Help Me with Tesla Math

[T3slaOwner]

I've checked this several times and I'm not getting it.

Trip of 124.8 miles, 300 Wh/mi average. 100 kWh battery started at 76%, ended at 33%, so 43 kWh used if no degradation.

124.8 miles * 0.300 kWh/mi = 37.44 kWh
+ 33 kWh remaining = 70.44 kWh starting.

Wait... that's 5.56 kWh short or about 15%.

So what does not go into the Wh/mi figure that would explain the discrepancy? My understanding this number includes ancillary energy uses like A/C, heating and headlights, no?

I've also compared my battery % to the kWh picked up when charging and those numbers seem to show about 4% battery degradation.

TeslakWhTrip_76

• T3slaOwner
• Aug 26, 2019

Trip numbers of trip starting at 76%

 

[ajdelange]

The car is trying to tell you about how much energy you use driving the way you do under the conditions you do. Thus the 300 wH/mi figure only represents consumption when the car is in D (or R, I guess). Once you park the car it continues to consume energy. This is "vampire drain" which can amount to a fraction of a mile per hour of sitting up to miles per hour of sitting depending. Security mode seems to be particularly demanding. Heating or A/C used to maintain or pre condition the car depletes the battery but is not counted in the Wh/mi calculations.

There are still some mysteries in all this. There is what I call "departure tax". You will often see your trip display showing thousands of Wh/mi in the first couple of tenths of a mile of a trip. Shorter trips usually report higher Wh/mi than longer trips. In cold weather this is explained by the fact that regenerative recovery doesn't kick in until the battery warms. In warm weather it isn't.

 

[T3slaOwner]

I'm not following your reasoning. This was a single trip. Get in the car, note the % charge, drive, stop at end of trip, take the photo you see above. What other current draws are there that don't appear in the Wh/mi rating for the trip?

People make all sorts of excuses by waving their arms in the air and incanting with the magic terms. But they never back it up with math or anything that can actually be verified. I've had people talk about how the loss of regen has to be significant without knowing anything about how I drive after a full charge. In reality my driving after a 100% charge uses the brake very slightly. It's not the loss of regen that costs kWhs. It's the use of the brake pedal. You can still coast to a stop sign just like I do in my truck only using the brake from a much lower speed than the speed limit which has a much lower energy content by the square of the ratio of speed. I'm not talking about you. Your post was pretty reasonable and sounds like you are as frustrated and confused as I am.

You reminded me that I left my car in sentry mode which I need to turn off. Thanks. Normally my car uses 1 kWh per day when not in use.

 

[T3slaOwner]

Seems I was mistaken about sentry mode. I thought I had turned it on while I was charging the other day, but I just checked with my phone and it's not on. Does it have to be turned on every time you park the car?

The reason I turned on sentry mode was because a big pickup was parked in a Tesla spot the other day. That's ok, those spots are marked for 15 minute general parking. But the truck being so big made me a bit nervous about my car being damaged when he got back in. lol So I tried to turn on sentry mode. Maybe I never got it turned on. He came back while I was reading the info. I did eventually find the control, I think I had to scroll a screen up to see it. It is hard to find anything in the manual if you don't know the name and I had forgotten the term "sentry" more lol Once I found it I guess I didn't turn it on. Just as well. Now I know I can turn it on from the phone.

 

[ajdelange]

It's not exactly rocket science but there are some things that are known only to Tesla like, for example, exactly what gets recorded in coming up with the Wh/mi number. That number is there to help you monitor your fuel condition whilst driving and it therefore makes sense that any load that is on during the drive should be counted. If you turn the A/C on it should be counted (and you can verify that because you can see it on the power meter) and if you open the glove box its light draw should be counted too (but you can't verify that because the draw is too small to be visible on the display). But I don't know that the glove box light load is counted. But it makes sense that the number that goes into the numerator is the integral of the product of battery voltage and battery current and that's what most of us assume it is. Thus if you drive 124.8 mi at 300 Wh/mi you are going to use 37,440 Wh which is 37.44% of 100 kW. If you get in the car, read the battery percent, drive the 124.8 mi and immediately read the battery % again it should be down by about 37.4%. If you sit in the car for an hour on a hot day with the A/C running it should be down by about 39.4%. But you say you didn't do that and saw the battery drop from 76 to 33 % equal to a 43% drop in capacity which is 5.56 % greater than the odometer data suggests it should be. You have an inexplicable discrepancy.

