Running out of Charge and Dead Battery

[ev.enthusiast]

Hi Everyone,

Over the weekend I found myself in a predicament: I had underestimated the necessary amount of charge in rainy/windy weather on the highway and ended up having the car run out of charge before I could reach the nearby supercharger. My car is fixed now but the experience which I went through has propped up several questions in my mind on how to deal with these kind of situations, given that I am not a car nerd. Just wanted to post them here so myself and others might benefit from the collective knowledge sharing.

1. When my car (Tesla Model S 2015 model 85D - the older shape with the nose cone and 125k miles mileage, battery still under warranty) gave me the 'Vehicle Shutting Down - Pull Over Safely' warning and I began to lose power in the car (the car was doing 45 mph and began to slow down gradually despite me pressing the acceleration pedal) the range which was being shown on the battery was 10 miles. I was only 2.5 out of the supercharger at that time. I pulled over my car and stopped on the shoulder afraid that if I keep going the car might shut down in the middle of the road at night time on an un-lit road would not be good. The first question is, could I have possibly driven the car while it was losing power and decreasing speed for another 2-3 miles to the supercharger after the car had given me the shut down warning?

2. Once I pulled over and called for a flatbed tow truck, while I was waiting for the tow truck to arrive I saw the range dropped to 0 miles after a few minutes. I had turned off all the lights of the car and the only thing which was on was the 17 inch screen + center display. I am confused on whether the 10 mile figure which I was looking in the dash was wrong before or the 0 mile range which it dropped to was wrong? At this time I got the 'Electrical System Power Reduced - Vehicle May Shut Down Unexpectedly' warning as well as the 'Unable to Drive - Pull Over Safely' warning. What caused the car (while it was stopped) to show the range as 10 miles and then suddenly drop it to 0 miles all while I had not driven it and even shut down the lights etc?

3. Once I towed my car to the supercharger and tried charging the car, two very frustrating things happened; firstly, the car wouldn't power on at all (no screen worked, couldn't open the frunk, the key fob however was able to unlock the doors). I managed to open the nose cone and open the frunk and jump start the 12V battery which at least powered on the screens. secondly, even though the car got jump started and I got the charging port to open - it would simply not unlock the charging port to allow for the charger to fit in the charging port automatically. I had to use the manual release lock located in the trunk to shove the charger in but in that case I'd get a red light on the charge port with the car center display showing me the 'Unable to charge - Service required' warning. Why didn't the car supercharge when I used the manual release lock to put the charger in the charge port?

4. Once the battery is dead on the car, is the 12V battery always required to be jump started for the car to charge? Or was my 12 V battery too old (my car's 12V battery has never been replaced) to sustain enough charge to enable the power needed for the HV battery pack to be charged?

5. Eventually after fiddling with my Tesla for a couple of hours at the supercharger and failing to get it to start charging, I gave up and had the car towed to the nearest Tesla service center. The replaced the 12V battery and eventually my charge was able to charge. The lingering question is that what could have I done differently - if anything - (apart from replacing the 12V battery myself) to get my car to charge once I had a flat battery.

6. I asked the Tesla folks if the car's HV battery had sustained any damage and they said it was not the case. However the Tesla guy did say that had I kept on driving the car till it had completely died down i.e. not pulled over, may be that would've caused damage to the HV. Is this statement true? I did drive my car back from the service center and have my usual range showing in the car again (~235 miles) in the center display - I don't trust it as much now as I did before after this fiasco.

 

[Rocky_H]

The first question is, could I have possibly driven the car while it was losing power and decreasing speed for another 2-3 miles to the supercharger after the car had given me the shut down warning?

Pretty sure no. I think you're down to just a minute or less when it's giving the "shutting down" message.

I am confused on whether the 10 mile figure which I was looking in the dash was wrong before or the 0 mile range which it dropped to was wrong?

Well, this is generally because of trying to represent the state of the entire pack as a whole with one number. There appears that one (or more) of the modules within the battery pack is a bit imbalanced compared to the rest, and it dropped down pretty quickly, which crossed the threshold of triggering the shutdown message. With the older packs that have a lot of miles, that last few single digit rated miles can be at that low level where that is a risk.

3. Once I towed my car to the supercharger and tried charging the car, two very frustrating things happened; firstly, the car wouldn't power on at all (no screen worked, couldn't open the frunk, the key fob however was able to unlock the doors). I managed to open the nose cone and open the frunk and jump start the 12V battery which at least powered on the screens. secondly, even though the car got jump started and I got the charging port to open - it would simply not unlock the charging port to allow for the charger to fit in the charging port automatically. I had to use the manual release lock located in the trunk to shove the charger in but in that case I'd get a red light on the charge port with the car center display showing me the 'Unable to charge - Service required' warning. Why didn't the car supercharge when I used the manual release lock to put the charger in the charge port?

