Range anxiety after almost 5 yrs??

[SmartElectric]

Let's have some perspective.

OP car stops at 19 miles on a P85, that translates to ~7% if he has 256 miles at 100% (3% degradation from 265 miles like many have on early 85's).

The battery cell voltage differences between 7% and 0% are fractions of a volt, the Tesla Battery Management System attempts to calculate % SOC from many factors, but if the cells are not balanced, the accuracy of these calculations may suffer.

The dotted line indicator of reduced power availability is a significant warning not to be ignored. It has been reported that coming close to this limit can cause spontaneous shutdown, which might have been what the OP experienced.

I've never taken our 2013 85 down below 7% SOC, so I have no idea what that's like.

We charge to 90% daily and 100% every weekend (yes, every weekend) and don't sweat it. We also drive on %age instead of rated km due to the cold winter in Canada, where the % is easier to work with. I use 3 km per percent in winter, and 4 km per percent in summer.

Lots of devices report remaining minutes of usage, my laptop reports that I have 48 minutes remaining on 15% battery, and has just dropped the maximum brightness of the display (similar to how Tesla limits power output with yellow dotted line). My laptop has never made it to 0%, usually shuts down at 9%.

Once voltage lowers below a certain level, BMS will save the battery health first as a priority, which can shut down your device (or car) at a low percent.

I don't know anyone who drives a car on an empty tank, that's just gambling and silly IMHO. I never take our EV's too low without good reason, because I don't like the chance of stopping before I get to my destination.

 

[TLej]

Not sure if you're aware of this, but if you use nav, your trip computer will do something very similar, I think actually a bit better, automatically: set destination and then display the computer below the map screen. At the start of the trip it will tell you how much battery you should expect to have at the end of the trip, then the percentage will move up or down as you drive. If the percentage climbs or holds steady, you're good! If she falls, be careful.

Fully aware actually, but I think my own reckoning is better. In winter it’s not uncommon to see the trip calc start out estimating 35% remaining early in the trip and constantly revise down as you drive, arriving with 25% remaining. Whereas after about 10-20 km I can calculate my own useage and come up with the same 25% figure about an hour or so before the car gets with the program.

 

[svp6]

This is very disturbing. I have driven in very cold weather and my experience has always been that the initial predicted range is off by a significant margin. However, after adjustments during the initial 10-15 miles, the trip indicator was always spot on - to the point that I too have arrived home with 5-10 miles left and did not break a sweat. Your experience is very concerning to me, as now I have to account for it.

Regardless of how you choose to display (percentage or miles remaining), it is unacceptable to be stranded with "something" remaining in the battery. I presume that 19 miles would be somewhere around 8% for P85+. How would displaying in percentage be any better than in miles? Would you be less reassured? It is not like percentage would display 0%.....

And to those blaming the driver for not being careful enough, just remember not all of us live in California - and have neither the clemency of good winter weather nor the density of superchargers to choose from. For me a winter trip to Minneapolis and back was always a 65 mph, temp at 67F, arrive with ~10-20 miles proposition.

 

[AB4EJ]

Did you try to see if the car would drive AFTER recharging the 12V battery, but before charging the HV battery? It might primarily be an issue with the 12V system.

Seems likely to me that the whole problem was caused by the 12v battery going out (not the main battery). I know from experience that my Toyota HIghlander Hybrid exhibits all kinds of weird behaviors & malfunctions when then 12v battery is going out. I suspect that your main battery is fine.

 

[scottm]

I wish the OP would repeat the experiment after having charged the car and drive it down to sub-19 miles remaining /7% SOC perhaps by circling near a chargepoint... see if it was a one time occurrence, or is repeatable.

Besides, this is the only way to get confidence back again and remove range anxiety, IHMO.

 

[Tam]

...that's just gambling and silly IMHO...

Whether the battery meter is displayed in percentage or in miles, there's an algorithm to justify its result.

