[yason]

Swapping in a live battery probably isn't a problem. They want to see if the device works or not.

What I meant that if I build a bomb into a laptop, and use its battery space to contain the explosive so that it looks 99.99% the same in the X-ray, I can just put the bomb in the checked in baggage and have it in the cargo space while not having to show anyone that the device doesn't boot up.

But if they can already detect bombs built into devices such as laptops for checked-in baggage — which they obviously(?) and presumably do — then why can't they detect these bombs similarly for cabin baggage? They could just do that instead of asking the passengers to boot their devices.