should you go with solar cells on the car, you may want to look into these.
assuming your voltage controller can handler higher input voltage to achieve the right charging voltage. you may want to use either 24 or 26 cells in series to get that high V-DC.
Price per 26 cells, $778, Based on a Constant Voltage charging system.
the other cell you might consider is this one.
as pointed out some are less efficient as this one is. using 14 of 3052288 will put your voltage above highest charging voltage to the controller.
Price for 14, $489, based around a Constant Voltage charging system.
one last solar sell i might suggest
with these above at .45v take about 375 cells in series. if you have enough area on the car to place that many, it would be the best. though the cost will be higher then the other two i listed.
Price for this .45v cell at 375 cells, $1,875, not including shipping. no weight listed for each cell so no way to calculate weight added to the EV. could be either Constant voltage or constant current charging.
Since im not sure how the charging is going to happen. Is it going to be constant current or constant voltage charging? that might help in which cell to use. my suggestion of using a few more cells in series for higher voltage. Is due to what i have been looking into for solar chargers. that they can take a higher input voltage for the same charging voltage to the batteries. what this means to me by using more cells. Is that with what sun is out i can collect enough power to charge the batteries. If its kinda cloudy and im still getting some good sun it should be enough to charge the battier. same if the sun starts to go down. say the charger has 170-180 V-DC input voltage to charge at 166 V-DC. that gives you more time early morning or late evening to charge the batteries. Might be even enough to try to meet your 3 mile.
One other thing i thought of, if you can pull it off with out looking silly. implement a low starting speed windmill/turbine on the car. it would even be better since as the car is moving it would be charging at the same time. if the body was designed a bit differently you could have forced induction straight to said windmill/turbine in a hidden area under the body some where.
im simply tossing ideas out there, how much will they work for this project i dont know. Though it does seem logical to me that using a wind type energy generation would be best for EV cars, that is built into the car it self.