and then recharge back up to 100%. As stated in the original post, I don't know whether improvements in MacBook/MBP batteries since then have changed this so that laptop batteries no longer drop from 100% when on the charger.

But if that's the case I wonder why there would still be a need for battery calibration, which as far as I know is still recommended by Apple for users who generally run their laptops on A/C and rarely use battery power.

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Answer 10

Sep 4, 2015 8:37 PM in response to dymar

But if that's the case I wonder why there would still be a need for battery calibration, which as far as I know is still recommended by Apple for users who generally run their laptops on A/C and rarely use battery power.

DO NOT calibrate a non-removable battery. It comes already calibrated, and running it down will dramatically reduce its useful life.

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Answer 11

Sep 4, 2015 8:58 PM in response to dymar

If the battery is healthy it will stay at 100% when fully charged. If the battery is defective or just really old and failing then it will show 99% (that's what happened to my old battery).

Check the status of your battery by holding down the Option key, and then clicking once on the battery icon in your upper right screen menu (where you see your WiFi logo). It will tell you the condition.

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Answer 12

Sep 4, 2015 9:04 PM in response to TheSnapDude

I think Coconut battery is and any other battery app is inaccurate.

I have two New MacBooks here, a 2015 15" MBP and a 2012 13" MBP.

Both are at 6 cycles now. The 15" health fluctuates between 98-99.9%. A few weeks ago it was at 98.4. I rebooted the compute and it went up to 99.9. A few hours later it went down to 98 something or other. Now it's at 99%.

The one month old 2012 MBP is at 97.5 again with 6 cycles. It was manufactured in June.

Both batteries show as normal as reported in about this Mac.

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Answer 13

OGELTHORPE

Level 9

57,305 points

Sep 5, 2015 3:09 AM in response to dymar

As a MBP gets charged when connected to AC, the led on the charger is amber. When it reaches a 100% charge, the led on the charger turns green. At that point, the charger is providing power to the MBP but is NOT charging the battery. The battery in effect starts to slowly discharge as if were in storage. When the charge level drops to about 95% or less, the led will turn amber and the charger will provide power to the MBP and charge the battery. Keep the charger connected and this will be a continuously repeating cycle.

Ciao.

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Answer 14

dymar Author

Level 1

21 points

Sep 5, 2015 7:23 AM in response to OGELTHORPE

OGELTHORPE wrote:

As a MBP gets charged when connected to AC, the led on the charger is amber. When it reaches a 100% charge, the led on the charger turns green. At that point, the charger is providing power to the MBP but is NOT charging the battery. The battery in effect starts to slowly discharge as if were in storage. When the charge level drops to about 95% or less, the led will turn amber and the charger will provide power to the MBP and charge the battery. Keep the charger connected and this will be a continuously repeating cycle.

Apple's own documentation (at least all the online help pages I've read) have always stated that a laptop battery needs to be exercised and should not be run exclusively on A/C.

In the past, various Apple Genius Bar employees have advised that running exclusively on the charger will lead to overcharging and battery burst.

Again, this is something that could have changed with improvements in battery specs, but I'm not aware of any.

Can you document your claim that it's ok to keep the charger connected at all times?

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Answer 15

dymar Author

Level 1

21 points

Sep 5, 2015 7:34 AM in response to TheSnapDude

TheSnapDude wrote:

If the battery is healthy it will stay at 100% when fully charged. If the battery is defective or just really old and failing then it will show 99% (that's what happened to my old battery).

Check the status of your battery by holding down the Option key, and then clicking once on the battery icon in your upper right screen menu (where you see your WiFi logo). It will tell you the condition.

Thanks, but my indication of a problem was specifically the battery staying at 100% while on the charger, and it turned out that there was in fact a problem.

Whether or not that was a coincidence remains to be seen. (I should know soon and will report back.)

Prior to that, my battery, when fully charged, stayed at 100% for perhaps several days, but then began to decline to 95% (MBP still on the charger), after which it would move back to 100%. That was the expected behavior based on all the Apple documentation I had read up to that point.

I disagree that Option-click (on the battery icon) is always reliable. It isn't.

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