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You are here: MacNN Forums > Hardware - Troubleshooting and Discussion > iPhone, iPad & iPod > iPhone Battery is Good Until it Isn't

iPhone Battery is Good Until it Isn't
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Thorzdad
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Mar 14, 2022, 10:37 AM
 
My 6s battery has suddenly developed an odd habit of suddenly dropping to near-zero charge. Typically, what happens is it will lose charge in the normal manner, gradually over the course of a day, but, once it gets down to around 40% charge left, it will just fall off a cliff. Just this morning, for example, I noted I had about 42% charge left. Then, about an hour to an-hour-and-a-half later, the charge had fallen to 1%. I had not even used the phone in that time.

Looking at the usage meter, confirms my experience. The battery health is gradually decreasing along a nice linear slope until, bang, it makes a sudden plummet to the abyss. The meter also shows that nothing is running during the plunge. Right before the plunge, though, it seems that the most common app running is the Home and Lock Screen. I'm not sure why that would be, but that's what it shows.

I don't live my life out of the phone like a lot of people. Phone calls and texts are pretty much it. I also have a weather app I check once in awhile. I don't allow background app refreshes. Bluetooth is off. The OS is up-to-date (15.3.1)

This is the second battery for the phone, and it's been fine until now. Typically, I've been able to go a couple of days between charges. With this sudden behavior, though, I find myself having to charge it at least once a day, if not twice.

Any guesses what might be going on? I know it's an old phone, but it's been rock solid until this battery thing appeared.
     
subego
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Mar 14, 2022, 02:26 PM
 
My first guess is the internal logic for estimating the remaining charge has to be recalibrated.

Let it die.
Plug it in and let it charge to 100 without unplugging it.
Let it die again without plugging it in.
Plug it in and let it charge back to 100 without unplugging it.

If that doesn’t fix it you may have gotten a dud.


For background, Li-ion batteries keep the same voltage throughout most of the drain, so there’s no way for the phone to know the charge by checking the voltage (like you can with an alkaline). The phone basically makes a guess, and those can drift waaaaay off.

Also, letting a Li-ion battery die is bad for it. You only want to let it happen in this specific scenario.
( Last edited by subego; Mar 14, 2022 at 03:17 PM. )
     
ghporter
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Mar 15, 2022, 11:37 AM
 
What subego said. Between battery aging and “optimized charging,” the “rule” the OS uses for how much charge is left gets set on its head. Recalibrating is the way to go.

When you “let it die,” you won’t get to actually 0%, but it’ll be pretty close. A full charge immediately after it dies minimizes the impact on battery life. So you should also plug it back in immediately after is dies the second time. This won’t prevent a hit on battery life, but it will be easier on the battery.

If you don’t see an immediate improvement in accuracy of the “charge left” indication, get the battery replaced. An iPhone 6 out of warranty battery replacement costs $49 at an Apple Store. I replaced my iPhone 5 battery that way, and it acted almost new afterward. How long? I dunno; I traded it in on a 13 mini several months later.

Glenn -----OTR/L, MOT, Tx
     
Waragainstsleep
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Mar 16, 2022, 02:05 PM
 
Is this the original battery? You almost certainly need a new one by now.
I have plenty of more important things to do, if only I could bring myself to do them....
     
Thorzdad  (op)
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Mar 16, 2022, 02:17 PM
 
No, it’s at least the second battery. It’s a hand-me-down from the missus.
     
ghporter
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Mar 16, 2022, 03:45 PM
 
Yep, get the battery replaced. A well used phone that you want to keep is worth the $49.

Glenn -----OTR/L, MOT, Tx
     
andi*pandi
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Mar 17, 2022, 01:40 PM
 
We replaced my daughter's 6 battery and also have a battery case.
     
OreoCookie
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Mar 18, 2022, 09:16 PM
 
Yeah, my iPhone 7 is also holding on a thread. In my case it is the charging port. The battery is brand new, but because it is being charged very erratically, the battery meter is off. Ugh. I just want it to survive until the next iPhone is released. 6 years is a good run.
I don't suffer from insanity, I enjoy every minute of it.
     
Thorzdad  (op)
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Mar 31, 2022, 04:35 PM
 
So, Apple just dropped an iOS update (15.4.1) to address...a battery drain bug.

I guess we’ll see if this is the problem...
     
   
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