Alternator mounted on the wheels to generate the electricity to charge the battery

RV or car-trailer also known as motorhome, "RV", the full English name is Recreational Vehicle, also translated as Motorhome or Trailer, or RV for short. It can be parked on beaches, lake shores, grasslands, hillsides, forests far away from the city at will.Cook delicious meals by yourself, take a hot bath, sleep in a soft and comfortable bed, watch TV, listen to music, play DVDs, etc.

For this reason, the RV need a lot of electricity.

The alternator is mounted on the wheel and driven by the rotation of the wheel to charge the battery. 

The alternator starts to generate electricity when the vehicle travels to 50 kilometers per hour, and it can output 2 kilowatts per wheel when the vehicle travels to 80-90 kilometers, and the two wheels output a total of 4 kilowatts.