New PiP Owners...More data please!!!

If you used 0.46kwh in 20 minutes then the 1.0 KW is the power going into the battery after charging losses. That is what I would expect it to mean.

I'm sure after a few charges you can approximate charging losses. A good conversion factor is around 1.18 times indicated kwh at the display for kwh used from the plug.

 

IRun, How many Gallons at the pump at each of your 2 fill-ups?

 

i came up with similar numbers today and was all excited for a minute until i realized that the prius electric motor is much smaller than the leaf's and can't provide enough torque to get you up to highway speeds quickly. you can get there slowly but if you mash on the pedal, you're going to engage the ICE.

the leaf on the other hand, while no race car, has way more torque and the electric motor's all you've got, so it has to be sized appropriately.

in other words, just like the electric motor in the prius lets you size the ICE smaller, the presence of the ICE lets the electric motor be small-ish. so it's not unexpected that it would consume less power.

 

The electric motor is not the limiting factor, but rather the power that can be delivered from the battery due to its small size. MG2 is rated for 60kW, but the battery can only deliver 38kW peak from its 4.4 kWh pack. The Leaf's 24 kWh pack can deliver much more power.

 

Low speed and low power is where battery is more efficient than the gas engine. High power is better for the high energy density fuel (gasoline). Using proper fuel also decreases the recharge time.

Prius PHV is the first plugin hybrid to choose fuel on driving condition rather than the range as the condition. Leaf only has one fuel so it has to use electricity from the battery for all conditions.

 

It is neither the size of the motor or the battery that determines the power usage, but rather the demand one places on them. Motor size and battery size place limits, but don't really improve efficiency much. Just as a 1.8L engine can, if used properly, be more efficient than a 1.5L, bigger motors and bigger batteries can actually improve efficiency, but add weight. But all of those are actually second or third order effects.

If you drive slower you use less power. Acceleration requires more power in a non-linear fashion, plus higher speeds increase drag non-linearly. On days I just run errands on side streets my volt will use < 240wh/mile. My best day was 190, my worst was 450 (testing cars EV limits).

 

I'm looking forward to hearing power split data in steady state highway driving in elective HV mode. Specifically, I wonder about the case where the car requires 20 - 40 kW, and lion's share is supplied by the battery. Does that force the ICE to run inefficiently ?

 

that was kind of my point - you can never put as much demand on the electric motors of the PIP as you can in leaf or volt. hence it's not surprising that the kwh/mi is lower. it's not a testament to some kind of super-efficiency that toyota has engineered vs. volt or leaf, it's just physics.

 

The driver will be important for that but I would presume that for the same driving the PiP will probably go farther as its lighter and slightly more aerodynamic.

 

On the same charge, a volt driver going the same speed as the prius driver will go about 10% shorter. YMMV though, and the faster you are going and the fewer stops the less advantage the prius will have.

Now the volt driver will go further with the charge in the car That's the main trade off. The prius has less rolling resistance and drag. The volt can accelerate faster and stay in EV mode at higher speeds and distances. The prius phv is also about $3K less after tax credits, but the lease on low miles per year on the volt may be less.

 

What did you use to estimate 10%.. I see it varying greatly with the Terrain and technique. I'm thinking it would be less of a difference (like 5%) for smooth regular driving (mass is mostly an issue for stop/start).

Drag differences should be < 5%, based on Coefficient-of-drag, for speeds < 60). I don't see rolling resistance being that much higher (I've not seen actual stats).

 

Yes YMMV. Prius phv has 29kw + 0.2 gallons/100 miles which I estimate to 33kw/100 miles if the battery could provide all the power to do the test. Volt is 36kw/100 miles. Around 10%.

rolling resistance should be higher on the volt. 215 width tires on 17" rims versus 195 width tires on 15" rims. Add in the extra weight and you get most of your mileage penalty. Cd is .28 versus .25, about 12% more, but idk frontal area, this should give only a small penalty at lower speeds.

The big difference is electric range though, not the prius efficiency for this short distance.

 

The 0.2 gallons of petrol adds about 33.4 kwh * 0.2 *0.35 = 2.338 kwh of energy at the PSD, so the battery only equivalent for 100 miles is 31.2338 kwh, not 33 kwh.

Compared to the Volt this way, the Prius will travel 36/31.2338 = 15% further.

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Addendum: A bit more accurate estimate can take into account the ~ 7.5% loss as energy exits the battery, and the EPA gallon equivalent is 33.7, not 33.4. So...
33.7*0.2*0.35 = 2.359 kwh.
2.359/.925 = 2.55027027 kwh additional energy in the battery

I agree that the Prius efficiency advantage can be mostly (if not all) explained by CD, tyres, and weight. Amazing really, that the Prius drivetrain has petrol efficiency that whips every competitor, while not sacrificing electric efficiency at all. It is the best parallel and best serial architecture in one small package.

Compared to the Volts EPA of 360 wh/mile
36/31.55027 = 1.141036194, or 14% further in the Prius.

 

Sorry I dont' get it. (or SageBrush's math).

I see 29kw + .2g/100 miles as .2 * 33.7 = 6.7kw
(33.7 is EPAs energy per gallon), so I see a total of 29 + 6.7 = 35.7.

I 33 nor do I see 31 (sagebrush what is that .35?)

Note my above calc is quite totally consistent with the EPA 95MPGe vs 94 MPGe, about 1-3% difference depending on how they round.
So what did I do wrong?

My point on the rolling resistance is that its already captured in their measurements, as the dynos really capture that fine. (Areo is tricky since dynos don't capture that well)


Totally agree that the electric range is the bigger issue. Seen some good numbers from the PiP for a car with 11miles of EV range, but nothing approaching the median on Volt Stats! Tracking real world usage of Chevy Volts in the wild... because the battery range is smaller.

 

I think you misunderstood my post; I was not talking about efficiency. I quoted and was responding to pfile's claim that the size of the Prius Plug-in's electric motor limits the amount of power to the wheels when running on only electricity. In fact, the battery is the limiting factor in supplying the electricity.

If the battery could supply more power, I would expect the Wh/mi to go up and the gas usage to drop.

 

My first tank was 685 miles from 2 week of driving. In those 14 days, I recharged 21 times. The refill took 8.504 gallons, which was just 3 miles after the blinking began. That calculated to 80.6 MPG. The values on the Drive-Ratio screen stated 237 miles EV and 439 miles HV. The total for electricity usage was 60 kWh.

It will get really interesting later, as the weather warms. Then, I'll be driving on longer weekend trips to go biking. HV is remarkably efficient. You wouldn't have thought there would be a modest improvement over the no-plug model. But that's what I've observed so far. It will bring my average down. I don't care though. Running around on short-trips is so much more efficient now. So, it all works out.

That HV/EV toggle button is really nice too. Getting to choose when to deplete is quite empowering. The system is extremely well thought out.

Needless to say, I really enjoying the discovery process.

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Lastly, here's the latest for my daily-data collecting:

 

ICE is not 100% efficient. Prius Atkinson cycle is about 38% efficient. We need to get the usable energy from ICE and work backward to get the equivalent electricity consumption.

I believe that is the reason sagebrush put that 0.35 in there.