Last week while relating the winter driving experience of the Nissan Leaf, I spent a lot of time discussing the way temperature impacts the range of the car, and two ways that the Leaf displays how much ground you can cover on the battery's charge. There are a couple other ways you can track the Leaf's energy consumption that I'll get into here, as well as a few other lingering techie frills that I haven't covered, yet.
I'll wrap up with an analysis of the maintenance that a Leaf needs, or rather the lack of maintenance. Basically, EVs don't need to deal with the extreme heat and friction that's generated from the rapid series of controlled explosions in an ICE (internal combustion engine). They don't need oil because there is so little friction in an electric motor. That's a little hard for some people to wrap their head around. There is no oil because there is no engine with super-hot pistons that need to be lubricated to prevent them from seizing up.
EVs sidestep that whole pit of design constraints, resulting in a system that needs much less maintenance. But before I get to far into that, let's talk about energy.
Energy, how do I measure thee? Let me count the ways...
With a relatively short range that can be as low as 50 miles in severe weather, keeping track of energy consumption is of critical importance in the Leaf. I've already talked about the GOM and the charge level meter as the two main ways that you can gauge how far you can go before you run out of juice. The Leaf also keeps track of how many miles per kWh you've driven on average. You can show this measurement on a monochrome LCD display that you can see right through the steering wheel, and it gives you the lifetime average for the car as well as a horizontal graph of the instantaneous value in the range of 0 to 8 miles/kWh. The average readout started off at 4.1 miles/kWh in January of 2012, if I remember correctly; crept up to 4.8 miles/kWh during last summer; and then leveled off at 4.5 miles/kWh by Christmas, where it has stayed ever since. I would imagine people further south would get substantially better averages because it doesn't get cut down by cold weather.
You can also see the average and instantaneous energy consumption on the color touchscreen display on the center console. I have to say, this touchscreen is really nice. I've used a couple other touchscreens in the Prius and the Ford C-Max, and those both suffer from some pretty small button touch areas. I would have to steady my my hand with some of my fingers resting on the edge of the display to use those screens, but not so with the Leaf's touchscreen. It has nice big button areas on all of the common screens that are easy to jab at while driving. I can easily hit any selection I need to, even when wearing gloves in the winter.
Getting back to the energy consumption display, the instantaneous readout is a vertical bar graph here, and unlike the monochrome display, the average can be cleared whenever you want to start a new averaging period. Each time you clear the average, it records the cleared value in a history bar graph so you can track how your energy consumption changes over time.
I clear the average at the beginning of each month, and from the history graph I found that my monthly average energy consumption varies from a low of 4.0 miles/kWh in the dead of winter to a high of 5.1 miles/kWh in the summer. If you figure in the 24 kWh battery, I should get a 96 mile range in the winter, but that 4.0 miles/kWh is a monthly average, and the battery isn't really a 24 kWh battery in the winter because cold temperatures reduce its maximum capacity. I suspect this measurement is a bit optimistic, too. According to it, I should have a range of about 122 miles in the summer, but I definitely do not. Maybe the useable capacity of the battery is more like 20 kWh, which would correlate much better with the 100-mile summer range I routinely see. If only I could always drive at 5.1 miles/kWh, right?
Another way to see the current energy consumption is with a set of radial gauges on another screen on the color display. This screen breaks out the energy consumption into the electric motor, the climate control, and all other accessories. The motor gauge has a section that goes negative for when the regenerative braking is recovering charge, and it's also the largest gauge with the largest range, of course. You can recover up to 30 kW when braking hard and burn up to 80 kW when accelerating hard. It's pretty easy to peg that gauge in either direction, but to really conserve energy, you obviously want to keep it as low as possible at all times.
The climate control gauge shows that it can consume up to 6 kW, but I've never seen it go that high. However, I don't spend a lot of time on this screen, so who knows. It could get there in the winter with the fan on high and all of the heated seats and steering wheel on high. Maybe I'll try it this winter. I did notice today, when I was experimenting a bit, that if you have the A/C on in ECO mode, switching to Drive mode gives the A/C quite a boost. It cools the cabin down significantly faster, but it more than doubles the energy consumption. If you can afford the energy, the A/C boost really works well. It's nice to have the choice.
The gauge for the rest of the system only has a range of 2 kW, and it has a baseline consumption of about 0.15 kW. The audio system barely registers on this gauge, even if I crank the radio much louder than I care to listen to it. The only think I've seen affect this gauge much is the headlights. Even though they're LED headlights, they add about 0.15 kW and the brights add another 0.15 kW for a grand total that's just under 0.5 kW. That's negligible compared to the electric motor consumption. Since the motor is the largest factor in energy usage by far and I can monitor its impact on other screens, I mostly ignore this screen. The 'Status' screen showing the current song playing along with smaller versions of the average and instantaneous energy consumption readouts is the one I use the most.
