In the race to bring Leaf to the market, Nissan engineers cut corners?!

 

Autopia published a very interesting article about Nissan EV, the Leaf.

Nissan's CEO, Carlos Ghosen, is very eager to win the EV race by bringing first to the market the first mass-produced EV. But, the are sacrifices to be made in order to achieve this, as the article explains.

Let's face it, the biggest competitor is GM's Volt, which will be launched about the same time. Carlos Ghosen recently told Bloomberg, �The engineers will always tell you, �Wait a little more,� and if you keep playing this game, you never launch any product.�

Since cars are complicated pieces of engineering, it's easy to understand that EVs present numerous fresh challenges  to the engineers. So, what are the shortcuts? I have summarized them below in order to be easier to identify.

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• The key engineering trade-off Nissan has made is opting not to include active thermal management. Instead, Nissan has opted to use only an internal fan that circulates the air within the sealed pack to evenly distribute the heat, which escapes by passive radiation through the pack�s external case.

• Thermal management in lithium-ion battery packs is critical to the long-term performance and quality of the battery. The manganese oxide pack is sensitive to high temperature and the primary consequence is that the pack will degrade more rapidly than one with active thermal management. This problem will be worse in hotter climates such as Phoenix, which Nissan has selected as one of its launch cities.

• Mark Perry, Nissan�s director of product planning for the United States, dismissed the importance of active thermal management. �We don�t need thermal management for the U.S., but we are looking at the technology for Dubai and other locations like that�. We�ve gone on the record saying that the pack has a 70 to 80 percent capacity after 10 years,� he told Wired.com.

• But Paul Hawson said a different story, a Nissan product planner who worked on the Leaf, when the automaker brought the Leaf to the Wired offices in November. Asked why Nissan chose not to use active thermal management, Hawson explained the engineers experimented with it but found it required a central tunnel on top of the pack. That would intrude on cabin space, splitting the rear bench into two seats with a hump in the middle. Nissan, he said, decided to use only passive cooling to preserve passenger space.

• General Motors has taken a different approach with the battery in the Chevrolet Volt. GM opted to use an active liquid cooling system. Doing so ensures optimal power and lifespan, said Tony Posawatz, vehicle line director for the Volt.

• The Volt actively manages both low-temperature and high-temperature conditions. �Additionally, we cycle the battery in a much friendlier way than our BEV competitors which need an 85 percent state-of-charge window to get their miles and this EV range begins degrading after day one of usage,� Posawatz added, referring to the fact that the Volt only cycles through 8 kilowatt-hours of the pack�s 16-kilowatt-hour capacity, which also contributes to longer life. Even with these conservative engineering approaches, Posawatz said, �our 10-year target still yields a battery with 70 to 75 percent of the capacity at the end of life.�

Verdict
Nissan�s confidence on this matter aside, early purchasers of the Leaf should consider taking the company up on its offer to lease the battery, which would leave any financial risk of early battery degradation where it belongs � with Nissan.

Source: Autopia (Wired)

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