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

[wk057]

oh, I like that. Really wish we had some form of advanced diagnostics.

As do I.

 

[LetsGoFast]

It is a challenging UI question. If their estimate has an 10 mile potential error and they hit 0 at the earliest point they protect more drivers from themselves, but build up the legend of the buffer. If they set it for anything else, once in a while someone is going run out at a positive number. Perhaps going to "---" once you get to a certain point is the best compromise.

 

[apacheguy]

Novel idea - how about stop displaying miles when it dips too low, but allow us to see the pack voltage? No calculation involved, just empirical data.

 

[tom66]

It is a challenging UI question. If their estimate has an 10 mile potential error and they hit 0 at the earliest point they protect more drivers from themselves, but build up the legend of the buffer. If they set it for anything else, once in a while someone is going run out at a positive number. Perhaps going to "---" once you get to a certain point is the best compromise.

Doesn't it say "Charge Now" when gone past zero?

 

[stopcrazypp]

Novel idea - how about stop displaying miles when it dips too low, but allow us to see the pack voltage? No calculation involved, just empirical data.

Unfortunately voltage does not tell the whole story of SOC. And most people will not know how to analyze voltage. That's best reserved for a "advanced" section of the UI.

 

[hiroshiy]

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

Hi, @gavine, thanks for the pointer to th thread, I actually read it once. However if I set AC to say 78F and outside is 77F would the AC change the vent to "foot"?

What exactly was the direct reason why she or her car spent so much energy in the last segment? Possibly too much speed, or high temp AC? Does elevation going UP to the Supercharger she missed?

 

[wk057]

I for one would LOVE to have the pack voltage displayed on the dash. It is an electric car after all.

 

[mknox]

I've gotten it down to 2%, and I remember the power being limited, but I'm sure I was doing around 65mph (don't recall the speed being limited to some odd value)

Last winter, I got a power reduction, a message to charge ASAP and something about the battery being cold at 20% SOC. I had just come off the highway after an hour or so of driving and the ambient temps were around 20F. I think there are a lot of variables that the car considers.

 

[stopcrazypp]

Last winter, I got a power reduction, a message to charge ASAP and something about the battery being cold at 20% SOC. I had just come off the highway after an hour or so of driving and the ambient temps were around 20F. I think there are a lot of variables that the car considers.

Cold temperature is a variable. When a cell is cold, the voltage drops and that drop can damage the cell if it reaches below the minimum point (2.5V per cell). Thermal management should mitigate that, but it depends on how cold the outside is and how long the heating system has been running (cold soak).

 

[Max*]

Last winter, I got a power reduction, a message to charge ASAP and something about the battery being cold at 20% SOC. I had just come off the highway after an hour or so of driving and the ambient temps were around 20F. I think there are a lot of variables that the car considers.

But no associated maximum speed reduction, correct?


I agree with whomever pointed it out first, the OP's 40mph speed reduction is odd...

 

[mspohr]

But no associated maximum speed reduction, correct?


I agree with whomever pointed it out first, the OP's 40mph speed reduction is odd...

At low battery levels I have observed a reduction in available POWER (yellow dashed line on the power meter) but no "speed limit".
It makes sense to limit the power from a nearly depleted battery but a speed limit would not be of any use... you could be going downhill in regen mode.

 

[mknox]

But no associated maximum speed reduction, correct?

Hmmm... there might have been. I do recall at least once seeing a limit on my speedo but don't remember if this was the time, but it probably was. I generally don't drive below 30 or 40 %, especially in the winter, and the fuss the car threw at me at 20% validated my operating methodology.

 

[LetsGoFast]

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've seen claims that this chart came from a Tesla deck, but I'm not sure I believe it. I know it used to be posted here often.

 

[wk057]

I've seen claims that this chart came from a Tesla deck, but I'm not sure I believe it. I know it used to be posted here often.

View attachment 91128

That chart is totally incorrect, for the record.

 

[mknox]

That chart is totally incorrect, for the record.

