The battery in the Prius is warranted for 8 years, and has been tested upwards of 180,000 miles.
Here is a Road & Track Technical Correspondence letter from last year March:
In reply to:
Bob, your straightforward question turned out to have a surprisingly complex answer. Toyota warranties the Prius battery pack for eight years, “but the expectation is it will last much longer than that.” How much longer no one is willing to speculate, so we’ll guestimate a 10-year lifespan from the nickel/metal-hydride unit.
Even more confusing to our Casio 10-key calculator is that the Prius battery pack is priced at $4000 by Toyota public relations, $3420 by our local dealer and is expected to cost only $1000 in eight years (Toyota’s estimate) due to greater economies of scale as more vehicles require battery replacement. While that may sound too good to be true, Toyota is insistent on this point. They also expect the batteries to get lighter and more efficient. What’s more, it’s forecast that reconditioned battery packs will be part of the picture. (You’d likely replace your conventional 10-year-old car’s engine with a rebuilt one, right?)
So, which is more financially sound, gasoline or battery power? At $1000 for the battery and a lifespan of eight years or longer, the battery clearly wins any contest of the calculators. At a worst case of $3500 for a new battery pack, installed, along with $1.65 per gallon of gasoline, we find the battery pack is worth 2121 gallons of gasoline. Our Road Test Summary rates the (first-generation) Prius at 40.3 mpg, which would yield 85,476 miles of driving. That would be a bit over 4 cents a mile for the battery, and a financial dead heat given 10,684 miles per year of driving in eight years. Adding even a little to battery life or subtracting from its cost makes the battery a winner; and that’s not to mention any change in the price of gasoline, which is only going to go up.
Installation costs are not an issue; the battery pack is easily accessible by removing the back seat, à la VW Beetles and Piper Cherokees.
A quick google brings up some reading about the battery and costs....all positive, and nothing that I think I would worry about if I went that route.
