~5v USB Battery Pack

My mobile phone can't go geocaching with the display-on and locating for more than about an hour before running the battery low. The phone battery is an impressive 3.6V with 1600mAh capacity, though clearly not enough for extended use. I needed a geo-battery-pack.

So I made this. It's a 4.8V, 2600mAH cell made from old cordless drill batteries.

Construction images below:

An old cordless drill battery pack disassembled with the dud "sub-C" cells removed.
Each cell is 1.2V, 1300mAh. I wired up x2 banks of 4 cells, creating a 4.8 volt, 2600 mAH battery bank.
Sizing up a block to mount them in. I carelessly oriented the grain 90 degrees in the wrong direction. Notice the end-caps have grain across their width, not their length. These are ULTRA flimsy, hence the bazillion screws holding them on in the final-block.

Trial fit. Space not yet hogged out for the plugs.


Trial fit with the USB plugs in place.

Filing out the USB plug gaps in the caps.