Prius Plug-in and Volt Pros and Cons

I did't live in a nice climate, had 100+ miles some weekend trips, even one 1,000+ miles trip to Canada, drove 70+ mph and PiP was the only car in the family. PiP still delivered an amazing results.

I used EV for short frequent city trips and HV for long highway trips. It worked out well per clever division of labor designed.

 

What was your mpg for your trip to Canada, did you record this. Find any chargers on the way?

 

I haven't yet reverse engineered exactly where miscrms's numbers come from. It would be great if more details were shared about how the 13 kWh numbers were calculated. In any case, I don't see an accounting for extra battery weight, or did I miss it? The scaled up PiP battery implied would seem to add at least another 200-250 pounds. I wouldn't be surprised if older plugin conversions added that much battery weight without added structure or suspension mods but I'm thinking Toyota would have to in order to preserve the originally intended reserve carrying capacity for heavy adult passengers, heavy luggage etcetera.

 

Its interesting, Argonne has also run the Leaf through the same driving cycles.
Argonne TTRDC - D3 (Downloadable Dynamometer Database)

DC Wh/mi for all EV UDDS urban cycle 20F:
2013 Volt (1st cycle): NA (35.0 MPGe)
2012 Leaf (1st cycle): 418 (80.6 MPGe)
2013 PiP (1st cycle): NA (40.0 MPGe)

DC Wh/mi for all EV UDDS urban cycle 72F:
2013 Volt (1st cycle / average): 223.7 / 217.4
2012 Leaf (1st cycle / average): 209 / 197.8
2013 PiP (1st cycle only): 162.1

DC Wh/mi for all EV UDDS urban cycle 95F:
2013 Volt (1st cycle / average): 298 / 291.5
2012 Leaf (1st cycle / average): 265 / 249.5
2013 PiP (1st cycle only): 231

DC Wh/mi for all EV HWFE highway cycle 72F:
2013 Volt (1st cycle / average): 241.1 / 231.3
2012 Leaf (1st cycle / average): 231/ 229.5
2013 PiP (1st cycle only): 176.9

DC Wh/mi for all EV HWFE highway cycle 95F:
2013 Volt (1st cycle): 249.9
2012 Leaf (1st cycle): 242
2013 PiP (1st cycle): Not tested

 

Just to be clear I make no assertion that the graph I put out is real. It is what it is. An extrapolation of existing data for all other things being equal. Yes, the added weight of incorporating the larger battery could easily nudge it down, or other factors could nudge it up a bit. I still think its interesting as a tool for observing raw relative efficiency of the existing vehicles as it strips away the most confounding difference, the size of the battery.

Basically for methodology I took the ANL D3 test reports:
Argonne TTRDC - D3 (Downloadable Dynamometer Database)
brought the numbers for distance, electricity, gasoline per cycle into Excel and added cumulative calculations. I also added calculations for AC/DC efficiency based on the same data reports, gasoline equivalence of electric consumption, and MPGe.

For straight Volt vs. PiP calculations, I repeated the statistics from the last fully CS run until arriving at the distance of interest. For the "PiP+" I continued to add CD runs between the first run and the first partial CS run until the total amount of AC power consumed was as close as possible to the reported number for the Volt. This is not exact, as I am only using integer numbers of runs, not trying to interpolate.

BTW here is the similar AC MPGe vs. distance comparison for the straight PIP vs. Volt case at 72F.



Rob

 

Its interesting, but I see a lot of plugin users seeming to conflate EV ratio with efficiency. IMHO it has much more to do with driving pattern and weather than efficiency in general. IE, a very inefficient driver could have a very high EV ratio if he/she never drove more than 5 miles at 30mph.

What would be interesting to try on the Voltstats data is to use CS mpg as a predictor of relative CD efficiency. IE if you get 10% better CS consumption than EPA, then you ought to get 10% better CD consumption as well?

Rob

 

The PiP really stands out as being 20 - 30% more efficient that either the LEAF or the Volt in EV mode. Why ? I mean is there an engineering reason to explain the difference ?

 

It would be interesting to search for correlations between CS (HV) mpg vs EPA with actual data of kWh usage but I'm not confident at all about making assumptions right now.

