If you find that your mobile device is always running out of juice before the days end then take comfort in the fact that you can always make your own emergency battery pack.
All you need are a couple of AA batteries, a couple of capacitors, a couple of resistors, circuit, USB type A female jack, a diode, a soldering kit……ok so maybe it’s not that easy! XDA forum member hockeyrcks9901 decided to have a go and follow the instructions that are widely available on the internet.
The XDA member has tweaked his battery build slightly in that it maintains a constant 5V output even as the voltage drops on the batteries. He states that it is possible to use rechargeable or alkaline batteries and apparently, it is also possible to add a third battery to further increase the capacity.
With two batteries, the set up can fit in the Altoids gum tin as per internet instructions, however the gum tin appears to be quite difficult to find and hence hockeyrcks9901 has used a regular Altoids tin. With the current set up, it is estimated that the batteries will give approximately 60-75% of a full charge.
For more information including pictures, check out the modification thread._________