in my experience iPhones take ~90 minutes to fully charge, but similarly to your experience they charge up to the first 50% much faster with a faster charger, though more like 30 minutes instead of 5-10. (I'm jealous!)

And you're right that it seems like they have smaller batteries! Like my non-large iPhone 14 pro has a 12.38Wh battery but it lasts all day easily. Never thought about it before but this must mean that Apple's chips/software just pull less energy. (also I was wrong before, if a 12.38Wh battery takes 90 minutes to fully charge then it's average charging rate is only 8W, even lower than the 10W-12W I guessed!)

That's rad! I'm sure it can use that full 65W when the battery is low. Though I'm pretty sure it can't use the full 65W of charging power the entire time it's charging. LiPo battery chemistry just doesn't allow it.

It's also easy to show this with math. According to the internet the OnePlus 8t has a 17.02 watt-hour battery. As in it stores enough energy to output 17.02 watts for 1 hour. (though it probably can't discharge that fast in practice). If a 17Wh battery charged at 65W the whole time it would take 17Wh / 65W = 15.69 minutes to charge! But because it takes 35 minutes, we know it must charge at 17 Wh / 35 minutes = 29.14 watts on average. Which is still craazzy fast. The latest iPhones, which can charge at 20W peak, but have an average more in the range of 12W.

I got into this stuff just by playing around with a USB-C power meter like this one. With that plugged into my charging cable I can finally actually see how many watts my devices are pulling at any given moment.

You can hook your iPhone up to a 240W USB-C PD charger no problem. I charge my iPhone off my 96W MBP charger all the time.

What happens though is the phone only pulls the current it can use. With the latest iPhones that’s about 20W or about 2.22 amps @ 9 volts. (And it can only pull that much when the battery is low, not when it’s nearly full).

Just looked up the upcoming 240W Realme phone and wow, that’s insane. It does sound like it can only pull and make use of the full 240W when the battery is nearly empty. But it goes from 0% to 20% in 80 seconds which is just insane. I highly suspect they had to sacrifice energy density, and total battery capacity/run time, to get a battery that can do this. Though with charging that fast I’d just hook it up for a couple mins before I leave the bough and I’d be good to go.