The majority of plastic based high explosives are designed to be very stable, and require both heat and pressure to detonate, so my educated guess is they implanted something along the lines of a blasting cap into the pagers. I’ve seen PETN mentioned, but again, that is designed to be stable.
Electrical charge? There are electrically initiated caps, but you can’t place a negative and positive charge into a stick of C4 and expect it to do anything.
So trigger some kind of process to cause the batteries to overheat + detonate the blasting cap after a short delay? I'd be interested to know how it was packaged if it was done in a way that wouldn't look suspicious if someone looked inside the pager. The bomb-in-the- battery theory is a good one.
Realistically it wouldn’t require much volume in the battery. For reference, the amount of explosive material in a blasting cap is about the size of an eraser head, and is easily capable of the explosions in the videos.
> So trigger some kind of process to cause the batteries to overheat
Where are you getting this part from? There's no evidence that the batteries were triggered to overheat; indeed doing so would be counter-productive, as it would cause the people holding the devices to know something is wrong and potentially move them farther away from their own body. The pagers exploded suddenly without warning. The only trigger/detonation involved was setting off the high explosive. The battery was uninvolved, only used to make the pager itself work.
