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BAE Systems Introduces Improved Version of HybriDrive

BAE’s HybriDrive applied in an inline configuration in a Daimler Buses North America Orion VII NG (next generation). Click to enlarge.

BAE Systems introduced an improved version of its series hybrid propulsion system that can be used on multiple bus platforms, is mechanically simpler, reduces maintenance costs, and makes possible the use of electric accessories. The company unveiled the latest HybriDrive system at the American Public Transportation Association’s Annual Meeting and Exposition in San Diego.

Based on the company’s series diesel-electric hybrid technology already in use, the new system can be configured with the diesel engine and generator arranged inline or transversely to make it adaptable to a wider range of bus models. It also can generate power for electrically operated systems such as air conditioning, power steering, engine cooling, and lighting, serving these electrical loads without belt-driven alternators.

The system consists of a generator, an electric motor, and an energy storage system. A diesel engine that turns the generator operates independent of the electric drive motor, allowing it to run at nearly consistent speed for optimum efficiency. The system uses no mechanical transmission, a major maintenance item on traditional diesel buses.

The optional accessory power system in the new configuration can further improve efficiency and reduce maintenance by eliminating alternators and their associated pulleys and belts. The system can produce up to 27 kW of electricity to run vehicle accessories and to enable the bus to be operated for brief periods in zero-emission mode, with the engine off. It also combines the starter and generator to eliminate the starter motor and flywheel, making the system simpler and lighter and further reducing maintenance requirements.

Buses equipped with the new hybrid system also will use a lithium-ion energy storage system that increases battery life and reduces vehicle weight, improving fuel economy and reducing emissions. The battery system is self-monitoring and easy to service for further savings in maintenance costs.

Applied in the Daimler Buses Orion VII NG (Next Generation) bus, the BAE hybrid system uses an inline configuration and features:

  • ± 200 kW peak Li-ion battery pack with A123Systems cells;

  • ± 200 kW propulsion control system;

  • 160 kW (215 hp) continuous, 200 kW (268 hp) peak traction motor;

  • 200 kW integrated starter/generator;

  • 6.7-liter 280 hp@ 2,300 rpm diesel engine; and

  • 28 VDC and 208 3-phase AC auxiliary power system.

Applied in the double-decker Enviro400 from Alexander Dennis, the BAE hybrid system uses a transverse configuration and features:

  • ± 200 kW peak Li-ion battery pack with A123Systems cells;

  • 320 kW continuous propulsion control system

  • 120 kW (160 hp) continuous, 175 kW (235 hp peak) motor with 425 Nm continuous, 650 Nm for 4 minutes, 900 Nm peak;

  • 145 kW generator, including starter; and

  • 4.5-liter 185 hp ISBe Euro 4 engine with SCR.

More than 1,500 buses powered by the HybriDrive system transport more than a million passengers daily in cities such as New York, San Francisco, Toronto, and London. To date, these buses have logged more than 70 million miles of revenue service. BAE Systems provides the systems for buses built by Alexander Dennis Limited, Daimler Buses North America, and New Flyer Industries.

Separately at APTA, Engineered Machined Products Inc. (EMP) announced that it is collaborating with BAE Systems on next-generation thermal management solutions for the hybrid municipal transit bus market.

EMP has developed a robust custom cooling system for hybrid electronics and motors specifically for BAE Systems’ needs. The cooling system introduces fully-controllable, long-life electric fans along with brushless electric water and oil pumps.



Apparently BAE just transfered this series hybrid technology from military trucks developed for US army. BAE is first and foremost a weapon systems company, not a green energy one.
There they use that truck (when stationary) as power generator for radars etc.
Additional benefit of series hybrid in military service is that it provides short range stealth mode.

Henry Gibson

MES-DEA has a much larger market with the TH!NK but any large bus or military vehicle should use the ZEBRA battery that has been in use for over ten years in buses and does not have the cooling problems that LiIon batteries have. Salt, nickel, iron and aluminum are much more available than lithium. Perhaps the competition with lithium will force MES-DEA to produce the ZEBRA battery at a price similar to what it promised years ago.

The ZEBRA battery solved the distance problem for electric vehicles ten years ago, but not even the 60 Minute report on electric cars mentioned it. Plug in hybrid vehicles are the answer. They can be made with modern techniques like the EFFPOWER unit. Firefly has the slightest clue that most of the required volume for lead batteries is the acid solution. They also have a clue that using lead for conductors limits the power, but they dont have a clue about actual getting into large scale production of anything. Their improved positive grid coating is usefull enough but they obviously want a fortune for it.

This hybrid could use EFFPOWER batteries at less cost and lower fire risk if EFFPOWER ever put its units into mass production. There is no need for Lithium batteries in hybrid and some plug in hybrid vehicles. Flywheels are quite nice. It is interesting that Caterpillar is the initial support for both Active Power Flywheels and Firefly. At least Active Power delivers. ..HG..


For those who are interested here is a good presentation on the Orion bus. Among other issues there is a life cycle analysis of cost using lead acid versus lithium batteries and lithium is about $25000 less costly than lead acid for the bus company. They also give information that shows they use about 80kWh of battery although it is not directly stated.


San Diego and Beijing are on a good thing.

I wonder why he battery / power conroler would be on the roof? Makes no sense I can think of.

Could be interesting for servicing esp a Double decker.



Stuff is on the roof because the packaging space is available without impacting passenger compartment, and with an overhead crane it is easy to exchange. Probably also for additional good reasons.


I saw the BAE stuff in San Diego, and here are some more tidbits - the battery pack is relatively small, around 8kwH, and uses the old A123 batteries in DeWalt packs (there was a display model, and you could see them). It is mostly like a big supercap for temporary energy buffering. 7kWh isn't going to get you too far on all-electric running which I'm interested in-

The engineers said however that the total system can easily accomodate any size or type of batteries with just software changes, so maybe it is usable.

ProTerra exhibited their fiberglass bus, and claimed to be using NanoSafe batteries (42kWh?). They put a bunch of packs underneath the floor to distribute the weight and lower the center of gravity. In Italy, ATAC put the batteries of the #90 express under some of the seats in the front to spread out the weight.

Designline wouldn't say what batteries they were using, but their system looks very good for a Nanobus.

There were lots of hybrids, but mostly using the Allison parallel system, which is unsuitable for a Nanobus, as you can't go all-electric mode.

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