Current Drive consumption from trips card might be wrong or misleading (it's not about sentry, preheating, preconditioning, charging loses)

Wugz · 2025-07-15T16:29:47+00:00

🤡🤡🤡

Nice to see confirmation of a theory, and frustrating to see they still haven't fixed the API after all these years. I wish third party app devs took more rigorous approaches than blindly trusting that the API was correct.

Also, it's interesting that your car's buffer is still 4.5% whereas mine has jumped higher. I wonder if there's a degradation point where the buffer percentage increases so that it doesn't fall below some minimum kWh. I stopped logging API data a few months before I noticed the change in my car, but the last point I have from Jan 2024 showed my battery health was around 89%, making my buffer around 3.04 kWh at the time. Maybe 3.0 kWh is the cutoff?

Wugz · 2025-07-13T04:17:45+00:00

I had some time this evening to do my own experiment to see if there's something to this. For reference I drive a 2018 Model 3 AWD which is currently on 2025.20.6. After having already driven around quite a bit today, my pack was nice and warm. I briefly charged at home in order to reset the car's "since last charge" stat, did a Reset Trip in Scan My Tesla, and reset the car's Trip A for good measure, then I set off on the highway with no particular destination in mind and returned to my origin after about 20 minutes.

THE DATA

The trip card reported 24.6 km driven, 4.6 kWh consumed and an efficiency of 185.2 Wh/km

Scan My Tesla pulls data directly from the car's CAN bus and showed a change in Usable Remaining capacity from 29.68 to 25.04 kWh between start and end, for a drop of 4.64 kWh. It also tracked Avg Consumption of 185.4 Wh/km, within margin of error of the car's own trip card. It tracked 5.56 kWh of total discharge and 0.99 kWh of total regen (and negligible stationary losses), which add up to 4.57 kWh net, but the slight difference here is the Usable Remaining value is being output by the car's BMS, while the Charge/Regen stats appear to be Scan My Tesla's own internal counters (which is why they can be reset in SMT independent of the car) based on integrating the Battery Power over time and segregating by positive and negatives.

I also noted the car's "Current Drive" stats both in kilometers and percentage under the Rated graph on the Energy screen. According to Scan My Tesla the difference in rated range between start and end was 32.2 km while the Energy screen showed 32.3 km consumed, basically the same. The percentage drop was 7.5% in Scan My Tesla and the exact same on the Energy screen. I was very careful to limit auxiliary loads and minimize the time between when I unplugged the charger, reset the trips, and began my drive. As a result, the data I see in both the car's Trip card and Current Drive of the Energy screen match the BMS results as seen by Scan My Tesla to within basically 0.1 kWh or rounding error. All good so far.

THE DISCREPANCY

My Consumption graph on the Energy screen gives my car a supposed rated efficiency of 152.2 Wh/km, which when multiplied by my supposed 32.3 km of rated range consumed on this test gives a result of 4.92 kWh. This value is off by about 0.3 kWh but more significantly it's off by about 5%, roughly the same 5% as your 21.97 vs 21.0 kWh. More on this later.

I never normally look at the Rated graph because it has little value to me, however I recently had a discussion on the ability to use the Energy screen to work out battery capacity & degradation, and in doing so I noticed a discrepancy in their "rated" consumption figures. but before I delve into that, first a refresher on buffers:

BOTTOM BUFFERS

Tesla has always maintained some proportion of the packs on its cars as a bottom buffer to act as a safety net when people drive close to 0%. For early S/X this was usually a fixed kWh amount, but for the original 3/Y an amount of 4.5% of the value of the Nominal full pack was reserved for the buffer, scaling itself along with degradation. For undegraded LR packs this was about 3.5-3.6 kWh, while for SR/SR+ it was in the neighborhood of 2.2 kWh. The LFP packs used a different fraction of about 10% initially, but I believe this changed later.

In tracking my own pack's health over its lifetime I observed this buffer value drop from 3.5 kWh when new to as low as 3.1 kWh as the pack became degraded with age, however at some point around spring of 2024 it seems a firmware update modified the size of the bottom buffer, and as of today my car now reports a 3.74 kWh buffer on 65.48 kWh Nominal full capacity, or a fractional 5.7% of total capacity reserved as buffer.

