The goal of this mod was to move away from a battery pack and make the Nerf Vulcan EBF-25 a stationary assault or defense weapon. This is ideal for target practice and fixed position defense.
Step 1: Find a 9V power supply
Rummage around the basement and find a spare 9V AC/DC power converter. Most if not all DC converters will have the output voltage and output current printed on the back. You will need to find one that can supply 9V at 600 mA. I didn't have any that were that large, so I combined two of them. The bottom one is 400 mA and the top one is 200 mA. I tried using just the 400 mA supply first and it just didn't have enough juice to keep the motor running. These power supplies came from old wireless phone rechargers.