After an iOS update iPhone stopped charging to 100% occasionally when Charge limit is set to 80%

Correct. You can only use either the Charge Limit or Optimized Battery Charging, not both simultaneously. If you want to use Optimized Battery Charging, you must set your Charge Limit to 100% for it to be available.

There is no clear definition of Charge Limit's "occasionally". Some users with it have seen their iPhone charge to 100% weekly, others monthly, it all varies by user. I use the Charge Limit and from my observations, my iPhone charges to 100% roughly twice a month. This is to calibrate the battery health and ensure accurate readings of the amount of recharges and discharges.

Yes, 80% and Optimized Charging are mutually exclusive. On Optimized Charging it charges to 80%, then, just before you are ready to use the iPhone (based on your usage history), it charges to 100%

If you set 80% it will occasionally charge to 100% to reset the state of charge gauge.

RajDot wrote:

Hello everyone, thank you for your responses. I really appreciate them.

Till some point, it used to charge up to 100% almost every 1.5/2 weeks, if not every week.

However, after one of the iOS updates, it stopped charging to 100%.

Could this be a bug?

I should also note that I had the charge limit set to 80% the entire time.

This is not a bug but is rather intentional and apart of the Charge Limit feature. As Jeff and I stated, there is no exact pattern for when your iPhone charges to 100%, it rather depends on your usage, conditions, etc and what is best to maximize your battery health. If your iPhone never charged to 100%, it wouldn't be able to properly calibrate it's battery health. Keep an eye on your iPhone's charge and I'm certain that sooner or later it will charge to 100% again.

There never will be a definition, because of the use of smart algorithms. The time is based on past charge history and it adapts as the charging conditions change. This can include temperatures, cell balancing, past usage, chemical changes in the batteries and more. It’s always evolving as the battery ages. The algorithms can even be updated as Apple learns about how batteries performed in the past.

A slight over or undercharging is most likely just rounding errors. If your said it was set to 80% and consistently stopped at 85%, then a software glitch might be a suspect, but one or two percent are really irrelevant. Heat can also play a role. The algorithm is following more than just numbers, but what’s best for the battery.

RajDot wrote:

I understand, it's been months (more than a quarter even) since it last charged to 100%. Is there a way to find that out? Perhaps in some logs

Are you seeing any sharp decline in Battery Health? Are you experiencing any overheating? Is charge depleting significantly more quickly than it did a couple of months ago? If the answer to those questions is "no," I wouldn't worry about it.

You’re welcome. The engineers would know, but that’s not something us mere mortals need to know or would necessarily understand. But smart batteries and chargers have been around for a while (camera industry for one) and we can look at what goes into those batteries (and chargers and cameras) and extrapolate what Apple is doing with a high degree of confidence.

Why? Extending battery life is in everyone’s best interest. Customers get increased performance, less warranty replacement issues, less issues for employees dealing with battery issues. Wins all the way around.

RajDot wrote:

Hello Moderator, the title does not reflect the problem statement.

a more accurate statement would be:

After an iOS update, iPhone stopped charging to 100% occasionally, when Charge limit is set to 80%

Can you please help re-title?

I have asked the community hosts to rename the thread for you.

RajDot wrote:

Thanks Zachary, It's been at least a few months, and I have not seen it go to 100%. On occasion it did however go to a wee bit above 80%, and then come back to 80% while still on charge, but I would think that would be a part of the algorithm to calibrate for accuracy and / or precision.

That's interesting. If it were to go over the 80% Charge Limit you have set, then I would assume that would mean the iPhone was charging to 100% to calibrate. But didn't quite get there due to certain reasons we don't quite know. But ultimately I wouldn't worry about it.