Prius Plug-in Versus Volt: Which Costs Less to Drive?

GM has been saying "Summer 2012" and I think at least once a GM employee said in a web Q & A it would be model year 2013. I assume, at minimum, that in Summer 2012 you will be able to at least order a Volt with AT-PZEV emissions with model year 2013 cars actually arriving in late Summer. We won't know for sure until the actual press release goes out. There was one rumor I saw in a posting online that they would submit the AT-PZEV data to CARB in February 2012 but I have no idea how credible that claim is.

I doubt that the EV range would be reduced by the AT-PZEV requirement but anything is possible. I assume you mean they would reduce the battery SoC range from 65% to something lower to help preserve battery life. They have claimed the battery in the currently shipping cars has been tested to 200,000 miles and designed to meet the 10 year, 150,000 mile AT-PZEV warranty. I assume they only did a national 8 year hybrid battery warranty because they didn't have to do better (much like Toyota Prius warranties outside of CARB states).

 

They don't have AT-PZEV rating now because of carbon monoxide. All other emissions were low enough. They wanted it becaus of HOV access, but Carb test protocols were being determined while and after Volt development. Cries of engineering for the test can start now if you wish.

The difference between Carb and Fed ICE vehicles is usually a point or two of horsepower and torque. Unless the car uses lean burn. I know Carb Hondas have that ability disabled.

 

Here is a couple of things that I was told at the 2009 LA Auto show. I may be remembering this incorrectly but I think the info came from Bob Lutz. Testing on the Volt battery indicated they would be at about 28 miles of range after 150,000 miles.

Originally the Volt was supposed to come with a Flex Fuel engine (ie would take E85) but they would need to develop a new engine for this application and that would have delayed the project so they went with one they had already developed even though they new that it would require premium gas and wouldn't pass CARB testing. The redesigned engine is scheduled for the 2013 model year Volt which should be available in mid 2012. Chevy have a big announcement going on at the LA Auto Show in a couple of weeks and it wouldn't suprise me if the 2012 Volt is rolled out then along with the Spark.

 

Did you mean they would roll out the 2013 Volt? The 2012 Volt is already out and being delivered to customers.

When Lutz said "28 miles" I'm assuming he meant there would be a 20% reduction from the EPA estimate of 35 miles. I routinely get 45+ miles of range so a 20% reduction for me would be 36 miles of range.

 

Some cars are destroyed in just a few years. I see thirty year old cars every day. If traction batteries last ten years, that means some people, not the average, will be replacing them twice and paying at least once if they are fortunate to squeak under the warranty for the first battery.

Maybe traction batteries will come down in price, maybe they won't. Maybe we will learn to live with lower range later on.

This is a "crap shoot" big time and I still maintain that the PiP is less of a gamble because it has a traction battery just over one quarter of the size of the Volt (16 Kw for the Volt, 4.4 Kw for the PiP).

 

I don't know. With an extra 2 years of laboratory accelerated battery testing and a year of real world use it's possible that GM could be more confident about their battery life projections and feel confident keeping the same capacity loss for the longer warranty. It's possible.....

Even if you take a more pessimistic view and project a capacity loss of up to 40-50% after 10 years or 150,000 miles you would still have a larger electric range than a new 2012 PiP.

 

^^This

Its like when the traction battery failed in my prius, it was still a fairly reliable little 4-banger. When the battery in a Volt doesn't hold a charge at all it'll still be running around as a 37 mpg compact, unlike a full EV that will turn into a yard ornament.

 

So long as petrol is available at an affordable price, your point is well made.

 

How are the warranties worded? Industry standard may not be the legal definition here.

 

Bingo. That heavy Volt battery is a dead weight if it has little life left in it. This is yet another plus for the PiP given similar circumstances. The PiP will simply become a regular Prius for the most part if nothing is done about the now less capable traction battery. At some point the traction battery must be replaced for the car to operate. I expect that something else will end of life of most PiPs before that happens.

