Design Article
Driving Impressions: Prius Plug-In Hybrid
Rick DeMeis
6/28/2011 1:02 AM EDT
The Toyota Prius Plug-In Hybrid I was lucky enough to test drive for a week (complete with flashy side decals so everyone knew what I was driving) was one of the fleet of demonstrator cars making the rounds of press, academic, and industry types here in the U.S. The program gives Toyota feedback on the technology as well as user experience and expectations.
The car had a prototype Li-ion battery with 5.2 kWh capacity. Toyota says a production version of the battery will likely be reconfigured to better fit the available space (the rear deck lid is fairly high on the demonstrator) by the time production cars are sold starting in early 2012 (Sales will start in the 13 states that have adopted the California Zero Emissions Vehicle mandate).
The "electric range" reserve of the battery was depleted when the car arrived (with a full tank of gas). It took only three hours to recharge the battery (using the 110V charger that came with the car), which then allowed the car to go 13 to 14 miles in an EV only mode. But the plug-in Prius is no slouch on only electric power and runs at up to 60+ mph without using the gas engine. If you stomp the throttle while in the EV mode, the internal combustion engine will come on for additional power.
Sizing the battery for the 13 mi EV range was a compromise between "size, weight, and cost of the lithium-ion battery pack, all of which we wanted to keep within reasonable limits," said Toyota spokesman Wade Hoyt. If one's driving is less than or not much more than 13 miles until you're back home or near an outlet for a short charge, this editor can see the plug-in becoming an "in-town" electric vehicle.
The charging process itself had the same minor problem I experienced with the all-electric Nissan Leaf, namely the outlet plug slipped from the wall socket if the power electronics control box on the cord was not supported.
Charging was aided by a "time to full charge" readout in the driver's center display. There was also a light on the dash visible from outside the car that goes out when the battery is fully charged. While on the charger, the driver is able to turn on the air conditioning, via the key fob, to precool the car in the summer using utility power. But there is no similar heating function for colder weather. I was also wondering why no remote window-roll-down feature is offered to help with summer cooling without use of the air conditioning.
On the road
Push the "start" button in the plug-in Prius and a "ready" light comes on to let you know all systems are go—the gas engine did not come on (as is often the case in a standard Prius to get it warmed up). I don't know if this was because my drive was in the summer weather or not. A self-centering shift "lever" (it's more like a sliding knob) puts the automatic transmission in the reverse, forward, or engine braking modes. The latter uses more aggresive engine braking to slow the car—but if you forget to return to the drive position, the cruise control won't activate.
But the big question with any alternative powertrain car is what was the fuel economy. First off, I noticed just a slight dip (only 0.1 miles) in the remaining EV range number when I switch on the climate control. After 310.4 miles, I filled up with 5.168 gallons of gas, for a mileage of 60.1 mpg (the onboard computer pegged mileage at 59.8 mpg). If you eliminate the electric range only mileage (I charged and depelete the battery through four complete EV cycles for about 53 miles), mileage was still a very respectable 49.8 mpg.
The car had a prototype Li-ion battery with 5.2 kWh capacity. Toyota says a production version of the battery will likely be reconfigured to better fit the available space (the rear deck lid is fairly high on the demonstrator) by the time production cars are sold starting in early 2012 (Sales will start in the 13 states that have adopted the California Zero Emissions Vehicle mandate).
The "electric range" reserve of the battery was depleted when the car arrived (with a full tank of gas). It took only three hours to recharge the battery (using the 110V charger that came with the car), which then allowed the car to go 13 to 14 miles in an EV only mode. But the plug-in Prius is no slouch on only electric power and runs at up to 60+ mph without using the gas engine. If you stomp the throttle while in the EV mode, the internal combustion engine will come on for additional power.
Sizing the battery for the 13 mi EV range was a compromise between "size, weight, and cost of the lithium-ion battery pack, all of which we wanted to keep within reasonable limits," said Toyota spokesman Wade Hoyt. If one's driving is less than or not much more than 13 miles until you're back home or near an outlet for a short charge, this editor can see the plug-in becoming an "in-town" electric vehicle.
