Hi, today I'm going to show you a very simple and safe way to build a battery powered phone charger! Disclaimer: I am not responsible for anything you do resulting from this instructable. First things first! Materials: 1: a 4AA battery holder purchased at radio shack. I recommend one with an on/off switch since they're the same price (You can use a 9v battery with a 9v battery clip it's just personal preference and rechargeable AA are cheaper) 2: a Zener diode purchased in a pack of 2 from radio shack 3: last but not least a female USB cord or a male that you change to a female using this instructable https://m.instructables.com/id/Make-a-USB-Female-connector-out-of-a-USB-Male-conn/ Tools: Wire strippers Soldering iron (optional) Steps: these are short and fairly straightforward. Go ahead and put batteries in (rechargeable works best) 1 bend the Zener diode so the silver ends form a "u" and a right angle with the middle thing 2 attach the red wire of the battery pack to the end of the diode with the black stripe ( and yes it's opposite colors I know) 3 attach the black wire from the battery pack to the opposite side 4 strip all four wires of the female USB chord 5 twist or solder the white and green wires together. 6 attach the red wire to the side of the diode with the black stripe closer to the end then the other red wire 7 attach the black wire to the other side also closer to the end than the other black wire P.s. when I say attach you can either solder or twist Tape female USB to battery pack for easier carry and enjoy your charger!!!!!