...and I believe it was put together by an individual hypothesizing how this all works. It's not something Tesla ever published.

 

[AmpedRealtor]

To protect the battery. Taking a large amount of power out of a low battery will heat up the individual cells and cause microcracking to occur shortening battery life (perhaps dramatically).

Actually, no, the car does not limit speed when it gets close. That is unusual behavior. I had no trouble driving above 65 MPH with less than 10 miles remaining. An energy limiter kicks in on the high end, which limits your acceleration, but not your speed.

Hi, @gavine, thanks for the pointer to th thread, I actually read it once. However if I set AC to say 78F and outside is 77F would the AC change the vent to "foot"?

Because in your scenario, the car's heater is turning on. When the car heats, it diverts air flow to the lower vents. When cooling, air flow diverts to the top vents.

 

[hiroshiy]

Actually, no, the car does not limit speed when it gets close. That is unusual behavior. I had no trouble driving above 65 MPH with less than 10 miles remaining. An energy limiter kicks in on the high end, which limits your acceleration, but not your speed.



Because in your scenario, the car's heater is turning on. When the car heats, it diverts air flow to the lower vents. When cooling, air flow diverts to the top vents.

Thanks, so if I set the AC to the warm side such as 78F, and the outside temp drops below that while driving, I can tell from the down-arrow vent indicator that the heater is on even though I "was" hot and AC "was" cooling cabin.

I have one more wild guess for Ellen. She might saw 40 and thought speed limited to 40mph, but in fact, it could have been 40kW limit. If that's the case, that's really severe limit. If she stops the car, it may well go into shutdown because it thinks it comes to a safe place.
Just maybe, if the power was limited to 40kWh, she could be able to keep driving without stopping, babying the battery for a little longer. Turning off AC could keep the car moving for just two more miles...

 

[Brass Guy]

There was a video (I can't seem to find it now) someone posted where they showed the screen as the car ran out and shut itself down. The dash started with the power limit as many of us have seen. The driver was hoping to make it the last few miles home, but as he drove, the power limiter kept slowly creeping down, all the way until he couldn't drive up the hill on his street.
I suggest the OP's car did this same behavior, and Ellen either didn't notice the power restriction with the cruise control on, or didn't realize just how significant it was. In order for the car to slow down, the power limit was probably already down to 30kW.

We don't know if Ellen was looking at the trip screen which may have shown the red "you won't make it at this rate" line.
This was an unfortunate event, but I think this shows it can happen any time to any of us. We can't expect we'll be able to drive at least until the guess-o-meter reads 0. When you see the power restriction start, you'd better have a plan.

 

[Jaff]

I wish new drivers would be educated on the buffer principle. Then again, maybe it's too hard to figure out that you need to watch, not your range, but what you have extra.

If I have a hundred mile trip to make, and give myself 130 miles of range before driving off, ten miles down the road I am able to tell how my range is going.

I should have 90 range and 30 buffer, or 120. If my buffer is down even 3 miles, I need to slow down a couple miles an hour. If my buffer is growing, I can pep it up. When you get to the destination, you want to still have those 30 miles, but IF you have trouble, high winds, detours, it won't be near as scary, because you have your buffer.

This ^^^...you simply can't only look at "the miles required to do the trip" vs." the estimated range" once, at the start of the trip and assume that you will be ok...you need to monitor these factors as the trip progresses, to ensure the desired outcome...lesson to learn, though sorry to hear it was learned the hard way...

 

[Rocky_H]

At low battery levels I have observed a reduction in available POWER (yellow dashed line on the power meter) but no "speed limit".
It makes sense to limit the power from a nearly depleted battery but a speed limit would not be of any use... you could be going downhill in regen mode.

Yes, this is a “which end of the telescope” perspective thing. The car will be limiting by a power level, not by a speed. People’s perception of their car’s performance, though, is almost always by what speed it can go. If it is in an uphill section, as some people had mentioned the end of this route was, then it takes a lot of power to go up that hill. If that power is being stopped by the limiter, then the driver’s perception is going to notice that the speed is being limited.