I think the Yemen raid discovered plans to replace the batteries in rechargeable battery packs with smaller, lower capacity batteries so the device will still turn on for inspection and use the extra room for explosives.
Batteries are now so powerful they themselves are a very potent incendiary device,people are building powerwall home battery packs out of 18650 batteries.
Remove the safety devices on any portable device and wire in a few strips of magnesium and there is your bomb. And a timer to create a dead short. Its easy to do for anyone with electronic experience.