The charging process itself had the same minor problem I experienced with the all-electric Nissan Leaf, namely the outlet plug slipped from the wall socket if the power electronics control box on the cord was not supported.
Charging was aided by a "time to full charge" readout in the driver's center display. There was also a light on the dash visible from outside the car that goes out when the battery is fully charged. While on the charger, the driver is able to turn on the air conditioning, via the key fob, to precool the car in the summer using utility power. But there is no similar heating function for colder weather. I was also wondering why no remote window-roll-down feature is offered to help with summer cooling without use of the air conditioning.
On the road
Push the "start" button in the plug-in Prius and a "ready" light comes on to let you know all systems are go—the gas engine did not come on (as is often the case in a standard Prius to get it warmed up). I don't know if this was because my drive was in the summer weather or not. A self-centering shift "lever" (it's more like a sliding knob) puts the automatic transmission in the reverse, forward, or engine braking modes. The latter uses more aggresive engine braking to slow the car—but if you forget to return to the drive position, the cruise control won't activate.
But the big question with any alternative powertrain car is what was the fuel economy. First off, I noticed just a slight dip (only 0.1 miles) in the remaining EV range number when I switch on the climate control. After 310.4 miles, I filled up with 5.168 gallons of gas, for a mileage of 60.1 mpg (the onboard computer pegged mileage at 59.8 mpg). If you eliminate the electric range only mileage (I charged and depelete the battery through four complete EV cycles for about 53 miles), mileage was still a very respectable 49.8 mpg.
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Bert22306
6/28/2011 5:34 PM EDT
I really object to people quoting high mpg numbers, when they don't include the cost (and pollution) caused by previous charging of the battery, from an AC source at home. That's a bogus number, pure and simple. Just as bogus as it would be for me to factor in the miles I ride on my bicycle, while the car is sitting idle, into the mpg number for the car.
Aside from that, the rest is pretty much what we have come to expect. Long, long charging time for a relatively tiny amount of actual joules of useful energy. In this case, 13 miles for an 8 or 4 hour charge.
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Bert22306
6/28/2011 5:41 PM EDT
To be clearer about my previous comment, I'm saying the 49.8 or whatever it was mpg is legit. The 73 mpg is certainly not.
Also, I read somewhere that the environmental benefits of plug-in hybrids depend very much on how the grid power is generated, where you live. In most of the US, there are none. You're just as good using the car in hybrid mode only.
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SantiGual
6/30/2011 2:03 AM EDT
take in account that EV charge is made at night, just when electricity generation is more green.
This is the main key of EV vehicles: flatering the consumption curve helps to avoid losses on grid generation and distribution. Excuse me, but someone had to tell this!
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sw555
6/29/2011 9:52 AM EDT
3 hours for 13-14 miles? A joke right? It would take me 6.5 hours to get to work.
Can you spell DOA?
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WKetel
6/29/2011 9:58 AM EDT
I would be most interested in knowing how much the replacement battery will cost, what the replacement labor charge would be, and exactly how long before the charge capacity is reduced to 50%, which many would consider to be a realistic indicator of the end of battery life. Also, how many KWH does the vehicle consume during a charge cycle? Also, how much energy does the regenerative braking actually recover?
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J_Wags
6/29/2011 10:11 AM EDT
So,
Why not talk about mpg, miles per gallon? The implication is that we're talking about a gallon of gasoline, right? And, when the consumer pulls up at the pump and shells out $20 or $25 to drive back and forth to work, talking about how many miles he/she drove on how many gallons seems like a legitimate discussion to me. That's all most consumers consider. Let's be honest, that's probably what you think about after you finish paying at the pump, especially as you watch the cost of gas skyrocketing and the resulting revenues lining the pockets of greedy men & women around the world. The less of my hard earned money I throw away the happier I am and I trust you think similarly.
Now, what we should ultimately discuss is the miles per dollar, or mpd. Since the cost of energy (joules as you rightly point out) is something that the market ultimately cares about, it would seem logical to me that this number will reveal the true impact on society of consuming any particular energy source. If the cost of one source of energy is somehow lower (because we can pick up lumps of coal from the surface of the earth somewhere at relatively low cost) than another then by all means, let's use the lower cost energy. When the consumer then factors in the jump in his/her electric bill we'll have that discussion in the public forum. But, that's not the discussion I see occuring just yet ... it's mpg (or mpd).
