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40 or 28 miles? Which AER driving profile did GM choose?

18070 Views 35 Replies 12 Participants Last post by  Tom
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What is your normal driving profile? It will have a huge effect on the Volt’s Average Electric Range, AER. Compare three common driving profiles the EPA75, HWY, and US06. We note that these profiles are dynamometer profiles. They are not done in the wind, rough roads, or on road grades, all of which lower AER. Nor are they done with max power (209 motor hp) to simulate passing. The goal of these profiles was to check and compare emissions, not evaluate EV performance, such as AER.

The EPA Federal Test Procedure, EPA75, is called the City Cycle. It consists of the Urban Driving Cycle, UDDS, followed by the first 505 seconds of the UDDS. It has a top speed of 56.7 mph. It uses a maximum of 37 hp road power. See attachment.

The EPA Federal Test Highway Procedure, HWY, has a top speed of 59.9 mph. It uses a maximum of 30 hp road power. See attachment.

The US06 Supplemental Federal Test Procedure (SFTP) was developed to address the shortcomings with the FTP-75 test cycle in the representation of aggressive, high speed and/or high acceleration driving behavior, rapid speed fluctuations, and driving behavior following startup. It represents an 8.01 mile (12.8 km) route with an average speed of 48.4 mph, maximum speed 80.3 mph, and a duration of 596 seconds. It uses a maximum of 89 hp road power. See attachment.

I did a detailed second by second Volt simulation with these three profiles. The results were an AER of 40.2, 39.6, and 28 miles for the EPA75/UDDS, HWY, and US06 profiles, respectively.

Does anybody have a recommendation for a representative EV driving profile? Google did some work for improved EV fuel economy profiles. I'll check into that.

The simulation is attached below.

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I did a detailed second by second Volt simulation with these three profiles. The results were an AER of 40.2, 39.6, and 28 miles for the EPA75/UDDS, HWY, and US06 profiles, respectively.
Tom, what do you use for mass, drag area (or factor), motor efficiency, charging efficiency?

I plug in:
kerb mass (of Prius) + half a tank of fuel + driver = 1432 kg;
drag factor (emperical for Prius) = 0.5 kg.s/m;
motor efficiency = 90%;
charge efficiency = 90%,
and get US06 cycle energy consumption of 484 J/m or 7.4 km/kWh. That gives an AER of 59.5 km on 8 kWh, which is closer to 40 miles than 28 miles.
All my assumptions, data, and methdology are in the attachment.
Did you account for the energy needed for the second by second acceleration and deceleration?
Ok, thanks.

While thorough, it is very hard to follow and to compare to my Excel based calculations because of the hodgepodge of units of measure.

The primary difference is in the assumed efficiencies. I was assuming much higher values for what you call GPE and TInvE.

But, can you please explain more clearly the difference between TInvE and IPEE? And where do you account for traction motor efficiency?
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