The design of the Nissan LEAF battery pack could reduce driving range during extreme temperatures, but might make it safer than batteries using liquid coolant.
"year ago, PluginCars.com contributor Tom Molougney wondered if Nissan made the right call to not use an active thermal management system—which could be the key to maintaining expected driving range in extreme temperatures. At the time, Nissan said, "We are confident the LEAF will perform well in all ambient temperatures."
New light is cast on that question, now that the Chevy Volt’s liquid coolant has been identified as a possible cause of fires that might occur weeks after a severe accident. The response from Nissan—which doesn’t use liquid cooling in the LEAF—has been to distance itself from the issue. For Ford, which does utilize liquid thermal management in its upcoming Focus Electric, the response is to reassure the public about its safety.
Nissan's U.S. product safety director, Bob Yakushi, last week told Edmunds' AutoObserver that circumstances that appear to have led to post-crash Chevy Volt fires simply don't exist in the Nissan LEAF. Yakushi points out that the LEAF's 24-kWh lithium-ion battery pack is encased in a damage-resistant steel enclosure and surrounded by a crash-safety structure that's located inside of the electric hatchback's overall crash-safety protection zone. "It's a three-layer system," said Yakushi.
Rather than employing an active thermal control system, Nissan relies on the existing airflow—sometimes referred to as “passive air cooling”—to regulate the temperature of the LEAF's battery pack. Therefore, the LEAF doesn't have any internal cooling lines that could break and potentially leak fluid after a severe accident. Without fluid, it's unlikely that the LEAF's battery pack would produce a fire after being damaged, according to Yakushi.
Maintaining Focus
Ford will launch its Focus Electric in the coming weeks despite the current fire safety investigation of the Chevy Volt.
Meanwhile, the Ford Focus Electric will launch in "limited numbers" in the coming weeks in New York, New Jersey and California. Like the Chevy Volt, the Focus Electric uses a liquid-based thermal management system—but the Volt fire incident will not delay Ford's rollout plan for the Focus Electric. The automaker said, "We still have limited information about the cause of the Volt fires in the government crash tests, so it is difficult to comment on how they relate to Ford’s electrification program. [We will continue] to work with the NHTSA as we prepare to launch our electrified vehicles over the next year.”
Ford claims that it continues to develop and test its electrified vehicles to ensure that it adheres to all safety requirements. The automaker also launched an initiative to educate responders and “secondary handlers” on dealing with crashed electrified vehicles.
While Ford and Nissan are figuring out how to respond to the controversy, the Wall Street Journal is casting some doubt on GM’s explanation that the coolant leak is the problem behind the three fires in crashed Chevy Volt cars. According to WSJ, “the National Highway Traffic Safety Administration isn't sure that explanation is correct, people familiar with the agency's thinking said.” Furthermore, the newspaper reported that it could take 90 days or longer to complete its investigation—which could leave the issue in limbo as the Focus Electric is launched and Nissan expands availability of the all-electric LEAF during its second year on the market."
Em: http://www.plugincars.com/nissan-ford-s ... 10873.html