I want to purchase a USB Power Bank, one of the tiny portable ones, to power my Pi Zero, I need it to last at least 12 hours, but preferably 15 hours, for a comfortable safety cushion of time. My Pi would not be using WiFi and would only be using a USB sound card and a USB camera. The processor would be at 75-100% almost all the time. This link shows the power consumption of the Pi Zero, which at max is 800mA. So what size power bank would I need to purchase?

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    Depends on the power consumption of the additional peripherals. Other than that, what's the question? 800 mA * 15 h * safety factor >= 12.000 mAh – Ghanima Nov 29 '15 at 19:40
  • Nice find with the power consumption stats by the way. – Ghanima Nov 29 '15 at 19:40
  • In other words a huge one. Also, many power banks seem to be "marketing" rated by the amp-hour capacity of their cell at the ~4v cell voltage - conservation of energy means you will have a lower amp-hour capacity available to draw after conversion to the higher 5v USB rail even with perfect DC-DC conversion, and the conversion is of course not perfectly efficient. You may want to look at something more like a large gel-cell and an efficient buck regulator. Even better, try to find a lower power consumption solution to your task, or a platform amenable to sleeping and use that. – Chris Stratton Nov 29 '15 at 20:03

For power saving tips: Have a look @ Raspberry Pi Zero - Conserve power and reduce draw to 30mA http://www.midwesternmac.com/blogs/jeff-geerling/raspberry-pi-zero-conserve-energy

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    While powersaving is of course a good and valid point (e.g. no HDMI in this application). Comparing idle values however are of little use here - after all the Pi has some work to do and just idle around all day ;) – Ghanima Nov 30 '15 at 9:16

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