I own a pool business that uses a 12v Battery powered pool vaccume that attaches and detaches from the rear of my truck. It has to be charged very 2 or 3 days in order to work properly. I would like to add a mini wind generator to it with a charge controller to keep the battery charged longer that 2 or 3 days. I drive about 100 miles per day, with average speed of 45 miles per hour but up to speeds of 65mph at times. I understand that the additional drag will cost me gas money and it's not possible to charge the truck battery, but that is not what I'm after. I want to charge a separate battery that is not hooked up to my truck. I have tried several mini permanent magnet motors, getting 6-8 volts, but not to sure on amps. Any help determining which motor to use would be much appreciated. As of now I'm looking at a rc plane motor and prop. Really just need to know what size motor (amp output/rpm needed) to use to get the effect I'm looking for. I would think I need at least 4 amp output to actually charge the battery for as much as it's used.