Nissan Leaf ‘Eco’ and ‘Drive’ modes studied

About 30 Nissan electric vehicle owners tested ‘Eco’ and ‘Drive’ modes to measure efficiency and range using the settings.

An EV’s range is determined partly by propulsion efficiency (km/kWh) and partly by battery energy holding capacity when fully charged, Flip the Fleet says. The coalition of EV owners uploads monthly data to a communal database to measure the performance of EVs throughout New Zealand.

Some participants noticed that the selection of the Eco or Drive setting led them to change their driving style, or to think differently about the way they drive.

The Eco setting increased efficiency (km/kWh) and range of ‘Generation 1’ Nissan Leafs by about 2.9% during summer.

This could add three or four kilometres extended range as a safety buffer to a 24kWh Leaf for long trips. But it delivers a minimal gain in practicality for everyday travel, Flip the Fleet says.

The Eco mode saves an average Leaf driver (who spends an average $36 monthly to power their car) around $1 in electricity costs per summer month but reduces the pleasure some drivers gain from increased vehicle responsiveness in Drive.

Future research could measure efficiency gains from Eco mode in winter, and from a mixed strategy throughout the year in which Eco is selected for downhill and stop-start conditions, but Drive is selected for flat and uphill travel and when steady momentum is expected.

Flip the Fleet says one reason for the study is that some of the earliest Gen 1 Leafs now have 70% battery holding capacity, so any mechanism for increasing their range between charges is important.

“One way a driver can extend the range is to select the ‘Eco’ setting on the dashboard rather than the ‘Drive’ setting. In the 2011/12 variant of the Leaf, this damps the accelerator pedal and increases the amount of energy that is ‘regenerated’ as the car slows or brakes.

“In the 2013-16 variant, the cabin climate control mechanisms are also curtailed to reduce energy consumption further.”

A ‘B’ setting in some models increases regenerated energy capture.

Some participants were surprised, and some disappointed, there appeared to be less gain in efficiency from using the Eco mode than they expected, Flip the Fleet says.

There was no sign that the Eco/Drive setting altered the distance travelled during each month of the experiment, as expected if the participants maintained their normal car use patterns for both treatments.

A much larger treatment effect might be expected in winter when the Eco mode suppresses the cabin climate control energy drain, and when wet driving conditions and overall travel efficiency is much reduced.

The study suggests that despite its ‘Eco’ label, drivers need to be realistic about this option. “At least in summer, selecting Eco only provides a minimal safety buffer and a much smaller extension of range than can be achieved by driving more slowly and steadily, and from switching off air conditioning, heaters and lights.”

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