The thing with plugin hybrids is that you will have some number of people with a regular commute that is just a bit longer than their EV range such that the cold gas engine starts up and runs inefficiently for a short distance and pulls down the gas mpg average. Since people have different commute lengths it may be hard or unpossible to separate that from longer distance gas engine driving and it make confuse any attempts to use gas mpg as a proxy for EV efficiency. Similar things apply for folks with other short driving segments on the gas engine that cools substantially between restarts. EV driving doesn't have equivalent inefficiencies from short trips.

Thanks for the added descriptions of your extrapolation and the new graph. I'll try to spend some time pondering it over the weekend.

 

One possibility is that the Prius and therefore PiP use 600v motors and inverters where most other cars like the Volt and LEAF are using 350v or so. Higher voltage could mean lower losses.

I'm still a little suspicious about the size of the differences, however. I drove a PiP over my normal commute pattern for a work week and got the same 130 MPGe EV efficiency that I got in my Volt. It's weird that I would see little or no difference between the 2 cars during real world EV driving of 140 miles (over 460 miles total EV/HV combined on each car) both on urban streets and in the highway.

 

Interesting thought -- thanks. No doubt the higher voltage helps some, but I'm skeptical that most of the answer lies here. It would be interesting to know inverter efficiencies. I know Toyota spent huge amounts of time and money developing the IGBTs that go into the inverter.

I cannot remember details, but IIRC the G3 Prius has a jump in voltage compared to G2, and as we know the city MPG did not improve. Now admittedly, the Prius does not use a lot of EV pathway in city driving so this is a weak data point.

 

I think the voltage boosting stuff (200+ volts to 600v) happened between 1st and 2nd gen but maybe there was a tweak to the boosted voltage that happened between the 2nd and 3rd gen. I'm not at all sure about the history here without doing more research.

BTW, I updated my earlier comment to note that I didn't see any real efficiency difference between the PiP and Volt EV mode in real world commute conditions even though ANL says there are large differences. Weird.

 

I'm way out of my league here, so take the following with a grain of salt ...

I gather electric motors have an efficiency curve analogous to combustion engines. Perhaps the fuel economy cycle plays to the PiP's strengths ? Or perhaps conversely, the inability to blend in ICE power for the Volt and LEAF force those cars into inefficient bands ?

Jeff, 130 MPGe is about 250 Wh/mile -- about as expected for the Volt, but quite a bit higher than ANL reports for the PiP.

 

Yup got 60 MPG with 3 full charges at hotels. See this thread for more details and pics.

4th of July freedom drive | PriusChat

 

I would say the weight and loss in charging and power inverter.

Also 2012 Leaf (rated 99 MPGe) was used. 2014 Leaf (114 MPGe) is about 15% more efficient.

 

Unlikely to be weight because the highway drive cycle shows the same differences.

Good point about the LEAF generation improvement. What did they do to improve ?

 

Thanks for putting it into a graph.

Also, it is only vehicle operation efficiency. It will be interesting how it will look if fuel production is considered.

 

Among the changes to the 2013 LEAF are improved energy efficiency due to refined aerodynamics, a wider range of regenerative braking, improved energy management and a newly available 6.6 kW onboard charger that reduces 220V charging time nearly in half to approximately four hours for full charge.

Green Car Congress: Nissan introduces updated 2013 LEAF; US assembly in Smyrna

...a new electric motor that uses 40% less of the rare earth element dysprosium, the power electronics were redesigned and integrated for a 30% volume reduction and a 10% mass reduction, which, along with other weight reductions adds up to 80kg/176lbs. The trunk is also larger, going from 330L/11.65 cubic feet to 370L/13.06 cubic feet.

2013 Nissan LEAF: Cheaper, Lighter, 14% More Range, New Motor, Etc : TreeHugger

 

Unfortunately, ANL doesn't have a 2013 LEAF test yet.

My impression from scattered skimming of the main LEAF forum site in the past is that real world testing does not seem to show noticeable differences in efficiency or range between the 2012 and 2013 model years with climate controls turned off. I suspect the new heat pump probably shows an improvement over the previous resistance heating but I haven't seen any actual comparison data from this past winter.

 

This is not true. The regular Prius gets 1mpg more according to testing by Consumer Reports because the PIP weighs 120 lbs. more due to the heavier battery. YMMV