Be aware that some power outlets will provide 'life support' to maintain a battery, rather than the ability to fully charge.
The power supply (on some aircraft) actually moves around the cabin in seat blocks; you'll get power for a period of time, then it goes off, or is reduced, and moves elsewhere.
Worth pointing out ( Sadly, I expect to be flamed for this) that the power on board is not free. It has to come from somewhere and in this case, it is ultimately from the engines. The electrical power required on an A380 to charge 300+ laptops, iPads, phones etc for ten or more hours is not trivial, and combined with the weight of the associated wiring and sockets means that there is a
very minor, but existing, fuel penalty. There is also an engineering and maintenance expense. Somebody has to pay for all that.