You say you jump started it, but did you keep that 12V power applied when you were trying to plug in to charge it? The car needs to use that 12V power system to close the contactors of connecting the main battery pack, and it probably didn't have enough power there. So the main pack was still disconnected. Sometimes when people have drained the 12V down so far that it's dead, it can be pretty damaged and may need to be replaced before things will operate fully normally, like being able to close connectors to charge.

Or was my 12 V battery too old (my car's 12V battery has never been replaced)

Oh, jeez!! On a 2015 car? Yeah, then that reinforces what I thought earlier. An already really old 12V battery that's degraded...and then it gets drained fully flat (more damage) and then trying to jump start it... I'm not surprised it couldn't really sustain enough power to reconnect the main battery to start charging. I have a March 2014 S85, and I got the messages of the 12V battery being low and needing replacement at about 3.5 years each time so far.

5. Eventually after fiddling with my Tesla for a couple of hours at the supercharger and failing to get it to start charging, I gave up and had the car towed to the nearest Tesla service center. The replaced the 12V battery and eventually my charge was able to charge.

OK, yes, not surprising--that battery was pretty trashed.

The lingering question is that what could have I done differently - if anything - (apart from replacing the 12V battery myself) to get my car to charge once I had a flat battery.

Two things:
Don't run out! I know it was by accident, but you should keep an eye on that and be more cautious to leave more margin. You're driving for an hour or two before that, right? Watch that % remaining estimate, and I recommend slowing down earlier in the drive to not let that estimate get below 10%, so you don't get down to only 10 rated miles left with 3 miles of distance left to go.

Second thing is just proactive battery replacement. Some people get really paranoid about this, thinking they die every year. I don't think that's the case, but you got VERY lucky having a battery go for 7 years before it died. That's highly unusual. So I would say it's prudent to do this precaution somewhere in the middle. About 3 to 4 years in, if it hasn't given the warning yet, I might still go ahead and get it replaced.

6. I asked the Tesla folks if the car's HV battery had sustained any damage and they said it was not the case. However the Tesla guy did say that had I kept on driving the car till it had completely died down i.e. not pulled over, may be that would've caused damage to the HV. Is this statement true?

The first part--yes. Maybe not on the second part. That shutdown feature happens with some reserve of about 4-5% (You'll see it referred to as the "anti-bricking reserve" here on the forum.) left in the battery for this reason, to prevent owners from really destroying their batteries. So the battery was saving itself from you.

I did drive my car back from the service center and have my usual range showing in the car again (~235 miles) in the center display - I don't trust it as much now as I did before after this fiasco.

There's probably some imbalance in there, so I don't think you should trust that last tiny bit below 10 rated miles on the display, but most of it should be fine.

 

[ev.enthusiast]

Thanks a lot @Rocky_H for your useful insights. I have a few follow up questions as well after going through your responses.

There appears that one (or more) of the modules within the battery pack is a bit imbalanced compared to the rest

There's probably some imbalance in there, so I don't think you should trust that last tiny bit below 10 rated miles on the display

Is there any way this imbalance can be fixed or improved i.e. some form of battery calibration which can be done to make it a bit better?

Does this imbalance mean one of the battery modules has supposedly started to fail and I should expect a 'Maximum battery charge level reduced' warning in the intermediate future?

You say you jump started it, but did you keep that 12V power applied when you were trying to plug in to charge it?

Yes I did keep it applied. However, after reading your response may be I didn't do it for long enough to get it charged to a level where the HVB would've connected back, or may be it was so degraded that it needed to be replaced first before the HVB connected back.

Don't run out! I know it was by accident, but you should keep an eye on that and be more cautious to leave more margin. You're driving for an hour or two before that, right? Watch that % remaining estimate, and I recommend slowing down earlier in the drive to not let that estimate get below 10%, so you don't get down to only 10 rated miles left with 3 miles of distance left to go.

