Three stories on range: which is accurate?

[tcaron3097]

Story 1: The picture of the graph below is from the main data screen on my 2023 R1T [trip A view]. My truck is a dual motor with max pack, but I don't think that matters.

When I divide my total miles driven [47703] by the stated kWh consumed [18783], my miles per kWh pencils out to ~2.54 mi/kWh. But what the car calculated was 2.17 mi/kWh. What this view doesn't show me is what my total kWh impact has been and I am trying to solve for the additional layer of overhead usage. I know the total kWh would be 21982 if my range was truely 2.17 but I would really like to see that detailed. And why give me a 2.17 mi/kWh value if I don't have the right data to validate the claim? Was it a recent update that made this happen?

Story 2: The second picture is from the power screen. Its from my trip to the gym today, that totaled 12 miles. 2.81 mi/kWh doesn't come from 12 miles/6.1 kWh but when I account for the regen the math kind of works, meaning that I divided 12 miles /4.4 kWh [6.1-1.7].

Story 3: My trip B screen shows the common sense calcs: 195.8 miles driven, 71 kWh consumed with the average being 2.76. Simple math tells me this is correct but I wonder if the data is incomplete.

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[mkhuffman]

I am not clear what your question is. But will point to out that 12 miles isn't a sufficient distance to get good efficiency measurements for comparison purposes. You need to compare 100 mile drives in similar conditions (elevation change, weather, load, etc.).

Also, your #2 item is one that is super confusing. That graph uses regen and battery usage to somehow determine energy used. I guess regen + battery = energy needed to move the truck but who cares? All I care about is how much battery is used.

I recommend you subscribe to @Rivian Roamer. It will allow you to track just about every metric you can think of, including trip efficiency and battery capacity. He has built an amazing tool, which is improved weekly.

 

[ElGuano]

The energy monitor graph has always been super unintuitive to me, and I have to take several minutes to back into the math to make it work (which negates most of the "at-a-glance" value).

I'm assuming it means you consumed a total of 6.1kwh. BUT, that doesn't include the 1.7kwh regen.

The breakdown however, does try to math in the 1.7kwh regen, evenly split amount the consumers of power. So while it shows 3.9kwh used for drive, it's really closer to 5.4kwh.

 

[ksurfier]

You could try this:

A) Reset trip B meter
B) at the end of the drive, record the 3 values
C) right before your next drive, log the values
D) repeat

you will likely start to see patterns where the vehicle is consuming energy and your efficiency drops but kWh usage does not increase. The idle consumption could include gear guard, heating/cooling, or a variety of other non-moving uses of the high-voltage battery.

 

[Rivian Roamer]

The energy monitor graph has always been super unintuitive to me, and I have to take several minutes to back into the math to make it work (which negates most of the "at-a-glance" value).

I'm assuming it means you consumed a total of 6.1kwh. BUT, that doesn't include the 1.7kwh regen.

The breakdown however, does try to math in the 1.7kwh regen, evenly split amount the consumers of power. So while it shows 3.9kwh used for drive, it's really closer to 5.4kwh.

Correct.

Agreed with other comments. That drive is way too short to get meaningful data. That's like trying to estimate how many calories you burn walking a quarter mile. Depends on what you ate before that, how you're feeling, stress levels.

With an EV it can be battery temp, wind, ambient temp, humidity, tire pressure, traffic. While it's fun that EVs give us these numbers there is even a margin of error with measurement. You'll never get tow numbers to look within a certain standard deviation.

 

[2kwik4u]

I did a ton of measurements and record keeping on my previous ICE vehicles. Tracking miles driven, gallons used, octane levels, ambient temps, and dash reported data. What I found is that most vehicles (or at least the 5 or so I kept track of over a decade) were really accurate within a very small window. For my Yukon it was right around 18mpg. The dash and the hand calcs would match very closely around there. If I got an actual 22mpg, then it would report 20, if I got an actual 15mpg, it would report 17. This is the nature of internal measurement systems, how accurate the sensors are, how well calibrated they are, and then purposeful rounding that is put in place to make a pretty dashboard.

All that is to say, you aren't likely to get stellar results from any "in vehicle" system outside of a small window. You'll get good enough information to plan a trip, but not good enough information to truly satisfy a critical engineer or accountant.

If you really want to track data, I suggest using ElectraFi. It logs all of your data, gives you a few more decimal points than the in dash nav, and logs a lot of the confounding variables like speed and temperature. It's $5/mo, but if you're a data nerd, it's good fun.

 

[freshpow]

I’m just as confused as OP on the trip meter. Total miles driven is a simple calculation. Total kWh used is a simple calculation. Why does A/B not equal C?

My trip meter is the same way. Pretty much spot on for my 1,500 mile trip A. Not even close over the lifetime 31k mile trip B.

 

[bbonkk]

My gauge has been stuck on 2.17 m/kWh for a year now. I think it must be a software glitch.

 

[VandalSibs]

I’m just as confused as OP on the trip meter. Total miles driven is a simple calculation. Total kWh used is a simple calculation. Why does A/B not equal C?

My trip meter is the same way. Pretty much spot on for my 1,500 mile trip A. Not even close over the lifetime 31k mile trip B.

I may be wrong, but the trip meter math also includes the power used for everything - HVAC, vehicle computer & other systems, etc. The number at the bottom of the Energy screen/app is the raw driving stat.

 

[ElGuano]

Some of the graphs also seems to include idling at a stop. I don't know why sitting at 0mgh would ever result in 10+ m/kwh (seems more like it should be zero m/kwh).

 

[mkhuffman]

One more thing to add to this discussion: the battery management system (BMS) is only providing an estimate of the charge remaining in the battery pack. It is not nearly as accurate as a fuel tank and fuel gauge where you can easily measure how much fuel is remaining. The BMS can get out of calibration if you don't regularly charge to 100% and discharg to 10%. When the BMS is out of calibration it makes efficiency and range estimates even more unreliable.

The BMS actually does a really good job of estimating battery capacity as long as it's properly calibrated. But it's still an estimate and not an absolute measurement.

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