BAE Systems

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BAE Systems is a defense, security, and aerospace company based in London, England. Electronic Systems, BAE's electronics division based in the United States, offers a hybrid system for trucks and buses. BAE has supplied propulsion systems to Alexander Dennis, ElDorado National, Gillig, Irisbus, Iveco Bus, New Flyer, Nova Bus, Orion, and Solaris Bus & Coach.


Initially developed by Lockheed Martin, the BAE Systems HybriDrive, is a series hybrid-electric vehicle system. BAE Systems acquired the product after purchasing parts of Lockheed Martin in 2000. The hybrid system was formally introduced in 1998 on a batch of Orion VI buses built for New York City. It remained largely exclusive to Orion buses, but has since become an option for multiple manufacturers. The HybriDrive system was initially used in 30 to 40 foot North American buses. In 2011, BAE launched a HybriDrive system for 60 foot North American buses, which was able to be used on vehicles with gross vehicle weight ratings of up to 63,000 lbs.[1] A HybriDrive system for lightweight European buses was launched the following year.

The HybriDrive system features a generator that is powered by a diesel engine, which is usually smaller than what would be used on a conventional diesel vehicle. The generator powers an electric motor which drives the vehicle. When the bus slows down, the motor recaptures the energy which is then stored in batteries for later use. The HybriDrive system initially used Sealed Lead Acid batteries, but BAE Systems switched to Lithium-ion batteries in 2007.

The HybriDrive system is capable of powering electric vehicle accessories, via the Accessory Power System (APS). APS1 functions as an electronic alternator to power conventional 28Vdc electric loads, such as cooling fans and pumps. APS2 provides electrification of additional larger accessories such as air compressors, power steering, and air conditioning. APS3 allows for the ability to power two accessories or two groups of accessories independently from each other.

BAE Systems introduced their third generation Modular Accessory Power System in 2021. The new system uses silicon carbide to improve heat management, lower weight, and increase power density. Wide band gap transistors with gallium nitride are used to provide faster switching, generate less heat, as well as decrease power losses and component size. They also introduced their new Modular Power Control System which provides power for central motors while also accommodating the power requirements of wheel hub motors, electric heaters, battery pack combiners, and fast and slow charging.

GEN2 specifications

GEN3 specifications

HybriDrive Series-E

Launched in 2012, Series-E allows the bus to operate strictly on electricity for a limited period of time. The system can shut off the engine when idling or picking up passengers, and it can shut off the engine and run the vehicle on electricity in environmentally restrictive or sensitive areas. APS2 functions as an electronic alternator to power all of the bus's accessories.

HybriDrive Series-ER

Series-ER (extended range), allows for extended electric-powered travel time and distance without charging and the associated equipment. The engine can be shut off for extended periods of time. The battery is larger than that used on the Series-E. APS2 is available to power large accessories, and APS3 is available to power multiple accessories at various times. King County Metro is one of the first operators to specify the Series-ER. They require buses to operate through the Downtown Seattle Transit Tunnel. Because of the confined space, emissions need to be kept at a minimum.


Series-EV is the fully-electric drive system, eliminating the internal combustion engine. The addition of larger batteries, which store more energy, provide a desirable range. The system can be fully recharged by plugging it in at the depot overnight as well as charging wirelessly enroute. Regenerative braking recaptures braking energy, storing it in the energy storage system for use later.

On November 5, 2016, the Central Contra Costa Transit Authority unveiled the first fully-electric buses powered by BAE Systems. The four 29-foot Gillig Trolley Replica buses were funded in part by a grant from the Federal Transit Administration.[2]

In 2019, Nova Bus launched the LFSe+, a long range battery-electric transit bus. The LFSe+ uses BAE Systems Series-EV drivetrain. Milwaukee County Transit System was the first to take delivery of the LFSe+ in November 2022.


Series-H is the hydrogen fuel cell electric hybrid system. Electricity is produced by the hydrogen fuel cell, which along with high voltage batteries, provides propulsion to the wheels and power to accessories. Like the standard HybriDrive with an internal combustion engine, regenerative braking captures kinetic energy and stores it in the batteries. The vehicle has the limited capability to travel solely on electricity. The first bus was produced for SunLine Transit Agency in 2011 in partnership with Ballard and ElDorado National.[3]

HybriDrive Parallel

In February 2011, BAE Systems launched a parallel hybrid system for heavy-duty trucks. This system is designed for vehicles with duty cycles that require higher operating speeds and less frequent stops. BAE Systems's integrated starter generator (ISG), which consists of both a motor and generator, is placed between the engine and transmission. The integrated electronic unit (IEU) controls the optimized blending of engine power and electric power. Energy during deceleration is captured and stored.[4]


  1. BAE Systems launches HybriDrive® series for articulated buses. 03 October 2011. Press release. BAE Systems.
  2. Zero-emission Buses in Service at Walnut Creek. Press release. BAE Systems, 31 Jan. 2017. Web. 15 Feb. 2017.
  3. BAE Systems Delivers Hydrogen Fuel Cell Bus for Sunline Transit,, retrieved on 2011-11-29
  4. BAE Systems launches Hybridrive® Green Parallel Propulsion System for Trucks at National Truck Equipment Association Work Truck Show. 09 February 2018. Press release. BAE System.