 

I prefer to think of it as being a Lexus HS 250h weight compact car.

I expect the peak power capacity to fade over time but it starts out fairly generous so even a 30% peak power reduction would hardly be noticed by most drivers over time. Maybe if you live at the bottom of a mountain pass and routinely drive to work in the morning to your job running a ski lift you might have a problem in EV mode. You could lose 20% of the peak power in the Volt and still have the same weight to power ratio as the Nissan Leaf with a new battery pack. In CS mode, much like the PiP, you will still have the gas engine generating power to fill any gap.

I live in the flat lands. Even on road trips through mountainous areas I would typically be in CS mode before getting to them -- especially after any reduced range capacity has occurred. If I'm still driving the car in 15 years and this becomes a problem I'll just swap in another battery pack from a junk yard. I'm sure there will also be companies that specialize in selling refurbished or rebuilt battery packs for a reasonable price just like parts for other older cars.

 

On the topic of weight.... the Volt's higher than average weight contributes to it's excellent impact safety scores -- almost like an SUV but with almost zero rollover risk because of the centered and low battery mass.

The automotive safety site informedforlife.org combines and summarizes safety ratings from crash tests done by the U.S. government and the insurance industry. They gave the 2011 Volt an overall score of 44 which ranks it as "Best 7% for 2011" among all cars and trucks rated. The 2011 Prius got a score of 61 which ranks it as "Medium Risk" due to it's poorer scores for frontal and side impact and rollover risk.

Some, but probably not all, of the difference is due to the Volt's larger mass which makes it relatively less vulnerable to impact by an average weight vehicle. On the other hand, the Lexus HS 250h compact sedan weights only 100 pounds less but only scored 63 for a "Medium Risk" rating.

http://www.informedforlife.org/demos/FCKeditor/UserFiles/File/MasterSCORE2011alphaOct92011.pdf

 

Yes, I meant the 2013 Volt.

This was before the EPA numbers came out and GM were talking about 40 mile range for the Volt so I assume he meant that the range would be down form 40 miles to 28 miles

Noel

 

But not the same discharge rate. Given the higher pack size of Leaf. Already the disacharge rate needed for Volt at peak power is double that of Leaf (may be one more reason they need an actively cooled battery).

 

Of course, the discharge rate is 50% higher at the same power output because the Leaf battery is 50% larger. The Volt has a motor and controls which are capable of higher output than a Leaf (80 kW versus 111 kW).

This, however, does not necessarily imply higher battery life stress. Battery chemistries and construction are commonly tweaked to favor energy density (pure BEV with larger pack) or power density (PHEV with smaller pack). The Volt battery is likely designed as a compromise (not necessarily a bad thing!) between these extremes. For example, the joint Nissan & NEC owned battery company, AESC, which supplies the cells and modules used in the Leaf also sells a PHEV cell with power dense characteristics. Even though both cell designs are described as using LIMN2O4 with LINIO2 they have different cell performance characteristics shown at Automotive Energy Supply Corporation. One difference which is apparent is the anode which is graphite for the BEV cell and amorphous carbon for the PHEV (I've seen claims that the Volt LG Chem cell uses an amorphous carbon anode but I'm not certain of that).

In other words, your statement about the Volt's power discharge ratio is true but not necessarily significant to the battery life point I was making earlier. In any case, discharge above 60-80 kW is uncommon in ordinary driving and would typically be of limited duration.

By way of example, the PiP battery has a maximum output of 27 kW or 6C of its 4.4 kWh pack and that power level is commonly required during typical driving. The Volt battery is only discharging at a 1-2C rate during typical traffic (and this comparison assumes the output burden is spread across the entire PiP pack).

 

I don't recall seeing official publication of the PiP battery max power.
Edit: If you take it from 134 hp total minus 98 hp engine, then it calculates to 28 kW.
Anyway, during 'typical traffic' as you put it, I believe the PiP will not need 27 kW (bare in mind the engine will kick-in much earlier than the Volt engine since it is designed to maximize efficiency).