Agreed. I did put in a margin of 40 miles in the charge. The physical distance which I had to cover was 140 miles and I charged my car up to 180 miles (~76% of the full capacity). However, it was raining heavily for the entire 135 miles I drove the car. I didn't particularly overspeed during this time except for the odd speed increase while overtaking a 18 wheeler. Mostly I drove the car on autopilot at 65 mph in a 70 zone. Did the adverse weather caused the car to be more inefficient? I know now to keep at least 55 - 60 miles of margin and slowing down significantly if I see that range margin is being chewed down quickly. I was contemplating why did the car chew up on the 40 miles of range and the adverse weather seemed to be the main reason for that margin being too low.

That shutdown feature happens with some reserve of about 4-5% (You'll see it referred to as the "anti-bricking reserve" here on the forum.) left in the battery for this reason, to prevent owners from really destroying their batteries. So the battery was saving itself from you.

That makes a lot of sense. I am, however a little low on confidence about the reliability of the HVB on the car now, especially at low states of charge. I have set a blanket rule in my mind to never to let the HVB drop below 10% SoC. The question then becomes is, should I really keep the car and keep relying on the HVB to perform to it's current capacity (barring the 10% rule - i.e. I'll be assuming that although the car 'theoretically' displays 235 miles at full SoC but 'practically' the reliable full SoC range is 215 miles)? The HVB and DU both are under warranty for another year. This is more of a question of perspectives but should I keep relying on the HVB or should I just sell the car and get a brand new Model Y? The car has already 125k miles on it so definitely the DU and HVB have been used a lot in the last 7 years.

 

[brkaus]

Adverse weather can have a significant impact on range. Wind to fight against. If the roads are wet, the tires have to push the water out of the way.

 

[ev.enthusiast]

Adverse weather can have a significant impact on range. Wind to fight against. If the roads are wet, the tires have to push the water out of the way.

That's a hard (and expensive) lesson which I learned over the weekend.

Cost me $1500 to get the car towed from where I stopped as the nearest Tesla service center was 200 miles away. A further $325 to get the 12V battery replaced. Costly mistake.

 

[Rocky_H]

Is there any way this imbalance can be fixed or improved i.e. some form of battery calibration which can be done to make it a bit better?

Does this imbalance mean one of the battery modules has supposedly started to fail and I should expect a 'Maximum battery charge level reduced' warning in the intermediate future?

I'm not going to overextend, so that may have to defer to others here who know the technical aspects better. There is a bit of auto-balancing that the pack does to try to even things out while the car is off, but that's temporary. But for permanent state, whatever block that was is just the weakest of the bunch now, and that is its permanent state of health, so I don't think there is anything you can do for it to try to "heal" or correct that. It's going to be the first one to drop off when the overall state of charge gets really low.

Agreed. I did put in a margin of 40 miles in the charge. The physical distance which I had to cover was 140 miles and I charged my car up to 180 miles (~76% of the full capacity).

I am one who also uses rated miles on my display most of the time, but for traveling, you need to put your destination in Navigation and let the car show you its estimated state of charge at arrival. What if that was all really uphill? 180 to go 140 wouldn't cut it, but the car would know that because it knows the elevation, and it would show you if the arrival state of charge was going to be -3% or something because you didn't have enough. So I keep charging until that estimated arrival shows some comfortable margin, like 15% or something, especially if it's really cold or raining.

I didn't particularly overspeed during this time except for the odd speed increase while overtaking a 18 wheeler. Mostly I drove the car on autopilot at 65 mph in a 70 zone.

And I'm still not hearing any reference from you of ever looking at that estimate while you drove. That's the most important thing you can do. If that number is rapidly dropping into single digit %, you get the chance to see that early in the drive! Take that time to slow down much earlier, and it will recalculate, and you'll have a chance to adjust and save this before it becomes a problem.

However, it was raining heavily for the entire 135 miles I drove the car. [...] Did the adverse weather caused the car to be more inefficient?

Yes--very. That takes extra force from the car for the tires to displace water out of your way, and the extra rain hitting your windshield and the rest of the body of the car. At this point, we sometimes hear people getting frustrated, saying, "What?! I have to account for every little thing like that?" No, not really. The car is detecting every bit of energy use from all of that rolled into one, so it knows the consumption and is showing you that in real time in the % remaining estimate. That's all you have to look at. Lower your cruise control speed a few miles per hour, and it will reduce that energy consumption.

That makes a lot of sense. I am, however a little low on confidence about the reliability of the HVB on the car now, especially at low states of charge. I have set a blanket rule in my mind to never to let the HVB drop below 10% SoC.

I think that's just wise. I've never had a problem with my 2014 S85, but I already was not going to trust that very low bit at the bottom of the battery. I just don't think it's a good idea to expect that much precision from it to take that risk. And that's fine. If it's another 5-10 minutes at a charging stop to keep it more comfortable, I'm fine with that, and it doesn't bother me.

