djwildstar
Well-known member
- First Name
- Guy
- Joined
- Mar 14, 2023
- Threads
- 2
- Messages
- 164
- Reaction score
- 201
- Location
- Atlanta, GA
- Vehicles
- 2023 Lightning Lariat ER, 2023 Mach-E GTPE
- Occupation
- Information Security
I think the main take-away here is that the test method used by the AAA test isn't necessarily comparable to the road-test conditions used by Out-of-Spec and the real-life use by forum members.
Reading the actual report, it appears that AAA measured rolling resistance by accelerating the truck (loaded and unloaded) to a specific speed, putting it into neutral, and then observing as it eventually rolled to a stop. From multiple runs, you can in theory derive a formula for the overall resistance at any speed, and if you plot this formula on a graph, you get the load curve.
On page 14 of the report is a note that "the integrated average of the road load force curves does not directly correlate to the amount of work exerted by the test vehicle during the drive cycles" ... or in other words, the load curves used in the report don't actually reflect real driving performance.
One possible reason for this is the difference between 'Neutral' in an ICE vehicle and 'Neutral' in an EV. In the Lightning, 'Neutral' disconnects the motors from battery power and from regenerative breaking, but doesn't disconnect them from the drive train. Since they are permanent magnet motors, they will generate and dissipate energy whenever they are spun (this is why you shouldn't flat-tow a Lightning). We don't know how much energy is lost this way, and the report doesn't give us a way to find out.
Reading the actual report, it appears that AAA measured rolling resistance by accelerating the truck (loaded and unloaded) to a specific speed, putting it into neutral, and then observing as it eventually rolled to a stop. From multiple runs, you can in theory derive a formula for the overall resistance at any speed, and if you plot this formula on a graph, you get the load curve.
On page 14 of the report is a note that "the integrated average of the road load force curves does not directly correlate to the amount of work exerted by the test vehicle during the drive cycles" ... or in other words, the load curves used in the report don't actually reflect real driving performance.
One possible reason for this is the difference between 'Neutral' in an ICE vehicle and 'Neutral' in an EV. In the Lightning, 'Neutral' disconnects the motors from battery power and from regenerative breaking, but doesn't disconnect them from the drive train. Since they are permanent magnet motors, they will generate and dissipate energy whenever they are spun (this is why you shouldn't flat-tow a Lightning). We don't know how much energy is lost this way, and the report doesn't give us a way to find out.
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