Help with fritzing circuit

Not a problem, if you don't know the solution its hard to know what details to provide. So there is a gas motor that will be driving the wheels and the generator and it only needs to charge the batteries? That makes things quite a bit easier (although the voltage is somewhat of an issue). What you probably want is a boost/buck regulator that will take the varying generator voltage and either increase it (when you are going slow and the generator is producing less than the battery voltage) or decrease it (when the generator is producing too much voltage. There are a bunch of these available on Ebay, but they typically top out at about 36V (and 1 to 3A) which is a bit too low for what you need. I'd search for boost/buck regulator 48V with google and see whats available. From there its fairly simple, the input to the regulator comes from the generator and the output (set to about 42 Volts for your 3 battery configuration) should charge the batteries. Looking for a module specifically designed to charge batteries would be a good bet too, as it may need a shutoff circuit to stop charging when the battery is charged (I'm more familiar with NMIH
and LIPO batteries which both object to being overcharged than lead/acid car batteries.