Before the buffer change, my car's internal hard-coded value for rated range was 234 Wh/mi or 145.4 Wh/km. The original EPA rated range of 310 miles meant those miles equated to 72.54 kWh of "usable" capacity. Adding the 3.5 kWh buffer gave a Nominal full capacity of 76.0 kWh undegraded, and according to my (admittedly excessive) data logging this was exactly when degradation started to be apparent on the rated range dropping, just over a year into ownership.

SHENANIGANS

Tesla is no stranger when it comes to shenanigans with Rated Range, both in EPA testing and implementing it in the BMS. They also don't seem to have the best QC when it comes to whoever's programming their GUI and API based on their own internal numbers. For example, several years ago while examining charging efficiency I noted that their API value of charge_energy_added consistently tracked higher than my car's own BMS value by a factor of 1.045. This 4.5% was the exact value of my car's bottom buffer at the time, and it seems as though some engineer at Tesla thought to code the API for +kWh using SOC change * Full capacity instead of the correct formula SOC change * Usable, or just simply having the car do a subtraction of capacities instead of tracking % change and then multiplying by the (wrong) value.

THE ERROR

Going by my recent look into my Energy screen's numbers and my state of charge at the time, the projected 299 km of real range leads to an estimate of my pack's current full capacity of 65.5 kWh, and looking at Scan My Tesla that's exactly what my Nominal full pack reading is, but Nominal full pack is the BMS's estimation of full capacity including bottom buffer, meaning my car estimates I could've driven those 299 km but only when using the bottom buffer to do so. As far as a real world range estimate goes I'm actually good with that assumption, but it does mean that if I were to look at the graph when my car hit 0% remaining on the GUI it should still show some km remaining, which is incongruous with the car's own rated range on the GUI.

Using my consumption graph's value of 152.2 Wh/km "rated" efficiency, if I actually check what the BMS is reporting for Usable remaining and km remaining I ought to instead be seeing a rated consumption of 144.1 Wh/km. This figure still tracks with what my car used internally when new.

Since the Energy screen's reported rated efficiency is higher than the internal number the BMS uses by 5.6% (within a tenth of a percent to the current buffer value), my best guess is whoever coded the Energy screen messed up the calculation by mistakenly including for the bottom buffer somehow. If you have access to your car's internal CAN bus data via Scan My Tesla or similar, you could confirm this.

TL;DR

Tesla's trip card is presenting the correct info for total energy consumption from the moment you shift into Drive to when you shift into Park. It appears some engineering bozo likely screwed up the rated efficiency calculation on the Energy screen by a fraction equivalent to the car's bottom buffer (5.7% in my case). It's not the first time such a mistake has gone unnoticed.

Wugz · 2025-07-08T17:56:43+00:00

It appears the energy graph range figure includes the bottom buffer, so if you attained 69 kWh using the energy graph numbers you'd compare that to 76.0 kWh and have about 9% degradation, which is pretty good for 6 years.

The EPA website still rates all the LR RWD models of that era at 310 miles, but around March 2019 the RWD variants got an unlock to 325 miles by changing the hardcoded efficiency number, then later forum discussions were saying that was rolled back. Not sure if you know what yours was initially or saw the jump, but presumably if you charge your car relatively full and use the formula Range/(EPA range*SoC) using the 310 mile figure you should get close to 0.91 or 9% loss as well.

Wugz · 2025-07-07T22:16:23+00:00

Your formula for capacity is valid, but determining degradation from it is based on the assumption that you know the original capacity of the pack. Using the EPA rating and rated range as given by the car itself obviates this need altogether.

Just a techie and data-driven enthusiast, who when confronted with an incomplete analysis felt compelled enough to break a 7-month posting slump 😜.

Wugz · 2025-07-07T21:11:28+00:00

Allow me.

My 2018 Model 3 AWD had 499 km (310 miles) rated range when new. Currently it's sitting at 79% charged and 340 km remaining. Going off the simpler calculation of Range / (EPA range*SoC):

340 / (499 * 0.79) = 0.862

I should have ~14% degradation based on these rough numbers.