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katgod
6/29/2011 12:37 PM EDT
Seems like a pretty efficient piece of transportation, thanks for the information. I do agree that as an eetimes article I would expect a little more detail i.e. what percentage of the 5.2 kW/hr. is used for the given range and I assume the battery will last as long as the present Prius battery system but it would be nice to know if that is true. As for the question about energy recovery on braking, it will be highly variable but as a percentage of total energy used, you recover very little energy even when you are braking on a regular basis, but it is better than nothing, hope that helps.
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selinz
6/29/2011 1:36 PM EDT
As is done in the rest of the world, we should talk in dollars/mile or (litres/100km). Using the inverse of our mile/gallon allows us to see the difference on a more level playing field. Suppose for the sake of argument, running the air conditioner results in a savings of 1litre per 100km for any car. (not a completely unreasonable assumption).
For a car that typically gets 10mpg (25.2 l/100km), he would see mileage of 9.59mpg (26.2 l/100km). The driver would probably consider that in the noise if he were looking at mpg.
Similarly, a car getting 15mpg(16.8 l/100km) would see a mileage of 14.15mpg(17.8 l/100km). Also difficult to detect. Consider the car getting a "normal" 50mpg (5 l/100km): the result would be 42 mpg (6 l/100km). This is not in the noise! One would find similar results by using dollars/mile. In short, the US's use of mpg gives makes high consumption vehicles insensitive to driving habits that can save money.
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selinz
6/29/2011 1:37 PM EDT
sorry, please change "savings" above to "Cost"
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selinz
6/29/2011 1:40 PM EDT
Oh, back to the article. Sounds like Toyota is making the highest mileage vehicle "electric capable" without sacrificing gas mileage.
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Besplin
6/29/2011 1:54 PM EDT
Recent research suggests that there will be huge changes in the automotive industry, including the growth hybrid and pure electric vehicles. Here is a recently published related article.
http://www.databeans.net/pr/pr-062711.php
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Bert22306
6/29/2011 3:44 PM EDT
J_Wags, I guess my point was that we shouldn't be pulling to wool over people's eyes. Especially in an engineering publication like EE Times.
Any engineer should be able to see that if you ignore the cost (and environmental impact) of the electricity you need to run that plug-in hybrid, electricity that you get without using the car's engine, you can achieve the absurd result that the car gets infinite mpg. That number, at best, is useful for the sales and marketing types. It is otherwise meaningless.
There would be significant costs if a non-trivial percentage of cars and trucks went to this plug-in hybrid or battery-electric solution. You don't get something for nothing.
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dthayden
6/29/2011 7:06 PM EDT
Traveling 13 miles at the regular Pruis mileage of roughly 50mpg is going to cost about $1.04 (at $4/gal). Charging the 5.3KWHr battery to travel the same distance would cost me about $0.42 (at my local electric rates). If I did this every workday, which is within my commute profile, it would save me $161/year. There is certainly no financial justification given the added vehicle cost and maintenance issues.
If you try and factor in the cost of intangebles such as operating pollution, manufacturing and disposal waste, military cost to maintain an energy empire, etc, you can probably rationalize whatever outcome you want based on your personal politics and beliefs.
Maybe this is a baby step to an improved solution. Toyota pushed the envelope with their original hybrid solutions and are now enjoying market success. Time will tell.
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Bert22306
6/29/2011 7:46 PM EDT
Exactly the sort of considerations one has to make. Right away, the concept of infinite mpg, which implies something is "free," is debunked. Your numbers show almost half of the cost of running on gasoline is still encountered, running pure electric mode.
Furthermore, though, one can't assume that a marginal extra load on today's electric grid, caused by the oddity plug-in hybrid out there now, is the whole story. If battery-electrics or even plug-in hybrids became the norm, you'd have to build more high tension lines, more coal-powered plants, and/or more nuclear plants. So that's not free either, and there's always a lot of pushback to these upgrades of the power grid.
The "plug in" hype, or even the entire battery-replacement gimmicks, are what ends up being misleading to the "innocent."
