ThunderVolt Hybrid-Electric Tow Tractor Completes First Phase of Operational Testing

Electric Vehicle Product Update from ISE Corporation
Volume II, Issue 3 * 1999.11.15

On 23 October 1999, the world's first hybrid-electric aircraft tow tractor successfully completed its first 100 days of operational service at North Island Naval Air Station in Coronado, California. The ISE Research ThunderVolt hybrid tractor, using an Entwistle Company MB-4 tow tractor chassis, is the first of three such tractors to be placed into service with the United States Air Force and United States Navy in 1999. The second and third tractors in the series are slated to be delivered to Air Force bases in Florida and Virginia during the last six weeks of 1999.

During its first 100 days of service, the first tractor in this series clearly demonstrated the ability to outperform equivalent diesel and alternative fuel tow tractors. The tractor was designed to tow aircraft as large as the Air Force C-130 cargo plane, which weighs as much as 180,000 lb. fully loaded. In testing, the ThunderVolt-equipped hybrid tractor has shown it has the capacity to pull loads up to 240,000 lb. In addition to exceeding the design requirement by one-third, this surpasses the performance of the standard diesel MB-4 tow tractor by 50%.

The high performance of the ThunderVolt hybrid tow tractor is made possible by the use of a high power "industrial strength" AC induction motor adapted for electric vehicle use by a team of ISE Research and Siemens technologists. The high torque 100 kW motor at the core of the ThunderVolt TB-MTH drive system was originally developed by Siemens for heavy industrial machinery, but also employs precision control capabilities that ISE Research has exploited to create a remarkably versatile vehicle drive system.

The ISE Research ThunderVolt drive system has several other features that are enabling hybridelectric technology to be successfully applied to a wide variety of heavy duty buses and trucks, as well as tow tractors. The ISE Research system employs an inexpensive pack of maintenance-free lead-acid batteries, augmented by a small, efficient internal combustion engine that supplies onboard electrical power. The ThunderVolt tractors use the Cummins 5.9 liter diesel engines that are normally installed into the MB-4, but have shown that they could be operated with much smaller engines.

A unique feature of the ThunderVolt hybrid tractor is engine "Auto-Control." An onboard computer network continuously monitors vehicle power and battery charge levels, and adjusts the electrical output of the engine-driven generator to provide the right amount of power to operate the vehicle. In fact, the onboard computers shut off the engine completely when its power is notneeded, enabling the vehicle to function as a zero emissions electric vehicle. The hybrid MB-4 tractors can operate continuously for up to two hours at a time without activation of the engine. Since the vehicle can be plugged into a normal electrical outlet for recharging between each aircraft tow, it can often be operated for an entire day without the engine ever being utilized.

ISE Research/ThunderVolt drive systems can be installed into virtually any type of heavy duty vehicle. ISE Research has developed variants of its ThunderVolt drive system for 30 and 40-foot transit buses and Class 8 trucks. With completion of the third hybrid MB-4 tractor later this year, ISE Research will have built a total of ten hybrid-electric demonstration vehicles in 1999, including four 30-foot transit buses and three Class 8 trucks, in addition to the three military tractors. The buses are presently being operated in downtown Los Angeles by the Los Angeles Department of Transportation, and the trucks are undergoing operational testing at ISE Research facilities in San Diego.