I really can't imagine why on earth Aircraft passengers must only take CHARGED mobile devices on to a plane -- surely if you were sophisticated enough to hide a bomb in a mobile phone battery compartment you could do it whether the battery was CHARGED or NOT.
As an Engineer experienced with some of the chemistry of explosive substances (was involved with mining and drilling at times in my career) I can say categorically that it actually doesn't require much material these days using modern materials to make an almost undetectable powerful explosive or even an incendiary device. These sorts of security precautions are 100% TOTALLY MEANINGLESS and all they do is just add to the ever increasing delays and frustrations of being able to board aircraft these days (or is it a conspiracy to get us to spend LONGER at the airport so we spend more money in the shops etc).
I'm all in favour of proper security - but this latest thing about uncharged devices !!!!! -- What happens if you've been 3 weeks say "out in the boonies" and you go straight to the airport to come home - where your phone / tablet and laptop are all totally discharged. !!! Quite normal for people who spend any time out in the field and there aren't always enough charging points at airports anyway -- and there certainly won't be now.
Aren't you fine though if you can plug said device in to a charger/power pack and verify it turns on? It would suck though if your charger is in your checked baggage and your phone battery went dead.
The problem isn't so much taking charged devices to the airport but say your flight is delayed for a long time or you are catching a connecting flight your device might be "out of juice" before you get on your connecting flight. Unless you are in First Class most planes don't have electrical outlets at your seat ( a very few do - but those seats are booked well in advance) and except for a decent airport like Schipol in Amsterdam if you are outside of the business lounges there are usually very few power outlets to be had for the general public .
Also if you've been "out in the boonies" away from any sort of civilisation before catching your flight you don't necessarily have access to charging points.
In any case is it so hard for any competent "Bomb designer" !! to install their wretched device into say a part of a laptop battery for example while the laptop appears to function totally normally -- modern explosives can operate with TINY amounts of "ingredients" -- you don't need a "classic bomb" to de-stabilize a plane -- just enough damage to make a SMALL puncture in the fuselage at 35,000 ft would be enough to probably destroy a plane - at that height even if the plane wasn't destroyed most people would be dead of Oxygen starvation before the plane could descend to 15,000 feet where breathable air is available - the emergency oxygen supply only lasts for about 12 mins - too short a time for the plane to descend to 15,000 feet and also isn't very useable if the pressure in the fuselage drops significantly -- you can't breathe in the oxygen. I'd better not say any more or I'll have the FBI on breathing down my neck - I WANT proper security like any other aircraft passenger - but this stuff is totally ineffective and it will take a competent "terrorist" !!!!! about 3 mins to devise something else.
What REAL security needs is to get people say at M.I.T or Cambridge university or even NASA to try and design undetectable bombs - and then get the security people / CIA or whoever to upgrade their devices to detect these.
The current regulations are a total joke and don't fool anybody -- DECENT security is necessary but this imbecellic stuff just brings the whole system into disrepute.