When its result is inaccurate, there should be some external factors that have messed up its calculation.

Bjørn Nyland saw his battery still had 14 km but the car stalled.

If it wouldn't go anymore, then it wouldn't be 14 km would it?







Indeed, shortly after the stall, the battery meter is automatically revised as 0 km, not 14 km anymore.




If you give the battery meter a chance, it would do its job accurately: It is not stalling your car because there are still 14 km but because there's 0 km left as shown by its latest calculation.

In this case, the inaccurate 14 km has pointed out other serious problems so it doesn't matter whether you have a 14 km buffer or 140 km buffer, it will fail!

Don't blame your battery meter. Look for factors that explain your battery meter results.

 

[Naonak]

Thanks for all the replies!
I believe I was managing my trip. I started the day with 193 miles showing. After almost 5 years with the car, I understand how temperature, driving habits, climate controls, heated seats, inclines and headwinds affect range. I had traveled 125 miles and the range suggested I still had 19 miles in the battery. Regardless whether the estimate was set to 'miles' or 'percentage', the indicator suggested the battery was NOT empty and the car should still function. If you consider your range indicator a "guess-ti-mator", what's your actual zero? 10%? 20%? 50%?

I totally agree that the car should never read as anything left in the battery and then shutdown unexpectedly. It should always shut down at or after 0. It's never acceptable to show remaining capacity and then shutdown.

While I understand your point of view, I fail to see the difference in displaying miles or percentage. The miles display is just a conversion using an assumption of the energy required per mile. (300Wh per mile?) How about the percentage display? Is that the based on the theoretical battery capacity? Maybe the initial delivery date capacity? Last fully charged capacity? Isn't the rate of change of the value on the display the important data for the operator?

The difference is the miles "estimation" is never accurate for basically everyone but a select few individuals. The battery percentage is generally accurate for basically everyone (unless you run into a situation like yours, which indicates a problem somewhere). Why would you want a display that's almost always incorrect vs one that is almost always correct?

Percentage is how much capacity is left in the battery. Miles is just a guess, and a wildly inaccurate one. The battery capacity left is usually *very* accurate.

As I said, nothing else displays "range" or "time left" like some EVs do. They always display percentage and it's up to you to decide if you have enough capacity left to perform the action(s) you want to with that device.

Just out of curiosity, question for the people who prefer a percentage display. You start the day with 42% and you want to make a round trip of 50 miles. How do you decide if you will need to charge during the trip? I assume you must know the battery capacity, 60kWh or 85kWh or maybe 100kWh? Do you then take your unique driving pattern into account? During the summer I average 280Wh/Mile, 350Wh/Mile in the winter. Will I be using the heat/AC today? The terrain might be a big factor. I'm guessing you've built up knowledge base over time and make an assessment. If during your trip the percentage drops faster than you anticipated you take appropriate action. BUT you have to trust the value displayed. The battery can't be empty when 19% is displayed!

You don't have to know your battery capacity. You just know you can go X miles for Y % generally. For normal, daily driving, I figure 2 miles = 1%. If it's colder, it may be a bit less, if it's warm out, it will probably be more. I routinely run my car down to 1% driving around... I know when my car will shut down. I would never, ever, in a million years try to run my car down to 1 mile remaining. It would be a meaningless number, and as you get in to the double and single digit miles remaining, your car could shut down at any time. As you get in to the single digits of percentage, your car won't shut down until it hits @ or very near zero (or it should, anyway).

Miles remaining is meaningless as your charge depletes (well, it's meaningless at all times, really, but especially at low SOC). Basically a random number generator at that point.

You need to help me with this one--your position seems completely irrational. If a person displays %, and has even a modicum of arithmetic ability, he immediately translates the percentage into miles and compares that to the distance remaining. Actually, without being able to do this, the percentage is meaningless/useless.

