Out of juice - battery issue, UI issue, or user mistake?

[Max*]

is extremely enlightening. Upon entering the exact inputs, it says the car would use 156 Rated Miles, which bears out EXACTLY to the reality we experienced. A few miles short.

Craptastic! :crying:

It would be great if the in-car trip computer had this sort of accuracy.

Cough...

Again, what did the trip tab of the energy consumption show? Did your green/yellow/red line go WAY below the estimated gray line? Was the estimated gray line set above 0% by the time you reach the SpC? etc.

This will help answer if it's an elevation issue, user error, or something else.

What did this graph look like, is my question:

I've seen it have REALLY good accuracy, including taking into effect elevation changes.

 

[qwk]

where was this documented? where did Tesla confirm it's existence and removal?

There was a whole thread about it here. Tesla never goes into detail what was changes in firmware with regards to driving changes. There definately was a reserve as my cars 50% charge changed by 15 miles, and so did the yellow, red bars.

 

[bonnie]

Should note that when a Roadster drops below around 20 miles of rated range, the display changes to indicate that it cannot accurately predict miles, and so shows either a "---" or displays 0. (Can be a bit nerve-wracking when cutting it close and all of a sudden you see nothing...) Because when you approach zero, there are too many variables that will either extend miles or chew them up. And no, there is no reserve. Agree with posters here that it's been a disservice when people insist there is a hidden reserve that can be counted upon.

 

[mknox]

There was a whole thread about it here. Tesla never goes into detail what was changes in firmware with regards to driving changes. There definately was a reserve as my cars 50% charge changed by 15 miles, and so did the yellow, red bars.

There's been lots and lots and lots of discussion about this, but I don't believe Tesla ever once said anything about a "reserve" below zero. I and others have noted absolutely no change in rated Miles at any SOC over firmware changes. Some have reported the car shutting down while still in positive numbers. The bottom line is you shouldn't really be getting close to zero if at all possible anyway.

 

[AmpedRealtor]

If the car shut down with positive miles showing on the range estimate on the speedo, then that's a problem that needs to be fixed. There is definitely some shadiness with the algorithm. One time I hit 0 miles as I rolled towards my garage. I did not receive any warnings. I thought what the heck, let me drive around the block a few times and see what happens. After I hit 0, I received the "Charge Now" in red. I kept driving around the block a few times, but at no point did the car say it was reducing AC or anything.

Fast forward a few weeks. I rolled into a Supercharger with 4 miles remaining. I received an alert along the lines that my AC and other systems were being reduced. In one case, no alert even past zero, and in another case, alert received with 4 miles remaining.

 

[Oba]

The BMS has a predetermined trigger voltage where it will enter bricking protection. It's not a guess, prediction, or estimate. It is an absolute certainty. Absolutely no error in the calculation should be tolerated at this point. Tesla needs to fix this... If it's still showing range, then that is indicating to the driver it is NOT at the trigger voltage. IMO, this is simply unacceptable.

Let's be honest; predicting the lowest cell is a bit artwork.

Yes, the BMS will open the main traction battery contactor at 2.5 volts on the lowest cell. Because the packs are always top balanced, and never bottom balanced, there could very well be significantly uneven bottom cell voltages, where XX miles could still be displayed as the calculated energy remaining, while having no programming to ANTICIPATE that one parallel cell string will screw up that calculation.

That's the special sauce that Tesla (and all of them, frankly) is missing. I honestly do not know how to predict that, but I'd suggest that:

1) as the cell voltage reaches 2.9 volts, the range algorithm begins to shift heavily to diverging cell voltages (very difficult under load). Basically, if the cell strings are within 0.050 volts for most of the discharge, at some point that voltage gap will get larger, and larger. That's the spread that I'm talking about.

2) for the driver, very, very light use of the go-fast peddle is required to not allow a voltage sag under load to trigger the 2.5v threshold


For this car, I would fully charge the car, and let it sit at 100% for 12-24 hours. Then, I would drive it once again to ZERO miles to repeat the event (closer to home!). While top balancing will not fix a situation where the lowest voltage stops the car prematurely, at least you'll have some ammo for the Tesla guys.

Have them get you a report of the variation between cell string voltages when the car stops. I'll bet that any situation where there is ample potential power available (showing significant rated range) and the car stopping will be shown to be a low voltage situation.

Of course, there is no fix, short of replacing that cell string (which Tesla isn't going to do).

 

[mknox]

Should note that when a Roadster drops below around 20 miles of rated range, the display changes to indicate that it cannot accurately predict miles, and so shows either a "---" or displays 0.

That is consistent with how a lot of ICE cars do it when the tank is getting near empty. Frankly, I think Tesla should implement something like this on the Model S. Too many people are taking the very low digits too seriously.

 

[yobigd20]

Should note that when a Roadster drops below around 20 miles of rated range, the display changes to indicate that it cannot accurately predict miles, and so shows either a "---" or displays 0. (Can be a bit nerve-wracking when cutting it close and all of a sudden you see nothing...) Because when you approach zero, there are too many variables that will either extend miles or chew them up.

wow I didn't know the roadster did that. makes sense though. I don't know why they chose the MS to follow a more inaccurate display. putting up '??' on the display would be much better lol

 

[jbcarioca]

In the first place range estimates are based on algorithms that change with time. State of charge is based on algorithms too. For that matter, the gasoline gauges in ICE cars are not entirely precise or necessarily accurate either. As one learns when doing aircraft pilot training, there is "unusable fuel" and there are gauge errors. Why are we so hung up on precision in something so inherently variable?

