The Delhi government’s delisting of the Tata Nexon EV
from its subsidy scheme for electric vehicles earlier this week raises
more questions than answers. Delhi Transport Minister Kailash Gahlot
tweeted: “Delhi govt has decided to suspend subsidy on an EV car model,
pending final report of a Committee due to complaints by multiple users
of sub-standard range performance. We are committed to support EVs, but
not at the cost of trust & confidence of citizens in claims by
manufacturers.”
For those who come in late, here is the backstory. The delisting
follows a consumer complaint over the vehicle’s failure to meet
company’s specified 312km range on a single charge. Last month, the
Delhi Transport Commission issued a show cause notice to Tata Motors. In
its response released on Monday, the manufacturer has said that it
stands by the Nexon EV’s claimed ARAI range, and will continue to engage
constructively to protect the interests of its customers. “The Nexon EV
is the only personal segment EV available in the market today that
meets the stringent FAME norms. The range at single full charge (312km)
for the Nexon EV is basis the certification received from the Automotive
Research Association of India (ARAI), which is the official body that
independently tests all mass produced vehicles under standard/defined
test conditions before they can be offered to customers,” its statement
said.
“As with conventional vehicles (with IC engines), the actual range
achieved in EVs is dependent on AC usage, individual driving style and
the actual conditions in which the vehicle is driven. The range
achievement is also a function of familiarity with the new technology,
and customers report improvements upwards of 10 percent within 4-6 weeks
of familiarity. We have been receiving several positive testimonials
from our customers and are encouraged to see them exploring new places
with the Nexon EV and sharing their experiences.”
As with every vehicle, real-world mileage (range) will vary from the
certified figure. Mileage will also differ widely from user to user and
is heavily dependent on factors such as driving style, traffic, and even
weather. For EVs, this variation is even more pronounced, as a
battery’s depletion rate varies far more than an IC engine’s fuel
consumption.
Temperature variations significantly impact a battery’s performance
and, curiously, if you drive an EV on a highway, you’ll get a lower
range than you would in the city. This is because on the highway, with
the throttle constantly engaged, an EV will only be depleting its
battery whereas in the city, it benefits from increased brake energy
regeneration, thanks to having to slow down for traffic.
This is a key factor, as it must be noted that for EVs like the Nexon EV, Hyundai Kona Electric, and MG ZS EV
that belong to category M1 (vehicles which can ferry up to eight
passengers plus a driver and their luggage), ARAI limits the range
testing to Part One (urban cycle) of the Modified Indian Driving Cycle.
Thus, a real-world figure with mixed usage will definitely show a big
difference compared to the ARAI figure. This is not to say the ARAI
figure or system is flawed. On the contrary, it represents a uniform
testing procedure applied to all vehicles, thus enabling a fair and
accurate comparison. However, it cannot be taken as an exact value that
all users will achieve.
For instance, drive an EV up to a hill station and the constant load
will rapidly deplete the battery. On a 280km drive from Mumbai up to
Mahableshwar, we came perilously close to depleting the Mercedes-Benz EQC’s battery,
this despite the certified 445km range. The return downhill journey,
however, was a breeze, and we coasted home with extra kilometers to
spare.
EVs and real range:
Last year,
we conducted a range test for the Nexon EV, Hyundai Kona, and the MG ZS
EV according to our set Autocar India Road Test standards. The range
test had the distance measured via GPS, drivers rotated, and all testing
carried out at the same average speed. Our tests, too, showed a
difference in the claimed range versus the real world figure for all
EVs.
ARAI’s testing procedures for electric vehicles
Before getting to the testing methodology, here are certain
prerequisites – the ambient temperatures must range between 20 and 30
degrees Celsius; tyre pressures should be as per what is prescribed by
the manufacturer, and all other mechanical bits must conform to the
manufacturer’s specifications and standards. And, finally, the electric
vehicle’s battery has to be fully charged. During the tests, all
electricals except those required to drive the car need to be switched
off, including lights, indicators, and auxiliary devices like air-con
and audio system, which isn’t the case in the real world where these
surely contribute to some power consumption.
ARAI conducts the tests on a chassis dynamometer (a sophisticated
rolling road used for vehicle testing and development) whose rolling
resistance is set in accordance with the car’s ramp weight (maximum
permissible weight).For example, if a car’s ramp weight is between
1,980- 2,100kg, then the rolling resistance will be equivalent of
2,040kg.
ARAI’s test doesn't include a highway cycle
For electric vehicles belonging to the M1 category, ARAI limits the
range testing to Part One (urban cycle) of the Modified Indian Driving
Cycle. Each vehicle goes through 22 testing cycles spread over 195
seconds each. During each of these tests the vehicle is supposed to
idle, accelerate and decelerate in a fixed pattern over a predetermined
duration. The driver or tester is supposed to follow certain steps,
including gradual pedal inputs, to avoid any sudden acceleration or
deceleration which could skew the findings. The average speed maintained
during the cycle is 19kph, with a maximum speed of 50kph. After 22 such
cycles, the total distance covered by the vehicle is used to calculate
its range.
To derive the total power consumption over the 22 cycles, the battery
is put for charging within 30 minutes of the completion of the test. An
energy measurement device, placed between the main socket and the
vehicle charger, measures the charge delivered (watt-hours) to the car’s
battery. In order to calculate the consumption (kWh per km), we divide
the charge delivered to top up the battery (watt-hours) by the distance
covered (km).
Consumption = Charge to top-up battery/Distance
To find out the maximum travel range from the final consumption figure,
divide the battery size by consumption to establish a theoretical
figure, which is what’s printed and advertised by the manufacturer as
the vehicles’ range.
Range = Battery Size/Consumption
Taking the Kona’s example, certified range is 452km and battery size is
39.2kWh, so going by the above formula 452km = 39.2kWh/Consumption,
hence consumption by reverse calculation would have been 0.086kWh per km
(or 8.6kWh per 100km).
Clearly, the delisting of the Tata Nexon EV is unfortunate, as it has
obtained its ARAI certification. ARAI certification is a mandatory and
regulated process conducted by government- approved facilities and
logically, queries should also be directed towards ARAI, the certifying
agency. At a time when the country is trying to promote EVs, this whole
affair will only prove to be a stumbling block and could have been
handled in a more nuanced manner.
