Re: Wrong Swelling
FYI - regarding battery swelling...
it's caused by the buildup of H2 gas inside the LiPo battery casing which is typically a somewhat soft material. There are a couple of things that can cause it:
1. mechanical damage, particularly during assembly
2. serious undervoltage with excess current being drawn over a long period of time.
The 1st is a production issue, fixable by swapping out the battery. The 2nd is a design issue, NOT fixable without re-doing the circuit board.
You can mitigate '2' by keeping your unused phone on the charger all of the time.
The reason it happens has to do with the chemistry of an LiPo battery. If you discharge it too much, the polymer breaks down and releases hydrogen.
LiPo batteries can self-discharge, so don't expect a charge to last more than a couple of month because of that. Additionally, if there is undervolt protection circuitry in the phone, it will draw a small amount of curent regardless of the state of the internal protection switch.
I recently designed such a circuit for a system where the entire circuit board + battery is potted in plastic, meaning you can't change the battery [it's waterproof though]. the batteries were having swelling problems. This was generically solved by an EXTREMELY low current battery undervolt cutout circuit, which draws only 10 microamps [or so] in the 'cutoff' state. It leverages a few other things to limit the current and the number of components.
/me takes a bow for the miraculous electronics engineering, a truly 'clever' hack, heh.
In the mean time, you STILL get trickle discharging of the LiPo, but you also get self-discharging. 10 microamps is about what a typical self-discharge is, and you can generally leave a LiPo on a shelf and let it self-discharge and not have it swell up like a pillow, even it it reaches zero volts. [it may still happen but from what I can tell, it's much much less frequent].
On the other hand, if you draw as little as 100 microamps from one of the smaller batteries [it may be more for a larger one], they tend to swell up like pillows once discharged down to 0V, and will do so within a month of being discharged, more often than not. So you can't just set it on a shelf unless your undervolt protection totally cuts off the battery [or gets trickle current down to about 10 microamps].
I've got on battery I've fully discharged at the ~10 microamp rate, and then re-charged, a few times. It's lasted for MONTHS this way, no apparent ill effects. It's as flat as a pancake, like it's supposed to be.
So I'd say Apple's problem is PROBABLY on the circuit board, and retro-fixing that is basically impossible, unless they can wire in an undervolt circuit between the battery and the circuit board somehow. Good luck fitting it in the case. I bet it's really *tight* in there.
/me withholds a comment involving a cherry