Allison EP System

From CPTDB Wiki
Jump to: navigation, search

The Allison Hybrid EP System is a two-mode compound split parallel hybrid electric system for diesel vehicles. The system is comprised of a a dual pulse interval modulator (DPIM2), Panasonic nickel metal hydride (NiMH) energy storage batteries, a control module, and an electric drive called the EV Drive. The hybrid system was originally known as the EP System with the "Hybrid" added and the "P" no longer stylized in superscript later in 2010.

The DPIM2 unit is usually located behind the NiMH batteries on the roof. It converts energy that is transferred between the drive/generator, which uses and produces alternating current (AC), and the batteries, which store direct current (DC). The energy stored in the batteries is produced through the generator connected to the diesel engine and though regenerative braking. Prior to the launch of the 2010 model, the Hybrid EP System used Allison's DPIM. This was replaced by the current DPIM2 which has more robust internal hardware and enhanced redundancy for greater reliability.

The Hybrid EP Drive Unit (originally known as the EV Drive) is an infinitely variable transmission in common with the Allison Bus Series. The Drive Unit is equipped with planetary gears and clutches and electronic solenoids and motor/generator. The generator/motor acts as variable clutches and controls the the planetary components.

Allison announced in December 2009, that for 2010, the EP System for buses and coaches will feature new and improved components for greater reliability, durability and performance.[1]The 2010 EP System will use Allison's Fourth Generation Electronic Controls which has greater processing power and memory capability. It also features a revised DPIM, improved energy storage system (called ESS2), and updated 2010 EV Drive for 2010-compliant engines. This system received its present name in 2010 and the drive motor and system designations were renamed.

Type Max. input tower of Drive Unit Max. input torque of Drive Unit Available engines Mass of Drive Unit (dry) Notes
H 40 EP 280 hp (209 kW) 910 lb-ft (1235 Nm) Cummins ISB 280 hp (offered by ElDorado, Gillig, Nova, NFI, and Optare)
Cummins ISL 280 hp (offered by NFI and NABI)
919 lbs (417 kg) Originally known as EP40 System
H 50 EP 330 hp (246 kW) 1050 lb-ft (1420 Nm) Cummins ISL 330 hp (offered by ADL, MCI, NFI, NABI, and Nova)
Caterpillar C9 330 hp (formerly offered by NFI and NABI, no longer offered as of 2010)
919 lbs (417 kg) Originally known as EP50 System


  1. 2010 Allison Hybrid EP System,, retrieved on 2010-01-29