For starters we note that the percentage numbers are rounded. Were the starting SoC 75.51% (rounds to 76%) and the ending SoC 33.49% (rounds to 33%) the difference would be 42.02% and the discrepancy 42.02 - 37.44 = 4.58% but that's still way too much and the odds of that particular rounding situation are vanishingly small.

Another idea comes to mind and that is while 37.440 kWh is 37.44% of 100 kWh it is 43% of 87 kWh (and 42% of 89 kWh). Now I don't even know if the % displays are of the battery capacity when it left the factory or of the current battery capacity. If it is the latter and your battery is 10% degraded then we have an explanation but not one we like very much. I am assuming that this is a relatively new X and while anything is possible 10% degradation is not usually seen until 10's of thousands of miles have passed under the wheels.

Were I you I'd be looking at lots of data. Perhaps this is a fluke. Perhaps not. In any case, it's a mystery.

As to the charging: the charger is not 100% efficient so the energy delivered to the battery will always be less than the energy taken from the mains. Nonetheless I have seen TeslaFi report more energy delivered to the battery than is taken from the mains. This is clearly an error in the API or in the way the app uses the data.

 

[Mewtwo]

This is mainly because battery capacity is not like gas in the tank or water in the bottle. The relationship of “speed of drinking”, time, and total volume of water in the bottle is linear, as we can say speed*time=volume. That is, if you have 500 ml water in a cup and you drink 250ml per minute, it will take you 2 minutes to drink up. If you sip at 100ml per minute, it will take 5 minutes.

However, discharge rate, time, and battery capacity is not linear. You can’t expect discharge rate*time=capacity. This is because the capacity is only achieved when discharging at rated speed. I don’t remember the exact number but for X 100D it’s around 330 wh/mi. If you drive faster, harder, at say 400 wh/mi, you will have less capacity.

See here for more details:
https://www.sciencedirect.com/topics/engineering/battery-capacity

 

[ajdelange]

Actually battery capacity is rather like water in a bottle or gas in a gas tank if you measure it in coulombs or ampere-hours i.e. units of charge. Lithium ion batteries are known for being "coulomb efficient" i.e. you put 10 in you will get pretty close to 10 out. There is a small difficulty here because the vehicle doesn't consume X coulombs to go a mile. It consumes Y watt-hours and a watt-hour is an ampere-hour times the voltage which changes as the battery discharges but, of course, the battery voltage is always available to the BMS so it can "linearize" the relationship and rate*time = energy used. Thus if you have 90 kWh in your battery and withdraw it at the rate of 300 Wh/mi you can expect to go 300 miles whereas if you are driving in heavy rain and consuming 400 Wh/mi you can only expect to go 225. This is the same as with an ICE vehicle. If you have a 20 gal tank and are getting 30 mpg you can go 600 miles but if the fuel demand increases to 20 mpg you can only expect to go 400.

The real problem with BEV's is that one cannot easily calculate the battery "capacity" from the measurements that one can readily make (battery voltage and current). That's why battery "health" charts are, at best, scatter diagrams with trend lines through them. The other problem is that the car provides various bits of data through its API and while I expect they disclose in some detail what those bits mean and/or how the car measures them that data is not available to me so I don't know how to interpret them.

As an example of this last Thursday:

Drive Tadoussac to Baie St. Paul: Consumption 23.7 kWh equal 26% ---> 91.1538 kWh capacity
Charge: 36.16 kWh equal 37% --> 97.7297 kWh capacity
Drive Baie St. Paul to Ogden: 70.31 kWh equal 76% --> 92.5132 kWh capacity
Charge: 60.7kWh 62% --> 97.9032

From these data I can only conclude that the capacity of my battery is between 91.2 and 97.9 kWh. As I mentioned in my earlier post a lot of this uncertainty is caused by rounding the presented percentages to the nearest whole percent. And I expect that this is done because reporting SoC to higher precision is not justified.

