Driving an electric car
4/5/2011 3:49 PM EDT
A few days of driving, and under the hood of, the Nissan Leaf EV shows the energy saving technologies in the car require a new driver mindset. The setup
The Nissan Leaf arrived late in the day for a weekend test drive with its Li-ion battery in the depleted zone (well under 17% of full charge, as indicated on the display gauge). But this was no problem, because the car comes equipped with a charger “cord” having a standard EV charging connector that uses a household 110V, three-prong grounded outlet. Power conditioning and control electronics are in a box on the cord about eight inches from the three-prong plug.
It turned out this arrangement was awkward in that the combination of the short cord from the electronics box coupled with its weight tended to pull the plug from the outlet. This would not have been a problem had the outlet been closer to the floor (as is standard inside a house) so that the box could have rested on the floor. But in a garage where electrical codes often dictate outlets be located about chest high (convenient for workbenches and away from moisture), some arrangement has to be made. A hook or restraint on the electronics box housing might help to attach it to a support, or Nissan could have made the distance from the plug to the box longer so it could rest on the floor. I used a cardboard box on a garbage can to support the electronics box.
Upon plugging the charger into the Leaf’s receptacle under a small door on the hood, the onboard computer told me it would take 26 hours for full charge (and about half that if I had a 220V charger available)! Turns out it was 35F outside air temperature (OAT) when I plugged in the charger in the evening, so the computer likely based charging time on that temperature. The actual full charge took about 20 hours, which is what Nissan says is nominal when using the 110V (1.4 kW) “trickle charger.”
Most Leaf owners would not want to put up with such a long charging time, unless they could limit their driving so as not to go below about half a full charge. But the others will probably opt for the available “home charging dock” (3.3 kW) that runs off a 220V line (view video). This unit costs roughly $2,200 (installed in new construction, but “the customer is eligible for a 50% federal tax credit up to $2,000,” according to Nissan) and allows a full charge in eight hours, adequate for commuters topping up overnight. A $700 option on the car provides a receptacle next to the standard charger socket that will mate to the cord on publicly available DC charger kiosks (50 kW) to give an 80% charge in 30 minutes. The Leaf also has a feature that can be set to only charge the battery to 80% capacity to extend battery life.
As the car battery is recharged, a set of three blue lights on top of the dash cowling and visible through the windshield light and flash through a sequence to indicate the level of charge. By late afternoon of the second day these lights were out, and the battery “topped up.” The dash display indicated a maximum range of 93 miles. The map display (navigation is standard on the Leaf to help with battery management and in locating charging stations) showed the 93 miles as well as a smaller, “anticipated” range circle of 65 miles. These numbers are based on how the car was driven in previous charging cycles and battery capacity (based on its temperature). OAT (46F at the time) could enter the calculation as well.
I turned on the headlights and windshield wipers to see if these power draws would affect the range numbers, but the figures stayed the same. (The Leaf uses high-brightness LEDs for its low beams to minimize their power drain on its low-voltage 12V battery.) However, when I turned on the climate control, the max range number dropped to 82 miles. But the car can run with outside air flowing through the cabin without the climate control on (much like back in the day when most cars did not have air conditioning).
Later in the evening, I set out on a short drive, which produced the following results:
- Start with OAT at 42F and 91 miles max range figure (with climate control off).
- After driving 2.7 miles over town roads up to 40 mph with heater and headlights on, display indicates 77 miles range left.
- Return trip diverted to use Interstate for three miles at 65 mph. Exiting Interstate at 7 miles total, max range is given as 70 miles.
- Drive home on town roads at 30 mph. At a final driving distance of 8.9 miles, max range stays the same at 70 miles.
- Turn off climate control and max range number jumps to 83 miles (“anticipated” range number then is 58 miles).
- Battery power is down to 87% and usage was 2.8 mi/kWh.
The remainder of the time I used the Leaf for short trips around town and kept the charge topped off so it could be driven to the next journalist who would test it.
Turning a Leaf
The car itself is a snappy subcompact that is fun to drive. With electric motor torque highest at low speeds, acceleration is quick, but I suspect that Nissan programmed the control electronics not to put out as much torque as possible to cut battery draw rate and increase battery life. That conclusion is based on independent tests that come up with a 0-60 mph time of 7 seconds (The company doesn’t quote acceleration times for its cars).
The Leaf is very quiet without an internal combustion engine, and produces its own unique electrical motor whirring. Because of the low sound level, below 19 mph (30 kph) a Vehicle Sound for Pedestrians system sounds a high-pitched tone as a warning. This is not noticeable in the cabin with the windows up (at least with my ears), and the system can be turned off if desired.
On the interior, the seats are manually adjusted to avoid power draw and there are no seat heaters. (The Chevy Volt uses seat heaters in an economy mode to heat the driver before heating the entire cabin.) The heater or air conditioning can be programmed to heat or cool the car at a specific time before driving, so as to use battery charger power to pre-heat or cool the car rather than tapping the battery.
Under the hood, the transverse-mounted electric motor and low-voltage systems’ 12V battery look like an ordinary gasoline powered subcompact. High-voltage orange cables are at a minimum to the eye.
Outside, it is evident that the Leaf has been fine tuned aerodynamically. Overall drag coefficient is 0.29, according to Nissan. At the front, the headlight housings stand proud of the hood and are pointed to the center, which directs airflow around the side mirrors, cutting wind noise due to the mirrors as well. The driver can also adjust the up/down angle of the headlight beam with a small wheel on the dash if needed under certain loading situations.
The car’s underside is flat to further lower drag, and diffuser elements direct the high-pressure air below the Leaf rearward as opposed to curving out and up the side, which increases induced drag.
The Leaf SV model I drove is priced at $32,780 MSRP. A U.S. federal tax credit of $7,500 cuts the cost penalty for new technology, and some states may even have further incentives (such as California’s CARB rebate up to $5,000 [Ed. Note: No wonder the state is almost bankrupt!]. An SL model for $940 more has a solar panel on the rear spoiler to charge the 12V battery for the audio, wipers, and lights. Also in the SL package are a rearview monitoring camera, fog lights, and automatic headlights.
The Li-ion battery is warranted for eight years or 100,000 miles.
All in all, the Leaf is a credible first attempt at a modern production electric car, ideal for commuting—as long as one has 220V overnight charging capacity.
Leaf specs and features