The question then becomes is, should I really keep the car and keep relying on the HVB to perform to it's current capacity (barring the 10% rule - i.e. I'll be assuming that although the car 'theoretically' displays 235 miles at full SoC but 'practically' the reliable full SoC range is 215 miles)? The HVB and DU both are under warranty for another year. This is more of a question of perspectives but should I keep relying on the HVB or should I just sell the car and get a brand new Model Y? The car has already 125k miles on it so definitely the DU and HVB have been used a lot in the last 7 years.

I don't see why not. I do less miles, but I'm out of warranty on my 2014 with 98K miles on it. Mine will show about 252 rated when full, and I try not to go below about 10%, and that's still very usable for me. I wouldn't replace it because of that; just be more careful about not running really low.

 

[ev.enthusiast]

And I'm still not hearing any reference from you of ever looking at that estimate while you drove. That's the most important thing you can do. If that number is rapidly dropping into single digit %, you get the chance to see that early in the drive! Take that time to slow down much earlier, and it will recalculate, and you'll have a chance to adjust and save this before it becomes a problem.

I did keep an eye out on the estimate but was confident that I'd make it with a few miles to spare. You are right, I should've slowed down much earlier when I saw the range dropping and margin reducing. It would've allowed it to recalculate and would've helped me before it became a problem.

Yes--very. That takes extra force from the car for the tires to displace water out of your way, and the extra rain hitting your windshield and the rest of the body of the car. At this point, we sometimes hear people getting frustrated, saying, "What?! I have to account for every little thing like that?" No, not really. The car is detecting every bit of energy use from all of that rolled into one, so it knows the consumption and is showing you that in real time in the % remaining estimate. That's all you have to look at. Lower your cruise control speed a few miles per hour, and it will reduce that energy consumption.

That makes sense. I've also decided to change the way the SoC is displayed on the center screen. I always used to have it set to show the 'Typical' range as I would find it to be reasonably accurate most of the time. Now I've changed that to show the % so I can always cross reference it with the navigation information and make sure that route to charging stops does not take me below 10% remaining battery.

I don't see why not. I do less miles, but I'm out of warranty on my 2014 with 98K miles on it.

I absolutely loved my S 85D before this event and even now I still love it as a car. However, the range anxiety has prompted me to think about alternatives and also the fact that I've got only one year left on the warranty. If I keep the car post warranty expiry and God forbid something happens to the HVB/DU, it will be an out of pocket expense for me. Not sure if it's worth the risk to potentially spend $15-18k on battery pack replacement (the battery has to fail one day eventually) in the future to keep the car running fine for another few years. I'm contemplating selling it and buy a new model Y which costs around the same (may be I'll need to add a couple of thousand $ depending on what I can sell my S for) and will solve both the range anxiety (hopefully, as it will be a brand new vehicle with more range and supposedly a new battery in better condition to last a number of years under warranty) as well as mitigate the risk for an out of pocket HVB/DU replacement expense just to keep the car driveable. I've test driven Y and although I felt that my 2015 S drives much better (and I do not like the single screen Y has got), but practically Y makes a lot of sense (it offers almost the same trunk space as S and interior is also roomy similar to S). Also, Tesla seems to prioritize 3/Y over S/X (that's my gut feeling given how quickly updates rollout for 3/Y).

Mine will show about 252 rated when full

How much range does your car show at full while in the 'Typical' setting?

 

[ATPMSD]

Let me explain what happened, at least as best as I understand it. As you know you have two batteries, the HVB and the 12v. When you are driving the HVB powers the drive units and HVAC, and also powers the 12v systems via a DC-DC converter, the 12v battery is not used and only charged.

As the capacity of the HVB drops the car begins shutting things down to protect the HVB. At some point it will also stop supplying power to the 12v system at which point the 12v battery is then being used. As time goes by it is drained and the car begins to protect the 12v battery as well, which is when you see those shutting down messages. At this point you really need to get to a charger urgently since without the 12v battery you cannot charge the car (without jumping it)

It is also my understanding that as long as the HVB has power (>0% or >0 miles) it is still drivable.

OK my fellow members, is this correct?

 

[NewbyMaybe]

If there's other chargers in your area like chademo or ccs then get an adapter, the superchargers are only going to get more crowded.

 

[Rocky_H]

Mine will show about 252 rated when full

How much range does your car show at full while in the 'Typical' setting?