But it's not, though. Do you have a miles indicator on an ICE car? Not until recently did they start adding these in, and I've never seen one that is accurate yet. You have a fuel gauge, usually divided into 1/8th increments. Do you know how many miles you have left when you have 1/8 of a tank? Not generally, you just know you can go a short distance, but you better fill up soon. Most cars stick at "F" for a long time then drop rapidly, it's not a linear drop, either. At least with the battery in percentage, it drops at a predictable rate from 100% to 0% purely based on your driving and the envrionment; no reliance on inaccurate floats or liquid sensors in your fuel tank, sloshing around.

Can't speak to how others do it, but for short trips I don't worry about what the indicator shows. For a highway trip, I look to see what my actual useage is and do some math. For example, if I start with 85% charge, and after 30 km I'm down to 70%, then I can extrapolate that I'm getting about 2 km for each 1% of battery, and given that I have 70% remaining I should be good for another 140 km. I'll do that calculation a couple of times during the trip to see if it's staying constant, and base my charging decision accordingly. It does depend on the battery indicator being accurate (i.e. 10% use is actually 10% use), but it also automatically factors in current actual power useage (heating, headwind, snow/rain drag, etc.) and has always been pretty reliable. I kind of also base my estimates on what I think my actual battery holds. At my rated 180 Wh/km, with a 90 kWh battery, I assume I should get about 5.5 km/kWh, or roughly 440km on a 100% charge assuming my "90" is more like 80 actual useable kWh (I'm a conservative fellow). When I'm using 350 Wh/km as I have been recently in the cold, I expect my range is about half that number. In the summer I've seen numbers around 150 Wh/km, so I know I should be able to get a little more range out of it.

In my opinion, rated miles are great if you live somewhere temperate, but with large variations in climate and with temperature having such a large effect on battery efficiency, they're not a reliable year-round indicator. The math I do above works no matter what the weather.

Yep, basically what I do as well.

 

[kavyboy]

Miles remaining is meaningless as your charge depletes (well, it's meaningless at all times, really, but especially at low SOC). Basically a random number generator at that point.

I won't disagree your post because of the negative connotations of that on this forum and because I agree with much of it, but this I do disagree with. You're not wrong, it's just that in my own, personal experience, this hasn't been the case. I've had no indication that rated miles and actual miles were off by more than a tiny bit. I concede I usually drive ideal conditions, though.

Also, no, there's no miles reading on an ICE car, but that's because it's not needed due to the ubiquity of gas stations virtually everywhere. I can (well, could back in the old days) drive until I got to 1/4 tank and then fill up quickly wherever I happened to be. I didn't care how far 1/4 tank was since it was enough to get me to a gas station***. One quarter of a battery, though, I've got to start doing some planning to find a charger I can get to, and now we're back to calculating miles.

*** The only exception for this was for some parts of the desert Southwest, where there are posted signs saying "X miles to the nearest gas", or something like that. When the ubiquity of refueling goes away, even in ICE, now you do want to know "How far does 1/4 tank get me?" and we're back to miles calculations.

(Anyway... good discussion, even if we disagree! Remember when people used to disagree without going to war?)

 

[Duke-U]

I do hope OP posts the findings of the cause of all this!

 

[DaveFite]

@CUBldr97

did you happen to update to 50.2 recently?

Yes, the car was at the service center last week due to a tire monitor control board failure. They updated the software at that time. I didn't observe anything out of the ordinary prior to my incident.

@Electric700

you just need to charge to 100% and leave it there for about a half hour after your car is fully charged. Then, drive it so your car doesn't stay at the higher charge level.

I have done that since getting the car back home. I did notice that the range display shows about 8 miles less range (216 versus 224) when I charge to my normal non-trip level since the incident.

@Tam

I don't think showing percentage helps. I agree that the problem is the inaccuracy of the meter and you explained it as "range" for any vehicle.

In this case, 19 miles is inaccurate.

If you switch 19 miles to percentage, it would say 7% which is no where near the accuracy of actual stalled car at 0%.

