Nissan latest in their series of online videos about the Nissan Leaf covers the performance of the battery pack, and the factory Nissan is building in Smyrna TN that will dramatically expand production of the Leaf. Earlier videos in the series covered optimal charging practices for the Nissan Leaf, and some basic concepts about the Leaf. The videos feature Nissan North America's Director of Product Planning, Mark Perry, answering questions posed on the Nissan Leaf facebook page.
Perry explains the purpose of the videos as an introduction to current and prospective Leaf owners into the electric car, and advanced battery, technology used in the Nissan Leaf.
What is covered in the Nissan Leaf battery pack warranty? First, the canonical reference for battery pack warranty coverage is the owners manual that comes with the Nissan Leaf. The warranty period is 8 years, 100,000 miles, which is a fairly standard warranty for electric car batteries. Perry explains the basic framework of the warranty as "Is the battery putting out enough power" and if not, if something's wrong, then "We'll cover it".
How is 'capacity loss' in the Nissan Leaf battery pack covered in the warranty? Perry first explains that any lithium battery pack from any lithium ion battery maker gradually loses capacity. This is the nature of batteries in general, that they lose electrical storage capacity. What this means is that when new the Nissan Leaf battery pack is rated to hold 24 kilowatt-hours of electricity, and that Nissan expects the capacity to gradually decline after an 10 year period to hold only 19.2 kilowatt-hours (80% of 24 kilowatt-hours). Your car will have a commensurately shorter driving range.
What Nissan warranties is not the loss of capacity, but energy output. These are two different measures. Battery pack capacity is measured in kilowatt-hours, which is electrical energy (kilowatts) measured over time (hours), the more kilowatt-hours stored on-board the car the further it can drive. Energy output is measured in watts (volts times amps) and is the amount of power going to the drive train at any one instance. Wattage is roughly the same as horsepower, and in fact the rule of thumb conversion is 750 watts of electricity equals 1 horsepower.
Perry explains that the warranty covers whether the battery is putting out enough energy (watts) to give enough acceleration so you can safely drive on the road. "If there's any kind of power drop, and it's a cell problem, that's what we cover" says Mark Perry.
What's a "cell problem"? Battery packs are made by linking together individual battery cells. Think of a "battery cell" as being similar to an AA battery, and when you put three or four AA batteries into a flashlight or other gizmo, what you've done is create a battery pack, by connecting several cells together. The Nissan Leaf battery pack is a lot bigger than your flashlight battery pack, but is still constructed of multiple cells strung together.
Are the individual battery cells covered separately in the Nissan Leaf battery pack warranty? The Nissan Leaf battery pack is constructed from 192 cells, packaged as 48 modules. The on-board computer equipment tracks each cell individually and technicians can look at the health of each module or cell. The chances of having to replace the entire battery pack are, according to Mark Perry, extremely small, however it will occur from time to time to replace cells or modules. Cell and module replacement is what's covered under warranty.
How will the Nissan Leaf battery perform in cold weather? First, if the car is plugged into a power outlet, that by itself provides enough residual power and heat to keep the battery warm enough in any cold weather to perform correctly. What Perry suggests as a worst case "What If" scenario is to park your car at Boston's airport (Logan) for a weekend trip to Maine in the dead of winter. The ambient temperature might be dipping into -10 to -20 degrees F, and there are no power outlets nearby to keep the charging system active to keep the pack warmed. Nearly any car will have battery problems in this scenario, and the Nissan Leaf is no exception. Perry explains "Your car is going to require some time to warm up, just like an internal combustion car". He states that a battery which reaches -30 degrees C (14-15 degrees below zero F) is going to have problems, but simply needs to warm up. In the 2012 model year Nissan made a cold weather package as standard equipment, including a battery warmer. Of course using the battery warmer will diminish the range, if the car is not plugged in, because the energy to operate the battery warmer comes from the battery.
A commenter on the YouTube page for this video explains that Mark Perry's answer does not cover our friends in Canada who routinely see much colder weather than we get in the States. Perry explains -20C as "worst case" but the Canadian describes -20C as quite common, and wonders whether the advice to simply warm up the battery pack will suffice for Canada.
What about heat, how does extreme hot temperatures affect the Nissan Leaf battery? Heat in the range of 130-140F or more is definitely not good for batteries. Perry claims "this is not a situation of you're parked in the parking lot and it's 110F out," instead he described the concern as "it's Death Valley, it's 130F out, in the middle of August, and you're going to leave it there for a week." If we put our thinking caps on, what Perry says here is that it is long-term exposure to high heat that is the concern. However, he describes "120F-140F" as the temperature range to be concerned over. There are plenty of places in the world where ambient temperatures are at or above 120F from time to time, and black asphalt parking lots have a way of increasing the ambient temperature. What Mark Perry did not answer in his explanation, is a scenario along the lines of living in Phoenix, you park at the Phoenix airport for a two week long trip to Alaska to cool off, but your car is baking in the sun on an asphalt parking lot, and ambient temperatures in the lot reach 120F every day. Is this a problem?
We should mention in passing that Coda's electric car contains a system to both heat and cool the battery pack, as needed, to prevent these sort of issues.
What's the status of the new Nissan Leaf factory in Smyrna TN? Nissan's plan for rolling out the Leaf is to go for mass production at a new factory, currently being built. So far Nissan Leaf production was entirely in Japan, at a modest production level, and the cars were allocated among different countries around the world. Mark Perry explains that the new factory is well under way, that they're starting to move stamping machines into the plant, and will focus first on using it for battery pack manufacture. Car manufacturing should start by the end of 2012, and capacity will be 150,000 cars and 200,000 battery packs per year.
How does this jibe with EV adoption? Nissan's goal is to be a leader in electric cars, and that it's about cost reduction and scale. He explains "you can't really do cost reduction on 1000 or 5000 or even 10,000 vehicles per year" but that volume has to be 100,000 or maybe even a million vehicles a year to get significant cost reduction. Between Nissan and Renault, they intend to construct manufacturing capacity for 500,000 vehicles a year, to lower costs, and make Nissan/Renault electric cars more affordable.
Nissan is taking questions now for future videos, so let them know your questions on Facebook at http://www.facebook.com/nissanleaf and on Twitter using the #LearnAboutLEAF hashtag.