107 MPGe for Prius Plug-In

Lets say Prius PHV can use the extra efficiency to charge the PHV battery.

For a 37 miles, Volt would use a gallon but Prius PHV would use 0.74 gallon with 0.26 gallon left to recharge the battery.

EPA uses 33.7 kWh as equivalent to a gallon of gas to calculate MPGe. We know the conversion is never 100%. The best Prius Atkinson cycle can do is 40%. So here is the math:

33.7 kWh x 0.26 x 0.4 = 3.5 kWh

Prius PHV can refill the empty PHV battery in 37 miles using the addition energy extracted from regular gas while Volt would have emit 26% of the premium gas out of the exhaust pipe.

That's the power of efficiency and it is essential to be green.

 

I follow the math calculation very closely, but do you see the possibility of that much regen in a 37 mile trip cruising at 65mph. Is it possible to regen the entire pack?

 

^^ Too complicated for my simple brain.
After 37 miles, the Volt has consumed its gallon of fuel while the Prius has ~ 13 more miles available

 

The calculation was based on 50 MPG. On a flat road at a speed of 65 MPH, Prius could get 50 MPG. The extra 3.5kWh can recharge it to near full since it takes 3.6 kWh to full. We still don't know if Toyota will allow this but if they include it as a feature, this shows what's possible.

If you were asking purely highway driving, it should take more than 37 miles since Prius will likely rated 48 MPG and Volt is rated 40 MPG. There will be only 2.3kWh extra from the 37 miles highway driving. A quick math says you will need to drive 58 miles (about an hour) on the highway to get a free full charge in the battery.

I just realized that's faster than charging from the quick 240V charger that takes 1.5 hours. You can think of it another way. The rate of energy (from gas) the Volt waste is faster than the rate it can charge it's battrry from the 240v charger. Pretty wasteful.

 

Thanks Usbseawolf2000, I am excited about any possible regen during highway cruising to the EV pack.

 

This graph explains why a small battery, aside from cost make sense.

PHV magazine Vol1 | TOYOTA MOTOR CORPORATION GLOBAL WEBSITE

Somewhere in the site, it states that Lithium adds an initial $500.00 dollars per mile of EV distance to the price of a car.

I know the Volt's battery is waranted for 8 years, but if something goes wrong after 6 years, it probably going to be prorated. The question is, will anybody replace a large battery in a car if the book value is less that the cost+labor of the replacement battery.

So, a smaller battery, aggressive regen and a good hybrid system is the way to go.

 

And I'm assuming that's if the main pack isn't totally depleted, which we don't know if it requires an external electric source. Of course it would be awesome if you could conceivably recharge using just gasoline and pulsing. Not sure how it will react to driver's input about electric selectability or how the battery will help when using it to help with regular hybrid mode.

Man this could lead to a whole new paradigm of strategies for fuel mileage. Can't wait.

 

Hopefully the reveal in Germany in mid Sept. will put an end to this line of speculation and the full specs will be available.

 

Also, a gallon of regular(Prius) today is $3.40 while a gallon of premium(Volt) is $3.70. Now if I put $3.70 worth of regular gas in the Prius to equate the Volt's cost of premium, then the Prius'mileage would be adjusted based on cost to a 54.41mpg.

Prius PHV Chevy Volt
107MPGe vs. 93MPGe
54.41mpg vs. 37mpg vs.

 

Unless they have changed the engine on the phv, and that is not even a rumor, running the engine higher to charge will decrease its efficiency, there is also a cost in battery charging. This scenario makes no sense, but if Toyota were to implement it, you should probably multiply power by a 25% loss. Given this, I'm not exactly what your use of the term free is all about. This seems like a wasteful use of gasoline. Now when state of charge is low, and power called for is bellow the efficient range of the engine, the car could efficiently produce power and and charge the batteries. Software could implement an virtual pulse glide charging to a certain level, then going electric. Larger batteries like the phv versus the stock prius can also charge more from regenerative braking if that system is implemented well.

And I thought this was about the prius. Burning more gas to pretend you have more charge is wasteful virtually by definition. Certainly the pathway of gasoline to power in the prius is more efficient than the volt. The pathway of plug electricity to battery to motor is also more straightforward than gasoline to electricity to battery to motor.

 

Quite right about MPG, but keep in mind that the MPGe ratings you posted are from different drive cycles. The Volt's is EPA, while the Prius' is NEDC.

 

Since non plug ins with multiple drive modes default to one when turned off, I'd say the same is true of the Prius PHV.

 

I agree. It is more fun if you are given the choice to use electricity, gas or a mixture of both.

Even if Toyota does not provide an option to recharge the PHV battery, you can intentionally do it with regen brakes -- especially when the lithium PHV pack can absorb the charge more quickly.

 

The point is, that wastefulness is still less than the Volt. Power loss for NiMH is 22% so Lithium should be less. There could be useful case if you cannot recharge it at work. You would recharge on the highway on the way to work when the engine is running than during stop and go traffic from work before highway.

The term "free" was in reference to Volt's 37 MPG. I thought I was pretty clear about that.

 

Well apparently, according to Toyota, they revamped the regeneration circuitry to be much more aggressive from heat sources as well as braking because they could, not because they were being wasteful. So the pulsing that is normal in any Prius is now much more efficient. My reading on this is that now that the engineers have a deeper well to fill so regen isn't throttled back like it is now. Perhaps, and this is conjecture on my part, they reconstructed the ICE to run at a more level RPM between the constant ups and downs of normal driving during highway speeds. Instead of constantly changing RPMs to match speeds and power requirements perhaps they are changing power output of MG1 to feed the battery more when driver power requirements are less.

 

The waste I was refering to was this scenario of running the ice extra high to charge the batteries back to full charge. There is no indication that toyota would do this. I was trying to argue against this speculation on the thread.

Toyota may very well be doing a strategy similar to what you are suggesting providing electrical energy to not go beyond an efficient range then recharging to a given state of charge when draw is not needed. They may even do engine off/recharge if that is more efficient, but they won't try to fill the batteries up to full in a misguided attempt to substitute gasoline for electricity.

 

These numbers are absolutely worthless. Post-charge mileage (when running as a regular hybrid) is what I care about. I can currently get infinity MPG on my Prius if I start it with a full charge and am lucky enough to get it to hold EV while I drive around my block at 9 mph.

 

Yes, you are right, this was from UK drive cycle of 128mpg adjusted for US gallon to 107mpg. So, if NEDC is more generous than EPA, then the number will be lower.

107-MPGe Prius Plug-in will debut in September | Hybrid Cars

 

How big is a British gallon?

 

I don't think this is going to work the way you think it will. The release I saw said Toyota is going to not limit regen so you don't dump any could be saved energy. Not that the pack would refill itself for free while driving around.

The chemistry is going to have some of the same limiting factors and they will try to limit charge discharge cycles, such as keeping it at a lower SOC after depletion. If you have a lot of regen in HEV mode, that regened power will get used before any gasoline energy until the SOC is back in the normal operating range. At least thats my guess.

Remember turning off "EV" mode doesn't force regular gasoline use, it enables normal hybrid mode, what happens in your hybrid when you're fat on charge? You burn less gas, hence the really good mileage numbers.