Drive System for First ThunderVolt Hypbrid-Electric Transit Bus Completed

Electric Vehicle Product Update from ISE Corporation
Volume I, Issue 2 * 1998.10.01

On 20 October 1998, the world's newest hybrid-electirc transit bus moved closer to operational status with completion and integration of the first advanced ThunderVolt TB30H hybrid-electric drive system, developed and manufactured by ISE Research Corporation to meet the need for cleaner, more fuel-efficient transit buses.

On 20 October 1998, the world's newest hybrid-electirc transit bus moved closer to operational status with completion and integration of the first advanced ThunderVolt TB30H hybrid-electric drive system, developed and manufactured by ISE to meet the need for cleaner, more fuel-efficient transit buses.

Engineers and scientists at the ISE Research Prototyping Facility in San Diego successfully installed the ThunderVolt drive system into a 30-foot transit bus chassis provided by ElDorado National. The completed chassis, pictured below, was shipped to the ElDorado factory in Chino, California for integration of the bus body. The bus is scheduled to enter operational service in downtown Los Angeles in January 1999.

The ElDorado-ThunderVolt bus represents a major step forward in development of clean alternative fuel transit vehicles. The advanced hybrid-electric drive system developed by ISE Research uses a distributed computer network to operate a clean burning propane engine in conjunction with an electric drive system, combining the best features of conventional internal combustion and electric vehicles.

ADVANCED BATTERY SYSTEM

• 48 sealed lead-acid batteries(maintenance free)
• Powers bus all-electrically, (no fuel consumption or emissions) during peak periods or in congested areas
• Automatically recharged by clean burning propane-fueled engine when battery charge runs low

The engine in this "series hybrid" configuration can be much smaller than engines used in avehicle of equal size, since the hybrid engine is used only as an auxiliary power unit (APU),generating electricity to augment and recharge the batteries. Further improving fuel economyand emissions, the engine is run at a constant, efficient speed. Preliminary tests of the installed drive system indicate this bus will produce, on average, less than 1 gram per mile of nitrous oxide, compared with 20-30 grams/mile for a typical transit bus.

• General Motors 5.7 liter V8 engine converted to run on propane (any fuel can be used)
• Small, permanent magnet generator provides up to 80 kW electric power
• Power routed to main drive motor and/or batteries as required
• Engine and generator controlled by custom-designed "APU node" microcomputer

The main drive motor in the ElDorado-ThunderVolt bus is an efficient Siemens AC induction motor with a peak power output of 140 kW, maximum speed of 5,000 RPM, and an efficiency of 94%. More powerful motors are available for larger bus applications.

MOTIVE DRIVE SYSTEM

• Siemens AC induction motor
• Peak power rating of 140 to 300 kW
• Air-cooled, low maintenance system
• Customized 2-speed gearbox

The ThunderVolt motive drive system is customized to each vehicle's acceleration, topspeed, and hill-climbing requirements. The electronic motor controller is programmed to provide fast, smooth acceleration. A regenerative braking system utilizes the motor to recapture electrical energy during braking. Dashboard controls allow the driver to select the desired level of regeneration, with recaptured energy used to recharge batteries.

MOTOR CONTROL SYSTEM

• Programmable acceleration profiles
• Adjustable regenerative braking
• All major vehicle controls located in one easily accessible console

In the innovative ThunderVolt adaptation of LonWorks distributed network technology, microprocessor "nodes" using a common base design are attached to each major component.

A central node at the vehicle dashboard control panel displays the status of each vehiclesystem to the driver. This distributed network approach simplifies diagnosis and maintenance, and allows maximum interchangeability of components.

The integrated chassis recently delivered to ElDorado National will be outfitted by ElDorado with an RE-29-E bus body (pictured below) by the end of this year.

Following run testing and fine-tuning of the vehicle controls in January 1999, the bus will be placed into regular operational service in the Chinatown district of Los Angeles. ISE Research and ElDorado have begun construction of a second bus, which will be deployed on the same L.A. route next March. The current bus program calls for a total of five hybridelectric buses of this model to be built and placed into service over the next year.

Funding for this five-vehicle Los Angeles hybrid-electric transit bus demonstration project is being furnished by the Los Angeles Department of Transportation, the Mobile Source Reduction Committee, and the Federal Transportation Administration via the CALSTART advanced transportation consortium.

The ThunderVolt hybrid-electric drive system can be installed in transit buses ranging in size from 22 to 40 feet in length, and with gross vehicle weights up to 40,000 lb. and above. A half dozen major variants of the ThunderVolt drive system, including both hybrid-electric and all-electric configurations, have been developed by ISE Research and demonstrated in trucks and tractors with weight ratings up to 80,000 lb.

 

Preliminary Bus Specification                                                                     

Power (peak): 200-500 Hp

Acceleration (0-50 mp): 40 seconds 

Range: 150-300 miles

Fuel type: Propane, CNG, LNG, or diesel

Transmission: Automatic

Battery type: Sealed lead-acid

Number of batteries: 48

Charger: 20 kW onboard or offboard

Emissions - NOx: < 1 gram/mile