Processing additional readings like this (38) I can only conclude that my battery's capacity is 96.8 ± 0.92 kWh.

 

[T3slaOwner]

This is mainly because battery capacity is not like gas in the tank or water in the bottle. The relationship of “speed of drinking”, time, and total volume of water in the bottle is linear, as we can say speed*time=volume. That is, if you have 500 ml water in a cup and you drink 250ml per minute, it will take you 2 minutes to drink up. If you sip at 100ml per minute, it will take 5 minutes.

However, discharge rate, time, and battery capacity is not linear. You can’t expect discharge rate*time=capacity. This is because the capacity is only achieved when discharging at rated speed. I don’t remember the exact number but for X 100D it’s around 330 wh/mi. If you drive faster, harder, at say 400 wh/mi, you will have less capacity.

See here for more details:
https://www.sciencedirect.com/topics/engineering/battery-capacity

I get that. But the issues I'm seeing aren't about the Wh/mi. That is carefully measured and reported by the car. There seem to be other losses that are not counted by the car which make the kWh seem to vaporize. I thought it was vampire drain I wasn't paying attention to, but some of the trips I track are just two days and one night.

That's my point. The data the car reports to the user isn't adequate to properly plan.

 

[ajdelange]

I've checked this several times and I'm not getting it.

You need to understand what these numbers are telling you in order to "get it".

Trip of 124.8 miles, 300 Wh/mi average. 100 kWh battery started at 76%, ended at 33%, so 43 kWh used if no degradation.

No. The battery is designated as a 100 kWh battery. That is not its usable capacity. Starting at 76% displayed and ending with 33% displayed means that somewhere between (76.5 - 32.5) = 34% and (75.5 - 33.5) = 32% of the battery's usable capacity has been expended.

124.8 miles * 0.300 kWh/mi = 37.44 kWh

37.44kWh is an accurate estimate of the energy used. If 37.44 is 32% of the battery's capacity the battery's capacity is 89.1 kWh. If 37.44 is 34% of the battery's capacity the battery's capacity is 85.1 kWh. Thus your actual usable battery capacity is in this range, more likely about in the middle (i.e. around 87 kWh).

+ 33 kWh remaining = 70.44 kWh starting.

It's not 33 kWh remaining. It's 33% of the usable capacity i.e. about 29 kWh. At 300 wH/mi that should get you around 96 miles.

Wait... that's 5.56 kWh short or about 15%.

So what does not go into the Wh/mi figure that would explain the discrepancy?

Unless you have the Relativity Condenser option, nothing.

My understanding this number includes ancillary energy uses like A/C, heating and headlights, no?

Yes.

 

[T3slaOwner]

You need to understand what these numbers are telling you in order to "get it".

No. The battery is designated as a 100 kWh battery. That is not its usable capacity. Starting at 76% displayed and ending with 33% displayed means that somewhere between (76.5 - 32.5) = 34% and (75.5 - 33.5) = 32% of the battery's usable capacity has been expended.

At least the math works when I calculate it. Get your answer closer to 43%, eh?

37.44kWh is an accurate estimate of the energy used. If 37.44 is 32% of the battery's capacity the battery's capacity is 89.1 kWh. If 37.44 is 34% of the battery's capacity the battery's capacity is 85.1 kWh. Thus your actual usable battery capacity is in this range, more likely about in the middle (i.e. around 87 kWh).

It's not 33 kWh remaining. It's 33% of the usable capacity i.e. about 29 kWh. At 300 wH/mi that should get you around 96 miles.

How do you get 29 kWh from 33%??? Are you assuming 6% capacity loss in the battery? Where would you get a number like that?

Unless you have the Relativity Condenser option, nothing.

Yes.

Exactly, the numbers don't add up, and often. I wish I had captured the final charge status which would have shown a number that would allow another estimate of the capacity of the battery.

 

[T3slaOwner]

Actually battery capacity is rather like water in a bottle or gas in a gas tank if you measure it in coulombs or ampere-hours i.e. units of charge.

