Plug-in Toyota Prius, Setting The Record Straight!

JAN 10 2014 BY DAVID MURRAY 44

Just How Far With The Prius PHV Actually Go On Electricity?  Well, That Depends...

Just How Far With The Prius PHV Actually Go On Electricity? Well, That Depends…

There seems to be a lot of confusion about the Plug-in Prius and the amount of EV range that it has.  A common misconception is that it only has 6 miles of EV range.  The window sticker of a PiP (Plug in Prius) shows 11 miles of gas+electric but then there is a footnote that says “All Electric Range = 6 Miles

Toyota Prius PHV "Sticker"

Toyota Prius PHV “Sticker”

Now I’ll be the first to admit the PiP has the weakest plug-in offering on the market.  But we should at least get the facts straight.  The PiP definitely has more than 6 miles AER (All Electric Range) and some simple math can prove it.  We know the PiP has a 4.4Kwh battery pack; but we also know, like all plug-in cars, that not all of that capacity is usable.  It turns out that 3.4 Kwh is actually usable.

So if you drive an EV you are probably familiar with the measurement of “Miles per Kwh.” which is analogous to “Miles per Gallon” with a gasoline car.  In a gasoline car if you know what MPG the car gets and you know how much fuel is in the tank, then you can easily calculate the range by simple multiplication.  The same is more or less true for an EV.

Good or Bad, The Toyota Prius PHV's Top Speed Of 62 mph Can Be Problematic For Getting A Good Read On The Car's Electric Driving Abilities

Good or Bad, The Toyota Prius PHV’s Top Speed Of 62 mph Can Be Problematic For Getting A Good Read On The Car’s Electric Driving Abilities

So lets take 3.5 Miles per Kwh, which is a very conservative number on the low-end.  If you multiply by 3.4 Kwh available, you get 11.9 miles.  If you are a good driver and can manage 4 Miles per Kwh then the range jumps up to 13.6 miles.

If math doesn’t satisfy you, how about some anecdotal evidence?  Just go over to priuschat.com and you’ll find any number of forum users saying they’ve managed to squeak out 20+ miles on a single charge.

So why does the EPA rate it at 6 miles?

Ok, so you must be wondering why the Ford Energi products are rated at the full 21 miles?  Well, there are some significant differences in the PiP and other plug-in hybrids.  There are two main issues at play.

  • Top EV speed – The PiP has a top EV speed of 62 miles per hour.  You can still go faster than that using battery power, but the car requires the engine to be running at speeds over 62.  The Energi products can do 85 mph in EV mode with the engine off.  The Chevy Volt can go 100 miles per hour without the engine running.
  • Acceleration Power – The PiP will automatically turn the engine on if the driver requests a certain amount of acceleration by stepping on the pedal.  There is no option to disable the engine.  With the Energi products, there is an “EV-Now” mode that will totally disable the engine so it will not start until the battery runs out.  The Volt by default won’t start the engine until the battery runs out.

Now, the EPA test requires running the car at certain pre-defined speeds and acceleration events.  You can see in the test chart below that these tests can take the car up to 80 mph for short times.  As such, the PiP must start the engine during the test, possibly several times. All this, despite the fact it may have plenty of battery power left.

thing

Driving Schedule Table

So how can Toyota fix the problem?  Part of it would just be a software fix – Give the driver the ability to lockout the engine.  As for increasing the top EV speed, that may require hardware changes to the drive train.  The problem with the type of setup that Toyota and Ford are using is that with the engine off, the smaller motor-generator can be revved dangerously fast.  The original Prius had a much slower EV limit, around 42 mph.  They fixed that in the 3rd generation Prius by adding some extra gearing to reduce the speed of the generator.  I would assume Ford did something similar in the Energi products to get the EV speed up to 85.

Toyota should be introducing a totally redesigned, Forth Generation Prius in 2015 or 2016.  It is likely they will solve this issue in the Plug-in Prius and I’m expecting them to increase the range as well.  I’m holding out hope that the next gen PiP will have an EPA label showing at least 20 Miles AER.

