General Motors today said its Chevrolet Volt, which came to market a year ago as a gleaming symbol of green-energy design and revitalized made-in-America electronics innovation, requires a safety repair of its lithium-ion battery.
The word came this morning to Volt owners in an email from Mark Reuss, General Motors chief of North American operations. General Motors refused to use the word "recall" and instead described the battery-repair actions as a "voluntary customer satisfaction program."
(Fair disclosure: I'm driving a Volt around the country for a year as part of the Drive for Innovation, in which we're interviewing engineers and other technologists about innovation).
In his email, Reuss, a Volt owner himself, wrote:
"We are enhancing the vehicle structure and battery coolant system to improve battery protection after a severe crash. We will notify you in February to schedule service to make these modifications." Battery fires
The Volt's lithium-ion battery pack
became the focus of a federal safety investigation after the National Highway Transportation Safety Administration conducted a crash test last spring on one Volt
. Weeks after the crash test, the Volt, sitting in an outside parking lot, caught fire, which started in the battery. The impact had breached the battery's liquid cooling system, causing a short, which caused a fire.
The NHTSA later in the year replicated the fault twice.
"Although there have been no real world customer incidents, we’re taking precautionary steps to ensure your peace of mind. The focus of this investigation has been on what happens days or weeks after a severe side pole impact test, followed by a roll over.
"We are enhancing the vehicle structure and battery coolant system to improve battery protection after a severe crash. We will notify you in February to schedule service to make these modifications."
A spokeswoman for GM indicated the fix should take no more than a day.Design differences
The all-electric Nissan Leaf by contrast has experienced no problems, perhaps because its lithium-ion battery is encased in steel and is not water-cooled. The Leaf has outsold the Volt this year
, although the Volt's sales have improved every month.
The battery issues highlight classic engineering tradeoffs, in which teams of electronics, mechanical and chemical engineers must balance concerns such as capacity, energy density, weight, form factor, placement and a host of other issues when it comes to large batteries (or other components for that matter). The engineering challenge
And while the NHTSA tests could be considered corner-case failures, they're failures nevertheless that must be addressed.
In a Drive for Innovation post, we asked how engineers might design the Volt's battery
for additional safety. The responses included:
- Make the battery pack replaceable
- Change the composition of the coolant
- Design a viable battery-kill scheme--flood the battery electrolyte with a "poison" to kill the electrochemical reactions
- Switch the battery chemistry from Lithium-Manganese Dioxide to Lithium-Iron Phosphate.
- Build a sealed casement around the battery (a la the Leaf)
- Redesign the entire vehicle to be lighter weight, requiring a different, smaller and safer battery.
Ann Thryft at Design News reports today on new design approaches and materials selection
that could make LiOn batteries last longer.
You can read more about the Volt on the Drive for Innovation
. Additionally, I've created a timeline of selected electric vehicle highlights from 2011
on my Storify page.