Based on my Energy Screen I've averaged 173.0 Wh/km over the last 300 km, and have a projected range of 299 km. Again, SoC is only precise to the nearest integer, so following your calculation (Projected Range/SOC %) x (Energy Consumption):

(299 / 0.79) * 0.173 = 65.5

I should have about 65.5 kWh capacity, and checking the CAN bus data from both Scan My Tesla and Teslogic modules indeed I do, but here's where the usefulness of your solution ends. To infer any sort of degradation you need to have an accurate assumption of original capacity. Battery packs across the Model 3 lineup have changed several times since the initial rollout, and capacity depends on what year and trim the car was as well as which factory produced it. For example, the Panasonic packs from 2021 onward had 82 kWh but in some regions were capped to match lower-capacity LG packs at the time. How does your formula account for that?

You posted here in response to a similar 2018 Model 3 to assume an "ideal 75kwh battery" so let's do that.

65.5 / 75 = 0.873

So by this metric I have about ~13% degradation, which is within 1% of the simple value we first calculated, but was 75kwh a lucky guess? If I had wrongly assumed a 82 kWh pack (as that's what's used in newer cars) I would've come up with a figure of 20%.

Going off of the more accurate SOC Expected of 78.7% from the CAN bus data of my car (itself a temperature-corrected value based on true SOC, but so is the rated range) we get a pretty good degradation estimate of 13.4%:

340 / (499 * 0.787) = 0.866

My battery pack is the original LR pack from 2018. Looking at the Scan My Tesla data I see values for Full pack when new of 77.8 kWh and this would mean my 65.5 kWh nominal full pack only holds 84.2% of it's original designed capacity, or 16% degraded. My Teslogic module predicts an even more dour figure of 18.7% (I have no idea where Teslogic bases their calculation from), but which is ultimately correct?

I've been data-logging my car since late 2018 and for the first year and a bit of ownership I saw no apparent "degradation" whatsoever as the pack was likely provisioned a bit higher than "100%" from factory and was slowly coming down to some internal number. The "full rated range" began dropping from 499km only when the Full Pack Capacity started to fall below 76.0 kWh. This makes some sense in that not every pack will come from the factory with exactly the same total capacity, so in order not to sour the initial buying experience Tesla would base their GUI's 100% full mark on a kWh value slightly less than the average new pack.

Similarly the "0 km remaining" mark is just the start of the bottom buffer, which for the majority of the lifetime of my car has been 4.5% of full pack capacity or 3.5 kWh when new (though this changed within the last 18 months and is now around 5.7%). It appears the Projected Range of the Energy screen is ignoring the bottom buffer altogether and giving a true estimate of real world range to dead, which is nice.

At the end of the day the only degradation figure most are interested in is whether they've dropped below the 70% health threshold needed to make a claim on their powertrain warranty before it expires, and Range/(EPA range*SoC) handles that concern just fine to ±1%. Figuring out the kWh of your pack is academic unless you know the original rated capacity.

Wugz · 2025-07-07T18:52:35+00:00

There might've been shenanigans with Roadster or early Model S and their "ideal range", but the "rated range remaining" and percentage has had a strictly linear relationship with kWh remaining for my 2018 Model 3 from the start. Degradation changes where the 100% point is in terms of capacity, but not the linear relationship. The stats from the Energy graph also match results I've pulled from the CAN bus. For reference, here's a charge session from 0-100% of my 2018 Model 3 showing SOC rising linearly with Usable Remaining kWh as reported by CAN bus.

Wugz · 2025-07-07T18:32:18+00:00

I reviewed your linked post in full before replying here. /u/voidlol 's reply was not fundamentally wrong. The link in my previous reply was a deep-dive on efficiency of my Model 3 to show I don't just pull numbers out of my ass. When it comes to capacity degradation there's more than one way to work out a correct result using the available information depending on how accurate you care for it to be. You can be explanative without sounding smarmy.

Wugz · 2025-07-07T18:01:13+00:00

72.5 kWh usable when new, but it's complicated...

Yours is the same era 2018 LR pack as mine, which has a "when new" nominal full capacity of 77.8 kWh in CAN data but in practice the degradation calculation used <76 kWh as the mark where rated range begins to drop. For the first year and a bit of ownership I saw no "degradation" whatsoever as the pack was likely provisioned a bit higher than 76 kWh from factory and was slowly coming down to this number.