Why would anybody intentionally allow battery level to become so low? Why would anybody allow ICE fuel levels to get close to zero, knowing that fuel filter contamination risk will rise as fuel level lowers, even if one does not actually run out of fuel?

All of us have done those things but all of us should know better. If we never go below 20% and rarely go above 90% our batteries will be healthier and happier and we will not need to worry. That is my choice, but then I have grown to hate running out of fuel almost as much as I have grown to hate threatening the health of the best car i have ever driven.

 

[Oba]

...at the supercharger it was putting in a decent charge but not more than 315 mph. Probably not a big deal but thought I would mention that when alone at a supercharger, we normally get 350. There was no one else there.

With a completely discharged battery, and without the benefit of knowing if the amps were lower than normal coming from the Supercharger (let's assume no issue with the Supercharger), then the extremely low battery voltage multiplied by the normal amperage would be a slower charge in mph.

 

[mspohr]

Just looking at evtripplanner for Santee to Charlotte it shows 155 miles distance but if you put in 500 pounds (you mentioned 5 people) and a 1.2 speed multiplier (you mentioned 80 mph at one point) and 85F external temp it comes up with 236 Rated Miles used which (P85 with 19" wheels).
Sounds like this is cutting it very close. If the weight or speed or temperature were more, it could give you the situation you experienced.
It would have been wise to just set the cruise control for 55 and enjoyed the scenery. Reducing speed is the best way to improve mileage.
The rated range display is only a estimate. The trip planner energy graph is most accurate and I watch this like a hawk if I have any concerns about range. It takes into account elevation, speed, etc. and makes minute by minute adjustments.

 

[Skotty]

How good are the tracking statistics for Tesla Model S cars? Ideally we would want to look at average power usage of this particular vehicle compared to the part of the trip in question, with particular emphasis on looking at power usage immediately before, during, and after the questioned event. This should give us a good indication on whether this was just perceived power drain above normal or whether there was indeed something amiss.

 

[gavine]

OP: What was the Wh/mile for the trip? That's the best way to tell if you're efficiency was compromised in some way.

 

[qwk]

How good are the tracking statistics for Tesla Model S cars? Ideally we would want to look at average power usage of this particular vehicle compared to the part of the trip in question, with particular emphasis on looking at power usage immediately before, during, and after the questioned event. This should give us a good indication on whether this was just perceived power drain above normal or whether there was indeed something amiss.

Nothing really sounds amiss. If the car is driven conservatively, it can malke that stretch very easily. If you go 80 mph up a hill, not so much. The logical thing to do when rated miles start dropping faster than expected is to slow down. Obviously this didn't happen. There is absolutely nothing wrong with the battery, just user error.

 

[gavine]

cabin heater kicks in and she'll lose 20% range. This could be happening when temp is gradually dropping.

I always wonder why Tesla didn't think about this. At least they could give us a separate "Heater ON" indicator to see if the cabin heater is on.

I started a thread about this last year. While Tesla never implemented a "heater-on" indicator like I would prefer, someone pointed out that the vent location indicator will show an arrow at your feet when the heater is on and that's how I know when it's on.

Here's a link to the thread:

http://www.teslamotorsclub.com/showthread.php/35078-Heater-on-off-Button

 

[dsm363]

is extremely enlightening. Upon entering the exact inputs, it says the car would use 156 Rated Miles, which bears out EXACTLY to the reality we experienced. A few miles short.

Craptastic! :crying:

It would be great if the in-car trip computer had this sort of accuracy.

Was the supercharger programmed into the NAV? What did the trip estimator say for percentage she's arrive at? Sorry to hear this happened. Driving at 70 instead of 60 actually does make a big difference if you are worried about range.

 

[dsm363]

Was she counting on the rated range to be the range she'd get regardless of other conditions (speed, elevation...etc)?

 

[StaceyS]

I think it is very important to note that "Rated Range" is just that: a projection of range at rated consumption.

Interstate travel speeds (especially 80 mph) will not get you Rated Range.

This is the same as a gasoline powered car. If the EPA states your car gets 30 mpg and you have a 10 gallon tank, you won't go 300 miles driving at 80 mph.

If your rated range drops faster than your actual driving, your consumption is higher than rated. If I'm driving along and notice my rated range is falling faster than actual miles driven, I immediately scan my situation and see if I can identify what it is that is causing the higher consumption. It could be driving style (driving quick, not driving steadily, using the brakes instead of regen, etc), geography, weather, or all of the above. If there's something you can do about it, do it if necessary. Otherwise, start looking for charge options.

 

[sorka]

Tesla said nobody really gets 260 miles in real world conditions - I get that but dang. When the last 70 miles gets you less than 30, and the car flatly shuts off, that signifies a problem to me.

I've gotten that on my P85D and it's only EPA rated at 253.

 

[AmpedRealtor]

Regardless of how someone drives, the car shouldn't shut down when there are still positive miles remaining on the range indicator, right? That's the part about this story that bothers me.