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Bob.Simpson_#1
7/1/2011 3:45 AM EDT
Bert, you have made significant erroneous assumptions about this topic. You need a little education on some basics here as you are truly misleading readers with YOUR statements.
1. There is an enormous power capacity available every night while you sleep that is enough power to charge up millions of EV's, ready to drive the next day without fuel. Look at the basic curve data of grid use vs capacity over time.
2. Our power source here in the Pacific NW has very little coal power(zero at night). In fact this year is a record and we cannot even use all the renewable power we have available.
3. Even if 100% of the power to charge an EV DID come from coal, you still reduce CO2 emissions by 27%.
4. If you install a solar array on your home roof, (like ~25% of EV drivers have) you can generate 100% of your own power, which goes onto the grid during on-peak hours, and you take the power back off the grid during off-peak time, IMPROVING grid stability. Cost wise, the EV driver/home owner actually makes money via this TOU metering.
5. Power companies come out better financially with better utilization of their infrastructure and are strongly supporting the transition to EV transportation. As millions of EV's come online, they are expecting and prepared for the occasional transformer upgrade, if there is a cluster of EV's in one neighborhood. Just like the during the home building boom.
6. Look into the V2G initiative. This makes the power even cheaper for EV drivers, giving permission for power companies to use the vehicle battery pack as a power resource when needed (if plugged in), again IMPROVING grid stability.
7. Grid power is significantly more stable than fossil fuels, take time to look at the history and what the power utilities have to say.
Do yourself and others a favor and research the topic before spewing. I expect higher quality feedback on this EE times site.
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honura
9/14/2011 10:51 AM EDT
I have yet to see any data confermint that comercially available solar panels are cost effective. BP has a plant nearby that has abandoned its solar panel at their silicone production site because maintenance was more expensive than the value of electricity provided.
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Bert22306
7/1/2011 5:14 PM EDT
Bob, surely you can see that you have based your assessment on a long series of assumptions that may or may not hold, right?
For example, do you think that apartment dwellers have enough rooftop solar panels to meet their energy needs, and access to AC in their parking spots? Or, for EVs, do you assume EV drivers live close enough to work for a round trip on one charge?
On road trips, do you assume that all the batteries exchanged every 60 miles or so (being very generous) will be charged en masse during the night only?
About a year ago or so, I heard on the radio and read up on something called the Iris engine. Look it up, if you get a chance. Similar case to this. Everything was based on the premise that the efficiency of an internal combustion engine is a proportional to its "working area." The problem is, it's not. Minor detail, right?
A long list of preconditions should give one pause.
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Bert22306
7/1/2011 8:44 PM EDT
Just to be sure my points aren't misinterpreted, I like the idea of EVs, but don't like or believe much of the hype around battery-powered EVs.
This is instead what seems to be a more credible approach:
http://www.greencarcongress.com/2009/10/dod-ehs-20091005.html
This approach would create EVs that truly can replace internal combustion engine cars. I'd put more resources into this research.
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honura
9/14/2011 10:55 AM EDT
St Johsberry owner had an EV back in 1970 that was manufactured in the 18 th century. This is not new. They stopped making them because they were not cos effective. The same goes for Hybrids there vere thousand manufactured during the first word war but went out of production because of the extra cos as soon as gasoline was again available with ot retion tickets. It is only the high price of gasoline that allows todays hybrids to survive.
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Bob.Simpson_#1
7/2/2011 11:45 PM EDT
Bert,
None of the numbers I state are assumptions, or based on assumptions. Check out my extensive data gathering on this subject on my website www.evdrive.com. Full details/specs in slide show format.
I have logged 9000 miles of driving without compromise other than range. When I need to go out of town, I take my Honda Civic. My gas consumption has dropped to about 10% (of my 10,000 miles/year) and I have not had to compromise on anything. In fact, the drive quality has improved over the original gas engine in terms of its performance.
We are currently working on a Range extender that will allow driving continiously on fuel of choice. It is small and light enough to not displace cells to maintain a 100 mile pure electric range. Then you have the best of both worlds, until better cells arrive on the market.
