PHEV – an exercise in technology

The big news from Mitsubishi is the new Outlander PHEV plug-in hybrid, which is causing quite a stir – in fact Daniel Cook, head of sales and marketing strategy, told me that the PHEV was driving sales of other Mitsubishi products, particularly the “ordinary” Outlanders, as many more people than usual were visiting dealer showrooms to see the hybrid.

And it’s a fascinating vehicle, with lots of twists and turns in its technology, all designed to make the transitions from one state to another so seamless that the driver and passengers never notice.

In fact it’s simplicity itself to drive, with just one lever that’s marked D and R, and a button you press for Park.

One of the reasons for this is that there’s no transmission at all, even though sometimes the two-litre Mivec 4B11 “range extender” petrol engine may be driving the wheels direct. But obviously that’s only at higher speeds. Most of the time it’s driving a big generator mounted just in front of the engine, and the generator charges the battery pack.

So here’s the buzz. The PHEV has two big electric motors mounted back and front, and these drive each pair of wheels via ordinary drive shafts so that the vehicle is always in all-wheel drive.

Electricity comes from the centrallymounted battery pack, giving great 55/45 weight distribution for better handling, and this battery pack is in turn topped up by either braking kinetic energy, or from the petrol engine mounted in the normal underbonnet position.

It can also be charged up by plugging the supplied cable and docking handle into an ordinary 13A household plug socket – but it’s preferable nothing else is plugged in on that socket as it draws 10A while charging.

If you want (but you don’t have to) you can set your charge time via an application on the in-car system, or better still, you can download a free app. for your iPhone or Android phone that will allow you to do this remotely.

In fact, by using the phone app you can do a lot of things, such as switching on the heater or the aircon so the car is the right temperature when you get into it.

Charging the batteries takes about six and a half hours, and that gives enough range for about 60km of beautifully quiet and pollution-free electric-only driving, with the range constantly shown on the dash display. The display also shows the range to be expected if the petrol engine is used.

But here’s the best bit. The computer inside the car calculates if the electric motors need help from time to time, and the petrol engine can kick in to give the batteries a boost – or as mentioned, when cruising at high speed, may even drive direct. There are three drive modes: The first is EV Drive Mode. This is the all-electric mode in which the front and rear motors drive the vehicle using only electricity from the drive battery, with zero on-road petrol consumption and zero CO2 emissions.

Then there’s Series Hybrid Mode, where the petrol engine operates as a generator supplying electricity to the electric motors. The system switches to this mode when the remaining charge in the battery falls below a predetermined level, and when more powerful performance is required, such as accelerating to pass a vehicle or climbing a steep gradient such as a slope.

The system switches to Parallel Hybrid Mode when the vehicle reaches high speeds. In this mode the high-efficiency petrol engine provides most of the motive power, assisted by the electric motors as required, such as when more powerful performance is required to accelerate or climb a slope.

Apart from charging at a plug socket, the vehicle can be switched to Battery Charge Mode, which allows electricity to be generated by the engine and stored when stationary or on the move (giving 80 percent charge in approximately 40 minutes when stationary), and Battery Save Mode, which maintains charge while driving.

The drive battery is a high-capacity lithium-ion battery developed for the PHEV System based on the technology used in the i-MiEV. It consists of 80 cells mounted in series housed in a battery pack enclosed in a secure frame, and has a total voltage of 300V and total storage capacity of 12kWh.

The motors are smaller, lighter, higher output versions of the permanent magnet synchronous motors used in the i-MiEV and have a maximum output of 60kW each, with maximum torque of 137Nm (front),and 195 Nm (rear).

As mentioned, the 87kW 4B11 twolitre inline-four petrol engine functions solely to generate electricity in Series Hybrid Mode and is mainly used to provide motive power in Parallel Hybrid Mode. It is fitted with MMC’s Mivec 8 technology, which keeps the engine in optimal efficiency ranges by continuously varying the timing of the air intake valves according to engine speed in Parallel Hybrid Mode.

Additionally, exhaust noise has been reduced and the engine compartment soundproofing increased to ensure the vehicle remains as quiet as EV Drive Mode, even when the engine is in use.

Taking advantage of the fact that electric motors require no complex transmission mechanisms, the front and rear transaxles incorporate simple single-speed fixed reduction gears for smoother travel free from “shift shock.”

The front transaxle also has a builtin clutch that switches the system to Parallel Drive Mode mainly for enginepowered travel at high speeds.

Leveraging its proven expertise in 4WD control technology, MMC has developed the new Twin Motor 4WD system that delivers power independently to the front wheels (from the front motor and/or engine) and rear wheels (from the rear motor).

The use of electric motors and absence of mechanical connections such as a propeller shaft mean the Twin Motor 4WD delivers better response and finer control than conventional 4WD systems, and reduces friction loss.

Twin Motor 4WD is coupled with MMC’s S-AWC (Super All Wheel Control) integrated vehicle dynamics control system, which combines front and rearwheel drive control and left and right wheel brake control to provide consistent handling and stability on the road.

Two modes are offered, selectable at the flick of a switch: Normal mode for ordinary conditions and Lock mode for enhanced all-terrain performance.

During deceleration, the motors function as generators so that electricity can be generated to charge the drive battery.

The regenerative braking can be increased when the brake pedal is pressed, and the strength of regenerative braking is adjustable using a selector lever, which has three strength settings, or a paddle selector on the steering wheel which offers six strength settings.

The regeneration level can be selected as the driver likes according to road conditions, such as when approaching a bend or descending a mountain road, or when seeking a sportier ride, allowing the driver to get just the right amount of desired brake force from the system.

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