This number is of little value to a driver since, as you say, it does not determine the energy stored in the battery.

Processing additional readings like this (38) I can only conclude that my battery's capacity is 96.8 ± 0.92 kWh.

The capacity of the battery will be determined by the amount of energy you can store in it. Unfortunately, unlike a gas tank, the battery does not provide back all the energy that was stored in it. There is a variable loss of energy between charging and discharging the battery dependent on many factors.

EVs are *much* more complicated than ICE when it comes to the act of driving. ICE have been massaged and tweaked and smoothed over for many decades until they are very workable devices. In forty more years EVs will likely have the same level of comfort with driving and will be treated much like current ICE autos where we just don't think about them much until we want to drive them.

Until then, ABC, always be charging. I can't wait until they finish the Supercharger near me. It seems to be presently held up by a shortage of pedestals. It is hard to understand sometimes how and why various problems arise with the plans of Tesla. At least we can be confident that next year Musk will again forecast the number of Superchargers will double as he has forecast every year for what, four years now?

 

[ajdelange]

At least the math works when I calculate it. Get your answer closer to 43%, eh?

Ooops! Looks like double fat finger syndrome here. The one thing I hate about this site is that if you don't catch typos in 15 minutes you can never thereafter correct them. I just don't see how that policy benefits anyone. In any case:

100*37.44/(76.5 -32.5) = 85.0909 kWh

100*37.44/(75.5 -33.5) = 89.1429 kWh

is the range of battery capacity indicated by an indicated charge level difference of 76% to 33%. Those are cut and pasted so I don't think there are any typos this time. Sorry about that.

How do you get 29 kWh from 33%??? Are you assuming 6% capacity loss in the battery? Where would you get a number like that?

We have an indicated usable capacity estimate of 87.1 kW taken as the center of the span indicated by the last trip data. Thirty three percent of that is 0.33*87.1 = 28.743. The important concept here is that NO assumption is made about capacity loss in the battery. Battery capacity is estimated from the last drive's data. Each drive and each charge give us an estimate, if not a terribly accurate one, of the capacity. We can use those estimates to determine the degradation if we like but it probably more important to look at the trend over miles driven. I think the usable capacity of a new 100 kWh battery is about 96.8 kWh. Based on that your last drive data indicate capacity degraded to between 88 and 92%. But I wouldn't be concerned about that single drive's indications as I know that these capacity estimates are not that good and that dozens of them need to be trended in order to detect actual battery problems. This is where 3rd party apps come in. They do exactly that for you automatically and while you have to take their reports with a grain of salt they do give a pretty clear picture of how your battery is performing.

Exactly, the numbers don't add up, and often.

Except that the numbers do add up. There is no relativity condenser. That was a joke. If there were and it's current draw would be measured along with all the other current draws and included in the Wh calculation that goes into the wH/mi display. First law applies: energy is conserved. Your failure to obtain closure comes from your assumption that the usable capacity of a new 100 kWh battery is 100 kWh. It clearly isn't. It is what it is and if you wish to plan a trip you must have an estimate of what it is and how much energy you will likely be using.

I wish I had captured the final charge status which would have shown a number that would allow another estimate of the capacity of the battery.

That's what you need to do to get a better picture of what your battery capacity is but why not let TeslaFi do that for you?

 

[ajdelange]

This number is of little value to a driver since, as you say, it does not determine the energy stored in the battery.

It would be of value to the driver because Li ion battery voltage is pretty constant over the normal range of discharge but as it is not displayed to the driver the question is moot.

The capacity of the battery will be determined by the amount of energy you can store in it.

No, the capacity of the battery is the amount of energy that must be transferred to or taken from the battery to move its voltage between two somewhat arbitrarily chosen voltages picked by the manufacturer.

Unfortunately, unlike a gas tank, the battery does not provide back all the energy that was stored in it. There is a variable loss of energy between charging and discharging the battery dependent on many factors.

There is evaporation in a gas tank. The miles per gallon depend on temperature because the density of petrol changes with temperature. Sometimes in some places the "gas" contains ethanol in varying percentages. Fuel RON is not the same everytime you fill. IOW, there are more parallels than you are evidently aware of.

