How does Apple discern battery life on iPhone?

[dyelton]

I have a first generation iPhone that only has ~4 hours of typical usage now (only about an hour and a half or two hours if playing a game).

I have Applecare on my iPhone and I know Apple won't replace the battery until it is 50% depleted. How does Apple know that a battery is 50% depleted? Do they have a device that will tell them this? I know the iPhone tracks usage stats, but obviously Apple isn't going to wait around to see how much use they can get out of it.

When Apple replaces the battery of a first gen iPhone (now that it isn't beings old anymore) and you have Applecare, will the Apple Genius give you a refurb first gen iPhone or are they still required to send it off for replacement?

Thanks!

 

[Tallest Skil]

Batteries record cycles and original capacity (in some abbreviation that starts with an m) and compare them against current capacity. Apple can find that.

 

[dyelton]

Batteries record cycles and original capacity (in some abbreviation that starts with an m) and compare them against current capacity. Apple can find that.

Any way for an end user to decipher that info?