Weird battery level graph

zorinlynx

macrumors 603
Original poster
May 31, 2007
5,896
7,729
Florida, USA
My mom was complaining that her phone battery was lower than it should be, and when I checked the graph I saw this. It looks like the battery suddenly jumped from just over 50% to around 25% around midnight for no apparent reason, and stayed exactly there for many hours. She didn't use her phone around that time at all.

Is this a sign that the battery is failing, or just a bug in iOS? Anyone else seen this before?

It's a slightly over four year old iPhone 6.

IMG_0067.PNG
 

zorinlynx

macrumors 603
Original poster
May 31, 2007
5,896
7,729
Florida, USA
Ugh, that'd be pretty bad timing since the $29 replacements are no more.

Though her phone is working fine at the moment. She's a pretty light user.
 
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C DM

macrumors Sandy Bridge
Oct 17, 2011
48,130
16,777
Ugh, that'd be pretty bad timing since the $29 replacements are no more.

Though her phone is working fine at the moment. She's a pretty light user.
I think they are at $49 now, which isn't too bad.
 
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now i see it

macrumors 601
Jan 2, 2002
4,894
9,774
It's not battery failure, it's the "digital battery level gauge" out of calibration.

Run the phone down until it almost shuts off, then charge it all the way back up to 100% without using it - use the standard slow/tiny apple charger. Not a fast charger.

Do that again one more time and the battery level meter should re-calibrate.
But don't make it a habit of running the battery down that low in the future. It's hard on it.
 
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luismedina

macrumors member
Aug 31, 2017
83
59
Monterrey, Mexico
I had the same during new year hoildays, I was in a place completely out of cell signal, phone in airplane mode all the time, and it went from 80% to 65% overnight, showing the same gap in the graph, my battery health is currently at 92%
 
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doxielover

macrumors 6502a
Apr 12, 2011
855
101
CA
I had the same during new year hoildays, I was in a place completely out of cell signal, phone in airplane mode all the time, and it went from 80% to 65% overnight, showing the same gap in the graph, my battery health is currently at 92%
I almost always have my 6s plus on low power mode does this mess up the calibration? How come most websites say when you calibrate use the battery until the phone shuts off.
 
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C DM

macrumors Sandy Bridge
Oct 17, 2011
48,130
16,777
No, they’ll replace the battery as per customer request even if it’s not 79% for $49 or $69 which is the out of warranty cost.
Now that the replacement program from last year is over, they haven't gone back to the established requirements for replacement?
 
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