Car’s energy consumption (lack of) accuracy

[RuiP]

As has been pointed out, it's not possible to know what energy in the battery is usable because it can depend strongly on what you will do in the future which is unknowable. Will you tow a 5,000 lb trailer up a 5% grade, or will you sit in the car with the AC running listening to music?

So sorry, but what's been pointed is that the car's BMS indicates the energy in the battery. It's an insurmountable fact. Pointing in the opposite direction is plain insanity.
PS: Towing, going uphill and using the AC has nothing to do with the ability to estimate the amount of energy left in the battery.... which the car does.

At the same time you seem to be in some sort of dream world where ICE vehicles always accurately report their energy efficiency by measuring the BTU content in the fuel, precisely measuring the remaining fuel and conveniently displaying that to the user both in total energy terms and available mechanical energy based on a near perfect estimate of the future thermodynamic efficiency of the engine./S

It's difficult to make an argument with someone who fantasizes about what other people said. Yes hacer, that's what I said or even implied in my posts. Additionally, ICE cars should have a flux capacitor inside the graphite membrane.

For any vehicle, you can only know your past operating costs and attempt to estimate future costs. The way to do it is the same for ICE and EV

On my home planet:

• ICE car users pay for the gallon or liter, and their cars show them the amount of miles to the total gallons used (or total liters/100km).
• In my Model S (don't know about your special S's or other EVs), I pay the electrical utility for kWh and my car shows me a Total Energy that's off by more than 10% regarding the energy that entered the battery.

Prepare to be mind blown: If you sit in your parked ICE car, charging your Nokia and pager, blasting your cassette stereo and playing with your infotainment, all sucking up that magnificent 12v led-acid battery, as soon as you fire up that beautiful ICE engine, the alternator will start to recharge the 12v battery, putting a load on the ICE engine and decreasing (increasing) the mpg (l/100km).
What??? Insane!!!! On La La Land it's called vampire drain, a thing that must not be measured!!

You also seem to think that this is a conspiracy on Tesla's part to fool the user about their operating costs which is ridiculous.

Yes, it's absolutely outrageous to even dream that automakers play with numbers. Well, it could make sense on hacer's planet (the 11th planet of the solar system (if you consider Pluto and Palo Alto a planet!).
On planet Earth, environmental agencies have to play catch up with automakers, tightening test procedures (cue in WLTP) to escape test-bench-"ingenuity", and some automakers either plainly cheat, or use "defeat devices" (pony car makers like like VW, Audi (whose CEO was arrested), Mercedes or Nissan).

In the case of Tesla, if you're willing to purchase a phone app (and trust someone with a login token for your car), you can have a very good measure of the total energy drawn from the wall outlet for each and every recharge without any other equipment. It's still up to you to translate that into cost. You also have an odometer at your disposal should you want to know how far you've traveled.

Please read the original post, and the other linked thread in it.
Just to be clear: I've gathered more than 300k records from my car's API (1 per minute) with 140 indicators each. Also have a MID compliant, modbus connected, energy meter dedicated to the car. Also sporadically connect to the car's CAN bus and read the data.

As a closing statement:
I know my numbers, did my transparent calculation (a division!) and decided to take my time and write about my experience on an internet subforum called Battery & Charging, inside Tesla Motors Club.
There (here), I wrote about my experience and findings, so that other people could point out other possible explanations and so that people that didn't run the experience could learn some numbers from it.
Instead, the sect members decided to attack:
"Preposterous, the Earth is flat!!!" they yell
"It doesn't matter!!!" they reply, when explained that the 1st post contains facts showing that the Earth is round.

To add insult to injury, the guy that shows up with data is repeatedly told to get lost, by the guys that wander an internet subforum called Battery & Charging, with no facts or data to show.

Elon Musk! (I was going to say Jesus Christ, but you wouldn't understand)... I'm the one driving a Model S (which I think is the best car in the world) and owning TSLA stock (which I believe will go past a $100b market cap) but some guys are clearly on a whole different level of cult.

Live long and prosper! Long live Musk!

 

[RuiP]

I'm certain most that people will simply charge their cars off-peak or at work for free and continue to have no clue what a 'kWh' is, how much it costs or how many their car uses. All they'll know is it's A LOT cheaper than the gas-guzzler they traded in and they won't give it a second thought. IMO it's likely that EVs will eliminate the need for efficiency standards entirely. Range will be king and that alone is enough to provide a market signal for efficiency. A more efficient car can make better use of a smaller battery => it's more cost-effective. The selling point will be the 310 miles of range and the 130mpge will be ignored...

Drive more, worry less.

Energy Star (ENERGY STAR | The Simple Choice for Energy Efficiency) closely monitors energy efficiency on dehumidifiers, dishwashers, refrigerators, room air cleaners, HVACs and even geothermal heat pumps, but indeed no EVs, so perhaps you have a point when you say "it's likely that EVs will eliminate the need for efficiency standards".


PS: I'm not worried. I'm on a Battery & Charging internet forum sharing some energy numbers regarding an EV.

 

[nwdiver]

Energy Star (ENERGY STAR | The Simple Choice for Energy Efficiency) closely monitors energy efficiency on dehumidifiers, dishwashers, refrigerators, room air cleaners, HVACs and even geothermal heat pumps, but indeed no EVs, so perhaps you have a point when you say "it's likely that EVs will eliminate the need for efficiency standards".


PS: I'm not worried. I'm on a Battery & Charging internet forum sharing some energy numbers regarding an EV.

The difference is that it's CHEAPER to make an inefficient appliance. It's MORE EXPENSIVE to make a 300mi EV that gets 350wh/mi vs a 300mi EV that gets 330wh/mi. That's why Tesla invested so much in crazy door handles; Those door handles save $100s in battery.

