My Biggest, Baddest Rant - triple digit mileage

[LCHIEN]

There's a news article today proclaiming that the new Chevy Volt will get 230 miles per gallon, but YMMV. http://ct.cnet-ssa.cnet.com/clicks?t...d=CNET-SSA&s=5

That just a pile of Crap. I'm so tired of all these companies and people and writers all claiming outrageous miles per gallon for plug-in hybrid electric cars.

I'm an engineer and my specialty is probably measuring things. gasoline mileage figures can only apply where gasoline is the sole energy source put into the car.

In a hybrid car like the Prius, where only the gasoline engine is used to charge the batteries, then a mileage claim of 50+ miles per gallon is correct. That gallon may actually propel the car 50 miles.

In converted Priuses where they have placed a battery charger and connected it to the power socket in their garage, the battery is charged by the electrical power grid and not solely by the battery. These privately converted Priuses are known as plug-in hybrids and their owners are touting 150 miles per gallon.

While its true they may only put in a gallon of gas for every 150 miles they travel, gas is not the only energy source, even though they may not pay for the additional power at the point of adding to the vehicle, they pay for it at the end of the month.

Similarly the Chevy Volt is a plug-in hybrid and you will recharge this car at home to supplement the gasoline energy. The gasoline engine will only kick in when the battery is nearly exhausted, if you don't drive much beyonf the range of a full battery you will use little gasoline. BUt then a golf cart uses no gasoline.

I'm not really sure what the proper way to quote energy requirements for a adaptable mixed-energy input vehicle is. Perhaps its a range of cents per mile at so-many dollars per gallon for gasoline and so many cents per KW-hour. For example a plug in hybrid that uses gets 50 mpg on gas exclusively and uses 25 KW per 100 miles at 60 mph could be claimed to get 2 to 6 cents per mile for exclusive electrical to exclusive gasoline usage, or 4 cents per mile combined (with $3 per gallon and 20 cents per KWH)

i think its irresponisble for Chvy, plug-in hybrid enthusiasts and especially the press to go along with this crazy charade. Most people don't grasp the hidden energy input but the technical editors at major newspapers and magazines should surely be aware.

I think they do it because
1. it's sensational and sell papers.
2. Makes the car companies look much better than they are
3. sells cars
4. the cost of electricity is hidden in the household budget and not a separate line item so it makes people feel better without actually doing much for them (I will admit the cost of electricity may be cheaper per mile than the gasoline cost however).

I think its irresponsible because it raises expectations rather than educating the public that the only really practical way to lower the cost of driving gasoline cars is to reduce size and weight and power.

Disclaimer: I am a disgruntled GM stock owner.

[chopnhack]

LOL, well said Loring. and dont forget the free energy obtainable by separating Brown's gas with a specific resonance!

[Alex Franke]

I think it's okay to say it gets 150 mpg (or 230 or whatever) so long as they follow it up with "but I plug it in at night" -- or something like that -- to make it clear that it doesn't quite fit in with the measurement standard.

I can almost picture the standard city/hwy mileage sticker on the car window right next to the "energy guide" sticker you usually see on appliances.

On a related note, I'd expect the hwy mileage to be a lot lower than the city for a car like that...

[LCHIEN]

But it just doesn't get 150 "miles per a gallon". Why should they be able to say 150 mpg even if they say they plug it in? MPG are very cleary defined units of measure. The term mpg is simply not correct for this application.

[OpaDC]

We sat around after the news tonight and were saying the same thing. Need real numbers to make real comparisons of cost differences. How much money per mile would I be spending gas vs electricity.
Something else I wonder. Does it retain the charge if you "fill er up" and then don't drive it for a couple of days (nice weather and I'm going to the topless Jeep ) is it still "full" like a gas engine is?

[jkristia]

That is exactly what I thought when I saw it in the news today, how can they claim they get 230mpg if they have to charge it from an outlet in between, and exactly how much does it cost to charge it, and how much does it pollute if the electricity comes from a coal powered power plant? (well it is most likely cleaner than a gas burning engine, but it still pollutes).

For any clean technology to take off (or over) the infrastructure must be in place. See, hydrogen cars have been around for years, but they are too expensive, the mileage you get to full tank is very limited (if I remember correct) and no place you can refuel them, but if they could resolve those issue, then I think that would be a better alternative to a green car than a car you have to recharge from an outlet.

