Volt vs. Prius: Which Will Be Cheaper to Drive?

Not to change subjects or anything but some have mentioned in this thread a tax credit for the Prius. I thought that ran out in 2009 or when the first 60k were sold?! Is there a new one? If so where can I find info on it. Already here in CT we don't have to pay sales tax on the Prius purchase.

 

A new tax credit will be on the plug-in Prius.

 

Thanks, not waiting until then. I'l take paying no sales tax and a few other benefits CT offers.

My 2 cents on the Volt; Nice idea and all for GM to throw their hat into the ring but at a higher cost and with mpg results that are unknown at the moment its a hard sell. GM thinks its hit a homerun here and seem to think they will sell like hot cakes but I don't think so. The Prius will still be number one for hybrids, just ask Honda what happened with its Insight. Not knocking Honda as I love Honda but some missteps cost them dearly.

 

Unless the government gives a tax credit of over 10,000 dollars it looks like it's going to be the Prius, or unless you're only looking at operating costs and excluding the original vehicle cost.

It's reasonable to believe a Volt owner could go for weeks without ever using a drop of gas but it's more likely that wont be the case all the time.

 

Cheaper to drive? The answer is the Prius -- at least according to calculations outlined by a reader in our local Triangle, NC, newspaper, The News & Observer, which I find plausible.
The essence of the writer's argument is that non-gasoline power (50 kWh of fuel generated at the power station for each 11.2 kWh expended by the battery) must be included to produce a meaningful comparison of energy consumption. Only on the longest possible trip within the Volt's range (400 miles?) can it match Prius mpg, but with the inconvenient complication of an overnight charge to continue further.

Link to his letter:

Not so impressive - Letters - News & Observer

 

If the small ICE only powers the car, and does not recharge the battery, the driving experience with the ICE will be limited to that of a small gas engine. There will be no battery boost for hill climbing, passing, or merging. This implies that the driving experience will change between all electric and series hybrid modes, unless, of course, the driving experience under all electric is limited to that of a small gas engine. If that is the case, the Volt has some serious performance problems. Consistent bad performance is not preferable to good electric performance and fair hybrid performance.

Tom

 

If the battery is being charged, how does the electric motor get power from the battery at the same time?

Battery can only charge OR discharge. Half of the battery pack can discharge and the other half can charge? Otherwise, the power from the generator have to be routed directly to the e-motor.

 

The ICE and battery will interact in the same way as on the Prius so there will probably be no noticeable difference between the two modes.

When electric mode stops the battery will still contain some charge (I've seen quotes of 30%). This can supply the motor the additional power needed for acceleration or hill-climbing. When the extra power is not needed the ICE can then restore the battery to the 30% level.

I suspect that it will operate in EXACTLY the same fashion in this mode as the Prius does, including running the battery down if you demand high-power for too long (e.g. climbing a very long hill).

Even at 30% charge the Volt battery will contain considerably more energy than a Prius battery so it should be a very unusual event.

kevin

 

There is no point doing that - all that happens is that if there is excess power available from the ICE, and the battery is below its sustaining level, then the excess will charge the battery.

Similarly if more power is demanded than is available from the ICE then the battery will be discharged below the 30% sustaining level.

If the ICE can supply all the power required (e.g. freeway cruising) the battery will be neither charged or discharged.

It will operate very similarly to the Prius, we are all used to seeing the arrow go in or out of the battery as conditions change. That will be the way the Volt will operate when it drops out of electric mode.

kevin

 

Grahmy,
Centralized electrical power plants vary by fuel used, and efficiencies using the same fuel. Newer fossil fuel burners reach about 40% efficiency, distribution costs about 10%, and charging another 5%, for a net furnace to battery of 34.2%.

That is not a whole lot different than gas tank to wheels in a Pruis, but of course does not account for oil-> fuel production or distribution energy costs.

Here though, the question is money and not energy efficiency. Ignoring differences in acquisition cost make this entire thread silly.

 

In charge deplete mode, the Volt spec is to ICE charge the battery about 5% over minimum for the occasional maximum electric motor output demand. A very long climb would exhaust that reserve and leave the Volt climbing by it's ICE only. Just like our Prius.

 

That's what I would think too but it is not what they are saying. They are saying ICE will never power the car. It will be there just to charge the battery since it is a range extender.

If the ICE power the e-motor directly (skipping battery), that would be what the rest of the world call, series hybrid.