The car still dies regardless of whether you want to default the display as 7% or 19 miles in this case.

I think it's better to learn why there are inconsistencies in Tesla battery gauge.

Could be it be drifting algorithm as the car ages?

Could it be cold weather?

Could it be 12V battery?

Could it be some other factors...?

Well said! I agree completely.

@hacer

Did you try to see if the car would drive AFTER recharging the 12V battery, but before charging the HV battery? It might primarily be an issue with the 12V system.

When I got the car back to my home charger, I attempted to connect my HSWC to the car. Without power from the 12V battery the charge port just stayed un-lit. I then attached a portable power pack to the 12V posts and the charging port turned blue. I connected my charger to the car but the lights stayed blue. Charging did not begin. I disconnected the cable and tried inserting it again. Same thing. The port then went un-lit. I believe the portable charging device was low since I had used it multiple times to get the car in and out of tow mode. I attached a trickle charger for about an hour to charge the 12V battery. Then when I attached the HSWC charging worked normally. I did NOT try and drive the car prior to charging the main battery pack. I did notice the display still showed 19 miles with the "Low Battery" warnings.

@Duke-U

I also think the 12 volt battery failed. This is an AGM gel battery, and I had one fail in our ICE car with start-stop system. All worked fine till after one stop it just didnt want to start. These batteries have a sudden death when plates touch and the voltage drops. In your case the High Voltage Contactors would immediately disengage, explaining the sudden stop of the car’s power. Also the fact that all 12V systems stopped working after just 20 mins, the big loads were already stopped and the other systems drained the last juice out of it. Age doesn’t really matter, I had ours fail at just a couple of months.

I agree 12V batteries fail BUT after recharging my 12V battery everything has acted normally since. I've had no warnings and have taken a couple 140+ mile trips. I have only drained the battery to where the display indicated 25 miles once since before stopping to supercharge.

@PeterHG

Not sure if you're aware of this, but if you use nav, your trip computer will do something very similar, I think actually a bit better, automatically: set destination and then display the computer below the map screen. At the start of the trip it will tell you how much battery you should expect to have at the end of the trip, then the percentage will move up or down as you drive. If the percentage climbs or holds steady, you're good! If she falls, be careful.

I use that technique often also and have found it very accurate in the past. Based on everything the car was indicating that day, I was very comfortable with 20 miles range showing and 8.9 miles to my destination.

@SmartElectric

Let's have some perspective.

OP car stops at 19 miles on a P85, that translates to ~7% if he has 256 miles at 100% (3% degradation from 265 miles like many have on early 85's).

The battery cell voltage differences between 7% and 0% are fractions of a volt, the Tesla Battery Management System attempts to calculate % SOC from many factors, but if the cells are not balanced, the accuracy of these calculations may suffer.

The dotted line indicator of reduced power availability is a significant warning not to be ignored. It has been reported that coming close to this limit can cause spontaneous shutdown, which might have been what the OP experienced.

I've never taken our 2013 85 down below 7% SOC, so I have no idea what that's like.

We charge to 90% daily and 100% every weekend (yes, every weekend) and don't sweat it. We also drive on %age instead of rated km due to the cold winter in Canada, where the % is easier to work with. I use 3 km per percent in winter, and 4 km per percent in summer.

Lots of devices report remaining minutes of usage, my laptop reports that I have 48 minutes remaining on 15% battery, and has just dropped the maximum brightness of the display (similar to how Tesla limits power output with yellow dotted line). My laptop has never made it to 0%, usually shuts down at 9%.

Once voltage lowers below a certain level, BMS will save the battery health first as a priority, which can shut down your device (or car) at a low percent.

A very reasonable approach. Why is 7% your 0? Why not 15%? I'm guessing your comfort level with the cars voltage sensors and software makes that reasonable. Seems arbitrary.

