Extra battery power

[lesleycs]

Need extra (external) battery power for long flight, preferably small and portable. Any suggestions please

 

[svim]

Wirecutter has a good guide on external batteries. Even if you don't opt to go with their recommendations there's a lot of information on how to decide on what you should look for:
http://thewirecutter.com/reviews/best-usb-battery-packs/

 

[Lateck]

I use Anker brand battery packs for all of my usb chargeable devices.
They make a number of different sizes.

Lateck,