Electric/hybrid question

As far as I can tell, basically what you save on petrol will be spent on battery packs. At least several thousand dollars, going on the UPS battery prices I've seen. (Banks of 2v/40ah or similar)

-mark

I own a '04 Toyota Prius with 37k miles and follow a couple of Prius chat groups. First, the Prius has 2 batteries: a high voltage traction battery and a 12 volt lead-acid battery, that is small compared to the typical car.

Toyota projects the traction battery to live the life of the car. The car's computer software is biased to optimize battery life, wherein the traction battery "operates" in the range of about 40% to 80% state of charge. While there has been specualation that a new traction battery would presently cost in the order of $3000, the projection is that prices will come down and/or market will develop for supporting battery repair/maintenance. The traction battery contains a number of individual cells which can be replaced individually or rejuvenated. There will also be batteries available from wrecks. So should a replacement battery be needed, what might actually happen is that an exchange for a reconditioned battery might be the typcial procedure. In the Prius, the traction battery is warranted for either 8 years/100k miles or 10 years/150k miles, depending on the emission warranty requirements of the state where the vehicle is sold (I hope I got this right).

The 12 volt battery is something of a different story as it is possible to run it completely down if one doesn't understand and allow for the way the car works. For example, operating accessories such as the radio when the vehicle is NOT in READY mode. Running the 12 volt battery down is abuse of the battery and will shorten its life.

Frankly, as an owner, I worry more about failure of one of the many computers, sensors, or the Multifunction Display out of warranty then I do of the battery. I bought the factory extended warranty for this reason and will have to decide whether to sell the car when the warranty is over rather than take the risk myself.

Incidentally, my wife is averaging in the mid-50s mpg with a 90 mile round trip commute in heavy surburban Washington, DC traffic. I am a large person and find my '96 Outback to be more comfortable and the Prius has peculiar visibility out of the split rear window, but in general the Prius is a marvelous car.

Ed P

Yes, it's a zero sum game. But supposedly there will be fewer pollutants.

But, the auto crash rescue teams are starting to get worrried. Why?

600V for the battery pack filled with acid. What happens when that cracks open in a crash? Do you want to pull someone out of a car that might have 600V on the frame? Will the sparking ignite any spilled fuel? And can you use water to douse any flames that do occur?

I haven't seen anyone address those questions except for the rescue workers.

Al

I googled this up a while back. Aussie site figured battery replacement in Prius would be $7,000. Toyota warranty, I believe is 7/70,000 except in California where it is

10/100,000. To me, this means, when warranty is over and batteries go, you junk the car - not something us Subie fans would want to do. Frank

That's why the cables are painted a nice fluoro, UV-reacting, glow-in-the-dark paint. Local firies are starting to buy massive grounding straps and stakes, grounding the car frame to earth just in case.

I've played with LV before (

thanks to all. I have seen the battery pack from the Toyota's. It reminded me of an insutrial circuit breaker panel. One can replace individual cells. A bad one should be relativly easy to find with a voltmeter.

A couple of things concern me. From what I can see the hybrid uses the battery pack/motor to average out power demands by peaking off the battery pack. That lets the fuel engine run in a more efficient manner but won't help under continuous heavy loads like pulling a trailer or stop and go traffic. You do get some recovery on braking but I don't know how significant that is. On the other side battery technology in use so far is mature technology. I see a lot of predictions prices will drop but I suspect they will stay the same or increase due to hard to get materials and/or deposits to ensure recycling of what is essentially reusable toxic waste. If I was not looking for high milage I would be interested but I am looking at a

200,000 mi life, not 100,000 as I seem to be averaging around 30,000/yr for work. It will be interesting to watch this for the next few years...

;-)

Stop and go traffic is where the hybrid/regenerative system has the GREATEST benefit. The car actually gets BETTER gas mileage in town than on the freeway, for three reasons: while other cars are idling in traffic, the Prius uses no gasoline--the engine is OFF. Every time the brakes are applied, power is sent to the traction battery, instead of going up as heat in the brakes. The engine starts only when the power is needed to recharge the battery, and the computer arranges for it to run at its most efficient operating point.

An aside: since the brakes are not used very much, brake life should be very long.

It's not likely all of the battery cells will die at the same time. You should be able to replace just the bad ones one at a time.

Yousuf Khan

I understand they are metal hydride batteries - I use such in my digital camera - expensive but long life. Guess it depends how assembled and how many cells. Maybe owners can enlighten us.

