2006 Honda Insight (© American Honda)Click to enlarge picture

The first hybrid on the road, the Honda Insight will reach its 10th birthday in 2009. Despite early fears about battery failure, Honda's hybrids have held up well.

Battery lifespan may not be at the front of a hybrid buyer’s mind as they bask in eco-satisfaction and new car smell. But for the person combing the Web for a deal on a second-hand hybrid — or the person whose hybrid is getting on in years — the question of battery life could be a pressing one. No one is eager for “The Talk” from their mechanic, the one where he has that look in his eye as he pats you on the shoulder and says, “Sorry bud. Your battery’s kaput.”

No battery lasts forever, even advanced rechargeables like those in hybrid cars. After a certain amount of electron traffic in and out of its cells, a battery loses its ability to hold enough charge and is ready for the smelter (or for a less demanding application than a car). But the question remains: How long will it last? Sadly, there is no perfect answer, just as there is no way to say exactly how long your transmission will last. Quite a bit of cynicism and anxiety hovers around the issue of hybrid battery life, but is it justified?

Long Warranties
The first vote of confidence comes from the automakers themselves. Toyota claims that its hybrid battery (which it calls the “traction battery”) is designed to last “the life of the car.” More than a little bit of controversy has swirled around this statement, much of it instigated by the now infamous “Dust to Dust” paper (think Hummer greener than a Prius).

But as far as Toyota is concerned, the life of the Prius is defined as 180,000 miles, and the nickel-metal hydride (NiMH) battery is expected to stay perky at least that long. Toyota stands behind that claim with a more-than-respectable battery warranty: 100,000 miles or eight years, in 42 states. In the eight other states that have adopted higher standards, it is 150,000 miles or 10 years.

Honda brought the first hybrid to market (the Insight two-seater) back in 1999, and now offers a battery warranty on its hybrid models similar to Toyota’s warranty (the same in the eight states; 80,000 miles/eight years in the rest). For the Insight, Honda has extended coverage on the batteries to 150,000 miles/10 years regardless of what state they are sold in. When the first wave of Insights comes out of warranty in 2009, we can be sure that the battery question will be coming up much more often.

But even if carmakers believe in their products, how many miles can a driver really squeeze out of a hybrid battery? The answer seems to be that we don’t know yet. Even with the first round of hybrids reaching their tenth birthday, those big batteries are still hanging in there. Gary Smith, Toyota’s National Service Technology Manager, says that the battery failure rate for a first-generation Prius is around 1 percent, but that the second-generation is down to less than one bad battery in 40,000, a stat he calls “fractional and insignificant.”

Is battery life a hybrid purchase consideration?

Hybrid odometers keep racking up miles long after they have outrun their warranties. Case in point: Andrew Grant, famed as the first hybrid taxi driver, drove his first-generation Prius 200,000 miles before Toyota asked for it back to conduct research (exchanging it for a new one, of course). Danny Cooper, the founder of PriusChat.com, has a special section of his site for members in the “100,000-mile club.” As made clear by hundreds of entries on his site, there’s certainly no epidemic of traction battery failures, or even gripes about declining performance.

But early fears about exhausted hybrid batteries have persisted despite the track record. “I remember when the 2004 Prius came out, there were many articles stating that buyers would be facing $10,000 costs to replace their [traction] battery,” says Cooper. “Here we are four years later with a .003 percent failure rate and the ability to buy used batteries on eBay starting at $500. It sounds to me like buying a hybrid isn't quite the gamble that people once thought it was.”