What you�ll need for this is:
+A DS or SP charger with their nutty proprietary plug on the end.
+A Radio Shack battery enclosure for 4 AA batteries (or AAA if you want it even more compact, but don�t mind it being weak)
+Swiss Army Knife/Utility Knife or Toolkit
+Soldering Iron + Solder - Optional (gasp!)
So all the above should be readily available. Lay it all out on a table in front of you and let�s get started.
Step 1. Grab that DS charger
Grab your Nintendo DS AC adaptor and pick a good spot to hack the end off. It�s a pretty long cord so I just chose to do it in the middle. Use your knife for a clean cut right down the middle.
Step 2. Get your battery case ready
Get your neat little case and hack off the ground wire, we won�t need it. Then unscrew the cover and keep it off until you put your batteries in.
Step 3. Stripping away and connecting
Strip away the wire a little bit, you�ll see a green wire inside. Strip that very carefully and reveal it�s golden insides. Then, take your red connector on your battery case. You can either solder it for a secure permanent connection, or just bundle the wires together tightly, cap them, and use a little tape to clean up.
Step 4. Finishing up and powering it up
Wrapping up, you can either tape the short wires from the battery case to the side or you can go further like we did and drill a little hole for them to go into. The finished product should look like this. Small enough to fit in your pocket and good for a little extra juice (not 9 hours of gaming mind you). You can even customize it if you want and it works by connecting it to your DS or SP, and hitting the �On/Off� switch on the battery case. Sweet, simple, and snazzy.
See? It fits right into your pocket with ease. Special thanks to Game Champ from Philadelphia. They hooked me up with a DS Charger for this which was really cool of them. You can call them at 215-405-0303 or visit them at 1509 Chestnut St. when you stop by Philly! Tell them Engadget and Hackaday sent you!