[Phlarp]

residential lithium fires are unlikely to be coming from phones. (unless people still have those exploding Notes still kicking around)

Far more likely to be lithium batteries being used or abused in a hobbyist capacity. E-cigs and RC are both ripe for it when users have lower quality cells to begin with, routinely discharge them above the rated current and then charge with sometimes questionable chargers. Worse yet when people try to charge them above the max voltage.

[wickedsmile]

What protection mechanism do we've of one of the SMD resistor or IC in the protection circuit fails?

[Phlarp]

I'm pretty comfortable assuming that Apple wouldn't design a lipo charging circuit that could fail in an unsafe way due to a single component failure, but I can't speak specifically to what those might be.