I never take our EV's too low without good reason, because I don't like the chance of stopping before I get to my destination.

If you never drive your EV, I can guarantee you will never stop due to a low battery.

@svp6

This is very disturbing. I have driven in very cold weather and my experience has always been that the initial predicted range is off by a significant margin. However, after adjustments during the initial 10-15 miles, the trip indicator was always spot on - to the point that I too have arrived home with 5-10 miles left and did not break a sweat. Your experience is very concerning to me, as now I have to account for it.

Regardless of how you choose to display (percentage or miles remaining), it is unacceptable to be stranded with "something" remaining in the battery. I presume that 19 miles would be somewhere around 8% for P85+. How would displaying in percentage be any better than in miles? Would you be less reassured? It is not like percentage would display 0%.....

And to those blaming the driver for not being careful enough, just remember not all of us live in California - and have neither the clemency of good winter weather nor the density of superchargers to choose from. For me a winter trip to Minneapolis and back was always a 65 mph, temp at 67F, arrive with ~10-20 miles proposition.

Thanks @svp6, you summarize my position exactly!! As my P85+ ages, I just trying to stay ahead and understand how to avoid potential problems.

@scottm

I wish the OP would repeat the experiment after having charged the car and drive it down to sub-19 miles remaining /7% SOC perhaps by circling near a chargepoint... see if it was a one time occurrence, or is repeatable.

Besides, this is the only way to get confidence back again and remove range anxiety, IHMO.

I agree, that may be the only way to regain my confidence! I thought about driving the car down and then circling a supercharger but wonder if speed would be a required factor. Travelling at 65 mph is significantly more of a battery drain then stop and go around a busy charging area. I've had one occasion since where I was about 15 miles from home with the indicator displaying 25 miles. In the past I would have had no concerns and just driven home. I opted to stop and recharge (Telsa supercharger). It was New Year's Eve and I didn't want to chance it!!

@Tam

Indeed, shortly after the stall, the battery meter is automatically revised as 0 km, not 14 km anymore.

Interesting that this did NOT happen in my case. The 19 miles displayed consistently.

@Naonak

The difference is the miles "estimation" is never accurate for basically everyone but a select few individuals. The battery percentage is generally accurate for basically everyone (unless you run into a situation like yours, which indicates a problem somewhere). Why would you want a display that's almost always incorrect vs one that is almost always correct?

Percentage is how much capacity is left in the battery. Miles is just a guess, and a wildly inaccurate one. The battery capacity left is usually *very* accurate.

As I said, nothing else displays "range" or "time left" like some EVs do. They always display percentage and it's up to you to decide if you have enough capacity left to perform the action(s) you want to with that device.

We agree that the bottom line is "it's up to you to decide if you have enough capacity left to perform the action(s) you want to with that device."

By displaying percentage you get an accurate (measured) indication of the charge. You then use your knowledge base to make your decision. 100% displayed, normal driving, 150 mile trip, level terrain... Good to go! The range display also begins with the same measured charge and uses some Telsa algorithm to present a miles indication. I use my knowledge base and make a decision. 224 mile range displayed, normal driving, 150 mile trip, level terrain... Good to go! Seems we're doing about the same thing except I'm trusting Tesla's conversion. So we both decide to venture out in our EVs on the 150 mile trip but things change. A freak cold front comes through, temperatures plummet. Your percentage display begins to decline faster. My range display likewise. Don't we both do the same thing? You continuously doing calculations converting % capacity into miles remaining, adjusting your X for Y% factors appropriately? I'm blindly letting Tesla's "wildly inaccurate one" produce one. Continue or charge?

We agree that the bottom line is "it's up to you to decide if you have enough capacity left to perform the action(s) you want to with that device."

