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Electric shock: battery power is back

John Deere unveils a prototype electric battery-powered tractor in Europe

Just as we’d got used to the idea that hydrogen is the fuel of the future for electrically-driven tractors — according to New Holland’s agenda at least — up pops John Deere with a prototype that puts battery power back in the frame.

The people behind the project say it’s the first fully electric battery-powered high-performance tractor providing comprehensive functionality for agricultural applications.

Inevitably, the prototype tractor is identified by an acronym: SESAM — Sustainable Energy Supply for Agricultural Machinery.

It’s the result of a research project carried out in co-operation with the Kaiserlautern technical research university located 60 km west of John Deere’s European tractor factory in Mannheim, and a Munich-based energy research consultancy. The project has received financial support from the German government.

The prototype is based on a Mannheim-built John Deere 6R Series tractor. Beneath the hood, where a diesel engine normally resides, is a 130 kWh, 670V Li-ion battery system.

Power control electronics and a battery management system are installed where the exhaust and emissions control technologies are normally located.

The battery powers a pair of 150 kW (200 hp) electric motors coupled to the tractor’s regular DirectDrive 24-speed powershift transmission. The motors can be linked to temporarily increase the power of the drivetrain up to 300 kW (400 hp), either for transport or for PTO and hydraulic work.

But in standard operating mode, one motor is used for traction, delivering 130 kW of continuous power, while the other drives the hydraulic pumps and power take-off.

One of the attractions of using electric motors in this way is the ability to reduce the speed of the auxiliary drives in partial load conditions.

The 130 kWh, 670V Li-ion battery system comfortably fills the space vacated by the diesel engine.
photo: John Deere

Also, being able to vary the power take-off speed continuously and independently of the driving speed could be useful in saving energy and fine-tuning seedbed quality when using a tiller or power harrow.

At present, one battery charge lasts up to four operating hours in typical mixed applications or for around 55 km of transport. Charging time for the battery, which is designed to last for 3,100 charging cycles, is about three hours.

As battery technology development accelerates as all the major auto manufacturers pile into the electric cars market, power duration and charging time are both likely to be substantially improved.

As it is, the system on the SESAM tractor has reverse-charging capability, so braking energy is recovered — with more than 90 per cent efficiency, say researchers.

And, of course, an electric tractor can stand idle cost-free, unlike a diesel tractor.

Like New Holland, the SESAM project collaborators envisage battery-powered electric tractors being part of a whole-farm energy concept that includes electricity generation from renewable sources, not only for on-farm consumption but also as a paying enterprise in its own right.

They also highlight potential for reduced operating costs from tractors optimised to exploit the high efficiency of electric power and the number of maintenance- and wear-free drivetrain components involved.

The technology is certainly evolving fast. As electric drive in road vehicles becomes more widespread so the cost of batteries and other components will come down.

But there are still barriers to the adoption of electric tractors; not least the investment in diesel engine production infrastructure that most major manufacturers possess, and the likely lack of used equipment outlets for early adopters.

Nonetheless, the Deere SESAM tractor looks to be a practical precursor to a commercial product. Future tractor drivers will surely have to forego the macho bark of a six-cylinder diesel in favour of the wimpish whine of electric motors.

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