This is one of those hacks that scares me a little bit. The ‘Bad Boy’ charger was created by Tom Martin to charge EV battery packs. [Pictured is one built by Mike Chancy] You can find the schematic under austinev’s tech files. This thing is a bare minimum power supply – it’ll deliver loads of essentially unregulated power into a set of batteries. If you check out the circuit, you’ll see just how scary this thing really is, but according to its users, it works.