Electric cars vs. plug-in hybrids: Which gets better economy?

for all the haters -


2012 Infiniti M35h vs. 2013 Lexus GS 450h vs. 2012 Porsche Panamera Hybrid - Motor Trend

Add in the activehybrid 3 and I doubt anyone thinks any of the 4 is low performance, poor handling, etc but there is the price.

How much do people pay for a smoother engine with better NVH? You get your answer on why we should not do a stupid payback conversion for a versa versus leaf, or a volt versus a cruze.

 

Yeah, those Volt owners are right. The topology is identical to a home-grown EV that has a range-extender generator on a trailer. Most of the time those home-grown EVs cruise around for 20 miles on batteries alone, wheels being driven by an electric motor, but occasionally they hook up their genset trailer for a long drive. Same thing goes for the Volt. With the minor exception of high-speed cruising when the motor may be coupled directly to the wheels when it is most efficient, but then that isn't any different than a home-grown EV which has a diesel pusher trailer on the back instead of a genset for long highway hauls.

 

That range chart is certainly not for 2013 Leafs with a heat pump. It also is ridiculously pessimistic. The EPA on 100% charge is 84 miles and that is easily beatable by 20% with modest speed and climate.

 

Rav 4 EV solves most of the arguments here. 100 mile range on normal charge, 120 with extended.

Great handling, nimble and FAST 0-60 in about 7 seconds.

Tons of cargo space. More room than my 2009 MDX thats for sure.

5 hours to charge on 40amp circuit.

Driving rather aggressively I still get 3 miles per kwh.

 

I still am confused. If Idle in a Prius during warm-up is inefficient, why drive that way in a PiP ?

 

short answer:
The Prius is first a low emissions vehicle (think Kyoto Treaty). Fuel efficiency is only a secondary objective for the Prius. The Plug-In-Prius(PiP) electrical usage is designed not as a range extender (e.g. Chevy Volt) or a part time BEV (e.g. Ford Energi), but as a super hybrid ( i.e. a regular Prius with a more powerful battery ...which just also happens to be rechargeable too ).

long answer:
The Prius warmup cycle is designed to minimize its emissions by aggressively warming up the catalytic converter to its most effective operating temperature. Normally, the highest level of emissions from a internal combustion engine vehicle occurs during the first five minutes (the warm up phase) of operation - because when a catalytic converter is cold it does not effectively reduce emission levels from the ICE exhaust. The Prius' aggressive warmup of the catalytic converter while being less energy efficient gives the Prius the lowest tail pipe emissions of all mass produced internal combusion engine based cars except the Smart two car (which I believe matches it with respect to emission levels). An engine block heater is helpful in reducing the energy cost of the Prius warmup cycle - but the BTU requirements is still there so unless you drive the Prius for a while - the Prius' high overhead for a cold start will always be gnawing at the Prius' fuel efficiency....%|

EV mode on a regular Prius:
IIRC the most fuel efficient speed for the Prius in EV mode on a flat road surface is about 15 mph - unless you have gravity assistance - beyond 15 mph, it is more energy efficient to just fire up the ICE if you want the Prius to go faster (since all electrical energy in a regular Prius is generated by mechanical energy created by the ICE anyway) .

 

Walter,
I think Bob's post was in regards to best fuel economy. That was my question at any rate.

 

Walter gave part of what happens:

During the first ~50 seconds, the catalytic converter is too cold to convert the emissions. So the hybrid control laws try to maximize use of EV for power. This gives a limited, EV window that allows acceleration to nearly 40 mph. Once at speed, shift into "N" and the engine speed returns to minimum fuel burn idle. But the engine coolant has only warmed up about 5-7C and that is a problem.

Now FrankTiger did some excellent work mapping engine efficiency as a function of coolant temperature. One of the things he found and I've confirmed from my own studies, ~60C is the threshold for engine fuel efficient operation. Depending upon starting temperature, this can take several minutes. This one of the rare times when minimizing engine power demands pays big dividends during the trip:

• choose routes that have down-grades
• choose routes that have low power requirements (i.e., slow speeds)
• maximize use of "N" but not at the expense of high ICE power (engine is exceptionally inefficient)

Once the engine reaches 60C, drive normally and for those Prius with a Stage-4, look for opportunities.

Paying close attention to the first, cold-soak, mile or two and it preserves MPG for both shorter and cold weather trips. So my morning commute starts driving through the neighborhood, posted at 25 mph. I have some gentle downgrades and know the flats and upgrades. So I choose the initial, neighborhood routes to minimize fuel burn while the engine, at idle, warms to 60-70C.

