Allison eGen Flex, new electric hybrid bus system with zero emission capabilities

Allison Transmission announces the launch of eGen Flex, its new zero emission-capable electric hybrid system addressed at the bus market. The US operator IndyGo has signed an order for the H 40 EP electric hybrid propulsion solution to power 27 new buses.
The eGen Flex will stand out for being the initial product offering under its new Allison eGen brand. The new system provides bus fleets with full electric engine-off propulsion and accessory power operation capability, ideal for zero-emission zones and depot operation, including when approaching, during, and leaving passenger stops for a quieter and healthier environment. The eGen product family will include Allison’s portfolio of electric hybrid and full electric products, including the company’s portfolio of electric axles, the supplier points out.

Allison eGen Flex hybrid system

The eGen Flex electric hybrid system includes an innovative new drive unit, inverter and rechargeable energy storage system. The drive unit includes a disconnect clutch that enables engine-off capability. The inverter has an innovative package improvement that reduces its footprint and weight. The inverter is now water ethylene glycol (WEG) cooled, which eliminates oil lines, decreasing installation complexity, reducing maintenance expense, and increasing uptime. The energy storage system incorporates the latest Lithium Titanate (LTO) technology, which significantly increases energy density, allows for faster charging and enables pure electric (engine off) extended range capability.

Two models under Allison eGen Flex range

With the launch of eGen Flex, Allison points out it will be offering two distinct models, namely eGen Flex and eGen Flex Max.

eGen Flex will be similar in feature set and capability to the Allison H 40/50 EP electric hybrid propulsion system, but with the package enhancements summarized above.

eGen Flex Max will offer fully electric propulsion for up to 10 miles, dependent upon duty cycle and accessory load requirements.

eGen Flex and eGen Flex Max will be offered in CertPlus model configurations for sale in California Air Resources Board (CARB)-adopting states. Similar to the existing H 40/50 EP nomenclature, eGen Flex and eGen Flex Max will also be available in “40” and “50” configurations based on fleet torque requirements. Increased Accessory Power 2 will be available with eGen Flex, and will be required with eGen Flex Max. This capability electrifies vehicle accessory systems, such as air conditioning and electric heat, allowing those accessories to operate at their optimal efficiency point, and with clean and quiet electric power, thus reducing emissions and strain on the engine, thereby protecting our environment. Allison is engaged with transit Original Equipment Manufacturers (OEMs) and transit fleets to support a scheduled 2021 commercial release of eGen Flex.

Allison hybrid system, a bridge towards full electric

“Allison understands that there is significant interest in electrification,” said Branden Harbin, managing director of global marketing at Allison Transmission. “We also understand that fleets are reluctant to go all in on electrification at this early stage. That critical feedback from our customers is what inspired Allison to deliver this enhanced capability for coach and transit buses, effectively serving as a bridge solution between conventional fuel and full electric solutions. eGen Flex will enable transit fleets to evaluate electric capability and their electric range needs, while still having the peace of mind of a diesel range extender, whether needed for longer routes, for route flexibility, unplanned congestion on routes, or an inability to recharge due to power grid challenges.”