Mitsubishi have been prominent in hybrid pickup truck manufacture and have recently developed a heavier, municipal, version of the light hybrid truck launched in 1995. Because added cost limited market acceptance of the lighter, Canter-based, hybrid the decision to build a heavier municipal version, below Figure was taken on the grounds of low noise, and greatly reduced emissions, which made the vehicle attractive for city-centre operation, a lift-platform version being particularly popular. The hydraulic pump for operating auxiliaries such as a lift platform is electric motor driven, with the benefit of near silent operation.
Series hybrid mode, (a) was chosen first, because the engine is used solely for power generation and so can be operated in a peak efficiency speed band and secondly, since the engine is isolated from the drive system, it results in a simpler and more flexible drive-system layout with greater freedom for hydraulic equipment mounting. Two electric motors are involved. typical operational modes of the truck: when the battery has high SOC the vehicle operates exclusively in battery mode. At less than 65% SOC the power-generating engine starts and hybrid mode is invoked; when 70% SOC is achieved again the vehicle reverts to battery operation. Provision is also made to inhibit hybrid operation until 30% SOC is reached so silent and zeroe mission night-time, or in-tunnel, operation is made possible. In hybrid mode SOC is maintained at 65–70%, at which point the generated power, from the generator, and the regenerative power, from the motor, provide sufficient charging.
The overall hybrid pickup truck package layout is shown at (c); dimensions are 5.78 m long 1.88 m wide 3.35 m high, with a wheelbase of 2.5 m. Gross vehicle weight is 6.965 tonnes and tyre size 205/85R16. While an elevating platform vehicle normally requires counter weighting, in this case the mass of the dual drive suffices with just modest additions. The central positioning of the battery above the chassis frame was chosen to optimize weight distribution and avoid the weight of cantilever frames. The motors, of 55 kW, are of the induction type and each develop 150 Nm at 3500 rpm, rated voltage being 288 V. The simple two speed transmission has a PTO for driving the hydraulic pump and reverse motion is achieved by altering the rotation of the electric motor. The generator has a maximum output of 30 kWat 3500 rpm; it operates at 220–360 V and weighs 70 kg.
The petrol engine is a 16 valve unit of 1834 cc which has a 1.935:drive gear to the generator. Lead–acid traction batteries are employed, 24 units each weighing 25 kg and having 65 Ah capacity at a 5 hour rate.