Can you point to the spec on this part, or something similar, I'm definitely curious about the circuit/algo design on this.
If they're regulating it this cleanly (zero battery transition/draw while plugged in at say 80%), why not allow the same at say 95%?
On my Xperia 1V, I can select 80% or 90% as the cutoff. I keep it at 80% because it's a bit less wear on the battery. Charge level makes a difference. Battery University covers this in a roundabout way in this article.
BU meta description needed...
batteryuniversity.com
Look at table 3, which shows how storing a battery at different charge levels (and temps, for that matter) can affect the capacity after long term storage. Setting a charge limit is effectively the same as putting the battery into storage, if I'm understanding things correctly, which is how that article is relatable here. Also notice that with elevated temps, battery capacity goes down quicker, but that excess wear is mitigated somewhat if it is at a lower charge level. Since a phone can get warm, and that I'm sometimes working in a relatively hot environment, 80% gives me better piece of mind.
Here's what my battery care page says when set to always on, limiting it to 80%.
And once I hit 80%, charging stops just like it would when it hits 100%. I can see that on Ampere. At this point, the charge rate drops to zero. Ampere sees that it's plugged in, but the charge current goes to nothing and stays there from then. Occasionally it'll drop to 79%, but that's it.