Hybrid vehicle drive system and method for fuel reduction during idle

A method of retrofitting a vehicle with a hybrid vehicle drive system, the vehicle includes a first prime mover, and a prime mover driven transmission, the method comprising:

• attaching an electric motor at a PTO or an interface to be in mechanical communication with the first prime mover, the interface being a gear attached to a flywheel coupled to the first prime mover, a ring gear, or a gear attached directly or indirectly to a crank shaft of the first prime mover;
• and
• operating the electric motor when the vehicle is stopped to drive the first prime mover at a speed, wherein when the vehicle is stopped and an accelerator is not depressed, an engine control module of the first prime mover reduces fuel provided to the first prime mover due to rotation of the first prime mover by the electric motor at the speed, wherein the speed is at or above an idle set point and does not cause the vehicle to accelerate forward while the vehicle is stopped.

A vehicle drive system for a vehicle including a first prime mover, a first prime mover driven transmission, and a rechargeable power source, the vehicle drive system comprising:

• an electric motor in direct or indirect mechanical communication with the first prime mover, wherein the electric motor can receive power from the first prime mover driven transmission, and can receive power from the first prime mover;
• and
• a control system, wherein the control system causes the electric motor to rotate the first prime mover at a speed while the vehicle is stopped, thereby reducing fuel consumption at idle for the vehicle in an idle fuel saving mode, wherein an electronic controller module of the first prime mover reduces fuel provided to the first prime mover due to rotation of the first prime mover by the electric motor at the speed, wherein the speed is at or above an idle set point and does not result in the vehicle accelerating forward while the vehicle is stopped.