Oh. There's a terminology difference between the North America versions versus the European ones. Mine called "rated" is basically equivalent to yours named "typical".
In the U.S. cars, we have "Ideal" and "Rated", but in Europe, they are called "Rated" and "Typical". I explained why in this linked comment from another thread.

M3 straight line in the energy graph shows "Typical" instead of "Rated"

My car is consistently reporting a range loss of 5%. But then I found out something interesting after a discussion with @TimothyHW3 (Charging everyday?). The solid straight line in my (European) M3 shows "Typical" range instead of "Rated" range in the Energy Graph screen. Does anyone else...

teslamotorsclub.com

 

[fuelsman]

At some time all EV vehicles will experience low charge battery due to weather, terrain, or speed. The solution to get to the next charging station is to slow down. The point to slow down is when reported range is within 10% greater than distance to the charger. The slower you drive the less battery is used per mile. Other drivers may glare at you for driving so slowly but it better and faster than risking a tow. Also always charge when parked with less than 25 miles. One time I checked into a hotel with 17 miles range showing. After a 15 minute check-in I came out to drive the car to supercharger 3 miles away. When I started the car it reported 7 miles of range. I lost 10 miles of range just parking car for 15 minutes.

 

[NewbyMaybe]

Maybe the battery should turn red when it shrinks to 20%.

 

[ucmndd]

As the capacity of the HVB drops the car begins shutting things down to protect the HVB. At some point it will also stop supplying power to the 12v system at which point the 12v battery is then being used.

There’s never a time when the car is on/driving when this is the case. The DC-DC converter is on and active at all times, supplying 12v as required.

As time goes by it is drained and the car begins to protect the 12v battery as well, which is when you see those shutting down messages.

The “vehicle shutting down” message as I understand it is generally the result of voltage falling too low in the HV battery. This can sometimes happen “early” in older cars with some module imbalances because one module hits that threshold earlier than the others. So even if there’s “10 miles” of energy left across the pack, one module depletes faster and the car detects it and shuts down.

 

[ATPMSD]

There’s never a time when the car is on/driving when this is the case. The DC-DC converter is on and active at all times, supplying 12v as required.

I appreciate that some messages do relate to the HVB but having seen messages posted by others (mostly the ones that start with “VC”) which seem to be related to the 12v subsystems, I think it does get disconnected. Also, we know that preserving the HVB is the most important consideration and shutting down the DC-DC converter seems logical. Finally, I suggest either the BMS shuts down the DC-DC converter to conserve the 12v battery or worse, the converter has failed, in which case charging the HVB does not resolve the problem

Not 100% sure of course, but this is my understanding. Do you have a source or is this your educated opinion?

Always willing to learn!

 

[NewbyMaybe]

I appreciate that some messages do relate to the HVB but having seen messages posted by others (mostly the ones that start with “VC”) which seem to be related to the 12v subsystems, I think it does get disconnected. Also, we know that preserving the HVB is the most important consideration and shutting down the DC-DC converter seems logical. Finally, I suggest either the BMS shuts down the DC-DC converter to conserve the 12v battery or worse, the converter has failed, in which case charging the HVB does not resolve the problem

Not 100% sure of course, but this is my understanding. Do you have a source or is this your educated opinion?

Always willing to learn!

Domino theory: crappy situation gets crappier due to aged 12v failing.

The 12v battery is the red headed stepchild (I'm ginger-ish). There could be a better monitor of the 12v but it was thrown in there last minute so there would be a backup for full meltdown.

 

[ev.enthusiast]

Oh. There's a terminology difference between the North America versions versus the European ones. Mine called "rated" is basically equivalent to yours named "typical".
In the U.S. cars, we have "Ideal" and "Rated", but in Europe, they are called "Rated" and "Typical". I explained why in this linked comment from another thread.

M3 straight line in the energy graph shows "Typical" instead of "Rated"

My car is consistently reporting a range loss of 5%. But then I found out something interesting after a discussion with @TimothyHW3 (Charging everyday?). The solid straight line in my (European) M3 shows "Typical" range instead of "Rated" range in the Energy Graph screen. Does anyone else...

teslamotorsclub.com

Ah. That makes sense now. In Australia we get the 'European' version of the car. 252 miles of rated (typical in EU/AUS) range on full is awesome. You must've taken good care of your HVB. I get 235 - 240 miles of 'typical' range when full.

If there's other chargers in your area like chademo or ccs then get an adapter, the superchargers are only going to get more crowded.

