This is my first attempt at using multiple quotes. I hope I haven't garbled anything!
I don't want to upset either of us by having an unnecessary argument but so far I haven't seen anything that indicates your phone has an issue.
You've had your phone for about six months and you got your car about three months ago, therefore your battery's cycle count should have approximately doubled since you got your car. This seems to have happened, indicating that your battery usage has remained approximately the same.
One cycle is equivalent to one full charge and one full discharge. The charging and discharging can be broken up and mixed in any way. Every percentage point counts towards the cycle counter, although it only shows us whole numbers.
39 cycles in six months is roughly 0.2 cycles (or 20 points) per day, which is one cycle every five days. This is very light usage (partly because the 15 Pro Max's battery is so big) therefore your battery should last years. You won't make it last longer by using it any less because batteries degrade over time even when not used at all.
Wired CarPlay won't cause constant charging. The phone will charge the battery until it decides to stop. If you have manually limited the battery to 80% then it will stop there. If you leave Optimised Battery Charging on then it'll notice that you are hardly using your battery and it'll limit the maximum charge automatically, to prolong its usable life.
When plugged in, the phone's electronics are powered by the charger, not the battery. Once the battery has stopped charging, if you leave it plugged in, the battery will rest, neither charging nor discharging – in other words, the cycle counter will stop. Since you only run your battery down a few points before you plug it back in, recharging won't take very long. In other words, for most of that plugged-in time, the battery will be resting.
That's why I was predicting that driving frequently with your phone plugged in, as well as leaving it plugged in while you sleep (with Optimised Battery Charging switched on), would prolong your battery's health. I was trying point out that running down the battery just for the sake of it would result in more charging later, which would be counterproductive.
Wired CarPlay is the most efficient way to use your phone for navigation because the battery will be able to rest once the limiter has stopped the charging. It might even be better than leaving your phone unplugged doing nothing since then the battery would be discharging very slowly instead of resting, but frankly the difference in wear between those two choices is too subtle to matter.
That's why I think that using another phone for navigation or getting another CarPlay unit would be unnecessary. Your time and money would be better spent replacing the battery in several years' time, if and when needed.
Your commute sounds really nice. I had assumed that you were worried about the effect of CarPlay because you were driving a lot, but you've driven only about 40 hours since January. This isn't going to have much effect on your phone.
Many things could have changed. You could be demanding more of your phone without realising it. You might be storing more data for it to process in the background. Signal strength may have got worse in your area. Updates could have accidentally made iOS or some of your apps less efficient. A charging limit could have been applied by you or by Optimised Battery Charging.
And let's face it, you might be misremembering. These percentages are so close together as to be inconsequential. Maybe you have gone from using 12 points per day to 20 but, firstly, your average is 20 per day for the whole six months and, secondly, at the rate you're using your battery, it'll fail because of age before you wear it out.
Anyway, I hope I've got my point across without offending you. I appreciate that you want to protect your phone – that's what I want too. Just don't worry too much – its battery will be fine! Now I'm going to try to relax, even if you don't 😉
I don't want to upset either of us by having an unnecessary argument but so far I haven't seen anything that indicates your phone has an issue.
You've had your phone for about six months and you got your car about three months ago, therefore your battery's cycle count should have approximately doubled since you got your car. This seems to have happened, indicating that your battery usage has remained approximately the same.
One cycle is equivalent to one full charge and one full discharge. The charging and discharging can be broken up and mixed in any way. Every percentage point counts towards the cycle counter, although it only shows us whole numbers.
39 cycles in six months is roughly 0.2 cycles (or 20 points) per day, which is one cycle every five days. This is very light usage (partly because the 15 Pro Max's battery is so big) therefore your battery should last years. You won't make it last longer by using it any less because batteries degrade over time even when not used at all.
Wired CarPlay won't cause constant charging. The phone will charge the battery until it decides to stop. If you have manually limited the battery to 80% then it will stop there. If you leave Optimised Battery Charging on then it'll notice that you are hardly using your battery and it'll limit the maximum charge automatically, to prolong its usable life.
When plugged in, the phone's electronics are powered by the charger, not the battery. Once the battery has stopped charging, if you leave it plugged in, the battery will rest, neither charging nor discharging – in other words, the cycle counter will stop. Since you only run your battery down a few points before you plug it back in, recharging won't take very long. In other words, for most of that plugged-in time, the battery will be resting.
That's why I was predicting that driving frequently with your phone plugged in, as well as leaving it plugged in while you sleep (with Optimised Battery Charging switched on), would prolong your battery's health. I was trying point out that running down the battery just for the sake of it would result in more charging later, which would be counterproductive.
Wired CarPlay is the most efficient way to use your phone for navigation because the battery will be able to rest once the limiter has stopped the charging. It might even be better than leaving your phone unplugged doing nothing since then the battery would be discharging very slowly instead of resting, but frankly the difference in wear between those two choices is too subtle to matter.
That's why I think that using another phone for navigation or getting another CarPlay unit would be unnecessary. Your time and money would be better spent replacing the battery in several years' time, if and when needed.
Your commute sounds really nice. I had assumed that you were worried about the effect of CarPlay because you were driving a lot, but you've driven only about 40 hours since January. This isn't going to have much effect on your phone.
Many things could have changed. You could be demanding more of your phone without realising it. You might be storing more data for it to process in the background. Signal strength may have got worse in your area. Updates could have accidentally made iOS or some of your apps less efficient. A charging limit could have been applied by you or by Optimised Battery Charging.
And let's face it, you might be misremembering. These percentages are so close together as to be inconsequential. Maybe you have gone from using 12 points per day to 20 but, firstly, your average is 20 per day for the whole six months and, secondly, at the rate you're using your battery, it'll fail because of age before you wear it out.
Anyway, I hope I've got my point across without offending you. I appreciate that you want to protect your phone – that's what I want too. Just don't worry too much – its battery will be fine! Now I'm going to try to relax, even if you don't 😉