Plug In Prius - Seattle Times Article

AutoblogGreen
post on the article. Lots of misconceptions in the comments, feel free to help correct them!

Disappointing results - just 51 mpg - for converted PHEV Priuses in Seattle - AutoblogGreen

 

man,i cant wait to see what happens when Volt comes in.... Take these reports and multiply them by factor of 100 as Volt will get mpg in 30's when out of electricity.

Oh I am sure few will give benefit of the doubt as it is AMERICAN, but that will last for few weeks at most .

I just read on Autoblog green about Fisker sports car with similar system to Volt, and OMG what a failure will that be.... 50 miles of EV in Perfect driving conditions, for a sports car... that means people will get 10-15 miles when ripping it and rest of their trip will be spent on 4cly engine... in +100k car... ooops.

 

Tip of the hat to miscrms for the great comments and analysis. Well done.

 

There's another consideration too. I live N. of Seattle, & work S. of it. My wife works in downtown, near where City of Seattle's main office builing is. I hate picking my wife up, because of the hills. They are steep, with short lengths between lights. If these cars are driven mostly to/from the parking garage there @ 6th & Columbia, these hills, combined with short trips (W/o use of EBH) would explain a lot. What's really lacking here is comparison with regular prius driving. And to really test it, they should track drivers to trip milage, then compare when a specific driver uses a regular prius vs a Plug-in one.

 

They just put this on the local news here in Seattle also tonight. Here is the news from their website.

City testing fleet of hybrid cars | Environment News | KING5.com | News for Seattle, Washington

City testing fleet of hybrid cars

[SIZE=-1]05:57 PM PST on Wednesday, February 25, 2009

[/SIZE]
[SIZE=-1]By DEBORAH FELDMAN / KING 5 News[/SIZE]

SEATTLE - A fleet of modified Prius cars is now rolling across King County as part of a test program to see how well electric vehicles can handle local streets.
It was expected that the cars would deliver more than 100 miles per gallon, thanks to a large battery that can be charged with an outlet. However, driving the vehicles around Seattle is serving as a reality check for some very interesting reasons.
When Rich Feldman drives around town in the hybrid -- he's pulling double duty. Not only is the car getting him to his destination as a city of Seattle employee, it's also helping collect data about the true efficiency of a Prius that also doubles as a plug-in car.
"It's great. Just knowing that you're kind of driving the future," he said.
It's one of 13 Prius cars being used in Seattle and King County with a 140-pound battery in the trunk.
"This is straight out of the labs from MIT. Lithium nanofosphate," Feldman said.
The cars are tracked by computers to see exactly how much fuel is being used.
The bumper boasts these cars can get 100-plus miles per gallon, but so far they're averaging just over half of that.
There are several factors that can put a real drain on the plug-in's efficiency, including cold weather, hilly terrain and aggressive driving.
The electric charge only lasts 30 miles before reverting back to regular hybrid mode.
It takes anywhere from four to six hours for a car like this to fully re-charge. So for someone who's using it just for a commute to and from work, they'll be able to have the car completely re-charged in between those two drives.
Seattle City Light employees are driving three of the test vehicles. They say when you couple their hydroelectric power grid with the plug-in car, a completely green drive is possible.
"From generation of the electricity to produce this, up until the point where that hybrid engine kicks into combustion operation, you are not putting any greenhouse gasses into the environment," Scott Thomsen said.

 

Just watched the news article on tv and the guy from Seattle City Light said he was able to achieve the 100 mpg. "With careful driving he often hits the average of 100 mpg and others can too."

 

I would recommend reading:

"PHEV Battery Requirements" by Rousseau, Pagerit, and Fellah, Argonnne Labs, Dec. 3, 2008
​

Their conclusions, pp. 18

• "Aggressive driving will put limits on all EV range, which in turn favors a blended mode operational strategy."
• Battery size is critical for the expected range
• Aggressive driving results in larger energy requirements

What this means is a PHEV probably won't work in fleet usage where the daily utilization is much greater than just commuting. For commuters, it can be wonderful, but if tried with a taxi cab, the results would be humbling ... there is no free lunch but you can sometimes get a great appitizer.

Bob Wilson

 

Bob,

I'd like to expand on that "aggressive driving" comment because it is easy to understand why that matters a lot more for gas use in a plugin than it does for gas use in a regular hybrid.

With a plugin Prius, the share of propulsion energy that comes out of the gasoline is determined by how heavily you use the throttle. Anything up to (maybe) 40 horspower load can be handled by the electrical side alone. Everything over 40 HP load has to be handled by the gas engine. So, until the battery depletes, the mix of electricity and gas used to propel the car is determined (largely) by the fraction of the total power demand that occurs above and below that 40 HP (or so) threshold.

So a lead foot not only increases total energy use, in this case, it radically shifts the mix from electric to gas. The "gas mileage" of a plugin is much more leveraged with respect to average power demand than is the gas mileage of a regular hybrid.

The car imposes some other limits on minimum gas use (e.g., idles the engine over 41 MPH in all circumstances, when you need cabin heat, etc.) But that's the gist of it. I wouldn't even say that the lightest possible accelerator use results in minimum total energy expenditure, but I'm pretty sure it maximizes the fraction of propulsion energy drawn from the battery and minimizes the fraction drawn from gasoline.

