iPhone 8/Plus iPhone battery percentage increases after restart

[AMSOS]

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]

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.

 

[now i see it]

I've seen my phone deviate a lot more than that. A couple times 20%

 

[zorinlynx]

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]

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.

 

[Libertas]

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.

I know this is an old post but speaking of my iPhone 11 and my wife’s iPhone X I have always heard never to let it go down to zero and try not to charge past 90% very often amd doing what suggested above you should never do, so I don’t know anymore.

 

[zorinlynx]

I know this is an old post but speaking of my iPhone 11 and my wife’s iPhone X I have always heard never to let it go down to zero and try not to charge past 90% very often amd doing what suggested above you should never do, so I don’t know anymore.

It's not "never let it go down to zero", it's don't ALWAYS let it go down to zero. As for charging to 100%, what hurts the battery is leaving it at 100% for very long periods of time. Charging to 100% and then using the phone is fine.

It doesn't even matter that much anymore; phone batteries have become so good that you'll typically get 3-4 years out of a battery before it needs replacing without worrying about state of charge. Just use your phone normally and you'll be fine. If you go out of your way to avoid doing one thing, avoid extreme heat. That hurts batteries more than anything else.

 

[ericwn]

I know this is an old post but speaking of my iPhone 11 and my wife’s iPhone X I have always heard never to let it go down to zero and try not to charge past 90% very often amd doing what suggested above you should never do, so I don’t know anymore.

Optimised battery charging in iOS will also help in that regard so that you can often times really forget to constantly care about the battery.

 

[Libertas]

It's not "never let it go down to zero", it's don't ALWAYS let it go down to zero. As for charging to 100%, what hurts the battery is leaving it at 100% for very long periods of time. Charging to 100% and then using the phone is fine.

It doesn't even matter that much anymore; phone batteries have become so good that you'll typically get 3-4 years out of a battery before it needs replacing without worrying about state of charge. Just use your phone normally and you'll be fine. If you go out of your way to avoid doing one thing, avoid extreme heat. That hurts batteries more than anything else.

Thanks.

 

[now i see it]

The battery % status is an imprecise calculation. It isn't a measurement of voltage, though it does use voltage in its estimation.
There is no method yet invented by anyone to accurately determine the precise charge status of any lithium ion battery. All the methods used today, including in electric vehicles, are estimates based on prior usage, rate of discharge, voltage and initial capacity (and a few other parameters). It's never exact and should only be used as a general reference.