Electric and hybrid-electric technology enables a vehicle to run on either fuel or electric motors that use batteries. Increasingly, this technology is being adapted for use in military vehicles because it boosts the vehicles' fuel economy and reduces the need to refuel them.
In fiscal year 1993, the Defense Advanced Research Projects Agency (DARPA) began funding a program to develop electric and hybrid-electric military vehicles. Collaborative research and development efforts involving several Federal and municipal agencies and private-sector manufacturers led to proof-of-concept tests of various vehicles designed for military use.
Seven companies were selected competitively by DARPA to form a consortium to develop vehicles with electrical propulsion systems for the military. Between 1993 and 1998, this consortium collaborated with Government agencies on more than 300 projects. Pushing the limits of existing battery technologies was a key focus of those projects, but they also concentrated on developing hybrid-electric transmissions, auxiliary power units and motors, advanced battery and charger systems, flywheels to augment or replace batteries, and lighter materials to reduce vehicle weight.
DARPA transferred its Electric and Hybrid Vehicle Technology Program to the Department of Transportation (DOT) in fiscal year 1999, and the development projects continue under DOT's Advanced Vehicle Technologies Program. DOT, DARPA, and the Department of Energy have worked in partnership with the consortium to further the development of electric and hybrid vehicles. The Army Tank-Automotive Research, Development, and Engineering Center in Warren, Michigan, manages the hybrid vehicle program for the Army.
Two models of a hybrid-electric HMMWV in testing at the ATC's Churchville test site in Maryland.
The Hybrid HMMWV
One of DARPA's goals was to develop a hybrid high-mobility, multipurpose, wheeled vehicle (HMMWV) that would average 25 to 30 miles to a gallon of fuel, compared to about 15 miles per gallon for a conventional HMMWV. DARPA also asked for a vehicle that could run up to 25 miles on full electrical power.
Two versions of hybrid HMMWV's were developed and tested for over 18 months at the Army Developmental Test Command's Aberdeen Test Center (ATC) in Maryland. Each of the HMMWV's tested has a 1.9-liter Volkswagen diesel engine instead of the 6.5-liter V8 engine of a conventional HMMWV and lead-acid battery packs that provide electric power to the motors. One model has two electric motorsone for each axleand the other has four electric motors. The hybrid HMMWV's have alternators that recharge the batteries and provide propulsion power when the vehicles are powered by the diesel engine. When the engine is turned off, the vehicles can be operated in an all-electric mode.
To help the Army evaluate the vehicles' ability to avoid detection, ATC test engineers collected data on the vehicles' infrared heat signatures, noise, and electromagnetic characteristics when operating in electric and hybrid-electric modes. The tests also provided performance data on batteries, electric motors, vehicle handling, and other operational characteristics.
The joint tactical electrical vehicle (JTEV), which is a "purpose-built" hybrid reconnaissance or scout vehicle developed as a demonstration project for the Marine Corps in 1994, also was tested at the ATC.
AeroVironment, Inc., of Monrovia, California, designed the JTEV powertrain and control system, which the company integrated into a chassis custom-built by Rod Millen Motorsport. AeroVironment modified commercial off-the-shelf equipment so that it could withstand the shock and vibration of severe off-road driving. Diesel engines, electric motors, and batteries already used in the private sector were "ruggedized" so they could be used in a military environment.
The JTEV contains a 2.1-liter Peugot diesel engine and lead-acid battery packs that provide power to a magnetic drive motor on each axle. Manufacturers across the United States are working to develop lighter, more efficient batteries, and the JTEV is designed so the lead-acid batteries eventually can be replaced with improved battery packs. Using other, more exotic batteries, such as the nickel metal hydride (Ni-Mh) or lithium polymer (Li-Polymer), would decrease weight, increase payload capacity, and improve vehicle performance. Like the HMMWV's, the JTEV has an alternator that recharges its batteries and provides propulsion power when the vehicle is powered by its engine. When the engine is turned off, the vehicle can function in an all-electric mode.
The joint tactical electrical vehicle underwent more than a year of testing at the ATC.
Hybrid-electric technology offers the Army a feasible option for increasing system capabilities and reducing fuel costs. Other potential adaptations of hybrid technology include the M2 Bradley fighting vehicle, the M113 troop carrier, the parallel hybrid electric-line haul truck, and a hybrid member of the family of medium tactical vehicles. ALOG
The Army Logistician staff thanks Mike Cast of the Army Developmental Test Command Public Affairs Office at Aberdeen Proving Ground, Maryland, for his contribution to this article.