Marcus Jenkins made a capacitive battery charger using Dirty Board PCB’s to revive rechargeable batteries:
This is really a basic, bare-bones circuit. I’ve prepared the PCB with a view that it could be used as a module in a rather more-sophisticated charging system. You could imagine using a microcontroller (e.g. Arduino, PIC, etc.) to monitor the battery voltage and disconnect the mains input to the charger module when voltage reaches a user-selectable limit. The microcontroller could also have a thermistor probe to attach to the side of the battery with elastic – a basic precaution to try and automatically disconnect in the case unreasonable temperature rise while charging.
Project info at Marcus Jenkins’ blog. You can order PCB’s for this project here.
His attempt to charge a lithium battery pack tells you all you need to know…
… that he’s by far the bravest among those of us who visit DP. Balls of steel… :-) :-P
Finally, a true dangerous prototype. :)