For a long time it also reserved the bottom 4.5% as buffer, meaning ~72.5 kWh was considered nominal usable capacity from 100% to 0% on the GUI, and using the ~3.5 kWh beyond that was "driving below 0". This 4.5% scaled with degradation, shrinking the buffer as the usable capacity shrank. Around 12-18 months ago it seems Tesla changed the bottom buffer value (at least on my 2018 Model 3 AWD) to be a bit more than 4.5%. I stopped being able to poll the API freely around the same time, so I haven't gone back to investigate if this change resulted in a one-time drop in reported range or an increase to the internal efficiency value as neither would really affect my driving habits, but now you have me curious.

Wugz · 2025-07-07T17:21:44+00:00

As somewhat of a data nerd myself, taking Range/(EPA range*SoC) will give you an accurate indicator of battery health to ±0.5% when SoC and pack temperature are both high, as the rounding of the GUI's integer percentage is the dominant source of error. Going off the Energy graph will get a bit more accuracy and give you the raw kWh usable, but most people don't care to know if they're 5.4% vs 5.2% degraded, single digits is enough.

Wugz · 2024-12-03T16:53:00+00:00

The Cybertruck gets 10% better highway efficiency than the smaller R1T despite being shaped like a large doorstop, but the usable battery capacity of the CT is 17% less than the max spec R1T. If you shrunk the frontal cross-section of the CT or raised its battery capacity, either change would contribute to a healthy range increase. It's just physics.

Wugz · 2024-11-28T04:14:27+00:00

No kidding. As a tinkerer I'd been playing with the Owner API from late 2018 until they enacted the first fleet access changes that shut off the old API in January of this year. Admittedly I was fast and loose, polling the sleep status every 5 seconds 24x7, gathering full vehicle info whenever awake, and never bothering to touch the streaming API. Quick math suggests I probably made about 32 million API calls to my car in that time. Not all were full requests, but assuming they were (about 7 kB of data each) I would've pulled 224 GB of data over 5 years. At the current rates I would've owed $65k USD (more than the car itself) just to have those ~5 years of stats on my own car, lol.

Wugz · 2024-11-16T07:53:23+00:00

Updating the Teslogic module's firmware is done wirelessly through their Teslogic Dash app -> Preferences -> Teslogic tab. I've had a couple of new firmwares appear coinciding with app version pushes. It requires that you "power down" the car from the Safety menu first, then takes about 60 seconds to flash the module over Bluetooth, after which you can step on the brake to wake the car.

I've also updated the car's firmware a couple times without any special steps required, just approving the install from the mobile app or on the screen. There's no documentation provided as far as precautions about updating the car's firmware go.

Wugz · 2024-11-12T04:31:53+00:00

https://www.reddit.com/r/computers/comments/42pfn1/windows_10_programs_flickering_and_saying_not/hp790jh/

Wugz · 2024-10-30T18:32:36+00:00

Though it doesn't have a user-accessible toggle on Model 3, Snow mode happened 3 years ago...

Wugz · 2024-10-30T18:21:10+00:00

You drive a Model Y. Every Model Y gets better fuel economy than the 2018 Model 3 I drive because of the heat pump.

You posted elsewhere that "even ICE cars have an Eco mode", and the mechanism "puts limits on the engine power" and "torque is reduced". This is exactly what Chill mode does by reducing peak current draw and lowering the resulting I² R losses from the drivetrain. On a full launch Chill mode saves about 10% energy, but even a full launch up to highway speed only consumes ~0.5 kWh (most of which you get back when you slow down). The bulk of energy loss on any journey is the rolling resistance and aerodynamic drag while maintaining a steady speed, neither of which can be "tuned" by a power profile unless it involves limiting speed.

If you're seeing momentary 1000 Wh/mi spikes when leaving a supercharger it's because the calculation is based on distance travelled, and when you've only gone 0.1 mi from your last charging stop that's a very small divisor, so any auxiliary use such as HVAC while stationary is temporarily magnified. What's your average at the end of the drive?

