LOS ANGELES (Bloomberg) -- Electric carmaker Tesla Motors Inc. said a blog post asserting Roadster batteries are at risk of failing if owners don't keep the cars plugged in stoked an "irrational" fear.
"A single blogger is spreading a rumor about electric vehicles becoming inoperable," a condition referred to as "bricking," the Palo Alto, Calif.-based company said Friday on its website.
"'Bricking' is an irrational fear based on limited information and a misunderstanding of Tesla's battery system."
Tesla was responding to a Feb. 21 post on a blog called the Understatement, which said if the battery in the Roadster electric car "is ever totally discharged, the owner is left with what Tesla describes as a 'brick': a completely immobile vehicle that cannot be started or even pushed down the street."
At that point, a $40,000 battery pack replacement may be required, according to the Understatement, which cited no one.
Tesla is preparing to sell its first wholly U.S.-built vehicle, the electric Model S sedan, starting in July. The company, named for inventor Nikola Tesla, this month also unveiled a prototype of the Model X, an electric crossover vehicle that arrives in 2013.
Tesla shares fell 2.3 percent to $33.75 at the close Friday in New York trading. The shares have gained 18 percent this year.
Instructions to owners
"You'd really have to not use the vehicle for an extended period for this to be an issue." said David Friedman, a senior engineer for the Union of Concerned Scientists, an environmental advocacy group. In such cases, "it raises the question: Why did you buy an electric vehicle if you aren't going to use it?" he said.
Tesla owners should keep Roadsters plugged in, both to recharge the pack for driving range and to keep "key systems within the car functioning properly," the company said.
The vehicle warns owners when the car's state of charge is falling too low.
Software in newer Roadster models is designed to contact the company, which in turn alerts owners who discharge the batteries too deeply, Tesla said.
The oldest Roadsters, on the road since 2008, take more than two months to fully discharge if not plugged in, the company said.
"A Model S battery parked with 50 percent charge would approach full discharge only after about 12 months," the company said today.
Nissan Motor Co., which sells the all-electric Leaf hatchback, said in a statement the lithium-ion battery pack it uses "will never discharge completely, thanks to an advanced battery management system designed to protect the battery from damage."
The Leaf's warranty booklet cautions owners against "leaving your vehicle for over 14 days where the lithium-ion battery reaches a zero or near zero state of charge," said Katherine Zachary, a company spokeswoman.
Toyota Motor Corp., which this year is to sell electric RAV4 crossovers using Tesla-supplied batteries and motors, said that model will "feature multiple safeguards to avoid full battery depletion," said Jana Hartline, a company spokeswoman.
Both Hartline and John Hanson, a Toyota spokesman, declined to elaborate on those steps. Toyota is an investor in Tesla.