Daimler Chrysler took the opportunity of its announcement to point out that it was the only major automaker actively building and testing plug-ins with lithium-ion batteries in customer fleets—an indirect swipe at the publicity generated by GM’s Volt concept plug-in unveiled at the North American International Auto Show. Unlike the Volt, with its electric-drive-only series hybrid architecture, the Sprinter PHEVs are parallel hybrids, offering a combination of electric and mechanical drive.

The future of plug-in hybrid technology rests on a number of improvements, the most significant being batteries. The battery systems in the PHEV Sprinter continue to provide valuable data on the possibilities with lithium-ion technology.

—Dr. Andreas Truckenbrodt, Executive Director, DaimlerChrysler Hybrid Programs

A number of the Dodge Sprinter PHEVs are equipped with lithium-ion batteries which are about half the weight and have much greater storage capacities compared to nickel-metal hydride batteries. Some of those li-ion batteries are from Saft, who in its joint venture with Johnson Controls is providing li-ion battery packs to GM for assessment in the VUE plug-in program.

The Sprinter vehicles in testing will yield technical information through real world driving conditions about lifetime, performance and cost of batteries.

One of the critical issues especially facing makers of parallel architecture PHEVs is the nature of the operating strategy, i.e., should the vehicle be designed to deliver a fixed all-electric, zero-emissions range (ZEV VMT), or should it operate in a blended strategy, in which the battery energy is equivalent to the ZEV VMT model, but in which the electric drive operates in support of the mechanical drive, rather than all alone.

The series hybrid approach represented by the Volt and by the concept Ford Airstream puts a different wrinkle on the problem, although in both designs there is still an urgent and compelling need for real-world testing and data gathering.

At the California Air Resources Board Zero Emissions Vehicle symposium in September 2006, Dr. Mark Duvall outlined the basic pros and cons of the all-electric and blended strategies for parallel PHEVs (see table below), noting that the blended approach could likely support a lower-cost, nearer-term commercial product. However, real-world data is critical for making that determination.

There is a difference between test cycles and real world driving which will determine electric-operation and the user’s experience. Even modest levels of electric performance could result in numerous all-electric trips or electric vehicle miles.

—Mark Duvall

Based on Mercedes-Benz commercial vehicle technology, the Dodge Sprinter PHEV has the ability to drive up to 20 miles in all-electric mode. A switch on the dashboard allows the operator to manually switch between modes as needed, or automatically by the vehicle control system.

Two different combustion engines are being offered in the PHEV: diesel or gasoline. The diesel version will yield the highest fuel economy benefit and is the first fleet test of a diesel plug-in hybrid system.

Resources:

• Plug-In Hybrid Electric Vehicles Technology Challenges (Mark Duvall, EPRI)

• Plug-in Hybrid Sprinter Van Program (Matt Miyasato, SCAQMD)