While I think hybrids are important, as a retired person who does not drive a lot and keeps cars forever, a hybrid would probably not be cost/effective for someone like myself.

Fank

Or it might be extremely appropriate for you. It looks like these cars are best suited for puttering around town rather than on the highway. And less you use it, the less likely any of the battery cells will die.

cost/effective

I doubt that. I have a friend that thinks cars die of old age rather than use. He's probably partially right, e.g. hoses, belts and tires will rot with time, even though not used. Also my metal hydride camera batteries lose charge when not used. I think when they are new, they lose as much as

1% per day. Hoses and belts, I can afford but batteries such as these?

I may have a hybrid one day, but I'll wait until they are time tested and prices become competitive. Much better are diesels. Newer ones are apparently much quieter, low sulfur fuel is in the making, and city mileage is equivalent to highway mileage and much better than gas engines. BTW I got a close look at a Prius the other day. Parked next to my Forester it appeared very small. I also thought it was ugly ;) Frank

There have been a number of quite technical discussions on the Prius traction battery at Prius_Technical snipped-for-privacy@yahoogroups.com. One individual bought a salvage Prius and described what he went through building his own traction battery charger. (Should the traction battery ever fail or become discharged, you cannot jump start the vehicle. The battery must be recharged by a special system that Toyota dealers have or replaced.) Another individual discussed taking a traction battery apart and the procedure for rejuvenating/reconditioning individual cells. If anyone is interested in the battery technology, I would encourage them to search the archives for this yahoo group.

With regard to a person who does not drive a lot or only drives short trips, be advised that hybrids do not shine mpg wise under such circumstances. They probably do as well as non-hybrids but the first five minutes and few miles of travel for any car drags down average mpg.

Incidentally, as I mentioned in an earlier post, my major out-of-warranty concern would be for failure of some of the high tech features of the Prius. Supposedly, the Multi Function Display retails for around $3000 but supposedly re-furbished ones are being used for warranty repairs and these are costing more like $400.

Ed P '96 Outback & '04 Prius

I get your point. Here is what concerns me. 1 Horsepower is 746 watts at 100% efficiency. I'm getting the idea that the battery is around 330 V so current =watts/volts. The comes out to about 2.25 Amps/horsepower. A 40 A/hr cell has been referred to and it sounds reasonable from what I have seen. If I assume a 10 hp traction motor that 22.5 A under load so that cell is going flat in under 30 minutes. Assuming the 20 - 80% charge range mentioned in another note further reduces amount of power stored thus reducing the cycleing time of the motor. If I then factor in that I am really pulling a 100+ hp gas engine out and replacing it with an electric traction motor and I wonder just how big that electric motor really is or how short the charge capacity of the battery really is. It seems that the charging system should hardly ever shut off. That also tosses in the issue of how much ewear and tear on the charging motor from all the stopping and starting. I could get more complex but I think this is enough to show why I am wondering if hybrid technology is really that good an idea. Fuel cells would be an entirely different picture.

FWIW: Cell replacement. I would expect a couple of cells to fail prematurely due to manufaturing inconsistency. I would expect most of the cells to fail together. Basically for the same reasons that large buildings replace all the lamp bulbs at once. Life is pretty consistent with a particular usage pattern.

On Sat, 08 Oct 2005 02:46:54 GMT, nothermark wrote in news: snipped-for-privacy@4ax.com:

The Prius has a 202V 6.5Ah battery with a 500V 50kW (67hp) electric motor and a 76hp gas motor.

How little use are you planning on not giving it? I mean for a car to be not used and have things fail because of rot would require years in most cases. Old age, together with heavy usage will rot things much faster.

As for the batteries losing charge, it really doesn't matter, you still have a gasoline motor there, it's not like as if you'll be stranded when the batteries are fully discharged. The gas motor will recharge the batteries while you drive. The only problem you're going to have is that your initial gas mileage won't be nearly as good as when the car is fully charged up. Besides, it looks like these manufacturers have a broad definition of what a fully charged battery is. As one other poster said about the Toyota Prius, the computer tries to keep the battery between 40-80% full before trying to recharge it. So even a 40% charge is considered a full charge for their purposes. I'm sure quite a few cells could become disfunctional and you could still maintain at least a 40% charge.

