When Do You Have to Replace a Prius Battery?

by Janet Mulroney Clark

The Prius might not be the prettiest car on the marketplace, but most owners aren't complaining. It's hard to find fault with a car that gives you 40 to 50 miles or more per gallon. But a question many people ask is: What about the battery? Since it partially powers the car, doesn't the owner have to worry about replacing it? Here's the good news and the bad news about the Prius battery.

Cost of Battery

The bad news (and it's not even as bad as some have said): The manufacturer's suggested retail price for a battery pack for a first-generation Prius is $2,299, while the price for the battery pack for the second-generation car--the 2004-2008 model years--is $2,588. The cost of labor is not included but still falls shy of the $4,000 that has been floated around.

How Long Do They Last

And the good news: The Prius battery is designed for at least 100,000 miles, and the vast majority do just that. Some do even better. The replacement rate to date is less than one-tenth of one percent. According to Toyota, no batteries have had to be replaced because of malfunction; the ones that have been replaced were because of accidents.

Why the Hype?

Many people have qualms about the Prius battery, and the roots of their fear might be a problem found in the very first models, about 70,000 cars sold only in Japan. The earliest Prius battery was a Panasonic Plastic Case Prismatic Module. The battery used now has a metal case. According to the Toyota website, a "small but significant number of (the vehicles sold in Japan) had problems with the battery pack. Furthermore, the battery pack was so large it took up the entire space between the trunk and the cabin. This led to changes in the Generation II models whose stacks were significantly smaller and far more reliable."

Why the Batteries Last

The batteries are designed to operate as efficiently as possible. "To get maximum life out of the Prius battery pack, the car's computer brain does not allow the battery to fully charge or discharge," said Rick Cotta of Consumer Guide Automotive. Since the battery doesn't experience the type of stress other batteries do, going from completely charged to almost completely discharged, it lasts longer. The battery is designed to stay charged at about 60 percent capacity, give or take 15 percent.

Future Improvements

Toyota is investing heavily in new battery plants, with a goal of producing a million batteries annually by 2011. As the technology improves, the price for new batteries will decrease. According to the "Wall Street Journal," Toyota plans to test a plug-in Prius with a lithium battery in municipal fleets later this year. This battery is expected to give even better gas mileage. And cars sold in Europe can be run on battery-only for a period of time, although they only go about 35 mph in that mode. Perhaps those models will come to the U.S. one day.

About the Author

Janet Clark has written professionally since 2001. She writes about education, careers, culture, parenting, gardening and social justice issues. Clark graduated from Buena Vista University with a degree in education. She has written two novels, "Blind Faith" and "Under the Influence." Clark has received several awards from the Iowa Press Women for her work.