If that's not enough ways to measure the Leaf's range, here's another one. There's a button on the steering wheel with a blue circle and a dot in the middle that you can push to bring up a road map on the color display. The map shows your current location with a white circle marking the extent of the Leaf's range and a concentric grey circle marking the extreme limit of its range in ECO mode. These are, of course, the Leaf's GOM estimate translated into the circles' radii, but it is nice to see it visually on a map.
The map also shows electric plug icons wherever there is a charging station, and the station information can be updated at any time with a few menu selections. You can download new stations for where you are right now, where your home location is, or where the map is showing. If you're running low on charge, you can calculate a route to one of the stations closest to you. You can also sort the stations by those closest to the destination set in the navigation system or the center of the map, so you can easily plan for your charging needs.
Already in Madison, you're never more than a couple miles from a level 2 charging station, and the charging infrastructure is expanding rapidly. With the Leaf's navigation system, you never have to worry about running out of charge in any city that's well stocked with stations. You'll always have options, and you'll know exactly where they are.
The Tree Game
One last way to track your energy consumption is with the tree game. To the left of the speedometer, (which is an excellent digital readout, by the way; so much easier to read than an analog gauge) a pine tree will grow in five segments as you drive conservatively, as judged by the car. There is a partial halo of square segments over this growing tree that acts as an instantaneous level of energy economy that seems to be related to the other instantaneous miles/kWh meters. When you complete a tree, it will line up to the right as a smaller version, and with the larger original, you can complete five trees. Here's what a full set of trees looks like:
I completely grew five trees on my 72 mile drive back from the dealership when I bought the Leaf. The peak of the last tree popped up right as I was pulling into the driveway. Even though the route was not especially kind to my range and I was forced to drive less efficiently than I wanted to, the distance alone must have been enough to allow all five trees to grow. Since then I have rarely grown a full tree regardless of the fact that my commute to work is much better for energy usage. The route is too short and the history clears every time you turn off the car, so I don't get a chance to build up any trees.
The only other times I've completed a tree are when I'm stuck in a lot of traffic on the beltline so that I'm creeping along at 5 mph for 10 miles, or when I bail and drive through the city, which ends up being twice as many miles of stop-and-go traffic. In neither of those cases does it seem like I've saved energy. In fact, I most definitely wasted energy because those are the days that I end up with less charge left when I get home. But I grow full trees those days. Go figure.
You also have the option of having the car upload your completed trees to a database and competing on a leader-board for most efficient Leaf driver. You've probably already guessed that I don't see much point in doing this, and I find the whole tree-growing efficiency measurement a bit dubious. If I wanted to game the system, I could, but I have better things to do with my time. Besides, the car is so much fun to drive, and I'd rather enjoy it. I get good energy economy out of it anyway.
Allow Me to Gush for a Moment
I know that a lot of cars have this feature now, but the Leaf was the first car I've driven with it so I have to rave about it a bit. Keyless entry/start is the best invention since cruise control. Seriously. I never have to take the key out of my pocket. It's not even a key and a fob anymore. There's a pseudo-key in the fob that can be used in an emergency if the fob isn't working, but otherwise the fob sits at the bottom of my jeans pocket. There's a button on both the front driver and passenger door handles that you can push once to unlock that door or twice to unlock all doors. Push the button on your way out of the car to lock all of the doors. The hatch unlocks when you push a button under its handle. The doors will only unlock when the car senses the fob is within an arm's length of the door handle. This is so much better than fumbling for the fob with your arms full of groceries or small children.
Once you're in the car, you just plop down and push the power button - no contortions to extricate your keys because you forgot to get them out of your pocket before sitting down, no fiddling with the steering wheel and jiggling the key in the ignition because it won't turn, and no keys dangling from the steering wheel and whacking you in the knee while you drive. After getting the Leaf, I got used to this feature so fast that I forgot my keys in my pocket every time I sat down in our Corolla. What a relief it was when we replaced the Corolla with a Prius with keyless entry/start! You have no idea how much you hate using a key until you don't have to anymore.
Maintenance? It don't need no stinkin' maintenance.
It's comical to think about the maintenance that does not have to be done to this car. After a year and a half, I've been to the dealership three times for maintenance. The first two times were for the 6-month and 12-month battery inspections. These are paid for and required by Nissan to make sure the battery is performing optimally in the first year, and it should continue to be checked once a year after that to maintain the battery warranty. At the 12-month battery inspection they also did a 5-point inspection for the brake lines, brake pads, charging port, drive shaft boots, and reduction gear oil.
