iPhone 8(+) iPhone battery percentage increases after restart

AMSOS

macrumors regular
Original poster
Nov 21, 2010
226
19
I normally charge my iPhone 8 up to 80 to 85%.

I've noticed that every time switch it off and then on, the available battery percentage increases by a couple of points.

e.g. I often see 82% when I take if off charge, but 84% when I have restarted it right afterwards.

First, why does this happen?

Second, does this have anything to do with battery health?

Thanks
 

ericwn

macrumors 601
Apr 24, 2016
4,577
2,836
I think the battery percentage in the status bar is an estimate. When you use your phone for a while you probably have more background processes running compared to a device freshly restarted.
 
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zorinlynx

macrumors 603
May 31, 2007
6,029
8,505
Florida, USA
If you've not charged to 100% in a while the charge controller may not have a good idea of how much capacity the battery has.

Let it run down to 0%, then charge it all the way up to 100%. That should teach the controller the current battery parameters, and things shouldn't get weird again for a while.
 

C DM

macrumors Sandy Bridge
Oct 17, 2011
48,427
17,086
I think the battery percentage in the status bar is an estimate. When you use your phone for a while you probably have more background processes running compared to a device freshly restarted.
It is basically an estimate for the most part. It shouldn't fluctuate by too much, but a few percent here and there after a restart won't be that unusual.
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I've seen my phone deviate a lot more than that. A couple times 20%
That would usually mean either the battery meter is quite a bit off and might need to be recalibrated (as mentioned in a previous post), and/or that the battery health isn't all that great.
 
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