around 38C

I was shocked when my new realme, which uses the same tech, didn't even break 30°C while charging at 8+ Amps (should be around 80W). This was in a relatively warm room (25°C) and using the case that came with it, which surely doesn't improve thermals. It gets warmer when charging from other sources with only 2-3A, like USB-PD or QuickCharge.

Coupled with the fact that it's only accurate if you are constantly charging from below 15% to 100%, these are ranges that I rarely get my phone into.

AccuBattery needs a session to have 60% charged, so <20% to 80% works. Doesn't need to be every single one. I actually asked support about it and they said this was the lowest percentage they were comfortable with. I was requesting to make it adjustable.

Accuracy of the measurement isn't the entire point. I see the same issue, but since it helps track relative degradation over time it can still add value by giving more information when you suspect the capacity is getting worse.