zlacker

Heat had nothing to do with it. The internal resistance of the battery increases as it wears out, lowering the peak output current.

Increased heat when operating near the current limit is a symptom, not a cause. Adding a fan or a chonky heatsink to your iPhone wouldn't magically raise this limit.

>>babypu+(OP)
I don't believe I ever said heat was the cause, if I did I misphrased my point. Excess heat was absolutely the symptom, but it was a symptom of a design that was pushed beyond the limits of regular operation.

A two year old lithium battery under normal use will hardly degrade at all. Any design that pushed the limits so far that a degredation of a few percent over promised and under delivered. In Apples case it could be remedied with a software update, but that doesn't mean the device held up to the original performance claims over a standard life cycle of device use.