iPhone 7/Plus Suddenly dip with battery percentage

[Aoligei]

This is second battery for this iPhone 7. Currently battery health shows as 95%. However, i start noticing some poor battery life. Especially, sometime will drop from 70% down to 50% in few minutes then went to 30%.

Since the battery health section reports 95%, I think this battery is still in good condition.

However, battery cycle reported under analytics shows 376 cycles. This is very close to 500 cycle as Apple’s website stated.

So I am very baffled. Is it really 95% health or is it need be replaced?

Has any of your iPhone’s battery experience sudden dip?

 

[now i see it]

My iPhone 6 original battery indicator can jump all over the place. It has 1791 load cycles on it and still has plenty of life left in it.
There currently is no way for anyone with any technology on any battery pack (including Tesla cars) to accurately determine the health of a Lithium ion battery cell. It's all gestimation. Degradation typically occurs on the microscopic/atomic level on the cathode which is impossible to measure.
Battery Health estimates like those used on iOS guess what the battery health might be by tracking discharge and charging behavior, but it's only a rough guess — that's why the numbers can jump around

 

[JPack]

So I am very baffled. Is it really 95% health or is it need be replaced?

Sudden and unexpected dip suggest failed cells within the battery pack.

The 95% capacity estimate is only a rough estimate.

The fact you have 376/500 cycles on the battery tells you it can't possibly be at 95% health.

 

[Aoligei]

Sudden and unexpected dip suggest failed cells within the battery pack.

The 95% capacity estimate is only a rough estimate.

The fact you have 376/500 cycles on the battery tells you it can't possibly be at 95% health.

Here is the battery health section report

And here is battery cycle count reported under analytics

And I think you are right about the battery.

The even weirder thing is: this iPhone 7 is used. According to the previous owner, he changed the battery once. According to his post, the battery is about 82%.

I didn’t really pay attention to the battery section when I purchased from him. All for all, I get this 128GB iPhone 7 for 130CAD.

After I got home, I immediately fresh installed the iOS 14.4.2. Then the battery reports at 95%.

LOL, I thought I lucked out, thinking no need to change battery.