I'm not sure if my Batavus produces AC or DC. I've got a great meter, so I'll check it out BEFORE I hook anything up. I was thinking that if it is AC I'll just add a simple full wave rectifier circuit with a small capacitor to filter the DC wave a bit. If I get the resistor right I should be able to limit the charge to the battery to around 50mah. This will trickle charge the battery and still leave enough juice for the lights and engine. As for as I can tell, my moped doesn't have a brake light specifically. Head and tails lights yes. But no light comes on or gets brighter when I hit the brakes. I can get a 2000mah 6V battery at the local hardware store for about $25 and I've already got all I need to build the charging circuit and to etch the board so I don't expect to spend more than $30 to get the whole thing up and running.