SAE Approves Method for Rating Plug-In Hybrid MPG

You all remember the weird 230 mpg number touted by GM for Volt and the bad press that garnered.

http://scienceblogs.com/goodmath/2009/08/the_chevy_volt_gets_230_mpg_on.php

So, here is the new method of calculating mpg devised by Argonne National Laboratory. Or rather announcement that the new method has been finalized - since the method is not available freely. They are also working on mpge method for EVs.

http://evworld.com/news.cfm?newsid=23611

Mike Duoba, a principal mechanical engineer at the U.S. Department of Energy's Argonne National Laboratory, and his colleagues are celebrating the recent approval of SAE J1711, the revised recommended practice for figuring out the fuel economy and exhaust emissions test procedures of hybrid and plug-in hybrid vehicles (PHEVs).
...
With the completion of SAE J1711, Duoba and his colleagues are now focused on supporting the development of testing standards for all-electric vehicles, known as SAE J1634. The development of this standard may be finished by year's end, with voting by SAE members to take place shortly thereafter, he said.

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I say the best way to measure is to simply ignore the battery aspect and rate the fuel economy based only on the gasoline mode of the vehicle. So for a Chevy volt, for example, they should run the battery down until the car enters charge-sustaining mode and then begin the test based on gasoline usage from that point. Any other way of calculating it is meaningless.

adric22 said:

I say the best way to measure is to simply ignore the battery aspect and rate the fuel economy based only on the gasoline mode of the vehicle. ..

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And I'd add a second number, miles per kWh. So a plug-in would have two numbers: mpg for gas-only and mpkWh for electric-only, say 50mpg and 3.1mpkWh for example.

De...
I agree, using two "independent" numbers is best: E-mode and G-mode operation.

However, one needs the "usable" kWh capacity of the battery for useful calculations.

Sorry... The method used will likely be tied to sales quotas, CAFE standards, and other black magic that allows auto manufacturers to get flex fuel allowances even if the vehicle doesn't see a drop of ethanol in it's lifetime. Straight electricity and straight gasoline numbers won't be meaningful for all the possible ratios of blended mode gas/electric operation. And multiple numbers will likely confuse the general public.

What a tangled web.

Look at this. This tells us where they were last year.

http://www1.eere.energy.gov/vehiclesandfuels/pdfs/merit_review_2009/vehicles_and_systems_simulation/vss_05_duoba.pdf

Major Consensus Items of J1711
* Do not combine fuel and electricity into a composite MPG Result
– Report both MPG and AC Wh/mi (from plug) separately
* Baseline charging assumption: 1 charge per day
– Missed charge = Opportunity charging
* Retain “Utility Factor” method of combining depleting with sustaining
* Emissions certification may not be the same procedure as fuel economy determination
* Typical Cold / Hot Weighting for UDDS not possible in Charge Depleting test

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Here is a Chevy dealer bold enough to post this estimation ... (he posts on gm-volt.com).

I believe that if there is just one number applied to a PHEV, then THAT number will be totally insufficient, thereby confusing and misleading the public.

For this kind of "dual mode" vehicle, the numbers should match BOTH what is commonly used to describe ICE operation, AND what is (or will be) commonly used to describe EV operation.

These are (or would be) easily understood in the USA:
1. MPG in G-mode (and possibly tank capacity if significant)

2. Miles per kWh (or, per 10 kWh) AND the usable battery kWh capacity, since that IS significant.

Are these in any way confusing?

I would not even consider buying an EV, PHEV, or ICE without these corresponding numbers.
Would you?

garygid said:

2. Miles per kWh (or, per 10 kWh) AND the usable battery kWh capacity, since that IS significant.

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The number people would really be interested in EV mode is range. Ofcourse usable battery kWh capacity would be part of the spec. From the above two we can calculate miles / kwh.

Why not put all of them in terms of the range per "fueling", regardless of the source of the fuel. It could be an average for the battery based on driving cycles, afterall, most people are used to seeing both City and Highway already. Even those two should be combined to a single value based on a full tank. I think the most simple would be a single range number with an average cost per mile based on an agreed upon nationwide average for the fuel source, whether it be electrons or gasoiline. Similar to what you see at a grocery store with a cost per unit in the small print. So it would be something like:

Electric
Range = 100
Cost per mile = $0.032

Gas
Range = 400
Cost per mile = $3.78

Think that would help sell electrics? I think it would.

But would more realistic fuel figures:
ICE $0.10 per mile
EV $0.11 per mile
help sell EVs?