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 an entire hour. If you want to extend battery life, you can add a separate battery circuit, such as the one demonstrated in this chapter, in parallel to the existing one. So, this would give you 1.5 amps for 2 hours or 3 amps for an hour.
In my own...
