iPhone 8 battery health maximum capacity ?

First, check it when it is fully charged. The life of the battery is measured in full charge cycles, meaning 0% to 100%, not calendar time or hours used. So charging it from 50% to 100% twice would be one charge cycle.

The battery is spec'd as 80% with 500 full charge cycles. Normally it takes about 2 years to reach 500 charge cycles in average use, so that works out to about .8% per month. in 5 months it would thus be 0.8 x 5 or 4%. So it sounds about right.

deggie wrote:

I like the engineers explanation much better. Which poster said that their battery went up 1%? Did you check it? What reports of over 100% capacity and can you explain to Lawrence, the engineer in question, how that would work?

Well - I'm an engineer although batteries aren't my specialty.

A new capacity rating is typical. I've seen plenty of batteries sold over the years that are marked as something like "2000 mAh typical, 1900 mAh minimum" to cover manufacturing variations.

It's a little hard to find that post among hundreds. However, battery capacity estimates going up and down is hardly a new thing. There are many technical papers on the topic of lithium-ion battery health estimation. I've seen the "battery wear level" from the Battery Life app fluctuate. Here's a guy who did a "battery calibration" on an older MacBook Pro battery and it jumped up and down.

Fluctuating Battery Health

My battery life has been fluctuating lately. The fluctuations are very large, over the last 2 days it has gone up and down between 39% and 84%, and now it is at 58%. My battery has 283 cycles since I purchased it last september. 3 or 4 days ago I reset the smc (pmu?) and then re-calibrated the battery. I did this because my battery life was very low (39%) After that the battery health increased to 84%. Has anyone else experienced this?

Here's a guy asking why his notebook computer battery is being listed as 101% battery health:

Re: How can my battery Health be 101%?

Your battery's full charge capacity is slightly greater than its design capacity. In other words, you happened to get a particularly good one.

Not sure exactly what maximum is, but there are manufacturing variations. I've even heard of reports of over 100% "design capacity". Besides that, it's not like reading a fuel tank. Battery health (and even listed battery capacity) is really just an estimate based on observations of how the battery is functioning. One poster reported that the battery health reading went up 1% one day. It's normal for there to be a slight decline in capacity, and sometimes you're dealing with rounding errors that make it look worse than it is.

If you're using it on battery power a lot, it's perfectly normal for any rechargeable battery to lose capacity.

I like the engineers explanation much better. Which poster said that their battery went up 1%? Did you check it? What reports of over 100% capacity and can you explain to Lawrence, the engineer in question, how that would work?

deggie wrote:

That is a bug in reporting the status. What type of engineer? Do you work with devices that depend on batteries. Can your gas tank when you fill it up be 101% full? 110% full?

Chip design, and yes many of the products I've worked on depended on batteries. There's the possibility that something you've used included my design in it. One of the things I had to worry about was the variability of timing in semiconductors based on voltage, temperature, and manufacturing. So the concept of something that's faster/bigger than the nominal rating is something I'm quite familiar with.

Fuel tanks are well known for manufacturing variations that affect capacity and capacity readings. If the owner's manual says 11.6 gallons, it could actually be 11.9. As with reading battery capacity, there are limitations in estimating fuel capacity.

https://pdfs.semanticscholar.org/c8d9/b69893173719a010eba515f23438244ce711.pdf

Sanchezsalim wrote:

Just checked again today , battery health maximum capacity drop down to %95

Unless it drops to 80% there’s really nothing you can do about it other than pay for a battery replacement service.

Unless it drops to 80% it’s still considered healthy. I understand that it seems alarming to see the battery health drop quickly, but Apple or an AASP won’t replace it under warranty or AppleCare unless it reaches that magic number.

You need to finish your question 🙂

That is a bug in reporting the status. What type of engineer? Do you work with devices that depend on batteries. Can your gas tank when you fill it up be 101% full? 110% full?