Developing an electric vehicle powertrain usually means a significant amount of engineering. Engineers need to select or design an electric motor and power control electronics and inverters, along with cooling systems for each. The motor then needs a final drive gear to match the road-wheel speed. Finally, they need to integrate a computer to act as a powertrain control unit (PCU).
It takes time and expense to engineer the drive system to meet power, torque, reliability, and safety targets, along with acceptable efficiency. Soon, however, there will be another choice: Buy it off the shelf.
Starting in the third quarter of 2011, MotoCzysz will offer its integrated D1g1tal Dr1ve aimed at making life easier for electric vehicle powertrain engineers. Developed in collaboration with Remy Electric Motors, the company claims it as the first model in a new category of products—integrated electric drives.
The package includes a Remy HVH 250 electric motor, integrated cooling, inverter-controller, and PCU enclosed in an aluminum shell. The cooling system is a MotoCzysz proprietary system, which is derived from the company's state-of-the-art electric racing motorcycles. Using a water/glycol mix, it is intended to be identical to the vehicle’s resident cooling system.
“You connect [D1g1tal Dr1ve] to a high voltage battery and cooling lines, along with vehicle signal connections to its integrated computer, and you are ready to run,” explained Larry Kubes, Remy's Director of Systems Engineering. Since all high-voltage components for the drive are internal to the unit, it improves overall safety of the vehicle. The only high voltage connection is to the battery.
The motor also acts as a generator and charges the battery during regenerative braking or coasting or from an ICE as part of a series hybrid architecture. The company points out that all the electronics are mounted on a single chassis, allowing for installation or replacement in approximately 30 minutes.
The unit is designed to physically attach as the drive unit between two independently suspended drive wheels via standard CV shafts. “This system is for electric vehicles or range-extended series type hybrid vehicles,” said Kubes. Integrated into the unit is a differential, which could be upgraded to a limited-slip type.
Operating voltage is a nominal 320 volts, making it compatible with many existing high-voltage electric vehicle batteries. Peak efficiency of the integrated device is 90 percent and gear ratios will range from 6:1 to 10:1, according to Kubes.
While providing power, an in-unit computer also gives vehicle engineers control over the entire powertrain. A CAN communication bus is provided. This means the unit can manage the battery function, if needed. It also controls two drive units combined on the same axle for increased torque applications.
“A unit can be slaved to a master,” Kubes noted. A USB connection is used to input programs for specific applications. With its computer, engineers will be able to program the unit for different driving modes, such as a "sport" or "truck" mode, depending on use.
Either the USB or CAN bus provides display information to a digital display device—to an IP cluster, for instance.
The company points to a range of D1g1tal Dr1ve models in different stages of testing as of this writing. Future models will extend the D1g1tal Dr1ve range to include more powerful drives as well as a smaller, more compact option. The first model of D1g1tal DR1ve is intended for compact EVs and light-duty vans and trucks.
There are always trade-offs with a plug-and-play system, Kubes explained. The integrated device may not be ideally sized for a particular vehicle concept, for example, or the all-in-one packaging may not offer optimal vehicle package in certain applications.
The concept's advantage is in engineering speed to create an operational vehicle with reliability throughout the vehicle’s life cycle. “This is a good way to get started learning about hybrid and electric vehicles, because it is a system that will operate properly from the start,” remarked Kubes.