11. SALVAGE THE RING FROM
THE END CAP OF THE AA.
You’ll probably find a plastic plug with a thin metal
cap stuck inside the end cap you removed from the
AA battery. You need to remove this plastic. Pick it
away with pliers, blades, or a drill (Figure L).
Once you’ve liberated the small metal ring from
the plastic plug, clean the ring with steel wool.
12. INSTALL THE AG13
Melt some solder onto the inside of the ring from
the AA, and then scuff the outside of the AG13
battery with fine sandpaper.
CAUTION: Don’t use steel wool to scuff the AG13 battery, as it will short-circuit the cell.
Place the AG13 on a heat-resistant surface with
its negative terminal facing up. Center the ring on
the AG13 so that its negative terminal is positioned
where the AA’s negative terminal used to be. Melt
the solder on the ring again to join them. If you can’t
get the solder to stick properly, use some spots of
epoxy to reinforce the weld.
Now the end cap should fit back onto the end of
the battery case, and be held in place by the magnets you glued in earlier (Figure M).
13. CREATE A NEW WRAPPER
FOR THE BATTERY.
A suitable piece of artwork can be downloaded
makezine.com/16/usbattery and printed onto
sticky-backed inkjet paper or film (Figure N). Before
you stick it on, use a cotton swab and solvent to
remove the adhesive from the bottom ½" of the
label. This makes it easy to remove the bottom of
the battery without it sticking to the artwork.
The battery should now look like an ordinary AA
battery, and also register a normal 1.5V voltage if
you check it with a voltmeter, thanks to the AG13
cell fitted to the end cap.
To remove the end of the battery and reveal the
USB socket, simply attach a small magnet to the
bottom of the battery and pull it away from the rest
of the battery.
You now have your very own secret USB drive that
you can use to smuggle those all-important Death
Star plans past those pesky Imperial stormtroopers.
To make it really blend in, you should cover some
other normal batteries with artwork that matches
the USB battery.
Andrew Lewis also wrote “Self-Destructing Object” and
“Checkmate, Mr. Bond!” in this volume of MAKE.