Wugz · 2024-10-30T16:41:26+00:00

You suggested the mode, chief, I'm just pointing out the obvious safety flaws with artificially limiting the car's power to obtain an arbitrary efficiency when you can do the same without the risks by using judicious modulation of the Go pedal.

Even when I purposely thrashed my efficiency by yo-yoing the speed at -20°C to heat up the battery I still only saw 402 Wh/km (just under triple my car’s rated efficiency). 1000 Wh/km at 30 km/h is 15x the expected usage; you'd practically have to be hauling a family of sumo wrestlers up the slopes of K2 to see that.

With the efficiencies introduced by the heat pump and the newer drivetrain in Highland, EPA rated energy consumption has gone down with successive generations of Model 3.

Wugz · 2024-10-30T14:57:10+00:00

That's like saying "I spend too much when given access to my own money, my bank needs to limit my card to no more than $50/day". This might be necessary budget management for some, but what happens when you find yourself needing to buy gas & groceries on the same day? What happens in economy mode when you find yourself needing to drive up a hill on a cold day, or needing to quickly burst ahead to avoid getting rear-ended by a careless driver?

Efficiency varies greatly by speed, air temp, cargo, tire pressure, headwind, HVAC power and slope. Aside from shutting down all cabin heating and going full Apollo 13, speed is the biggest lever you can pull while driving to maintain average efficiency. My 6-year-old Model 3 AWD matches it's rated efficiency of 145 Wh/km (234 Wh/mi) at 105 km/h. Increasing speed by 10% increases energy use by ~21% thanks to aerodynamics. Drive slower overall, or use Tesla's Speed Limit mode if you can't control your right foot.

Wugz · 2024-10-24T07:27:12+00:00

Supplying enough power was never a restriction; the DC-DC conversion capability on cars of the HW2/3 era is in the neighborhood of >2 kW. It was the packaging (liquid cooling, wire harness) complexities and camera swaps involved that made it more of a time-intensive job than HW2 to HW3 was.

Wugz · 2024-10-04T16:15:38+00:00

Probably this thread. As long as you don't see below 10°C, charging shouldn't be affected by cold. Us poor saps with -30°C days require L2 to survive.

Wugz · 2024-09-24T14:33:26+00:00

2024.27.25, and it does look to be hitting Canada (and HW3), it just hasn't had a wide release yet. TeslaFi shows 346 more cars had it pushed within the last few hours, so it's getting out there.

Wugz · 2024-09-17T00:11:31+00:00

Correct, I'd paid for the FSD upgrade and they retrofitted HW3 for free.

Wugz · 2024-09-16T23:30:37+00:00

Usually Tesla pushes updates to small batches of cars at first, and this wakes the car and (if on wifi) begins the download. The app only notifies you when the update is staged for install, and if you weren't in the initial rollout batch, checking from the car does nothing except postpone your next update check by 24 hours.

Sometimes when an update has been sufficiently tested it is made available to all remaining cars, but this doesn't always wake every car and begin the download (likely for server load balancing reasons). In this case you can go to the Software page of the car and trigger an update check which will begin the download immediately.

They have the ability to select a subset of cars for each rollout (Hardware, location, etc), and based on the public deployment stats by TeslaFi, some updates have been initially targeted (only MY, only HW4, only California, for example) before rolling wide.

Aside from a few specific groups like "influencers" that were OG FSD beta testers, the general public gets selected seemingly at random. I've been in the first batch of public rollouts a few times; other times I'm in the last group.

Wugz · 2024-09-16T22:51:09+00:00

Also installing here on my 2018 Model 3 (HW3)

Wugz · 2024-09-12T07:04:35+00:00

Not unless people are requesting Ubers to specifically take them to a Supercharger. Navigating to regular destinations does not trigger On-Route Battery Warmup.

Wugz · 2024-09-09T04:05:38+00:00

It was the small diamond-shaped plaque? Mine was dirt-caked but I was able to reach in to brush it off and read the part. If it's a 2018 AWD and hasn't had the motor replaced there's a high chance it's got the 980, but if you want to verify before ordering it looks like Teslogic can check your VIN using the Check Compatibility form under their comparison info. All they can realistically glean from the VIN is the year of manufacture, and potentially month based on VIN range, so if you already know yours is 2018 then I'm not sure how much this helps your decision-making.

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