Test driving the UK's first range-extended series-hybrid truck from Tevva

Freight in the City's sister publication Commercial Motor took a JAC 7.5-tonner for a spin to see how it performed in an urban operation. Group technical editor Colin Barnett reports.

The current fashion for electrically powered trucks has invariably been accompanied by high-profile launches and promises that each new contender is THE answer. However, some have now been around long enough for the gloss to become dulled. Only a few weeks ago, we stumbled across a sound looking Modec abandoned on a Swindon industrial estate, presumably because it had become uneconomical to keep in service.

So it is refreshing then, to encounter a new contender which actually presents an honest view of its company business model and a realistic assessment of its product's potential. The company is Essex-based Tevva, which has so far built three development examples of what is the UK's first range-extended series-hybrid truck.

In hybrid-speak, a series-hybrid powers the vehicle entirely by an electric drive-line, as opposed to a parallel-hybrid which has a conventional internal combustion engine working alongside the electrics.

Whereas a regular electric truck is limited in range by its battery capacity, a range-extended series-hybrid similarly leaves the depot with a fully charged set of batteries, which are then topped up as required by a combination of regenerative braking and a generator driven by a secondary power unit.

In Tevva's case this is a 1.6-litre turbo-diesel from a Ford Focus, but it could be whatever power source best serves your operation. Diesel, natural gas, hydrogen or a small nuclear reactor, all you need is something to drive a generator in the way that suits you.

The power unit doesn't just charge the batteries, though. It can just as easily by-pass them to directly drive the traction motor, saving them for when zero-tailpipe emissions are required.

For example, take a hypothetical depot in Reading, and a delivery schedule involving Heathrow Airport and central London. The secondary power unit would provide direct electric drive along the M4, then change to pure electric around the airport, then secondary to continue the drive eastwards, and pure electric again in the centre.

The clever thing is that the driver doesn't have to choose, or indeed know, which method is being used. Pre-programmed GPS geo-fencing selects the appropriate source according to the truck's location.

And the beauty is that if the batteries become exhausted due to extreme cold weather, abnormal traffic, or any other unexpected factor, you can carry on going for as long as your secondary power unit has fuel, which is likely to be several hundred miles beyond the regular battery range. In the case of Tevva's demonstrator, this is around 100 miles, and few hundred more on diesel.

Does it work in real life? Well it seems to, as one of the three trucks is a UPS parcel van built on a ’61-plate Mercedes-Benz Vario chassis-cowl, and operated between Barking, Essex and East London on a regular delivery schedule.

The 80- to 100-mile route involves 100-plus drops, and while the conversion has a payload penalty of around 500kg, this isn’t a problem as the vans always bulk out first.

Using the range-extender for around 40-50% of the time, the overnight battery charge is saved for the city sections. In fact, the only problems with the operation have been when no-one has remembered to plug the van in for the overnight charge. Otherwise, feedback has been positive.

Extra maintenance is limited to an occasional squirt of grease for the motor and a six-monthly service on the little Ford diesel engine. Brake wear monitoring, however, is predicting a 50% increase in pad life, and UPS has even saved a bit more cash by finding new homes for the removed driveline components.

But is it economically viable? Here is where Tevva's financial realism comes into play, providing the answer "no, not at the moment!"

Although there is an eventual payback time of the £60,000 conversion cost, it's currently about nine years, well beyond the service life of most vehicles of this type. That's calculating the vehicle's costings on a straight operational basis, and is not an unusual state of affairs for new technology ahead of the inevitable economies of scale that will follow initial acceptance.

Currently it only makes economic sense when potential buyers fund the acquisition through their corporate responsibility budgets.

Tevva expects the next 20 or 30 sales to be from companies that can afford some flag waving, but realises that isn’t the answer. Looking ahead, Its target is a 25% saving on total cost of ownership over a five-year vehicle life, which it expects to achieve within three years. Like the rest of the industry, Tevva is still waiting for the desperately needed breakthrough in providing a cost effective increase in battery storage density.