You don't have to know your battery capacity. You just know you can go X miles for Y % generally. For normal, daily driving, I figure 2 miles = 1%. If it's colder, it may be a bit less, if it's warm out, it will probably be more. I routinely run my car down to 1% driving around... I know when my car will shut down. I would never, ever, in a million years try to run my car down to 1 mile remaining. It would be a meaningless number, and as you get in to the double and single digit miles remaining, your car could shut down at any time. As you get in to the single digits of percentage, your car won't shut down until it hits @ or very near zero (or it should, anyway).

Unfortunately, we'll never know what a percentage display would have shown on my car when it powered down. I find it hard to believe that Tesla's software would show 19 miles with 0% capacity.

You don't need to know the battery capacity but don't you need to adjust your X miles for Y% as the battery degrades over time? The charge in a 100% charged 85kWh battery day one must be different than that of 5 year old one.

Miles remaining is meaningless as your charge depletes (well, it's meaningless at all times, really, but especially at low SOC). Basically a random number generator at that point.

What's the magical point you define as "low SOC" 3%, 5% 19%?

 

[jb007gd]

I didn't see much discussion of the Energy screen in this thread. I think we all agree that the battery icon in the bottom left corner of the dashboard is a bit of a fibber at times. I'm curious if most find the energy screen to be truthful?

 

[AustinP]

Having now driven our car for 2.5 years and 100.000+ km, I've always had the confidence that as long as I'm not at 0km estimate, there is still enough energy to drive. Of course, understanding the km on the display is to be interpreted as explained above.

Your experience is indeed worrying.
And would indeed add to range anxiety.

Reading your replies, it seems a 12V battery issue could be the cause, although you managed to recharge it. Or did you also replace it now? Could it be the system responsible to maintain that battery is not fully operational?

Are you still expecting an explanation from Tesla or is the case closed for them?

Anyway, appreciate you started this thread, I for one would be more careful when reaching the lower end of the battery charge level.

 

[Snowstorm]

This is very concerning and is the very kind of stuff that would fuel sketisicm around EV adoption. The lowest I had ever ran my battery was 7%. the hotel that I stayed at said they had level 2 charger, but actually do not. They offer a 110v wall socket but circuit breaker tripped both nights after like 30 minute of charging. Luckily still had enough to make it back to the super charger in the way back home.

If zero is not at 0%, but some higher value, then it is really bad news. It effectively means you cannot safely use some percentage of your battery. Is that 3%, 5%, 10%, who knows?

What's also concerning is Tesla's refusal to cover at least the tow fee for this dude. Something is obviously wrong with his battery or BMS, it isn't a totals failure but a fault landed him in this situation. They should at least cover the tow given that is still under warranty. M experience and expectation is that Tesla will care and go the extra mile or two, this doesn't seem right to treat an early adopter who bought the top end vehicle at that time like this.

Maybe what AAA needs is a mobile SC station.

 

[Chopr147]

Be careful with that phrasing, please. Tesla as a company has never officially made that claim. Salespeople who work at Tesla stores it seems don't know the products all that well and make mistaken and uninformed claims frequently, though, so that might have been where you heard it.

Tesla and temperature:

Tesla has never made that claim? Here is a screen shot for potential Tesla buyers on their website.

As you can see it is set up for temp., speed, heat on etc......


"The actual amount of range that you experience will vary based on your particular use conditions."
I am at 27,000 miles on my S and I am impressed at the accuracy in temp.'s above 50 degrees. Go below that and the accuracy % starts to get unpredictable.

 

[Rocky_H]

Tesla and temperature:

Tesla has never made that claim? Here is a screen shot for potential Tesla buyers on their website.

View attachment 270977

As you can see it is set up for temp., speed, heat on etc......


"The actual amount of range that you experience will vary based on your particular use conditions."
I am at 27,000 miles on my S and I am impressed at the accuracy in temp.'s above 50 degrees. Go below that and the accuracy % starts to get unpredictable.

If you would stop changing your story and moving the goal posts, we could have a real discussion.

Here was the first statement, made by @fcharland:
"I can tell you... Tesla navigation isn't programmed (or badly programmed) to estimate properly at cold temperatures."

So notice, the application being talked about was the estimate in navigation in the car. You quoted that line and replied to it:

"Agree here. Though Tesla claims temp is factored in I have learned it is way off."

I pointed out that the original statement is correct, that navigation doesn't figure in temperature, and Tesla has never claimed otherwise. Then, you just posted links and screenshots to an entirely different energy estimator program that is on Tesla's website--not the navigation in the car. That website estimator does have extra variables and accounts for temperature. You don't get to still say you're right when you change the subject.

 

[Naonak]

Unfortunately, we'll never know what a percentage display would have shown on my car when it powered down. I find it hard to believe that Tesla's software would show 19 miles with 0% capacity.

Well, I would find it hard to believe the car would shut down with 19 miles remaining, as well... but here we are? ¯\_(ツ)_/¯

You don't need to know the battery capacity but don't you need to adjust your X miles for Y% as the battery degrades over time? The charge in a 100% charged 85kWh battery day one must be different than that of 5 year old one.

No, you certainly don't. Do you know the remaining minutes on your phone when it reads 5%? Do you even know the battery capacity on your phone? Why is your car any different?

What's the magical point you define as "low SOC" 3%, 5% 19%?

Anything below 10%, generally, is just a highly entropic random number generator as far as miles remaining display goes.

 

[DaveFite]

@AustinP

Reading your replies, it seems a 12V battery issue could be the cause, although you managed to recharge it. Or did you also replace it now? Could it be the system responsible to maintain that battery is not fully operational?

Are you still expecting an explanation from Tesla or is the case closed for them?

I have not replaced the 12V battery. After recharging it and charging the main battery, the car is acting completely normal other than my normal daily charging range has declined from 224 miles to 216 miles. Possibly due to the battery being re-balanced? or the latest software update?

I don't expect anything from Tesla.

@Snowstorm

They should at least cover the tow given that is still under warranty.

The car is no longer under warranty. I'm not sure what the Tesla battery warranty covers or it's status. I was extremely disappointed with Tesla, the company, and their road side assistance service.

@Naonak

No, you certainly don't. Do you know the remaining minutes on your phone when it reads 5%? Do you even know the battery capacity on your phone? Why is your car any different?

While I think your phone analogy is a good one, I do believe the difference in the two uses is fundamental to the discussion. A mile is a fixed distance. Yes, there are other factors such as terrain (uphill vs flat vs downhill), and headwind. But most of my trips are round-trips where the ups and downs average out. A phone call isn't a fixed time. The hassle of being out of charge in the breakdown lane of a busy highway can't be equated with a dropped phone call. Would you feel differently about knowing the battery capacity or how many remaining minutes if the call you were about to make was life critical?

I seem to be having a problem understanding how percentage remaining is enough information. If I present you with two EVs, both fully charged and ask you to drive a 150 mile round trip in one of them, do you jump in the Model S or the Volt? Seems you need to understand a little more than just the current battery percentage. And even if you know the current battery charge, don't you need to know the "X for Y%" for each unique vehicle?

 

[Galve2000]

I guess maybe it's because my rated miles always match actual miles almost exactly, and that's not the case for other people.

I wish this was true for me also.. but I like to drive my Model S FAST!! (I may be the worst hyper-miler in all of EV land)

Seems likely to me that the whole problem was caused by the 12v battery going out (not the main battery). I know from experience that my Toyota HIghlander Hybrid exhibits all kinds of weird behaviors & malfunctions when then 12v battery is going out. I suspect that your main battery is fine.

I fully agree that this is the culprit here and is what was messing up the BMS or whatever you guys call it..