True that, I have a CCS Type 2 adapter so I can charge on majority of non-Tesla DC fast chargers. EV charging infrastructure in Australia is still in it's infancy (when compared to what the US has), and Tesla superchargers here are not open for non-Tesla EVs so Tesla superchargers are still the best option when it comes to DC fast charging on the Australian East Coast.

Also always charge when parked with less than 25 miles. One time I checked into a hotel with 17 miles range showing. After a 15 minute check-in I came out to drive the car to supercharger 3 miles away. When I started the car it reported 7 miles of range. I lost 10 miles of range just parking car for 15 minutes.

Great advice there. I experienced similar when I pulled over during my empty battery ordeal happened. While waiting for the tow truck, the typical ('rated') range went down from 10 miles to 0 miles by just being parked for 15 - 20 minutes.

The “vehicle shutting down” message as I understand it is generally the result of voltage falling too low in the HV battery. This can sometimes happen “early” in older cars with some module imbalances because one module hits that threshold earlier than the others. So even if there’s “10 miles” of energy left across the pack, one module depletes faster and the car detects it and shuts down.

If that's the case then my question would be that is there a way the said potential module imbalances can be diagnosed and somehow corrected?

 

[EastCoast85D]

Ah. That makes sense now. In Australia we get the 'European' version of the car. 252 miles of rated (typical in EU/AUS) range on full is awesome. You must've taken good care of your HVB. I get 235 - 240 miles of 'typical' range when full.



True that, I have a CCS Type 2 adapter so I can charge on majority of non-Tesla DC fast chargers. EV charging infrastructure in Australia is still in it's infancy (when compared to what the US has), and Tesla superchargers here are not open for non-Tesla EVs so Tesla superchargers are still the best option when it comes to DC fast charging on the Australian East Coast.



Great advice there. I experienced similar when I pulled over during my empty battery ordeal happened. While waiting for the tow truck, the typical ('rated') range went down from 10 miles to 0 miles by just being parked for 15 - 20 minutes.



If that's the case then my question would be that is there a way the said potential module imbalances can be diagnosed and somehow corrected?

None of those fixes for imbalances last from what I have read. The only real solution for you is to get an extended battery warranty. Should have a few options over in Europe for one.

 

[Tyl]

2013 MS 146,000 miles approximately on this HVB pack.
On cruise control at 75mph for the last hour.
I'll arrive with 5%.
1/2 miles from supercharger.
11 miles indicated.
no warnings whatsoever, "to slow to make destination" or "reduce speed to 65 mph to make destination."
Car shuts down. "Pull over safely car is shutting down." ...that warning did appear.
AAA tow. 0$.
Car charged fine.
Lessones learned.
never trust indicted range less than 30 miles. I use to be able to trust to within 1 mile.
now i must charge an extra 45 miles for every 100 miles I intend to travel. Think wind, rain, heat, range hills and dales.
My question remains. Why are we not getting warnings to slow down to make destination. Those warnings use to be very helpful.
Where have they gone? Has Tesla deleted the warnings??

 

[ucmndd]

My question remains. Why are we not getting warnings to slow down to make destination. Those warnings use to be very helpful.
Where have they gone? Has Tesla deleted the warnings??

They still exist. They work as intended for “normal” navigation-based scenarios that the car can observe and predict.

What you experienced is a different thing, likely related to a weak module or pack imbalance in your aging pack that unexpectedly dropped below a voltage threshold at very low state of charge.

Your general assessment is correct - with aging / high mileage packs you probably don’t want to implicitly trust that last 10% or so. Many similar reports to yours.

 

[Worldfishnski]

I have taken my 2016 X down to zero % (I have the car set to show % not miles) on multiple occasions. I have never actually run out of battery where it was undriveable.

I keep a log of miles and %s for nearly every charge and trip I make to help me determine my needed % to complete my trip. Most of my driving is highway driving.

I have only slowed down significantly (15mph) three times (over a mountain in winter in Colorado, wind in Wyoming and AC+5 people in the car in New Mexico) but I still made it to the next Supercharger.

There will be trips where I might slow down 5 mph in the middle of a trip when my own (not the car's) calculations show me pushing the limits but often I can usually return to "normal speed" a 10-15 miles later.

If I see that I will arrive to a Supercharger with a higher % than I planned, I will speed up to take the battery % more for my arrival.

I have noticed no decline in my battery's storage ability.

The car has 160000 on it.

I use the same battery % to get from Point A to Point B now as it did 5 years ago. Obviously driving conditions make a huge difference but in the 100s of log entries I have made I can't discern a decline in the battery's "health"