US Patent 7514803 Trailer with integral axle-mounted generator and battery charger

A working surface incorporates a means for transferring mechanical energy produced by a rotating member of the working surface so that the energy rotates a shaft attached to an alternator that charges a bank of 12 V batteries. The alternator is responsible for converting the mechanical energy being input by the rotating shaft to electrical energy that is fed to the batteries. The batteries transfer the energy into an inverter for use depending upon the required amount. Thereby, backup electrical power may be generated and stored, taking advantage of excess horsepower at cruise provided by a vehicle as well as better utilizing travel time. Additionally, the added cost of ownership and noise of a portable power generator is avoided.