EVs are *much* more complicated than ICE when it comes to the act of driving.

That statement is simply untrue. Now I recognize that there are some people who just never get the hang of some things and you may be one of them WRT to BEVs in which case you probably shouldn't be driving them. But for the majority, once they get past the foolishness of range anxiety, it should be as easy or easier to drive a BEV. In the Tesla I jump in, look at the battery indicator, look at the miles I have to go and know right away whether I'll have comfortable margin at the destination. Same as in my Lexus. But in the Telsa I can pull up a graph and see what my battery will be all along the route taking into consideration terrain. What a luxury! The Lexus only tells me how far I can go. Now the Lexus could present displays as informative as the Tesla's if they wanted too. They can get the map data over the net just as the Tesla does. They can measure fuel flow rate... As of my model year they haven't chosen to do that but the trend now seems to be to give the driver more rather than less information as was the legacy from the "idiot light" era. Whether they choose to do that or not will be determined by market forces.

Until then, ABC, always be charging.

Were I able to top off my ICE vehicles as easily as I can my Tesla I'd always be doing that with them too! [/QUOTE]

 

[T3slaOwner]

It would be of value to the driver because Li ion battery voltage is pretty constant over the normal range of discharge but as it is not displayed to the driver the question is moot.

The battery voltage is very much not constant. It has a large dependency on temperature as well as having some dependency on state of charge.

No, the capacity of the battery is the amount of energy that must be transferred to or taken from the battery to move its voltage between two somewhat arbitrarily chosen voltages picked by the manufacturer.

Not at all arbitrary. These limits are chosen to minimize damage to the battery. That's why they recommend you don't use the bottom or top 10% of capacity, to minimize wear and extend the life of the battery.

There is evaporation in a gas tank. The miles per gallon depend on temperature because the density of petrol changes with temperature. Sometimes in some places the "gas" contains ethanol in varying percentages. Fuel RON is not the same everytime you fill. IOW, there are more parallels than you are evidently aware of.

LOL! The evaporation from a gas tank is extremely minimal. They capture that gas and recirculate it... since the 70s I believe. The gas volume is measured as it is pulled from the ground at a very consistent temperature.

Your "parallels" are essentially made up stuff. None of them have any measurable impact on driving an ICE. That's why all the complications of driving a BEV seem so bizarre. Give it 10 or 20 years and the industry will have figured out the best ways to report status without asking the driver to take measurements with special devices or do math. Mostly the issue will be solved by ABC, always be charging. Drive to work, there will be level 2 chargers to plug into. Drive to shopping, there will be level 2 chargers to plug into. Drive on a trip, there will be 150 kW chargers at every highway exit along with restaurants to provide a rest stop while waiting for the charge.

One of the worst things that will happen will be speeding up charging so you can add 80% in 30 minutes. That's not enough time to eat. if they still have idle fees it will be a PITA.

That statement is simply untrue.

Maybe you are right. I haven't really driven other EVs much. Maybe it's just Teslas which are trying to be different.

Now I recognize that there are some people who just never get the hang of some things and you may be one of them WRT to BEVs in which case you probably shouldn't be driving them. But for the majority, once they get past the foolishness of range anxiety, it should be as easy or easier to drive a BEV. In the Tesla I jump in, look at the battery indicator, look at the miles I have to go and know right away whether I'll have comfortable margin at the destination. Same as in my Lexus. But in the Telsa I can pull up a graph and see what my battery will be all along the route taking into consideration terrain. What a luxury! The Lexus only tells me how far I can go. Now the Lexus could present displays as informative as the Tesla's if they wanted too. They can get the map data over the net just as the Tesla does. They can measure fuel flow rate... As of my model year they haven't chosen to do that but the trend now seems to be to give the driver more rather than less information as was the legacy from the "idiot light" era. Whether they choose to do that or not will be determined by market forces.

I like the way you dismiss the many issues of charging an EV as "range anxiety". I don't just form opinions by my own personal experiences like many do. I talk to other Tesla owners (and a few other EV owners) at the chargers all the time. Some have reported drives which had taken them 10 hours with an ICE being 16 hours in their Tesla. That's not "range anxiety", that "range angst".