 

You have to view the generator, battery and motor by analyzing NET power to/from the battery. As long as the generator is producing more power than the current motor demand, the battery can be charged; if more power is needed by the motor than the generator is currently producing, the battery must be discharged.

In the series hybrid design, power does not go through the battery - instead both generator and motor are coupled to a power bus that either charges or discharges the battery, as required. The plug-in series hybrid takes power from the battery in preference to running the generator.

But this is no different from the Prius; to produce peak torque, more power is needed than the battery alone can supply and power is generated by MG1 to power MG2. Some diagrams might suggest a direct connection but there is not; because of the different speeds of the motors, and the fact that the waveforms to drive each motor must be in sync with the motor itself, power generated by MG1 is rectified back from AC to 200V DC (Gen 2) before being converted to AC again with the appropriate voltage and frequency to drive MG2. As with the series hybrid, the car adds any power from the battery that's necessary, or takes generated power to recharge the battery. Indeed all the time that the engine's on, it's taking generated power through the DC/DC converter to run the computers, stereo, lights, and other 12V systems (air-conditioning is run at high voltage through its own inverter, on Gen 2 and 3).

The car does not show the two motors on-screen at all, showing only one motor as a simplification.

 

GM said Volt is not a series hybrid. It is an electric car with Range Extender (RE).... or so they say...

GM said the ICE will not power the wheels but only to charge the battery. So you can't have extra power from the ICE routing to the wheels. May be I am taking it too literally but it is really what it means. Electric car will be powered ONLY by the battery. RE will be there to recharge the battery. If RE power the wheels then it is really a series hybrid; this is what GM is trying to avoid.

ICE will turn on to charge the battery. When the battery needs to discharge, ICE will need to turn off. When cruising on the highway, battery will be constantly drained so ICE will never get a chance to charge the battery. This will be a problem and Volt will have to operate in the series hybrid mode.

All I am trying to say is that Volt is really a plug-in series hybrid. They way GM is trying to call it an electric car is not possible since there are too many restrictions in that model.

 

If they do say that it is probably just marketing license. This is from their recent press release:

GM Media Online

"When the battery reaches a minimum state of charge, the Volt automatically switches to Extended-Range mode. In this secondary mode of operation, an engine-generator produces electricity to power the vehicle. The energy stored in the battery supplements the engine-generator when additional power is needed during heavy accelerations or on steep inclines."

It clearly states what would be the most obvious approach which is pretty much the same as the Prius.

kevin

 

Thanks. That description of the Range Extended mode is really series hybrid mode. It will use a combination of ICE and Battery to power the car; hybrid. It will never get better MPG than Prius due to the lack of mechanical path.

Volt will only get better MPG than Prius only if you plug it in.

 

Whick is the whole purpose of its design. For commuters that drive less than 40 miles each day and plug in at night it will have a mpg of infinity. If you have trips of more than 40 then it is still a little bit of an unknown as to how enjoyable of a driving experience that will be.

The Volt will be a success. Not in Toyota terms but if they only make 20,000 and sell them all then it's a success. It's just not planning to be a replacement for the masses as is the Prius.

I'll probably be happy with my Prius for a while I'm sure.

 

I want to drive 230 miles on Interstate 95 in a Volt and measure gas usage. Then drive 230 miles on Interstate 95 in a Prius and measure gas usage. Simplest comparison in the world.

 

Its marketing. Its GM. Its basically a lie. The Volt is a series hybrid.
Period.

However you want to word it.... There is a power bus/controller in the car. When the generator is on it routes power to the motor and the battery. The motor gets first dibs, and if it needs more then the generator provides the batteries fill the gap.

In most driving the battery will be charging when the generator is on.

 

GM recently recanted on their insistence that the Volt is an "EREV", and now call it a plug-in hybrid. When I read that I couldn't help but laugh.

As for your statement that I bolded, I'll side with Prof. Andy Frank who on this question said it depends on implementation specifics. Although I agree that the Prius drivetrain has one advantage over a series hybrid in having a partial direct mechanical path, that is not the entire story by far. E.g., a larger storage battery may allow ICE control algorithms that keep the ICE operating more efficiently. I'd also point out the partial electric pathway of the Prius from ICE to wheels is more complex, includes a mechanical link, and I suspect more inefficient than the Volt pathway. Here is the component pathway as I understand it:

Volt: ICE -> G->M/shaft
Prius: ICE -> PSD->G->M->G->M/shaft

Disclaimer: I am not an engineer. Take my words with a grain or three of salt.