Rated range during trip dropped faster than expected for averaging 223Wh/mi

After a brand new drive unit install yesterday (not remanufactured), new battery contactors, and an update to v .251, I am concerned that something may be wrong with energy usage or range calculations. I have a 190 mile round trip today (no dest charger) so I only charged to 90%. I decided just to "drive slow". Previously on long trips I observed that if you drive slower, the rated range doesn't drop as fast (common sense if your going 250Wh/mi vs 350Wh/mi).

I'm at my destination halfway and the rated range seemed to drop much faster than they should have given how slow I was driving and how little energy I used.

Rated range at start: 222
Rated range after 94.6 miles: 130



Display:
Total energy used: 21.1kWh
Avg energy: 223Wh/mi

Now the problem for me is that those numbers do not make sense. They do not look accurate. By my calculations, since I drove so conservatively and used little kWh, my range should have only dropped by about 70 miles. Instead it dropped by 92.

AFAIK Tesla's rated range calculation is done assuming about 300Wh/mi. Since I only went 223Wh/mi, that means I saved about 77Wh/mi by driving conservatively. Over 94.6 miles that is 7284Wh of savings. Using 300Wh/mi , that means I should have saved about 24.2 miles, effectively meaning that rated range should have only dropped by about 70.3 miles. Instead it dropped by 92 miles. IMO that's a pretty significant error difference.

You can do this calculation several ways. I'll do it another way. If I only used 21.1kW, at the rated range calculation of 300Wh/mi, it should have only dropped 70.33 miles, not 92 miles.

Again, assuming Tesla's rated range calculation uses 300Wh/mi, common sense says if I drove 94.6 miles at an average of 300Wh/mile the rated range should drop by about 94.6 miles (duh). It dropped by 92 miles. Very close. However , 223Wh/mi is a significant difference from 300Wh/mi. About a 25.6% difference. I should have got about 74.3% of what 300Wh/mo would have got. The difference between 92 and 94.6 is not 25.6%. Guess what 74.3% of 94.6 is? 70.3.

Am I calculating this wrong or does something look off to you all too?

kennybobby said:

It looks like the slower driving will get you home okay. The range estimator started at 222 and you drove 95, so you would have 127 left. But your good driving caused the range estimator to say you have a few more miles available, 130.

It seems that if the estimated and the actual are really close then that would be a good thing?

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Right, I "gained" like 3 miles. But driving that slow and getting 223Wh/mi should have allowed me to "gain back" much more like 20 miles. (I say "gain back" but it's more like "used less").

And FWIW the question here is the range calculation. I'm not worried about not making it back as I know I can (also I can go to a supercharger out of my route if I really felt like it ).

sorka said:

It would be more helpful to know what percent your started at and ended at. That won't change based on how you drive.

i.e you should have used 27.8% of your battery. If it showed a lot more than that, I'd be worried.

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I started at 90%. I'll check the % when I get back to the car but the slider looks like it's at 50%. Aka it thinks it used 40%. That's why it all looks wrong. I'll confirm this later today.

3mp_kwh said:

It would be a good thing, if Tesla's 'rated range' values didn't more resemble an SOC %. He's losing about 1, for 1, at a very low 223Wh/mi. I wonder if two different sensors are involved. Perhaps one aft of the new motor unit, and one before it possibly reporting some artificially low wh/mi, as it gets broken in? Just speculating.

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This. ^^^^ This is what I mean I'm worried about. It should NOT have been 1:1 for only going 223Wh/mi

hiroshiy said:

Did you turn off range mode during your drive?

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No (range mode meaning reduced AC/heater). I always leave that on.

So I did the same exact run today from the original 1st post. This time I started with a 90% charge of 220 rated miles, and ended with 145 miles rated range while getting an almost exact same Wh/mi and distance (the .3 mile difference in distance was because in the OP I stopped to go wee wee and this time I didn't haha). But wow what a difference! In the op, rated range dropped 92 miles for 223Wh/mi, but in this trip it dropped 75 miles for 220Wh/mi -> a 17 mile discrepancy in the rated range calculation. THIS CAR MAKES NO SENSE. Therefore, I conclude, the car pulls numbers out of its own arse for rated range display.

Cyclone said:

Just to make sure I understood correctly. Right after the drive swap, this trip would use 223 Wh/mi and reduce your overall rated range by 92 miles. Now, a couple weeks later, you are getting about the same Wh/mi, but seeing less of a rated range drop. Correct? If so, are you still on .251 like before?

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Yep and yep

trils0n said:

hvac usage, etc.

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all of my trips i've been monitoring since the DU are during the day in 70 degree weather and no hvac on at all so there should be absolutely no variation like this ....

Matteo said:

maybe you left the car in park mode for long time.

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I understand what your saying but nope, not the case for me. Majority of the nights I plug in around 10pm with like 30-50 miles left and leave at like 4-5am right after it finishes charging so it's not left on or anything. Besides I have a habit of turning off the hvac if I had it on whenever I arrive home just for this specific reason of not wasting energy of doors are open or something while I'm loading or unloading my car.