Chip Keen

Hybrid batteries: How durable?

Saturday, April 07, 2007

A few years ago I was seriously considering buying a Prius hybrid. I was told the batteries had a finite life span, and cost a great deal to replace. What's been the experience on longevity, and what do replacements cost?
J. Peter Bentley, Portland

I turned for help with your question to my friend Craig Van Batenburg, hybrid education resources director at the Automotive Career Development Center in Worcester, Mass. (

He replies: "The nickel metal hydride (NiMH) batteries used in today's hybrids last a really long time, more than anyone thought they would.

"The oldest battery packs are now nearly 10 years old in Japan. Most are still original, and still working fine.

"In the U.S. they are over seven years old. ACDC, my hybrid-training company, owns two 2000 Insights, a 2001 Prius, a 2003 Civic Hybrid, a 2004 Prius, and a 2005 Ford Escape Hybrid. ACDC also bought two other hybrids for experimental purposes, a 2000 Insight, and a 2001 Prius. All of the battery packs are original.

"ACDC owns the factory scan tool to monitor and test the battery packs, and all signs are OK on all of our vehicles.

"My suggestion is to look at a NiMH battery pack like you do a transmission. It should last the life of the car -- many do -- but after 200,000 miles and 10 years, it really doesn't owe you much."

Seven years ago, the estimated replacement cost of a hybrid battery pack was $10,000. Today, it's between $2,500 and $3,000; yet price is nearly moot because few are replaced.

According to Toyota ( "The Prius battery (and the battery-power management system) has been designed to maximize battery life. In part this is done by keeping the battery at an optimum charge level -- never fully draining it and never fully recharging it. As a result, the Prius battery leads a pretty easy life. We have lab data showing the equivalent of 180,000 miles with no deterioration, and expect it to last the life of the vehicle.

"We also expect battery technology to continue to improve: the second-generation model battery is 15 percent smaller, 25 percent lighter and has 35 percent more specific power than the first.

"This is true of price as well. Between the 2003 and 2004 models, service battery costs came down 36 percent. We expect them to continue to drop, so that by the time replacements may be needed, it won't be much of an issue.

"Since the car went on sale in 2000, Toyota has not replaced a single battery for wear and tear."

The Canadian website, The Hybrid Experience Report (, lists expenses for the British Columbia government's fleet of 2001 Toyota Prius hybrids. Comprising 64 vehicles, the fleet traveled 1.59 million miles during the study; the average cost per mile for maintenance and repairs was $0.043 USD per mile.

The study states: "There were no costs identified that were specific to the hybrid components of the vehicles."

Initial reports are certainly encouraging, but as the Canadian study observes: "Only when tens of thousands of hybrids have been operated for many years, and over 400,000 kilometers (about 248,000 miles) each, will reliability issues become clear."

Chip Keen, a writer from Washington, owned a car repair business for many years. He has an ASE certification as a Master Automotive Technician. Mail questions to him c/o DriveTime, The Oregonian, 1320 S.W. Broadway, Portland, OR 97201, or send e-mail to Only published inquiries will receive responses.