Failed range calculation left me stranded

It’s no different “now”, you never could trust that the range is that accurate. Battery state of charge can not be measured directly. In any car, even a Porsche. It’s always an estimate, and it can be more or less accurate depending on how you’ve charged recently. You just shouldn’t be cutting it that close. Sorry, I don’t agree that you had a “reasonable amount of range in excess of your destination”.

 

We had a pickup that done that. Yup. Said it had some fuel left. Then it got me.

Worst day of my life. Took her out behind the barn and put a bullet in her radiator while the kids were at the neighbors. I still miss the old gal.

Son, once a car bites you, you gotta put it down. It just ain't safe to have it around kids.

 

I mean I've run out of gas in ICE vehicles where I swore the needle was not on that E.

Have fun with the Porsche, and the lack of superchargers.

 

First I've heard of a Tesla shutting down before the zero. We know not to trust the listed range, but I too would have assumed a listed range of 6 miles would have been enough to cover 2.5 miles. I.e. if I was 2.5 miles from home and my range said 6 miles, and there was a L2 charger a block away, I would not stop to charge.

 

On a slightly more serious note, there have been MANY reports of owners being able to drive for a few miles after the rating says 0mi left. Funny how those people didn't complain about an inaccurate range meter. This is why most prefer to leave it on a % vs a rated miles scale.

 

If I was in ANY car I would not let it get that low. My butt puckers once anything says its below 40 miles left. Any range calculation is an estimate not a 100% sure thing. I thought everyone knew this?

 

Why? So you can then say, ‘it’s okay, I can drive another 8 miles before I really hit 0’. And then come here to report it only went 7 below 0 and you got stranded again?

How about just being reasonable and logical and not running the battery down to nothing? It’s just like driving a fossil fuel car, run it to E often enough and eventually you’re going to have to walk the rest of the way.

Zero sympathy. End of story.

 

It is also well known and common knowledge that it is technically difficult to calculate how much usable energy is left in a battery. The science and technology behind measuring how much power you have left in a battery is shoddy at best. Combined that with a computer that has to extrapolate how many miles it thinks you can drive, that's asking for trouble.

 

Calculating battery state of charge is not like measuring the amount of fuel in a gas tank. The only 100% accurate measurement is made by draining the pack at which point the value is no longer any use to you. Otherwise it's measured through indirect proxies like pack voltage, voltage change rate, delta between measured charge and discharge power, etc. It's like measuring how full a barrel of water is by listening to the sound when you bang on the outside or watching how fast it pours out when you open the spigot.

Tesla does actually design their capacity reporting to attempt to over-estimate on the low end. There are many stories of people driving several miles past "0" but you can't count on it because it's just a (fairly accurate - relatively speaking) estimate. You were just unlucky to be a few miles off in the other direction.

I sympathize with your frustrating experience, but now you know better about the state of battery capacity measurement so you're equipped to avoid this situation with future EV trips.

 

Let’s compare. How many of us would continue to drive an ice car if it said 6 miles of range left? Most wont even show a distance to empty below one gallon for this very reason.

It’s also my understanding it’s bad for the cells to go below 10%? Correct me if my assumption is off. Why anyone would do this then complain when the car shuts down is beyond my comprehension. There were no places at all to put an extra kWh or two in the battery? Come on.

 

Somebody please correct me if I'm wrong:

The battery computer looks at the voltages of all modules independently. The battery shutdown is based on the lowest module. Not all modules will read the same.

The Guess-o-meter is based on the pack voltage.

 

As lithium batteries age their internal resistance increases, which in turn reduces the amount of current which can be drawn from the batteries for a given voltage level. The battery pack has hard cut off limits for the voltage ranges, so to try preventing an early trip of the lower cut off voltage, Tesla puts a power limit in place at low charge levels. This helps but is not 100% fool proof, especially if you suddenly draw a lot of power or if a given module is weaker than others due to aging, then the cut off limit could potentially be hit earlier than predicted.

 

I try not to even drive my 90D down to the point the range meter turns yellow. The is like the low fuel light in an ICE car.

 

Although I won't lie, I've driven my car down to 3 miles before. but if I ended up stranded, I wouldn't have been mad at Tesla since it was my own damn fault for bringing the car down that low, and I most certainly would've have thrown my arms up in the air and declare im buying a whole new different car after one incident lol.

 

Again, this is the first time I’ve seen a post about a Tesla shutting down above zero (have there been others?). So it’s a useful PSA type learning experience worth sharing among the Tesla community. I can’t be the only person that would have thought the same as the OP in this scenario. Now I know differently. Learn something new every day on these forums.

 

I arrive home with <10 miles on a pretty regular basis with no issues, though I don’t go< 5 !!!

 

It is not that unusual, the range will only be an estimation based on the calculated energy left in the battery. It is not a exact measurement but an (often good) estimate.

 

I am sure you have had your mobile phone or laptop shutdown on you before it said 0%... this is no different... did you buy a new device?