Another thing I was thinking about, how long does it take to recharge, imagine you are on your way somewhere and you run low on battery, can you stop at any place and recharge the car in a few minutes?, usually batteries needs to be recharged slowly - oh well, I'm not in line for a Volt electric cars, and with a price tag of 40K ... forget it .

[cgallery]

Another thing I was thinking about, how long does it take to recharge, imagine you are on your way somewhere and you run low on battery, can you stop at any place and recharge the car in a few minutes?

Apparently some charging stations will allow 20-30 minute recharges. These will be available at some Wal-Mart stores, etc.

The home-installed units will take (I think) about 6-8 hours at 220-volts, and 12-14 hours on 110.

[cgallery]

So Loring, how do we rate these cars? Should they provide a spec. for the MPG while running on the engine, plus a second spec for their efficiency in converting your household 110/220 to travel? Like a gasoline equivalency or something?

[LinuxRandal]

Elsewhere, people are laughing because part of it says, 230mpg, and part says 230mph.

The ones stating the mileage however:
http://www.youtube.com/watch?v=VLpx_yioYik

[Tom Slick]

They could claim it's mileage is equal to the to their bail-out money but until they actaully offer any for sale its make-believe.

[Alex Franke]

But it just doesn't get 150 "miles per a gallon". Why should they be able to say 150 mpg even if they say they plug it in? MPG are very cleary defined units of measure. The term mpg is simply not correct for this application.

MPG is a clearly defined metric -- it's the number of miles you get with a gallon of something. If *all* we're talking about is miles and gallons (like in traditional cars), then it's not only clearly defined, but also it's very meaningful. If we're making a point *mostly* regarding distance and gasoline (specifically gasoline), then it's also appropriate (but can be misleading out of context) -- just like saying, "it uses less gasoline," and to some people that's a lot more important than saying "it uses less energy" (especially with gas prices and carbon footprint stuff in people's minds).

That said, I agree that MPG alone is not appropriate, so I think we agree on that. Plug-in cars break the mold IMHO, so if the manufacturer really wants to communicate the amount of energy they require, they should use an energy metric. But most people probably won't understand that, so maybe something along the lines of "X gallons + Y KW-hours per 100 hours of typical City driving..."

[Alex Franke]

I just found an interesting related article here from SAE (society of automotive engineers): http://www.sae.org/mags/AEI/6559

[tjr]

So how many miles per KWH are these cars supposed to get?

Now for my ranting: Back in the early 90's I bought a Geo Metro for just over $5000 that, on a warm day with 12" tires pumped up full, would get 60 MPG going down the freeway at 60ish MPH (recall that in those days many states still had speed limits of 55 and more or less enforced them.) There was absolutely nothing high-tech about that car; as I recollect it even had a carburetor instead of fuel injection. The first couple times I took it for its annual smog test it barely registered on their test equipment. Sure, it was pretty spartan and junky. But mileage was super. The catch? The dealer complained he only made 50 bucks on a car that cheap.

Rather than playing along with auto manufacturers' desires to sell us complex, expensive cars that get excellent mileage while still delivering high profits for both manufacturers and dealers, consumers should be demanding cars that are cheap to operate AND cheap to purchase and maintain.

Disclaimer: After 98000 miles in the Metro along with 60000 in its predecessor the Sprint, I bought a pickup at 27 MPG. Two pickups later, I'm at 20 MPG.

[jackellis]

I'm an engineer

Same here and I work in the electric side of the energy business.

IMHO the public is typically clueless about such things and often has trouble understanding anything that's not drop dead simple. Working out the cost per mile, which is the correct metric, requires dealing with sometimes sizable variations in local electricity and gasoline prices.

Still, the math can be made pretty simple. The Tesla uses something like 200 or 250 watts per mile. On average one kilowatthour costs between 8 and 15 cents, depending on where you live. Therefore, the Tesla costs between 1.6 and 3.8 (round to 1.5 and 4) cents per mile to drive. I just filled up my pickup at $3.09 per gallon and got 28 MPG this last tank (4 cylinder Tacoma). That's ten cents per mile.

I'll dispense with the math around amortizing the cost of batteries, which are life limited.

[tjr]

A note on the SAE article

Unless I'm mistaken, the way they're showing electric vehicle window sticker "mileage", a lower number is more economical. Won't this be a bit confusing? Or is that the idea?

It would make a lot more sense to me to show miles per KWH. In the example shown that would be roughly 3.