Regarding appartment dwellers lack of plug access for charging, is that a reason to not do anything and not begin the gradual transition by those that can?
Once you see the engineering data, then make your judgements. There are some amazing specs on components now and this is just the beginning.
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Bert22306
7/3/2011 3:36 AM EDT
Sure, it's okay to start small, but my original premise was an EV that can replace internal combustion engine cars with no apologies. Rather than EVs that give people the excuse to say "it's not an option for me," as people love to do. I'm not sure what you are referring to when you say "range extender." My goal would be, and EV that can do without the battery, or just have a small battery to provide regenerative braking.
And it isn't just apartment dwellers that are at a disadvantage with battery-powered EVs (and plug-in hybrids). There are many people who own houses with no garage. Check out a lot of older cities up and own the East Coast. There are many people who own houses with garage, but the garage is full of junk (e.g. many or most of my neighbors). We happen to own only one car. I use public transportation to get to work, so even for me, it would be less than ideal to have to rely on one car whose range is limited. So all I'm saying is, I'll get excited when EVs are for the masses by design, rather than being only a second car. And there is work toward that end, has been for some time, but it doesn't get much press. And even when it gets some press, it seems like the press "doesn't get it."
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GREAT-Terry
7/4/2011 11:43 PM EDT
Before BEV really can be efficiently and quickly charged, a PHEV seems to be the most reasonable choice for greener life. We need to pay the cost for greener life. So, green life is not for poor people.
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M_S
7/19/2011 10:27 AM EDT
There are those of us whose commute is far more than 13 miles. My commute in my car is about 27 miles round trip to a park & ride parking lot (no place to recharge) and then riding in a van with up to 13 other people the rest of my 185 mile round trip commute. By the way, my gasoline-only car averages 35 to 40 mpg. If there was a better range and lower battery replacement cost for the hybrid cars, it might be worthwhile. As it stands, I don't see it as a viable solution for me. Regarding the length of my commute, I want to work and that distance is where I found a job.
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honura
9/14/2011 11:07 AM EDT
I do not see any mention of the carbon foot print that is additional to the normal car's manufacturing vs. hybrids and EVs. I want to know, what is the total difference for the life of the vehicle? If it takes twice the energy to make an EV then it is very unlikely that, that will be made up for in even a 200,000 life. If there is no additional energy input into the manufacturing of these vehicles then the comparisons are OK. Since the great majority of all electrical production in the US is fossil fuel based: Coal, Oils, Natural gas, I do not buy that you can assume that your energy comes from renewables. Furthermore as far as I know all renewables except for hydroelectric, cost more than they produce. What happens is that the costs are shifted from the owner to the US public. So buy EV you will be subsidized by me involuntarily when you buy it and again when you use it. This is a rip off for the rest of us. Why is this never in print?
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KevinCBaxter
9/14/2011 12:41 PM EDT
I hate the term “Zero emissions vehicle” which is such a misnomer. Coal provides 50% of the electric power in the US which is used to charge these vehicles, and the generating process is on average only 34% efficient. There are power line transmission losses of 7%, the power supply to the battery charger is about 90% efficient, the battery charging process (not including the charger) is about 90% efficient, and the re-transmission of torque to the wheels via electricity through the electronics and motors is how much? Simple math sows that using coal to charge these zero emissions vehicle is less than 24% efficient whereas an efficient all diesel vehicle can exceed 50%. The true kumbaya tree-hugger who is not a political lackey should be embracing small diesel vehicles. The truly ignorant claim to want to use solar panels to charge these vehicles but the numbers there are even worse, don’t get me started on those efficiencies…
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Sasha Change
10/3/2011 11:18 AM EDT
A plug in hybrid is not for everyone. Just like a moped or city bus is not for everyone. We all don't drive around in the same type of car. There are a dozen choices people make when buying a car.
What people don't have is a choice to use their own electricity to drive a production car that has a gasoline engine as backup for long journeys. Some people would like to have a PHEV. There are issues about charging access, there are issues about renewable power, there are issues about oil. We are already hearing that elctric cars have lower mechanical maintenance costs... an interesting topic to follow. If someone drives 10km to work in electric mode and charges up at work, the PHEV set up may be a reasonable choice.
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