Nissan prototype 60-kWh battery pack - Nissan Technical Center, October 2015
Will the next-generation 2018 Nissan Leaf offer an option that could provide 200 miles or more of real-world driving range?
Based on the concept car and prototype battery pack that officially bowed this past week, coinciding with the Tokyo Motor Show, it’s increasingly likely.
Nissan’s IDS Concept from Tokyo is noteworthy on several levels.
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One of them is that it points to how a new generation of vehicles with autonomous-drive modes might look—and function with pedestrians, normally driven cars, and the immediate surroundings.
With the concept Nissan also dropped some hints about a potential styling direction for the next-generation Leaf electric car.
Furthermore, the concept officially threw in a 60-kWh battery—which, if it’s affordable enough, could be the key to stay competitive against a raft of rivals including the Chevy Bolt, and Tesla Model 3.
Nissan IDS concept, 2015 Tokyo Motor Show
Although a Nissan official told us that 60 kWh isn’t a hard-and-fast capacity number, the approximate size is something that the automaker plans to offer in the next several years.
And that pack isn’t just concept-car fantasy. It exists (pictured above), developed internally by Nissan, and they’re calling the pack a working prototype, aimed at providing a 500-km (300-mile) range in the very generous European or Japanese driving cycles.
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In all, it's quite different than the currently available 24-kWh pack in the Leaf or its upgraded 30-kWh pack that's going to be available beginning in a few months. The latter will offer an EPA-rated 107 miles.
At least for now, any claims that the automaker is planning to move to an external supplier are premature.
Lithium-ion battery pack of 2011 Nissan Leaf, showing cells assembled into modules
A true second-generation pack
This past week, at the Nissan Technical Center at Atsugi, Japan, we were about to learn more about this pack from some of the team overseeing its development. Here are some key points of this next-gen, 200-mile battery:
- Different chemistry. The prototype moves from a nickel manganese cathode to a nickel manganese cobalt one. The anode remains made of graphite, and the electrolyte remains a lithium compound.
- Flexible pack structure. The current Leaf battery uses four cells per module (with 48 modules in the entire 24-kWh pack)—a structure that allows a uniform height and shape for the pack. But this one moves to a multiple-cell configuration; Nissan will be able to adjust the number of cell stacks (and thus height) depending on packaging and capacity demands. An official said that they were conservative with the number of cells per stack in the original battery design, but with essentially no failures or issues, they’re fine perhaps dramatically increasing that number.
- Faster charging. Engineers have made an effort to reduce impedance, through the increased quantity of cells and a revised electrode material. This allows longer charging at maximum current—and will potentially allow faster-rate 100-kW charging versus the current 50-kW. Higher voltage is under discussion.
- More weight, but a lot more power density. Using the 24-kWh pack as a baseline, Nissan says that the new 60-kWh pack weighs just 220 pounds more. So with that older pack weighing in the vicinity of 660 pounds, that ups overall weight to nearly 900 pounds. It's impressive, considering the gain in kWh per pound.
- Air cooling. Nissan made the original Leaf battery pack completely air-cooled, and while there were some early, isolated issues in very hot climates like Arizona, those seem to be largely solved today. Liquid cooling isn’t being considered for an entirely new, larger-capacity battery—at least in this prototype form. Forced-air cooling isn’t likely either.
- Increased state-of-charge range. That's thanks to a wider voltage range—which runs at about 2.5 to 4.15 volts in the current battery.
- Longer service life. Nissan has revised the electrode material and optimized the lithium electrolyte (it won’t say how in either case), with the net effect being less of a performance drop over years and hundreds of charge cycles. Suppressed lithium corrosion will help durability, too. One of several charts we saw but were instructed not to publish, if to scale, suggested that instead of a standard capacity degradation to 80 percent after five years, it now might be 90 percent.
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