We may need some improved transparency in the future on idle losses since those can be significant without affecting range but I think the market mostly has this one...

To add insult to injury, the guy that shows up with data is repeatedly told to get lost, by the guys that wander an internet subforum called Battery & Charging, with no facts or data to show.

Um... no... the guy with the data was educated on how his interpretation of the data was wrong because... physics. Which oddly you claim to already be aware of. More curious is the fact that your own data clearly shows the increase in DISCHARGE INEFFICIENCY that I referenced above...

The plotted data shows a very interesting pattern:

'Interesting'?... don't you mean exactly what I should expect based on.... physics? And why do you keep using the term 'accuracy' to refer to 'efficiency'?

Man, I know all of that!!!

.... Obviously not....

The consumption meter is simply multiply Current x Voltage = Power; Simple and accurate for what it's measuring...

What you want is (Current) (Voltage) (Age Factor) (Temperature Factor) (Cell Generation Factor) (Current Multiple) etc, etc.... But you already knew that.... right?

On La La Land it's called vampire drain, a thing that must not be measured!!

Please explain how I can measure the self-discharge of a 18650 cell without discharging what's left and counting the Ah....

 

[nwdiver]

On my home planet:

• ICE car users pay for the gallon or liter, and their cars show them the amount of miles to the total gallons used (or total liters/100km).
• In my Model S (don't know about your special S's or other EVs), I pay the electrical utility for kWh and my car shows me a Total Energy that's off by more than 10% regarding the energy that entered the battery.

Side Note:

Have you ever ordered Sushi then complained it was undercooked? Just curious...

 

[RuiP]

More curious is the fact that your own data clearly shows the increase in DISCHARGE INEFFICIENCY that I referenced above...

Why is that curious? It's clearly stated on the 1st post that that is the overall conclusion of the experiment: "Model S is NOT measuring the battery’s discharge (in)efficiency"
It was right there on the 1st post!

And why do you keep using the term 'accuracy' to refer to 'efficiency'?

The word accuracy is referred in relation to an indicator that Tesla calls: "Total energy".
If I used the word "efficiency" like you're suggesting, the phrase would be: "I don't believe the car's energy meter has a good efficiency". English is not my mother tongue, but that doesn't seem right to me.

The consumption meter is simply multiply Current x Voltage = Power; Simple and accurate for what it's measuring...

Tesla says it's measuring Total Energy. They forget to add that it's Total Energy of Part of The Energy.

Please explain how I can measure the self-discharge of a 18650 cell without discharging what's left and counting the Ah....

You can't. It's impossible. The graph on the 1st post was achieved using dark magic.

 

[nwdiver]

You can't. It's impossible. The graph on the 1st post was achieved using dark magic.

Your graph is showing discharge loss not self-discharge; You can certainly estimate discharge loss... how to you measure self-discharge? Despite sounding similar they are very different.

If energy is transferred cell to cell how do you measure the efficiency loses? Should each module measure and report balancing losses too? You're trying to make something complicated sound as simple as a tank of petrol. It's not.

What algorithm do you want the consumption meter to use to satisfy your definition of 'accuracy'?

The word accuracy is referred in relation to an indicator that Tesla calls: "Total energy".
If I used the word "efficiency" like you're suggesting, the phrase would be: "I don't believe the car's energy meter has a good efficiency". English is not my mother tongue, but that doesn't seem right to me.

The consumption meter is ACCURATE. The battery is not 100% efficient because... physics. You were measuring the efficiency of the battery NOT the accuracy of the consumption meter. The meter is ~99% accurate at 280wh/km... the battery is ~82% efficient... which is probably about right because... physics...

Maybe Elon can add a $5k Space X sensor package in the future that includes all the complicated variables needed to calculate TOTAL energy consumption...

 

[RuiP]

Just a sec. Let me just upload the code to Github.
Or I would happily sell Elon or Space X the graph on the 1st post for $5000.!

 

[nwdiver]

Why is that curious? It's clearly stated on the 1st post that that is the overall conclusion of the experiment: "Model S is NOT measuring the battery’s discharge (in)efficiency"
It was right there on the 1st post!

Side Note;

Have you ever ordered Sushi and commented 'I don't think my fish was cooked'?

 

[Mark_T]

I love these debates, they go on pretty much everywhere that lithium cells are used from hobby to car sites.

There is a large fortune waiting somewhere for the first person to discover how to actually measure the remaining energy in a cell without discharging it to empty, until that happens we will have to make do with inferring the remaining energy from the cell voltage or trying to keep track of what goes out after charging up to a known starting point.

All else is just smoke and mirrors

 

[nwdiver]

Just a sec. Let me just upload the code to Github.
Or I would happily sell Elon or Space X the graph on the 1st post for $5000.!

??? Didn't you use energy used to RECHARGE for data in that graph? How is the consumption meter supposed to get that information? Tachyons?

I can see the headlines 'Man invents time travel to determine how much energy his Tesla uses'

 

[RuiP]

Because calculating the consumption in relation to 100% of the energy that entered the battery is something that would have a small margin of error (much smaller than the energy that's currently not being accounted for), you prefer to have a super precise measurement of the energy that is leaving the battery, not knowing if that corresponds to 80% or 95% of the energy that entered the battery.

I can see your point (not being sarcastic now), but we'll have to agree to disagree.

 

[nwdiver]

you prefer to have a super precise measurement of the energy that is leaving the battery, not knowing if that corresponds to 80% or 95% of the energy that entered the battery.

That's not my preference. I would love for the consumption meter to indicate TOTAL consumption. There's just no way to do that without introducing a larger error and potentially making it less accurate or additional expense that simply isn't worth the benefit...