The third time I went in for service, it was for a software upgrade, and while I was there, I decided I might as well have the tires rotated. I could have done it myself, but it was only 20 bucks and it would save me an hour. The software upgrade was a two part upgrade. The on-board charger was upgraded to interface with more types of charging stations, and the battery charge level measurement systems were upgraded to include the improvements that were made to the 2013 Leaf.
Now that's a nice gesture from Nissan. They're giving all of their 2011 and 2012 customers a free software upgrade so we can benefit from the improvements they've made to the 2013 Leaf. Granted, I don't get the improved regenerative braking, but that's a more significant hardware upgrade. I'm happy they're supporting the loyal early adopters wherever it's reasonable.
The upgrade made noticeable improvements, too. The GOM isn't nearly so jumpy anymore. It used to be overly sensitive to variations in driving conditions, like changes in acceleration getting on and off the freeway or when driving up and down hills, especially when there was a lot of charge left. Small variations in energy usage extrapolated over a large amount of charge resulted in the GOM dropping or adding 5-10 miles at predictable points during my commute. My best guess is that they're using an exponential averaging function with a smoothing factor that was too large, and the upgrade corrected that, making the GOM less sensitive. There were likely other optimizations as well, and it made a big difference in the apparent accuracy.
It also seems like the charge level meter is more linear. It used to be that the charge level would stay on certain bars for a relatively long time and then drop two bars in a correspondingly short time without any changes in driving conditions. Now the meter seems to drop bars at a much more consistent rate. I'm not completely sure on this observation, though. I never took accurate measurements of its behavior, and it could all be in my head.
Okay, back to maintenance. Basically, I have to take the Leaf in once a year for a battery check and a multi-point inspection. Every 30,000 miles the brake fluid should be replaced, but I'm not sure why because the ERB does a lot of the braking. At some point the brakes will have to be done, but I'm not sure I'll still have this car at 200,000 miles. That's when I figure they might need to be replaced, but I'm really not sure. It could be longer. Assuming it's 200,000 miles, at the rate I'm driving, I would reach that sometime in the year 2045. I'm likely to have a new car by then.
The one thing that will have to be replaced at a normal rate is the tires. The Leaf won't do anything to slow down tire wear. It's also possible that something could go wrong with the car mechanically. However, that's the beauty of EVs. There is so much less that can go wrong with them and so many less wear-out items. Think about what an ICE has that an EV doesn't:
- Gas tank
- Fuel lines
- Fuel pump
- Spark plugs
- Air intake filter
- Oil, lines, and filter
- Catalytic converter
- Exhaust pipe and muffler
- Timing belt
There is one major point of failure that a lot of people worry about, though - that ginormous battery. It's expensive, too. An estimate from 2010 put it at $18,000, which is half the price of the entire car, but it has certainly come down from that as production increases and manufacturing improvements are made. The price of a 2013 Leaf is almost $4,000 less than the same 2012 Leaf, and it has quite a few improvements that come with it. I'll bet most of that price drop was from reduced battery costs.
As a point of comparison, Nissan recently announced a battery leasing program where you can get a replacement battery for $100/month, and the program guarantees at least 70% capacity on that battery for the entire life of the car. If you assume, for the sake of argument, that the $100/month is paying off a new battery at a cost of $18,000 (with zero interest), it would take 15 years to pay it off. That's not even taking into account the replacement cells you could get during the program to maintain 70% capacity. I would bet that Nissan is really estimating a 5-year payoff, which would equate to $6,000 for the replacement battery. It's pretty clear that batteries will get a whole lot cheaper in the coming years, or Nissan wouldn't be offering a program like that.
At the same time, these batteries are much more reliable that a lot of people think. As I mentioned a couple weeks ago, Nissan is guaranteeing their batteries to a 70% charge capacity for 6 years/60,000 miles. They are pretty confident that most of the batteries out there in Leafs are going to last at least that long. If you actually do have to replace the battery after 6 years, it will likely be much cheaper. How much cheaper? I don't think anyone can really say, but you could always enter the battery leasing program at that point for $100/month.
I don't think the program will still cost that much by the time most people would need it, though. And most people aren't going to need it for quite a long time. I know I won't. Even if my battery is near 70% capacity in 5 years, that will be enough to get me to and from work twice on a charge in the summer, and more than enough for one commute in the winter. But I seriously doubt the capacity loss will be that bad.
Next week I'll have a better idea of how much capacity I've lost over the last year and a half, and thus, what I can expect for the years to come. I've kept track of the mileage I've driven for every charge, and I plan to try to make some sense of it for my next post. It should be interesting.
The Rest of the Leaf Series:
Part 1: The Acquisition
Part 2: The Summer Drive
Part 3: The Winter Drive
Part 4: Frills and Maintenance
Part 5: The Data
Part 6: The Future
Part 7: The Energy Efficiency Meter