This issue impacts literally every phone ever sold.

Manufactures can hide it any number of ways, but a new battery is always better even if your phone is exactly 1 day old. That’s what continuous degradation means.

> This issue impacts literally every phone ever sold.

No, actually, most phones did not release an update like this, deny the situation, and then also refused to let people purchase replacement batteries.

The issue is that Apple did this update, did not tell people about the whole thing, however you want to describe it, and then also did not allow people to buy replacement batteries.

All that tells me is that other phones aren't getting the most out of new batteries, and are instead limiting themselves to the performance of an old battery. But yes, I agree, they should have permitted replacements - in fact replacements should have been permitted at home. Batteries deserve to be user serviceable.

> All that tells me is that other phones aren't getting the most out of new batteries, and are instead limiting themselves to the performance of an old battery.

That's only one possible explanation.

Imagine two phones that can both draw 5 watts max. Phone A has a battery that can supply 5 watts brand new, and phone B has a battery that can supply 10 watts brand new.

It's true that phone A is "getting the most out of new batteries", and phone B isn't. But phone B isn't "limiting itself to the performance of an old battery". The 5 watt limit is there for efficiency and heat reasons, and it just so happens that the battery is never the limiting factor.

Is there some reason to think that's the case? Batteries are pretty consistent technology, roughly equivalent across manufacturers and all sourced from a pretty small pool of OEMs. If that's the case I'd love to know more!

Lithium ion chemistry can vary things significantly, but I was picturing simply putting in a larger battery for the hypothetical. The motivation is more hours of runtime, but as a side effect you have more peak watts available.

Now you’re paying to change voltage, which adds cost and heat. Sure, users don’t really notice that something’s wrong, but they get a worse device that costs more money and needs to heat throttle anyway.

Not a higher voltage battery. A physically larger battery. More watt-hours and more watts.

Voltage drop is minimally impacted by battery size, it only helps in that the battery would have less usage, but it still ages for time passing.

> Voltage drop is minimally impacted by battery size

That makes the job easier! Just cut the battery in half. Let's say the original battery could handle 5 amps before the voltage drop got too bad. If a half-size battery can handle 4 amps, and you put in two of them, now you can handle 8 amps.

Most phones aren't redlining the battery when brand new. There's degradation but it only affects battery life. By the time you have performance impacts you're typically in "replace the battery" territory.