Bob Wilson

 

On the Maryland side of the Washington DC Metro Region, we currently pay about 15.2 cents per kwh (after taxes and distribution fees) while regular 87 octane 10% ethanol gasoline cost about $3.52/gallon. A BEV and plug-in hybrids in BEV mode get about 3.5 to 4 miles/kwh ( this is kwh as measured from the battery, there is about a 10% to 20% power transfer loss when recharging the battery pack from residential power outlet but we will ignore this loss a this time to simplify this analysis, fyi - 240 VAC recharging is more energy efficient than 120 VAC recharging) . The Plug in Prius BEV range is only about 12 miles while the Nissan Leaf BEV range is about 75 mile....$3.52 of electricity give 23.16 kwh of electricity which translates to 92.6 miles for a 4 mile/kwh BEV like a Nissan Leaf. Even with hypermiling in the summer, the best fuel efficiency I can achieve on a Prius is between 63 to 71 mpg from a $3.52 gallon of gas. The the current energy pricing scheme, the Nissan Leaf BEV beats a regular Prius by about 40% per $1 spent on fuel, but the Prius' advantage is that it can go +600 miles and the Leaf has a top range of about 100 miles before it needs a recharge. Another advantage a Prius has over a BEV like the Nissan Leaf is that refueling a Prius takes only a few minutes but a Leaf may need several hours to recharge.

With respect to carbon foot print, if one uses the regular electric utility in the DC area (PEPCO) most of electricity is generated with fossil fuels ( 50% coal, 30% natural gas, 10% nuclear, 10% alternative energy) ... even if you select a *clean* energy supplier, you must buy *dirty* energy from fossil fuels generated by PEPCO to distribution the clean energy into your home. For every 1 kwh of clean energy one buys - 0.30 kwh of dirty energy is needed to distribute the clean energy to your home.

 

Ahh, now I think I'm following, but please correct any misunderstanding:

During warm-up fuel consumption is ~ constant up to ~ 40 mph, so go 40 mph;
Avoid much more than 40 mph during this stage, because then fuel consumption will spike for relatively little gain in speed.

 

Let's include the wall losses ...

1.2 kWh to travel 4 miles -> 4.56 cents a mile for EV
$3.52 to travel 65 miles on petrol -> 5.4 cents a mile Petrol.

Petrol is 19% more expensive per mile of fuel. Or, if you like your pennies whole, about one per mile.

All this figuring though is IMO missing the looming issue ($ wise, anyway): An EV is very unlikely to have the longevity of a Prius. The shelf life of that 25 kWh battery in the LEAF is optimistically a decade or 100k miles of driving, whichever comes first. So as one sorry example, the LEAF saved $1000 in fuel costs after 100k miles, but now you have a rock. The Prius is just getting nicely broken in..

 

A used EV with a big battery will probably not worth much in the future imo, buyers may not want to take that chance. On the other hand: Story of a Prius Owner’s Saga Totals More Than 500,000 miles And Counting; http://www.cleanmpg.com/forums/showthread.php?t=46659

Nissan Leaf battery replacement will cost $100/month, offers new pack at any time

 

That is the calculus in a nutshell: Pay $100 a month extra to save $10 a month in fuel.

 

http://www.cleanmpg.com/forums/showthread.php?p=371553
Has anyone seen similar tests for electric vehicles, Kwh energy consumption at different MPH, Nissan Leaf or Tesla?

 

I'm liking the PiP more and more every day.

 

In most cases, that is indeed the case. However, there is the exception of a well-timed switch from EV to HV mode.

As already pointed out, the system strives to maximum use of the battery-pack during cold engine warm-up. With the regular Prius, this is difficult to quantify without having a tachometer available. With the plug-in Prius, the behavior is quite pronounced. It's obvious.

I've been taking advantage of this, waiting to push that button until just prior to the approach a steep hill climb or highway entrance ramp. That way, the engine speed is restricted to 1500 RPM, rather than exceeding the usual 3000 RPM that type of power demand would require. It's been working well. I can get up to speed without the engine straining (high emissions & consumption) and still have reserve power, just in case. I have dropped the pedal to the floor in those scenarios, to confirm the system will override that green behavior. It does.

Calling Prius PHV a "super hybrid" seems a very effective way of conveying the design objective. You have a larger battery and a plug, but the intent of the system is still very much one of delivering significant improvement at an affordable price rather than calling it a short-range EV.

 

You can calculate it from the range at speed if you want for tesla. Their calculator even lets you put in temperature, a key variable for hybrids and plug-ins.

Your Questions Answered | Tesla Motors

If the 85 mile epa aer at 100% charge is good enough after aging the 2013 leaf should be more efficient at speeds lower than 70mph.

 

Here is one for the Roadster and Model S (scroll down to the second graph):
Model S Efficiency and Range | Blog | Tesla Motors

 

I think Zythryn was pointing to this graph: