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Repair information and guides for the fifth generation of iPhone. Model: A1387

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How does the iPhone calculate battery percentage and with what parts?

In an iPhone what allows it to calculate the remaining energy percentage of a battery, both in programming and parts? Also why do certain conditions affect this reading such as temperature? Mine was lost for two and a half days then turned up literally frozen to the asphalt of a parking lot at my church. the outside case and the phone itself were both frosted over and once thawed out for a few minutes without being charged decided it wasn't dead when I tried to turn it on and powered up with 44% battery and later after it completely thawed went up to 66%. I have also seen similar effects on camping trips before where it thought was low on power but really had a nearly full battery. It is an iPhone 4S that I got for Christmas last year (2012). What causes this to happen and how does this system work?

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you'd have to talk to someone with more electronics knowledge, as its to do with the battery cells themselves... the percentage and estimation is done by a chip on the logic board, usually referred to as the SMC (systems management controller) or PMU (power management controller), but it doesn't actually know what capacity the battery has, which is why when the battery cells begin to die off, the percentage drains quicker than usual. its an estimate based on what the battery is currently holding and what the phone is doing to see how long it will drain based on its current usage...

On a computer it is much more comprehensive, as it allows you to see not only the current charge capacity in mAh (miliamps per hour), but also what capacity the battery would have had originally (Volts x Watts = Amps/1000 =mAh)) but the iPhones system is not able to tell these details... but the cells will react differently based on the temperature, as cold weather will slow down the lithium cells... but thats the extent of my knowledge. sorry

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