Categories: Toyota

Tags:

Leave a Reply

44 Comments on "Plug-in Toyota Prius, Setting The Record Straight!"

newest oldest most voted

The PiP is a smart marketing move. Toyota took a vehicle they already had, add battery capacity, and a AC charger and charge a ton of money for that, and also collect the government incentives.

Nicely played!

They also changed the chemistry to Li-ion (after they said Li-ion is not ready for cars LOL).

Yeah, Toyota and Honda really grind my gears, but they’ll be dragged kicking and screaming into the plug-in age. That’s my prediction, we should add it to the database!

Great, so if I feather the pedal, avoid steep inclines and stay off the highway I can exceed the 6 mile EPA all electric range? Some get 70 EV miles in a Volt but the EPA rated it as 38. The Prius is rated at 6 miles, owners think it’s 11. When the new Prius touts that it has 10 pure EV miles, the common person will think that’s worse than the mistaken gas + electric 11 miles…

MrEnergyCzar

Dr. Kenneth Noisewater

Volt is really the minimum I’d consider acceptable. In winter I easily dip down to 2.5mi/kW and having a vehicle gimped while operating on electricity is unacceptable to me.

BTW Volt likely could do well over 100mph on pure electric, but that’s its speed limiter cap.

What is the source of cabin heat during the 11 miles or so of EV operation?

None. If you turn on the heat, the engine will start.

Electric heated seats or gas cabin heat.

The source of cabin heating during EV operation is the driver and passengers. If you want the car to provide heat, it turns the engine on. If you want to defog the windows, it turns the engine on. If you press the accelerator a little hard for a moment, it turns the engine on. Once the engine is on, it stays on until it is fully warmed up. On a cold day, I have driven over 30 miles and had the engine running so much that I still hadn’t used up the electric range. This is the difference between a plug-in hybrid and an extended range EV.

David,

Thank you for the insightful explanation!

Indeed, if nothing else hopefully the competition from the Energi line will force Toyota to make the PiP a more viable PHEV.

Toyota’s goal was to achieve max efficiency of both fuels. They realized that there is no “typical” commute, so instead of focusing on fuel ratio, they balanced both power sources for max efficiency and trunk space.

I drive my PiP in EV mode mostly in the city. Last year, I averaged 12 miles per charge (132 MPGe with 15% charging loss included) and that’s plenty for city dweller like me.

Using gas, I averaged 56 MPG. As for my fuel ratio, 40% EV and 60% HV.

I am happy with Leaf beating EV efficiency and regular Prius beating HV efficiency in a midsize 5 seater.

“Acceleration Power – The PiP will automatically turn the engine on if the driver requests a certain amount of acceleration by stepping on the pedal. There is no option to disable the engine. With the Energi products, there is an “EV-Now” mode that will totally disable the engine so it will not start until the battery runs out. The Volt by default won’t start the engine until the battery runs out.”
————–

Note the Energi 0-60 time goes from 8 seconds to 15 seconds when you put it in “EV-Now” mode.

You know, I don’t see that as being a crippling flaw, kdawg. It ain’t great, but it is something you can choose, power or efficiency.
The Energi is pretty quick off the line for a PHEV, and it can be an EV when you want it to be one. Albeit a pokey one.
I think that if I could take feature A from the Volt, (at least 38 miles of AER range) and add feature B from the Energi (better performance and much roomier back seat) I would have the car I thought I was going to get way back in 2008 when I first started following the Volt.

