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The Nissan Leaf’s 24 kilowatt-hour battery pack relies on air cooling, rather than a more complex liquid-cooling system. Credit: Nissan

For months, Nissan Leaf owners in Arizona have complained about degrading battery capacity from high heat. Now, a group of Leaf owners have performed a test that appears to add credence to those claims.

A group of Nissan Leaf owners on Saturday performed a controlled range test in Phoenix to measure how far 12 of the electric sedans can go compared to the car’s new battery range. The data, published yesterday on the EV enthusiast site Inside EVs, show significant loss of range for many of the cars tested. They were model year 2011 and 2012 Leafs.

The range loss is due to the loss in battery capacity and not only a dashboard instrumentation problem, as Nissan has told drivers, says Tony Williams, a Leaf owner who collected the data. “A significant percentage (of affected Leaf owners) have owned electric vehicles prior to the Leaf, and many, if not most of those who have traded their faulty Leaf have gotten another electric powered car, like the GM Volt, and like me, another LEAF,” he wrote.

The battery capacity complaints, which are documented in detail on driver forms, appear to be centered in places with hot climates, such as Arizona and Texas. 

It’s well known that temperature extremes—either very hot or very cold–degrade batteries, along with other factors such as driving and charging patterns. (Here are some tips on how to improve battery life for people who live in hot climates.) The actual range of an electric vehicle will be affected by topography and the interior electric load, such as air conditioning and heat. 

The Nissan Leaf relies on air cooling to maintain battery temperature, which is different from other automakers’ battery-powered cars. For their electric vehicles, Tesla Motors, General Motors, and Ford all have more sophisticated–and expensive–active thermal management systems, where a liquid is circulated around batteries to keep them close to their optimal performance temperature.

In July, Nissan Americas’ senior vice president for research and development Carla Bailo wrote a letter to Phoenix-area Leaf owners, saying Nissan will take back Leafs to study the problem. She also noted that the problem was isolated to less .3 percent of Leaf owners in the U.S.

In a statement today, Nissan said: “Nissan has been working hard to understand some Leaf customers’ concerns in the desert southwest. We’ve tested a number of individual vehicles and will be contacting those owners to discuss their individual results in the near term. We also anticipate having more information to release to the wider Arizona customer base soon. We are taking Phoenix customer concerns seriously and are working hard to ensure their full satisfaction.”

Battery capacity, and thus range, will degrade over time for all plug-in vehicles, which will be affected by climate and charging habits. Nissan has said battery capacity will decrease 30 percent in ten years, but noted that exposure to hot temperatures could accelerate degradation. (See, Electric Cooling Battery Test.) 

Nissan-Renault CEO Carlos Ghosn told the Wall Street Journal last week that Nissan will introduce a better battery with an upcoming version of the Leaf, which he said will help sales. Nissan sold under 10,000 Leafs in 2011.

Updated at 7:13 p.m. ET with statement from Nissan.

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Tagged: Energy, batteries, Nissan Leaf, ev

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