Your personal account starts with "I jump in". If you don't know whether you can make a trip or not before you get in the car, you have already lost the fight against ICE vehicles. Right now, without even thinking about it, I know my truck has enough fuel for me to drive my weekly trip Friday, drive around town Saturday and Sunday, then return me either Sunday or Monday and I will pick the cheapest spot along the way to buy gas for the trip the next weekend if I take the truck loaded with kayaks (which don't seem to affect the range at all, just like rain, temperature, etc, etc). If I pulled a trailer with three kayaks behind my X I would have no idea how far I could go, but I would be absolutely certain I would need to charge twice on this approximately 400 mile round trip. Oh, yeah, at one point the truck sat for 2 months without any perceptible evaporation of fuel. The battery didn't go down either. The thing started right up with just barely tapping the key to "start".

I also know my Tesla will get me to the next Supercharger if I take it on the same trip, but only because I have pulled up the Tesla app on my phone to check it a couple of times today. Seems it has lost significant charge while sitting the last few days. At some point I'll either need to drive it to a charger or I'll need to plug it in here at home. I used to do that, but I found it didn't actually reduce the number of times I needed to charge for this trip. The few charging locations don't allow me much choices. If I drive the first part of the trip without charging, it is hard to do the rest of the trip and reach a charger. So even if I start with 100% when I leave home, I have to charge on the first leg so I can still reach a charger on the return leg.

I would go into how the Supercharger network is not growing fast enough, but that can be discussed in another thread.

Were I able to top off my ICE vehicles as easily as I can my Tesla I'd always be doing that with them too!

Lol!!! Tell me that the next time you take a trip somewhere that isn't along a major highway. Last night i needed a part for my truck. I stopped at several auto parts stores along my route. I could have filled the tank by any of them and dozens of other places right along the highway. It is still way too early to say a Tesla will be remotely as easy to drive as an ICE. One real concern is about Tesla going the distance. If they fold, it may well be that the company will be sold for assets and the cars orphaned. The Supercharging network may be abandoned or at best operated for profit with $0.50 per kWh or higher charges since it is a very captive market. It's not like we have much of a choice.

 

[ajdelange]

The battery voltage is very much not constant. It has a large dependency on temperature as well as having some dependency on state of charge.

You are sort of arguing against yourself here as it is the flatness of the discharge curve that makes it difficult to estimate SoC of lithium ion batteries. About 7 mV per %C for a Panasonic Li(NiCoAL) cathode cell (this is not necessarily the battery they supply to Tesla but Tesla does use a similar cathode chemistry. Pretty constant I'd say but you can choose whatever threshold you personally prefer. WRT temperature: at mid discharge the voltage changes by about 0.2 V between -10 a + 30 °C. That's not a whole lot but keep in mind that battery temperature is regulated in the Teslas. That is one of the factors that lets the BMS give such good estimates of battery condition.

Not at all arbitrary. These limits are chosen to minimize damage to the battery. That's why they recommend you don't use the bottom or top 10% of capacity, to minimize wear and extend the life of the battery.

Arbitrary. Tesla gets to choose what they want to set as the two (full and empty) voltages and they can set them wherever they like in accordance with what they want to present to the driver. They could set "Empty" to 3.6V or they could set it to 3.5V thus allocating the 1/6 of the nominal capacity (about 50 mi) to "hidden reserve" or not as they choose. Of course those 50 mi would come out of otherwise available range. They can also decide how much head room they want to allow at the top end.

LOL! The evaporation from a gas tank is extremely minimal. They capture that gas and recirculate it... since the 70s I believe. The gas volume is measured as it is pulled from the ground at a very consistent temperature.

When your ICE vehicle measures fuel flow (if it does) and when the float floats it is measuring fuel at the temperature of the gas tank. Not the service stations storage tank.

Your "parallels" are essentially made up stuff. None of them have any measurable impact on driving an ICE.

