The battery issue has attracted the attention of plaintiffs' attorneys, who said they were weighing whether to add it to existing legal claims that the Civic hybrid delivers lower gas mileage than advertised.
Attorney Nicholas Chimicles of Haverford, Pa., said he was reviewing the new software update to see whether it has bearing on a suit he filed against Honda seeking class action status. That case, filed in 2007 and still pending after a proposed settlement was thrown out in February, alleges that the advertised mileage ratings of the Civic hybrid proved unattainable in real-world driving. If that is caused by faulty batteries, he said, it could bolster his case.
Like other hybrids, the Civic uses a combination of a gasoline engine and a small electric motor — powered by the battery behind the rear seat — to drive its wheels.
To deal with failing batteries, Honda's letter urges installation of software that protects the battery by limiting the role of the 20-horsepower electric motor while boosting use of the car's 93-horsepower, four-cylinder gas engine.
According to the letter sent last month to Civic hybrid owners, the update tunes the Honda hybrid system, known as Integrated Motor Assist, to limit cycling the battery, which means the electric motor often won't kick in to give an added power boost when accelerating.
It also curtails how often the gasoline engine will shut down when the car is at rest, such as at a red light, a key fuel-saving feature in hybrids.
The software update, which is also being implemented in Japan, doesn't apply to other model years of the Civic hybrid or to other Honda hybrids.
Honda's first hybrid, the Insight, was introduced in 1999. Drivers loved the quirky hatchback, but because it was a two-seater, it had limited commercial appeal. In early 2002, Honda extended the hybrid system to its top-selling Civic compact sedan, hoping to find broader audience.
Like the Insight, it uses a small electric motor driven by a 158-volt nickel-metal hydride battery (separate from the 12-volt lead acid battery) to assist a primary gasoline engine; unlike the Toyota Motor Corp. Prius and other hybrids, it cannot run on the electric motor alone.
Early adapters embraced the Civic hybrid, particularly when the redesigned and slightly more powerful 2006 model came out.
Unlike its predecessor, which received few complaints of battery failure, the second-generation Civic hybrid began showing signs of a problem after several years on the road.
A self-proclaimed "hypermiler," Larry Greenfield of Fountain Valley felt justified in dropping $22,600 for his 2006 Civic hybrid because of the 56 mpg he could squeeze out of the car.
But after 3 1/2 years and 40,000 miles — far below the 10-year, 150,000-mile warranty on the components of the hybrid system required under California law — Greenfield noticed that the battery would no longer hold a charge, leaving him, joltingly, without electric assist.
His dealer acknowledged that the battery was damaged but refused to replace it because it was not completely deteriorated, Greenfield recalls. Instead, the car was given a software update, which Greenfield says decreased its fuel economy 20% without eliminating the battery failure.
After Greenfield threatened to sue, the dealership replaced the battery as a "warranty goodwill gesture" last September, according to receipts. But the dealership said it could not reinstall the original software, and Greenfield said he now can get only 46 mpg. "They fundamentally changed the way the car operates," he said.
Honda's Martin declined to say what replacing a battery under warranty costs Honda, but said the current suggested retail price of a replacement is $2,100, not including shipping or installation.
Martin declined to provide nationwide failure rates for the battery because that data is proprietary, but said Honda had noticed some issues with shortened battery life "under certain circumstances," such as with drivers who use the air conditioning constantly and those who drive in stop-and-go traffic.
That's because the stresses of those conditions demand lots of electricity, forcing the battery, which is charged by the motor, to run through more cycles. In addition, Martin said, the chemistry of batteries degrades faster in hot regions of the country, such as Arizona.
Until receiving Honda's letter in the mail recently, actor Adam Pilver of Los Angeles didn't know what to think of the intermittent battery crashes on his 2007 Civic hybrid.
The only problem, Pilver said, was getting up hills when the electric assist conked out. But now that he's aware of how Honda is handling the issue, he said, he'd prefer not to get the update at all.
"It sounds great for Honda but bad for us if we're losing the hybrid part of our hybrids," he said.