Plus another thing you have to think about is that they're only ever trying to fill up to 80% of its maximum capacity before they stop charging it. In a digital camera or any other consumer electronics device, the batteries are usually taken up close to the 100% mark. The close to the top of the line it's at, the more it leaks out, much like a spring that's been stretched to its maximum for too long, it never goes back to its original shape.

If you think that's small, then check this out:

These cars have gotten extremely popular up here in Canada. It's made by DaimlerChrysler. They're economical, and cute as a button.

Yousuf Khan

You gotta remember, the savings you get from electric motors is as a result of essentially zero energy expenditure during idle situations. When you're in stop'n'go city traffic (assuming you're not using electricity for other purposes like listening to the radio or running your A/C, but even still the energy draw should be pretty miniscule), the car uses zero watts when it's stopped. A gas car that is stopped has to keep its gas motor running for the moment it's gotta getting going again, not so with an electric motor.

When at high speed, the electric motor is probably hardly being used, it's the gas motor doing all of the work. So the electric batteries are being recharged during high speed life. At most, I think the electric motors might kick in at speed when attempting to accelerate, so that the gas motor will get a bit of an assist.

Yousuf Khan

I would suggest that you have over simplified and misunderstand the operation of full hybrids such as the Prius. In the Prius there is no separated alternator or starter. A small 12-volt battery provides power to boot up the computer which in turn switches the high-voltage traction battery into the system. To start the ICE (internal combustion engine), the traction battery provides the power to one of the motor/generators to spin up (start) the ICE. Dead traction battery, means NO START -= period. I believe the biggest part of the fuel efficiency gain comes from an integrated system of ICE and electric motor/generators that allows for a relatively small ICE to operate in a higher efficiency mode than in a regular car. The electric motors provide added torque when needed to allow the use of the small, high-efficiency ICE.

Besides, it looks like these manufacturers have a

First, it is a mis-statement to say that Toyota ever considers a 40% SOC to be full charge. I believe there are two primary issues: The traction battery must always be protected to have enough charge to start the ICE and fully charging or fully discharging the traction battery has an adverse effect on its life expectancy. Apparently, Toyota determined that a SOC range of 40% to 80% was close to optimum for battery life. Also, regenerative braking can only function if the battery has room to accept the charge.

In hybrids, the most efficient operation is under power of the ICE. There are conversion losses in using gasoline to run the ICE to charge the battery which then drives the electric motors. On the other hand, regenerative braking recovers energy that would otherwise be dissipated as heat.

I think many buy the Prius in part because it is such a technological marvel. Clearly, as demonstrated by the Honda Accord Hybrid, the hybrid approach can be tailored to better acceleration or to best gas mileage with reduced emissions in both cases. Of great importance is the various hybrids now on the market demonstrate that you don't have to give up acceptable performance to be cleaner and more fuel efficient.

Ed P '96 Outback 99k miles '04 Prius 37k miles

An over simplification. As I mention in another post, the Toyota hybrid

*system* allows for the use of a small gasoline engine (ICE) that operates at higher efficiency than a normal car. All of the external energy that runs a hybrid comes from gasoline. Yes, the system recovers what would have been wasted through regenerative braking, but it is the total system that achieves the high mpg results.

I admit thought that it is fascinating to observe the energy screen display while in stop & go, or even stopped, traffic. The Prius has an electric, variable speed compressor for its AC. In traffic jams leaving Nationals baseball games in Washington, DC, this summer, we had our AC auto-climate-control set to 70 degrees with outside temperature in the

80's and 90's, and the ICE would only run for a minute or two at a time to keep the traction battery above the 40% SOC. Note: That in stop & go situations, the system doesn't even try to charge the traction battery back to "full" charge; it just keeps the battery a little above the 40% SOC low point.

I have never experienced it, but apparently if one accelerates hard enough and long enough (up a long grade perhaps) to deplete the traction battery down to the 40% SOC, overall acceleration is reduced until the charge can build up again. Nevertheless, Prius owners have successfully driven up MT. Washington in New Hampshire and drive the mountain roads out west without problems.

A final point of interest. Back in August, five guys drove a Prius around a 14 mile loop near a motel in Pittsburg to see how far they could go on one tank of gas. It involved stops and starts and they never went over 40 mph. They went approximately 1400 miles on a little over 12 gals for an average of approximately 110 mpg! The ICE only ran

27% of the time.

Ed P '96 Outback 97 k miles '04 Prius 37 k miles

Thanks Ed, this is the kind of information that helps the rest of us understand the issues.

nothermark