Your ICE vehicle is subject to the same laws of physics as a BEV. It is also subject to the laws of chemistry (adding EtOH to petrol decreases its energy content) and physical chemistry (petrol density changes with temperature, total enthalphy required for phase change depends on temperature, combustion air density changes with temperature...).

That's why all the complications of driving a BEV seem so bizarre.

These complications, alas, seem to plague only you.

Give it 10 or 20 years and the industry will have figured out the best ways to report status without asking the driver to take measurements with special devices or do math.

The current displays are more than adequate for anyone who understands his car. No math necessary,

Mostly the issue will be solved by ABC, always be charging. Drive to work, there will be level 2 chargers to plug into. Drive to shopping, there will be level 2 chargers to plug into.

This statement only reinforces that you do not understand how to operate one of these vehicles. Sell it.

One of the worst things that will happen will be speeding up charging so you can add 80% in 30 minutes. That's not enough time to eat. if they still have idle fees it will be a PITA.

That's already a problem even with the 40 and 50 kW chargers. Most people (i.e. those who understand the system) only charge for a few minutes at Level 3 chargers. Not really enough time to get to even an adjacent fast food joint and have a relaxed burger.

Maybe you are right. I haven't really driven other EVs much. Maybe it's just Teslas which are trying to be different.

I haven't driven other EV's at all but I've seen the "road trip" videos on you tube for many. The basic info the driver wants and needs seems to be displayed adequately by most. Tesla is the only one I know of that has the trip consumption graph. That one is the real winner.

I don't just form opinions by my own personal experiences like many do. I talk to other Tesla owners (and a few other EV owners) at the chargers all the time. Some have reported drives which had taken them 10 hours with an ICE being 16 hours in their Tesla. That's not "range anxiety", that "range angst".

Why do you care about other people's angst? It is whether you find the vehicle angst inducing or not that counts. If it is, you shouldn't be driving it. Not that I question your tale but those numbers indicate average charging rate of less than 40 kW. I imagine it possible to find an itinerary that would be limited to charging opportunities less than 40 kW but most superchargers are the highways are capable of more than that.

Your personal account starts with "I jump in". If you don't know whether you can make a trip or not before you get in the car, you have already lost the fight against ICE vehicles.

I have to look at the "gas gauge" same as I do with my Lexus.

Lol!!! Tell me that the next time you take a trip somewhere that isn't along a major highway.

What I meant was that if I could stick a bowser into the Lexus in my garage as conveniently as I can plug in my Tesla at home that's what I would do.

I don't know about the next time I go somewhere but last week I went up along the north shore of the St. Lawrence well beyond where the Tesla SC's ended. No problems whatsoever. Jump in the car, read the SoC, realize I can make it home without stopping to charge. Makes the SO nervous when the display says I'll only have 11% left when I arrive but at this point I know my car. Followed the progress on the trip graph of course and watched the estimated arrival climb gradually because I know I drive a little better than the estimate. That's what I mean by knowing the car.

 

[animorph]

My favorite:

Car’s energy consumption (lack of) accuracy

Go slower and you'll get more energy out of the battery, on top of powertrain/aero efficiency gains.

These threads pop up about once a week. A search should return a day's worth of reading.

 

[T3slaOwner]

My favorite:

Car’s energy consumption (lack of) accuracy

Go slower and you'll get more energy out of the battery, on top of powertrain/aero efficiency gains.

These threads pop up about once a week. A search should return a day's worth of reading.

The problem is how the car tracks it. They count the energy used in the motor and electronics, but not the battery. So one trip it will show an energy usage that corresponds to some percentage of the battery and on another trip the correspondence is very different. In other words, they don't account for the energy lost in pulling the energy out of the battery. That piece is completely missing from the ledgers in the car.

Just to be clear, I'm not talking about the actual mileage of the car. I'm talking about the information the car provides. AJD thinks it is ok to expect the driver to do double-entry bookkeeping while you drive. I think the car should be as easy as an ICE to know how far it can go. They've got a bazillion computers in the thing. They just need to program it right.

