As long as you have an extra USB wire with male USB end, and the thing you want to power runs on three AA or AAA or C or D batteries, you can hack it to run on USB power!
Step 1: step1 clean/dismantle
dismantle and clean the thing you want to hack.
usually its very simple to take something apart,
the Darth Vader bank im hacking is held together with just 4 screws, which allows me access to the back of the battery tray
you dont want old battery acid all over your power leads so make sure its clean!!