How long will it last?

Battery capacities are measured using mAh (milli Ampere hour):

  • By adding batteries in series, such as in this design, you do not gain more capacity but more voltage
  • By adding batteries in parallel, you gain more capacity but stay at the same voltage.
  • Finding the best balance depends on your requirements

To properly calculate how long your batteries will run can become a very complex calculation. You need to take a lot of things into consideration. In this design, using a higher voltage gives us more time because the voltage regulator needs to use less current (amps); a higher draw of charge reduces battery usability.

In an ideal world, you could say that we will be able to supply 1,500 milliamps per hour. This is 1.5 amps for ...

Get Raspberry Pi 2 Server Essentials now with the O’Reilly learning platform.

O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.