Technology

When you do the initial setup it asks if you'd like to optimize for battery health and most people say yes. Most recently it wouldn't even tell you that it was only charging to 80%.It would still charge to a hundred but that would actually be eighty percent. Around a year ago they changed it so now it says eighty percent when you're at full charge if you have the battery health turned on.

If you turn on the battery over provisioning you would see the same battery life at about a year and a half and then after that the provision battery will last longer. After the exploding phone they also provisioned five percent of all batteries.

It's all up to where you live and how you use the phone.

One day heavy usage is the goal. I charge my S24 to 80% but only lightly call, and moderate chatting. I can make it from 6am to 8pm and still have well over 25% when I get home. Little to no gaming or social networks though.

It helps that I live and work in an urban area with good antenna coverage. So the phone doesn't use too much power talking to the network. People who live out in suburbs and rural areas have worse phone battery life because the phone has to struggle talking with antennas further away. Battery life is complex and it goes beyond what personal anecdotes can show.

OnePlus offloads heat to the charger

Some of it. They omit some circuitry that would have generated additional heat in the phone, and have it in the charger instead, but that doesn't magically mean the battery itself wont generate the inevitable heat caused by being charged faster. The battery itself only accepts one voltage, so the only way to charge it faster is amps.

And my feeling is that they aren't using the gains from this to make the batteries last, as SUPERVOOC is faster than pretty much every other standard. That makes me think they turned in any and all gains in battery health, for speed.

Most chargers send the additional energy via the cable in the form of extra voltage, because that doesn't require a special cable. Turning that voltage into amps in the phone produces a little bit of extra heat, but that doesn't mean that by eliminating that step, you get none from the battery itself as it charges. You can technically charge with a higher voltage, if you set up a phone such that it has more than one lithium cell. Some phones do this, but this doesn't require the OnePlus approach of using a special charger that provides a higher current, since any fast charger that can do the usual higher voltage method of providing extra power will work.

Like you say. I'm curious how they test this. Even if one battery gets more cycles, it'll degrade with time, as well. iPhones fast charge, too, but not with the chargers that used to come with the phones. You have to get one specifically for fast charging to get faster-than-normal charging.

Also, a tip. You may want to use something like AccuBattery to actually measure the state of the battery. Batteries, being chemical devices, have different capacities straight off the production line simply by virtue of not being chemically identically down to every molecule. (My Xperia 1 V unfortunately came with 93% design capacity, still within manufacturing tolerance, but the lowest I've seen on a new battery, it can be a bit of a lottery)

The built-in battery health monitor will just say "all good" until it isn't. AccuBattery has allowed me to monitor every percentage of degradation over the lives of my last few phones.