To achieve a higher EV speed and better EV range, Toyota would simply need to ‘invest’ in a larger battery pack, to load in more electric power for longer EV range and more hybrid assist. The Ford Energi models(7.6kWh) and Volt(17kWh) can both have higher EV speeds and longer EV range, simply because they have larger battery packs than the Prius plug-in(4.4kWh), and Toyota has to hold back much of the battery power for hybrid assist to maintain the 50mpg in the heavier plug-in model. It is doubtful that the next Prius plug-in would be offering 20 EV miles. That’s a big leap that Toyota is not really interested in reaching. Toyota was clear then they stated battery electric vehicles are not viable, and they are moving toward fuel cell technology….Period! Just look at the rest of their hybrid lineup, each hybrid models is using the same nickel batteries from 10+ years ago. While every other manufacturer offering a hybrid, has moved to to lithium battery packs. Anther way to put this into perspective, the Prius lift back has had a 9mpg city and 7 mpg hwy gain from 2001 to 2014, or in 3 generations. An 8mpg combined or… Read more »

They would need a larger traction motor.

And more powerful controller. Maybe redesigned gearing too. There is a cascade of items Toyota must do and that is why it wasn’t done already.

The problem is space and weight.

As AER increase, battery size increase, motor size increases, interior space suffers.

Volt and Energi are far heavier than the Pip. Volt is also smallest among them but has the most powerful EV motor and largest battery.

Also, the more EV range you have, the lower the MPG it will be in the extended mode due to heavier weight of the car and efficiency of the powertrain.

Pip > Energi > Volt > i3 with REx in mpg in extended range.

It is a plugin designed to operate in EV for City and gas on Highway. You can blend it automatically also.

Any chance that with in the few generations, all Prius models have a plug? The extra electrical components cannot be that expensive, and surely will come down in price.

Very nice write up David. I keep after Jay about building a 101 tab for such articles as these. There needs to be a place here where newcomers and even the not-so-new can go for an explanation of how things work in the EV mix.
Thanks again for covering this.

They need to improve the PIP. The current one pales in comparison to the Volt or Energi.
11 miles EV, and only if you light foot the drive? and not turn on AC/Heat?
lol

This car is a turkey on wheels in that Ford has even said that they plan to cut the price of their C max plug in lower then the plug in Prius to go after it’s market share. And with that said when you look at it a car with 20 miles of EV range that is a few thousand cheaper then this one the plug in Prius is going to get creamed. The only way I could see raising this car’s numbers if the plug in option replaced the standard none plug in Prius.

Other then that the Chevy Volt if it cuts it’s price down to this car would cream it. Ford’s line of plug in products are already jumping in to attacking it in that they plan on selling them a lot cheaper. And with me wanting to own a EV I want something that I can drive in full EV mode to the store and back and to work and this car doesn’t cut it.

The author is splitting hairs. The EPA tests for AER is what it is. The Chevy Volt has people getting 50, 60 and even 70 miles AER under ideal conditions, but the EPA rating is 38 miles AER.
The PiP battery is too small and electric peak power too low for doing much better than 6 miles AER.Get over it.

By driving in EV mode only in the city, you raise the efficiency of electric miles (MPGe).

By minimizing the number of gas engine warm up penalties (short trips taken care of by EV), you raise the efficiency of gas miles (MPG).

That’s the design philosophy of PiP. Unfortunately, EPA test requires running both city and highway in EV mode. That’s why funny numbers came.

miniscule range, no defending

The article asserts that 3.4 kWh of the Prius Plugin battery is usable for achieving the full electric range. This is incorrect. It only takes 3.2 kWh to charge the car from the wall socket and that includes charging overhead. The actual usable part of the battery is closer to 2.75 kWh.

The 6 mile figure from the EPA is likely due to power limitations from the battery. At best, the Prius Plugin can draw a maximum of 38 kW from the battery even though the larger drive motor is capable of 60 kW. This is a limitation due to the relatively small 4.4 kWh battery. The larger batteries used in the Ford Energi and the Chevrolet Volt are able put out more kW primarily due to their larger overall size.

I have a 2012 Prius that’s 6 years old sometimes when I charge it the battery only charges to a nine or ten my charge. Is this a sign that the battery is starting to fail