 

[T3slaOwner]

I would also note that the numbers many people post for mileage are not useful numbers because those numbers usually aren't based on energy drawn from the outlet or even the charging port. The losses in the internal charging circuit, charging the battery and discharging the battery are not factored in. If they wanted to Tesla could give you an accurate calculation of kWh/mi as consumed from the power meter (ignoring the tiny loss in the house wiring). But they choose to ignore that since it would have another ~20% loss.

 

[ajdelange]

The problem is how the car tracks it. They count the energy used in the motor and electronics, but not the battery.

They don't count the energy used in the motors. They don't count the energy used by the battery. They don't count the energy "used" in the battery. They count the energy drawn from the battery. Knowing how much available energy is in the battery at the start of a trip and the rate at which usable energy is being withdrawn the car can estimate the SoC at any point in a trip, the energy consumed per unit of distance traveled and, assuming either that the usage per mile will remain the same or using the rated consumption for the car, predict the amount remaining at any point in the remaining journey including at is end.

So one trip it will show an energy usage that corresponds to some percentage of the battery and on another trip the correspondence is very different.

What is that supposed to mean?

In other words, they don't account for the energy lost in pulling the energy out of the battery. That piece is completely missing from the ledgers in the car.

All the energy withdrawn from the battery is measured. The energy used by the motors is measured. The energy used by the windshield wipers is measured. The energy used by the seat motors is measured. The energy used by the heater or A/C is measured. The energy lost as heat in the inverters is measured. The heat lost to the battery's internal impedance is measured. Etc. These are not, of course, measured separately. It would add complexity to do so and there is no need for that detailed information. What counts is how much energy is available in the battery and the rate at which it is being drawn out. This is exactly, of course, what is done in an ICE vehicle that displays a range estimate or mpg display except that the units of energy there are gallons where here they are kWh.

Just to be clear, I'm not talking about the actual mileage of the car. I'm talking about the information the car provides.

I am not at all clear about what you are talking about. The car provides amazingly accurate information about the battery's SoC even though determining exact SoC of a secondary battery is a tough problem. It is a real testimonial to the sophistication of Telsa's BMS software.

AJD thinks it is ok to expect the driver to do double-entry bookkeeping while you drive. I think the car should be as easy as an ICE to know how far it can go. They've got a bazillion computers in the thing. They just need to program it right.

What AJD really thinks is that the car is as easy to drive as an ICE because he could, if he wanted to, just read the % battery indicator in exactly the way he reads a gas gauge and be done with it. But AJD is smart enough to know that a gas gauge alone doesn't give as much information about ones "fuel condition" as one might like to have. However AJD really likes the trip energy monitoring graph because it gives him more information about his fuel condition than just the battery % meter and thus he finds the Tesla much easier to drive than his ICE cars.

I would also note that the numbers many people post for mileage are not useful numbers because those numbers usually aren't based on energy drawn from the outlet or even the charging port. The losses in the internal charging circuit, charging the battery and discharging the battery are not factored in.

In determining available charge the losses in the internal charging circuit are, in fact, factored in. In looking at a TeslaFI or Stats report of a charging session where the car's internal rectifier/booster is used to charge you will see values for the energy used (drawn from the mains) and energy added.

If they wanted to Tesla could give you an accurate calculation of kWh/mi as consumed from the power meter (ignoring the tiny loss in the house wiring).

As I have pointed out they do. But who cares about how many miles he goes per unit of electricity purchased from the utility? He may, in fact, care about that when bragging to his friends about how little it costs him to drive a mile but what he really cares about on the road is how many kWh are available to him here, now, in the vehicle, and how many he is going to use for each additional mile he is planning to drive.

Thus the numbers people post for mileage are very useful to, for example, a new owner who doesn't know what to expect other than that he will be using something like 315 Wh to go a mile in a non Raven X. When someone reports that he is getting 280 (which I just saw) I want to know how he did that. When someone reports 480 (which I've also seen) I want to know how he did that. Sometimes these guys tell you, or give clues at least, and sometimes they don't.

But they choose to ignore that since it would have another ~20% loss.

In fact, as you would see if you bothered to check any of your assertions before you post them, the car charger's efficiency averages a little over 90% implying loss of 10%.

So do you think you might, in the future, be inclined to check on the validity of some of your notions before posting them?