Electric cars

Every time the price of gasoline goes up a penny it costs the US Postal Service $8 million
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It is my understanding that stop and go driving is what electric cars do best. I would think the post office would be the best candidate for electric cars, at least in heavy populated areas.
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high volume stop starts are energy wasteful, overall efficiency drops rapidly the more an electric vehicle has to stop and start.....electric is best on long straight runs even more so if this includes batteries.

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But with an electric car you can use the motor as a generator and do regenerative braking converting most of the kinetic energy back to electrical energy in the battery. In a conventional car the kinetic energy is lost as heat in the brakes.
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True. But the energy gained is, IMO, somewhat exagerated. In true "stop & go" driving when you want to "stop" you want to STOP and you don't want to screw around with "slowing down" with regenerative braking first. Regeneration would work best on a long downhill stretch (without STOPPING) after a long uphill stretch.
A hybrid has many of the same advantages although unless the power management is somewhat predictive the cells might already be at 100% charge when the regenerative braking is call upon.
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John Gilmer wrote:

In my normal driving I don't make many fast stops. Prius has smaller than normal brakes because of regenerative braking. And the city mpg (stop and go)is better than highway. Regeneration must be quite effective.

I read Prius wants to keep battery charge between 40 and 60% of capacity because it gives longer battery life (NiMH). I suspect on a long descent they would run it up to 100%.
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snipped-for-privacy@isp.com says...

There is no benefit to a hybrid at highway speeds because the engine has to run anyway. .,..and you're lugging the weight of the batteries along for no benefit.

I would seem to be a *LONG* descent charge .4C or the batteries are too small to be of much use.
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krw wrote:

>>>

"stop &

>>

. You can use a smaller engine, with battery/electric motor added for when you need more power - acceleration, ascent. (For a very long fast ascent where battery assistance is required you can run out of battery.) The smaller engine operates at a more efficient point. The benefit - around 44 mpg highway for a Prius.
And with a conventional car you are lugging the weight of the higher horsepower of the engine that is not being used most of the time.
In a Prius, at higher speeds the engine - through the transmission - does not turn the wheels fast enough. One of the 2 electric motors is used as a generator feeding the 2nd motor. That operates through a planetary drive to increase the wheel speed. [See Hybrid Synergy Drive in Wikipedia.]
The engine, by the way, is a variation that uses an Atkinson cycle (which I had never heard of). .

. Design of anything is a series of trade-offs.
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pat wrote:

That's true of any vehicle, if you have a lot of stops, an electric vehicle should have advantages in that the engine doesn't need to idle while the vehicle is stopped.
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| | pat wrote: |> high volume stop starts are energy wasteful, overall efficiency drops |> rapidly the more an electric vehicle has to stop and start.....electric is |> best on long straight runs even more so if this includes batteries. |> | | | That's true of any vehicle, if you have a lot of stops, an electric | vehicle should have advantages in that the engine doesn't need to idle | while the vehicle is stopped.
That and the brakes can return most of that energy back to the batteries.
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snipped-for-privacy@ipal.net wrote:

In theory, yes, in practice, I don't know how much actually makes it back into the batteries. I suspect dynamic braking is much more effective in long steady braking such as descent down a long hill than in small, low speed stops. I have no data to back this up though and would be curious to see real world measurements.
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James Sweet wrote:

The only hybrid I have looked at is a Prius. It is rated 48 mpg city, 45 highway - the regenerative braking must be pretty good. The brakes are smaller than they would be on a 'normal' car. If you stop too fast, less energy is captured. (Driving stupidly in a 'normal' car lowers gas mileage too.) On very long descents you can capture more energy than the battery capacity. For that there is a mode that runs the engine for compression braking.
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For all the cool technology it contains, I'm afraid I'm just not impressed by the Prius. When I was a kid, my parents had a Mercury Topaz diesel that got 55-60 mpg, and that was 25 years ago. 100 mpg would pique my interest, but 45-50 is old hat, even with current fuel prices it's more economical to drive a conventional car and not have the complexity of two powerplants, batteries, computers, etc. I suspect these things will be a nightmare when they reach 10 or so years old and the batteries are failing.
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What happens when it goes to 50 Degrees F below zero? I suppose the batteries will have to be heated, and that will cost more than they save.
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On Mon, 16 Jun 2008 08:59:42 -0700 (PDT), Gerald Newton

Don't use them at those temperatures.
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metspitzer wrote:

Where does it get to 50 below?
Certainly in most of the populated areas of North America the temperature range would not be an issue.
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Fairbanks, Alaska it gets 50 below in the winter and has freezing temperatures for six months out of the year. We use electric battery blankets, head bolt and transmission heaters in the winter. It used to cost about $100 a month to plug in a car from October to March, but that cost has risen by about 50 percent. Battery powered cars are out of the question here. The same applies to solar power and wind power. There are about 100,000 people living noth of the 63 meridian that have this problem in Alaska.
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----------------------------
wrote:

Fairbanks, Alaska it gets 50 below in the winter and has freezing temperatures for six months out of the year. We use electric battery blankets, head bolt and transmission heaters in the winter. It used to cost about $100 a month to plug in a car from October to March, but that cost has risen by about 50 percent. Battery powered cars are out of the question here. The same applies to solar power and wind power. There are about 100,000 people living noth of the 63 meridian that have this problem in Alaska.
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Do you use in hose water heaters? - I have found these to be more effective than the typical block heater in that they set up a natural convection of "hot" water. While having only occasional experience of -50, I remember many -40 days in Alberta, Manitoba and Quebec. Now, on Vancouver Island, it is much balmier so these memories do fade. Through places like Juneau and Ketchican, electric cars would work and as there isn't far that you can drive there-they might do quite well.
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That's a pretty tiny minority of the population really, and a special case for sure. With a population of over 300 million, 100k is but a drop in the bucket, and I'll stand by my assertion that for the vast majority of the population, the temperature is not an issue. Obviously not everyone everywhere could get by with an electric vehicle, but the same can be said of any type of vehicle.
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I think there are other northern states where batteries would be a problem including Montana, Minnesota, North Dakota, Michigan and Wisconsin. For these new hybrid cars to be accepted they will have to operate in freezing temperaures of at least 20 degrees F below zero.
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Gerald Newton wrote:

Growing up in Michigan, I can attest that it gets colder here in NY. Michigan has the Great Lakes to help moderate the temperatures of any artic air coming down from Canada. International Falls, Minnesota is often in the news as a cold place. And here in New York we see -10F to -20F a few times each winter.
daestrom
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