I picked up one of these to go to weeknight bar jams and bring minimal equipment. 4 effects in one small package, analog, no digital menus, the size of about 3 packs of cigarettes. It’s a VERY sturdy steel case. The problem is that it uses an external 9vdc supply so the wire and finding an outlet is always an issue. So... I was thinking about modding it with an internal rechargeable 9v battery. I would also like to add a “low battery indicator” led and don’t want to reinvent the wheel. Has anyone ever done this? Got a circuit diagram?