 

ya saw same shows online and on TV and one is much more realistic in admitting that some of the fleet duty cars which NEVER see opportunity charging will only get incremental mileage boosts (Seattle is like San Francisco or any other West Coast Pacific town in that its nothing but hills) but remember "just over 50 mpg" is still more than a 25% improvement over regular Pri's due to the severe driving conditions.

now, take away the "duty" part of the drive, make it just a commuter car, and BOOM, now we are seeing 100 mpg and there are people in the study who are getting that. what the one article centers on is the WORST CASE results.

now create an environment that caters to EV's (iow, REQUIRE companies to provide a plug in option) and now we most likely see a fleet of cars that never burn gas during the weekly commute

no one said it was supposed to be easy, and if you look at the transition 100 years ago from horse to car, i think you will find that this transition is actually much easier

 

I remember reading (in a HISTORY BOOK!) an article about how superior horse was because it does not get stuck in the mud with a photo of an early 1900s car stuck up to the axles. The moral of the story is that horses are better than cars. <grins>

Bob Wilson

 

Yep,
If I had a doller for every So Cal Edison leased RAV4-EV that blew by me on the freeway, or from the red lights in the city, I'd be retired. Employee driven cars ... there must be a motto written somewhere that if it belongs to the boss, tear it up. At least Edison trains their people how to plug 'em in. Even worse, here at disney, the employees destroyed the chevy EV pickups via abuse & neglect. what a waste.

 

Just highlighted the important number there. People are focusing on the "barely over 50mpg" without looking at the fuel economy the same cars are getting when run in charge sustaining mode.

 

Well I live in Phoenix and over the last 4,000 miles or so of driving I have averaged 51.1 MPG... this includes several trips to Flagstaff (driving from a 2000' elevation to 7000'+ and back) and a trip to the Grand Canyon and back in november... So I cannot imagine why a plug-in should only get what my often loaded-down Gen. II unmodified Prius averages on a daily basis...

 

For me personally it is overhyped. But I'm not going to make any judgements about anyone else's opinions. As the vehicles are foreseen now the range is too short and the cost is too high compared to a 'traditional Prius' with respect to my own needs and value.

I would find it perfect for my wife's usage but the cost is too prohibitive for the driving she does.

It's a necessary niche that must be developed but for the future but IMO it will remain a niche only in the intermediate term such as 5-10 years.

 

According to the data-report posted earlier, they are only averaging 40mpg when the pack is empty, vs. 59mpg when its working. Their 40mpg to your 51.1 should tell you somethings up.

Rob

 

Google's study found 93.5 MPG with the same plug-in conversion.






Test Methodology:RechargeIT.org

 

That's beautiful...

 

driving conditions is the key here. driving in Downtown Seattle you are lucky to get 40 mpg. cant pulse and glide when every other stoplight you are sitting on a 15% grade hill facing UP.

if i had a car that had that range, i personally would be getting 100+ mpg easy. but that is because my ROUND TRIP commute would be all EV. because speed is low, very few stops, and range is only 7 miles one way. i can plug in at work, so i would not burn gas during the week at all unless i had to take an extra trip out of town.

 

Right, but their fleet numbers are not that different than Seattle's fleet.

Google.org PHEV Fleet Data

	Column 1
0	Prius: 42.8 mpg
1	Prius PHEV: 54.9 mpg
2	Escape Hybrid: 28.6 mpg
3	Escape PHEV: 37.7 mpg

Those fleet drivers are hell on PHEV fuel economy. I was looking at the Seattle data again, and it seems that even the slightest bit of aggressive driving kills PHEV fuel economy. It seems that if they took a chill pill before going out and driving they'd use a lot less gasoline.

 

Yep. Correct. See my earlier post. I own one, I can watch the MFD as I drive it. You have a low-powered electric motor to use, gas-free. Demand more power than the electric motor(s) can deliver, and the excess comes from gasoline. The result is highly leveraged gasoline use, depending on how you drive -- anywhere from none (feather foot, low speeds) to pretty much like a stock Prius (pedal-to-the-metal).

Lesson: If you want to build these for rednecks to drive, and want most of the miles to be electrical miles, make the electrical side beefier.

Otherwise, for the car as it exists now, the only way to get mostly electric miles out of it is to drive with a very light foot.

Which is fine by me. I grew up driving great big trucks. Real trucks I mean, not pickups. So I kind of enjoy babying the throttle and keeping the momentum up -- reminds me of driving moving van, which is what I did for a summer job as a kid. A lot more interesting than driving most cars.

But if you've got your basic point-and-shoot driver, who has never had to drive a vehicle with lower horsepower-to-weight ratio, well ... you're going to use a lot of gasoline. Aim. Floor it. Apply brakes as needed. That's not going to keep power demands at the level where they can be supplied by the relatively small electric motors in the Prius.

What I want to make clear is this: What you are seeing is NOT a generic fault with plugins. It's an artifact of retrofitting a Prius, to run as a PHEV, when the Prius electrical side has been optimized to work as a straight hybrid, not as a plugin.

Do the same thing with a (hypothetical) Volt, and your lead-footed fleet driver will get the same electrical mileage as your light-footed driver.

Another way to say that: If you designed a plugin from the ground up, taking note of the habits of the typical driver, you'd design in a beefier electrical motor than you would for a stock hybrid.

Hope that's clear: the crappy mileage from indifferent drivers is due to the retrofit nature of these cars. The strength of the electrical side is optimized for being a hybrid. When converted to plugin, it's too weak for optimum electrical use, if your typical driver is a leadfoot.