For my part, I follow the rule that 0 means 0. I think once upon a time the Tesla algorithm included a small buffer (some have driven 20 miles or more past 0 in the early days) but I think as people complained that they were not getting the full 265 miles of range from an 85 (to give one example) Tesla changed the algorithm over time giving people access to more range and allowing for a less conservative buffer past 0. in many ways this makes sense.. with thousands of hours of real world driving data collected since 2012, Tesla was able to asses that such a large buffer past zero was no longer necessary.

so in the recent past, 0 means 0.

full disclosure: I have driven my 85D down to 1 mile of range remaining on at least one occasion. possibly 2 if I think about it.. and I was pretty nervous about it -- but made it to the level 2 charger just in time.

I hope the OPs 12 V battery is replaced under good will. it saddens me that he has had multiple such failures especially now that his car is out of warranty and I hope OP had the foresight to get the extended warranty. I have AAA and while it is not a free service -- it provides piece of mind -- and a free tow!! -- so I don't know if Tesla covering the cost of the tow would make much difference. of course, it would go a long way in generating good will and happy feelings so there is that.

 

[DaveFite]

@Naonak
I appreciate your thoughts! You do having me thinking about why I prefer the range over the percentage indicator.

Why percentage? I would think you'd advocate for Tesla presenting charge in the display. kWh would certainly be better than normalizing to percentage. Your "X for Y%" would then become X miles for Wh. Makes your on the fly math a little tougher. 74.3 kWh displayed and your current factor of 324 Wh per mile. Can't to that division in my head... So you simply to 50%, 2 miles per 1%... Ah 100 miles.

The range display hides all the technology and algorithms. I dumbly trust Tesla to know what factors are important and how to convert from charge remaining to miles. I allow them to incorporate or ignore any factors in their calculation. I got burned and spent 5 hours on the side of the road. I'm not sure if I would have been saved had percentage been displayed.

The percentage display you advocate is a compromise. You don't allow Tesla engineers to use their knowledge in the conversion to miles and you normalize the display to simply the math.

Keep me thinking!

 

[Naonak]

@Naonak
I appreciate your thoughts! You do having me thinking about why I prefer the range over the percentage indicator.

Why percentage? I would think you'd advocate for Tesla presenting charge in the display. kWh would certainly be better than normalizing to percentage. Your "X for Y%" would then become X miles for Wh. Makes your on the fly math a little tougher. 74.3 kWh displayed and your current factor of 324 Wh per mile. Can't to that division in my head... So you simply to 50%, 2 miles per 1%... Ah 100 miles.

The range display hides all the technology and algorithms. I dumbly trust Tesla to know what factors are important and how to convert from charge remaining to miles. I allow them to incorporate or ignore any factors in their calculation. I got burned and spent 5 hours on the side of the road. I'm not sure if I would have been saved had percentage been displayed.

The percentage display you advocate is a compromise. You don't allow Tesla engineers to use their knowledge in the conversion to miles and you normalize the display to simply the math.

Keep me thinking!

I actually would like to see a kW remaining graph, but as you say, it would require some mental gymnastics that would reduce it's usefulness to almost nothing. Couple that with the fact that I don't think you can calculate how many kW are left in a battery anyway (someone correct me if I'm wrong?).

The % is based on the voltage presented to the sensor, so the % and the kW remaining would be effectively the same number.

With either of those, you'd have an accurate (or at least MORE accurate than distance) number to tell you how full your battery is. For my P90DL and my two P85s, the 1% = 2m rule seems to hold pretty well with a built-in fudge factor, and allows for an "oh *sugar*, I seriously miscalculated and need to drive a lot slower" factor.

With a "distance remaining" number, you drive and see "Oh I have 200 miles left" ... 75 miles later "Hmm, I have 75 miles left" .. 50 miles later, "WTF I have 10 miles left... no 9... no 8... no 7, but I only drove 1 mile! WHY GOD WHY?!?!" In the end, will the car go the same difference regardless of which display you have? Of course, but with the percentage, you aren't tricked in to believing you have a certain range available and become lazy and rely on it. With %, you have to be active and constantly consider the reality of your range.