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Comment by usefulcat | Hacker News Reader

I've been trying a similar experiment for several years now. I have a four year old iPhone, and for most of its life, the battery level has been kept between 30% and 70%. Settings => Battery => Battery Health and Charging says that the maximum capacity is 91%.

No idea whether that's better or worse than average, but I mention it so others can compare. I can say that this is the first time I've tried this experiment, and this phone has already outlasted any previous phone I've had.

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I have 2-year iPhone 13 Mini which I didn't care much about keeping some charging regime. It reports 100% capacity. I wouldn't trust this number. Another data point: 2-year MacBook Pro 16" which lives on my table (I don't think I've ever used it without charger), keeps its battery at 80% and reports 91% capacity.

I'm on the 12 Mini without any care with charging, it's at 89% capacity. I do have "Optimised Battery Charging On" apparently, not sure when that was added? Might've always been on not sure. From the description:

"To reduce battery ageing, iPhone learns from your daily charging routine so it can wait to finish charging past 80% until you need to use it."

So I imagine it stops charging or fast charging after 80%. And slow charges that last 20% for when it expects you to need the phone. Not sure how much this differs from only ever charging up to 80%.

I also use Carplay wired, so it's always charging in the car as well.

Just checked my iPhone 11 (work phone) it's at 86%, that's the normal sized model.

Did you have an automated way to do that?

I wish I did but I haven't found one yet. I'm at my desk a lot, and that's usually when I charge it. I mostly use an old, low-current charger (originally for a bluetooth headset) so it charges slowly, about 5% per hour.

Which begs the question: if I charge my new Mac with an iPhone charger (8W), will it lengthen the battery life ?

I don't think so. You need 20V to charge a laptop

Probably not, seeing as that's not enough power to charge it up.

Answering peer comments: oh but it DOES work.

I forgot my charger in another town so I bought a USB-A/C cable and tried it out. Again, the iPhone charger is 8W. This is also the value reported by '/usr/sbin/system_profiler SPPowerDataType | grep Wattage'

When the Mac is open and in use (2023, M2) the iPhone charger can just about keep the charge level level, depending on usage.

But then when I close the Mac, it can easily take 10 hours to reach a full charge... but it does hit 100%.

So I am wondering if this is in fact a gentler way to charge the battery.

My crude understanding is the charging speed wouldn't directly have an effect, but the heat generated by faster charging would.

Also if it takes hour and hours to charge with 8W, then it becomes easier to unplug it at or around 80%. So maybe it's the best way to charge the Mac - a way that all the cool kids will be doing :)

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