I was under the impression that was the trigger.

They couldn't pack a full bomb inside the pagers (prob too easy to detect the primer?), so they just added explosives and to trigger the reaction they overheated the battery.

And yes, you can absolutely heat up an AA to 100°C and more by shorting it. But in this case controller sorted it on command Im guessing.

So AA can violently explode. You just had to add explosives :D.

(But honestly, I replied just because I found it amusing you thought I assumed new battery tech did it, I should have added the "/s" next to the flying car reference - after all, in the early age of dumb phones (late 90s) unregulated dumb li-ion batteries killed a few people in China iirc)