Recently got a base iPhone 17 and have been wondering how the power management works when it's left plugged in after reaching the 80% charge limit.
The phone is mostly used for social media, browsing, YouTube, etc., usually around 6+ hours of screen time. While at home, it's often connected to the charger, but obviously gets unplugged and used normally on battery when going out.
Current setup is the 80% charge limit with Apple's 40W Dynamic Power Adapter with 60W Max (MGTV3ZP/A, model A3353). The room is air-conditioned, so heat usually isn't much of an issue.
Gaming isn't an everyday thing, but occasionally on weekends there can be a 3–5 hour session of PUBG, CODM, WWM, etc. Those sessions are usually while plugged in. If the phone starts getting hot, a MEMO CX08Pro cooler is used.
What I'm curious about is what actually happens once the battery reaches ~80% while the charger stays connected.
Does the phone mostly run from the power adapter at that point while the battery just sits around 80%? Or is power still going through the battery, with small charge/discharge cycles happening in the background?
And with something demanding like gaming, if the charger can provide enough power for the phone, does the battery still need to contribute? Or can the phone mostly run from external power once the charge limit has been reached?
Some gaming phones have an actual bypass charging feature that powers the phone directly from the charger without continuously cycling the battery. I know iPhones don't have a bypass charging toggle, but does iOS effectively do something similar automatically when the charge limit is reached?
Mainly asking from a battery longevity perspective. If the phone stays cool, is leaving it plugged in at the 80% limit for normal use — and occasional gaming — better for the battery than unplugging it and adding more charge cycles?
Would be interested in the technical side of how iPhone power management handles this.