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Watt/Mile to rated range
- Thread starter jmdavis
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- Driving Dynamics Model 3
The Model 3 LR has 78,270 Wh usable capacity (source: page 6 footer here) and many people have reported 313 mi at 100%. That means 78.270 Wh / 313 mi= 250 Wh/mi for rated range. By the way, lifetime average Wh/mi appears to be between 230-240 Wh/mi with the 18" wheels.
Lot of folks out there with a much daintier touch on the throttle than me, I guess. I'm hanging around 270.
Theory is one thing, what the car actually displays is another. If you are consuming 250 wh/mile in the Model 3 your rated miles will be going down faster than your actual miles.
EPA states 259Wh/mi combined city/highway, but that includes charging losses. I don't know what EPA assumes for charging losses (can someone cite a ref?), but I've seen numbers of ~90% efficiency at 40A from 240V for the S. Assuming 90% charging efficiency, you'd be looking at 233Wh/mi from the battery.
FWIW, I've calculated 237 Wh/mi as the "breakeven" level which consumes 1 range mile per actual mile.
On my 85D, it was about 273.
So far, the 237 has been much easier to achieve than the 273 ... especially with aero caps on (and these make a noticeable difference).
Of course, with a few days of actual winter weather -- daytime in the 50s vs. the 70s/80s we'd been having -- neither car is coming close to rated miles this week.
On my 85D, it was about 273.
So far, the 237 has been much easier to achieve than the 273 ... especially with aero caps on (and these make a noticeable difference).
Of course, with a few days of actual winter weather -- daytime in the 50s vs. the 70s/80s we'd been having -- neither car is coming close to rated miles this week.
The EPA doesn't assume anything for charging losses. Tesla tests the car according to an SAE spec and provides that data to the EPA. The test involves filling the battery, driving on a dyno until it can no longer maintain the directed profile, then measuring the amount of energy required to refill the battery. In that data submission to the EPA for the 3 LR, Tesla also happened to include a comment that the usable capacity was 78,270 Wh.
So the empirical data for rated consumption (~235-237 Wh/mi based on the 2 data points mentioned above) disagrees with the rated range (310-313mi) and the expected usable capacity (78,270). One of three possibilities is correct:
- The empirical data is in error or otherwise biased and the rated consumption is actually 250 Wh/mi [78270/313]. See @Troy above. More empirical data would prove or disprove this.
- The usable capacity is less than 78,270Wh, and more like ~73000Wh [310*236], and the EPA data submission was incorrect or our interpretation of the comment is wrong.
- The actual usable range is greater than the indicated 310-313 rated miles. This would only be possible if there was a significant buffer below 0 rated miles that was accessible to the driver. Here I estimated that buffer would need to be about 7%. Driving the car until it's depleted and noting the energy used after the rated range was zero would help prove or disprove this.
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Thanks for the correction. I mixed up the EPA MPGe procedure with the CAFE procedure. I apologize if I confused anyone.
If we assume 271 mi rated range at 100% charge when the car was new (without range mode), then 273 Wh/mi breakeven would mean 271 mi * 273Wh/mi= 73,983 Wh usable capacity which is too low compared to the actual usable battery capacity which is around 77,500 Wh. See the screenshot here that shows 77.5 kWh after a hypermiling run. Therefore I'm not sure how rated mile is possible at 273 Wh/mi in an S85D. It should be 77,500/271= 286 Wh/mi.
The mods really need to implement a feature on this forum that electrically shocks a person through their keyboard when they type "watt/mile", "W/mi", "kW/mi", or any other variation thereof.
The correct units are watt-hours per mile (Wh/mile). Watts/mile makes no sense.
What is the difference between a watt and a watt-hour? | MyEnlighten Help
Battery capacity is measured in kWh (kilowatt hours, units of 1000 watt-hours).
Your logic makes perfect sense.
I was only commenting upon what I've observed. Driving at efficiencies above the 273 Wh/mi figure used more rated miles than actual miles covered. And, arithmetic showed that one-for-one (RM/AM) would have been achieved at 273 Wh/mi. All of which was based on the figures displayed by the trip odometer rather than any kind of higher reality.
If you don't trust the empirical data provided so far by quite a few different users, how much empirical data would you deem sufficient to prove this?
(btw, my best guess at this point is #3 above, but I'm not going to be the one to try and prove or disprove this.)
That’s where I’m at. I guess I’m the opposite of hypermiling.
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