First of all, it is absolutely wrong to use a car generator. Additionally, a feature of a car generator is that it cannot transmit energy over long distances. You can ask people who know cars well about this. You have to turn on the car. The distance between the generator and the battery is very short. The car generator itself is designed to operate at high speeds. This speed can only be achieved by using gears, but it's absolutely not worth it. . Second, except in very special circumstances, using a wind turbine will never save you objective costs. Additionally, fans of 3300 W, or any power, cannot be installed on the roof, which is very dangerous.
According to current specifications, it is impossible for 12 magnets to have this much power. If you want to wind the wires yourself and make your own motor, it is better to need more magnets and the number of coils should be based on the actual situation. You can do 20 rounds first, then roughly calculate the number. tension of each turn, then deduce approximately how many turns will be required.
But the prerequisite for making a wind turbine is the local wind speed! If the local wind speed is not high, making a generator will not give you any significant results other than fun.