How to power the RaspberryPi for more than 7 hours with a single 18650 battery

  1. Get a good 18650 battery by a dealer who knows what he's speaking about (and who has done some test to be able to tell it's not fake batteries).
    Maybe I was just unlucky, but the red UltraFire battery I got from eBay was just crap. The good one was a Sanyo/EVVA 3400 Protégé got from PuissanceLed:  
     

  2. Get this 1€ battery charging board, and use this wiring:
     

  3. Ready to run for more than 7 hours!

 

During this test, the SamplerBox software was constantly running (so there was a non-negligible CPU usage), and these devices were connected to the RaspberryPi, taking some power:

so this means it could even be longer without these devices! I also read somewhere that it's possible to completely disable USB hubs, this could be useful for some other project.

And some other ideas for even longer battery-life (see this discussion):