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I assume aircraft have batteries that power up all electronic devices on board. But how are these batteries recharged? When the aircraft is on the ground, it can be connected and recharged in the airport, but mid flight? Is there a way to charge the batteries in the air ?

Next question, bit trickier: how many devices must be plugged by the passengers (via USB) and how long it takes to drain all energy on board of a 787 ?

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  • $\begingroup$ Welcome to Aviation.SE! $\endgroup$ – DeltaLima Mar 1 '17 at 17:32
  • $\begingroup$ What sort of aircraft are you asking about? My Piper Cherokee uses an alternator that (as far as I can tell, anyway) is exactly the same as used on a mid-60s Chrysler automobile. $\endgroup$ – jamesqf Mar 2 '17 at 4:23
  • $\begingroup$ Just like car—with engine-driven generator(s). Why should it be any different? $\endgroup$ – Jan Hudec Mar 4 '17 at 11:15
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The engines turn generators which supply the electrical power to the aircraft, including a battery charger that keeps the battery at 100%. (Normally, power coming "from the battery" on the diagrams, is actually coming from the battery charger or another component like a Transformer-Rectifier converting AC to DC current. The battery is very rarely actually being drained in flight.)

If you had an aircraft battery & went to deplete it with USB devices, it would take a lot of them & a really long time. Aircraft batteries store power way beyond what our normal cell phones & iPads do, and can power all the emergency systems on the jet for an hour or more (radios, INS, flight instruments, minimal lights, GPS, flight management system, etc). Of course, if you're down to just the battery, in-flight entertainment is NOT one of the systems being powered!

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    $\begingroup$ According to the following link, the 787 has 6 generators with a total generating capacity of 1.45 Megawatts. That's a lot of USB! boeing.com/commercial/aeromagazine/articles/qtr_4_07/… $\endgroup$ – Adam Mar 1 '17 at 18:04
  • $\begingroup$ @Adam Well, they'll need 1.21 gigawatts to get they 787 into the future $\endgroup$ – TomMcW Mar 1 '17 at 19:09

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