Five years is pretty short term for my family.

Does the study include the cost of replacing the battery every five years?

Where is the evidence that the traction batteries only last five years?

I agree that the lead-acid batteries are only good for about 60 months. However, the traction batteries use a different chemistry and are well protected.

From a recent posting of the sales history of the Prius, it looks like there are 15,556 Prius that are 5-6 years old:

The Prius traction batteries are not failing in droves. The facts and data shows claims about traction battery replacement, at least as far as the Prius is concerned, are not accurate.

BTW, the Honda Civic hybrid and Honda Insights have been in service for nearly the same time frame. There was a problem with Honda Insight batteries in the first year that was fixed but to the best of my knowledge, the Honda hybrids have not suffered a sudden "five year" expiration.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

The US warrenty on the battery is 8 years 100,000 miles and in California it is 10 years or 150,000 miles. It is very unlikely the manufacturer would design a part to fail under warrenty. I read somewhere that Toyota designed their battery pack to last the "life of the car" and estimate it to last at least 15 years or 200,000 miles.

Several Priuses have gone over 200,000 miles on the orginal hybrid traction battery already.

The battery either failing or needing to be replaced has nothing to do with whether it works or not, but entirely to do with its capacity. For example, after five years and 100,000 miles of agressive driving, Tesla Motors' estimates that the Tesla Roadster's battery pack will still have 70% of its original capacity. The fuel economy of a Toyota Prius will become almost identical to a regular gasoline vehicle long before its battery "fails."

When I refer to the point in time when the battery needs to be replaced, I am referring to when it has lost approximately 30% of its capacity, a range within which I would expect many five year old Toyota Priuses have fallen.

I am not talking about when the battery fails. I am talking about when the battery has lost 30% of its capacity and therefore needs to be replaced. You could probably drive a Toyota Prius for thirty years without its battery failing, because the notion of a battery failure is very loosely defined and short of an explosion, no one knows exactly what that means.

By the way, Bob and Nash, I am wondering exactly where did I specify "battery failure" in this thread? Both of you seem to think that I typed that, but I cannot find it so I would appreciate it if either of you could quote exactly where I used the term "battery failure".

I get that none of us realizes what is going to happen for sure. I agree with Nash's post however. I have seen identical estimates (180k to 200k miles) for battery life, and those with 90% of new capacity. Even if this is not true and the battery must be replaced at 100k the cost for a Gen II Prius would not be more than 2 times the expected cost which I believe will be in the $1000 to $1200 range with trade in, in say 2008. So deduct $2500 and you still come out $15k to the good. There is nothing bad about that.

Alden Bowles
2005 Toyota Prius II HSD

Wow, that is some battery. What type of chemistry does it use?

Nothing out of the ordinary. I don't remember how many cells but they are
NiMH. The most important factor is the charge/discharge cycling. This is why they are estimated to last so long. Because the pack is usually never discharged below 40% or charged above 90% each pack can go through tens of thousands of charge/discharge cycles with nominal performance impact. You can get more details at privateNRG.com.
It has some great engine cut-away views, and gives a great explanation of the charge discharge cycle near the bottom, along with tons of other neat stuff.

Alden Bowles
2005 Toyota Prius II HSD

Do you recall exactly how many years the 180,000 to 200,000 mile battery life estimates included?

I am interested in telling everyone in my family that the batteries in Toyota's Hybrids maintain most of their capacity much longer than five years, with figures to support that.

Ahhh, I see the problem now:

We have fleet performance data for the Prius (and all hybrids) that show even with reduced battery capacity, the cars still get nearly new MPG. The MPG performance is not coupled tightly with the battery capacity. It is only when the battery fails that performance drops . . . to zero.

http://avt.inel.gov/hev.html

http://avt.inel.gov/pdf/hev/edta_van...conference.pdf

pp. 27 of 33 - shows Prius 1 from 6.5 Ah to 2.5 Ah and Prius 2 down to 2.6 Ah.

pp. 29 of 33 - shows MPG has barely decreased from the new vehicle MPG.

The point is the battery Ah capacity is important but there is NO linear relationship with the vehicle MPG. A Prius with a 'worn out battery' still gets better mileage than a brand-new Echo/Yaris. This has also been the experience of individual owners who have had the battery replaced.

They report some improvment, 44 MPG -> 48 MPG, but this is in the 10% range. It is only battery failure that causes the car to become either immobile or so crippled that all you can do is get it to the dealer.

The reason why has to do with the cyclical nature of Prius operation. Below 42 miles per hour, the vehicle swaps from ICE and battery power. As the battery capacity goes down, the frequency of ICE operation goes up but the vehicle energy demand does not change. No more additional gas is consumed beyond the small fraction needed to start/stop the ICE. Thus the car continues to get outstanding MPG.

When you get a chance, visit the Prius forum and look at the chart that shows the drag and energy curve. It is drag and nothing else, that dictates how much power is needed. But the Prius hybrid system is able to keep the ICE running in very efficient power ranges. The Atkinson cycle also helps a lot by giving very high specific fuel consumption. The battery simply provides the means that allows the ICE to stay in the 'sweet spot' until the battery fails.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

bwilson4web, I have a relative who is planning to replace his Chevrolet Blazer this year. My relative is not considering a hybrid on the notion that long term maintenance of the battery will outweigh a hybrid's benefits. I am asking for figures concerning the capacity of the battery as functions of both time and mileage, so that I can relay them to him. I am a student therefore I do not have time to do vast amounts of research to verify the figures stated by others in this thread and also to procure the figures I requested in this thread so that I can put my credibility on the line and tell a relative of mine that the notion that kept him from considering a hybrid is unfounded.

In both of your posts in response to me, you have acted unprofessionally towards me. If this level of professionalism continues, I will forget everything that I have read in this thread and my relative will buy a new SUV, without ever considering a hybrid, because you alienated me. I recall roughly stating in another thread that individuals with similar philosophies as yours "must consider other people's needs and desires and not only what you perceive them to be." When I said that, this is one of the things that I meant.