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

[bonnie]

Roadster perspective (but I've had the same experience on a Model S loaner): While Rated range and Ideal range rarely ever match (heavy foot at times, a/c on, etc), when I need to get every last mile, it's possible to actually exceed the Ideal range.

This last weekend I headed to Monterey - my expected spot to charge my Roaster (Fremont factory) was unavailable, due to a power outage. Coming home with a couple of detours planned along the way, I had issues with charge rate due to the excessive outside temps, so just said whatever and stopped charging. In both cases, with judicious driving (staying at 55 and yes, a/c off most of the time) I was able to exceed the Ideal miles without a problem. (Should note that on both legs of that trip, I had backup stops planned if I started cutting it a little too close. Always have a backup stop in mind.)

Not fun. But it is possible. Those numbers are not fantasy.

 

[mknox]

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.

Yeah, but the more I think about it, the more I like the idea of the display going into some sort of generic "Low" display when the battery gets to some nearly empty state. ICE cars do this with their range estimators. We all know the Rated numbers aren't always realistic even at higher values. Why would we expect any difference when it starts approaching zero?

 

[Cyclone]

Yeah, but the more I think about it, the more I like the idea of the display going into some sort of generic "Low" display when the battery gets to some nearly empty state. ICE cars do this with their range estimators. We all know the Rated numbers aren't always realistic even at higher values. Why would we expect any difference when it starts approaching zero?

What I would really like (maybe in v7?) is for the Projected Range from the Trip app to make it as an option on the Odo in addition to Rated, Ideal, and %. Perhaps something based over the last 30 miles so this canbe calculated without a destination programmed into the Nav preferably; but at least make it an option that when a destination is active in the Nav, this can "override" the rated range.

I suspect that some are reading that range estimation and (sub)consciously thinking it is based on their driving, rather than a specific set of conditions.

 

[mspohr]

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.

In my ICE car, I start to get "range anxiety" when the needle goes near "E" and stop for gas immediately when the light comes on even though I know that there are a few gallons left in the tank which could take me 20-40 miles. I do the same in my Tesla. I don't go below 40 miles unless I have a charging solution close.
The OP doesn't say exactly how many miles were on the estimated range indicator but I bet it was less than 10. Would you drive your ICE car with less than 1/4 gallon of fuel in the tank?
(My lowest was 7 miles coming home in a snow storm but I had three charging options on the way close to home that I could have used if needed. Just turned off the heat, put on coats and drove slowly.)

 

[TexasEV]

What I would really like (maybe in v7?) is for the Projected Range from the Trip app to make it as an option on the Odo in addition to Rated, Ideal, and %. Perhaps something based over the last 30 miles so this canbe calculated without a destination programmed into the Nav preferably; but at least make it an option that when a destination is active in the Nav, this can "override" the rated range.

I suspect that some are reading that range estimation and (sub)consciously thinking it is based on their driving, rather than a specific set of conditions.

One of the early firmware version had that option then it was dropped.

 

[jerry33]

Yeah, but the more I think about it, the more I like the idea of the display going into some sort of generic "Low" display when the battery gets to some nearly empty state. ICE cars do this with their range estimators. We all know the Rated numbers aren't always realistic even at higher values. Why would we expect any difference when it starts approaching zero?

Right.

1. Even if there was a reserve (and I don't believe there ever was), you should act as if there wasn't one.

2. When getting close to 0 pay attention to the energy screen. If the projected range is lower than the rated range, charge well before it becomes critical.

3. Ensure you have a 20% reserve (more if the weather isn't great) and have an alternate charging stop--even if it's a slow charge--in case it's needed. It only takes a wrong turn or an unexpected headwind to start eating range. One of the factors contributing to the sinking of the Bismark was that they didn't fill the tank when they had the opportunity. (It was at 80% and so they skipped the top-up). This limited their route choices. Had they topped up, they could have sailed further into the Atlantic and become untraceable. They made a few other blunders as well, such as breaking radio silence, but the extra fuel might have saved them.

 

[MikeC]

Why was the car limited to 40 mph at 10%, though? Or at any SoC, for that matter.

That is definitely not normal and should be addressed by the service center.

 

[jerry33]

Why was the car limited to 40 mph at 10%, though? Or at any SoC, for that matter.

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).

 

[Max*]

Why was the car limited to 40 mph at 10%, though? Or at any SoC, for that matter.

That is definitely not normal and should be addressed by the service center.

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)

 

[wk057]

With 2 rated miles remaining I was still able to do 75 MPH on the interstate without issue.

 

[Neo]

When EPA certifies the range, they do it for the window sticker. To sell a car in the US, the manufacturer needs to certify the range and show that in the window sticker and any sales advertisement. (side note: Tesla was fined for selling the Roadster without an EPA certified range.) However EPA doesn't care what the display inside the car shows. When EPA tests are performed, they do the 5 cycle test. Two of those are 31 minutes each. The other 3 are around 10 minutes each. The entire test is about 1h 30 minutes. They measure consumption and range and then extrapolate to whatever capacity is available to the user. For the 85 kWh models, that's 81.1 kWh. That includes the range you can drive below 0 rated miles because technically that's available to the user.

-17.....0........................................248

In other words, the 265 EPA score is from 100% charge to when the car stops moving. It would be more accurate if the car displayed 248 rated miles instead 265. Why doesn't Tesla do that? I think because other car manufacturers don't do it either. It would be a disadvantage to Tesla if they use a more accurate in-car display. Another reason is (this is pure speculation) because the 17 miles below zero is used up over time to compensate for degradation. In the past the dashboard showed 0,-1,-2,-3 etc when you go below zero. Tesla changed that. Also some cars have much less range below zero. Both of these suggest the reserve might be used for degradation.

 

[islandbayy]

A 600+ elevation gain is significant, particularly over a long distance.
The speed was killer here I bet. When you see that range vs distance mismatch you have to start slowing down. What did the Trip meter say while she was driving? I think this is a "ran it out of juice" situation too.
What was the temperature outside and what were the climate settings?

To me, this sounds like it was avoidable if changes had been made 20-30 miles before it became critical.

That all said, I wasn't there. If it car truly said there was range left in the pack, then it's hard to fault her. But having run a battery dry in my car, it tends to give you more than ample warning.

While I agree the elevation gain is significant, I just did this same drive 3 weeks ago on road trip, and averaged 280w/mile with AC on full blast and it roasting and humid out. Speed was set on the cruse at 80mph, and I arrived with plenty of range left.

 

[kennybobby]

The holy grail of electric cars, both diy and oem--an accurate 'fuel' gauge...


On the topic question:

The pack is fine if they said it was okay. They can see the logs which have the voltage of each of the 96 'Cells'. If one of the 'Cells' was low with respect to the rest that would indicate a defect.

For example the Canion app for the Miev shows a lower voltage for cell #10 of the 88 total. This pack was subsequently replaced under warranty.

 

[gavine]

"I'm running low on battery (or gas)....I better hurry to get to a charger (gas station). Time to speed-up." In all seriousness though, it's human nature to want to speed-up when you are in those situations. It's very difficult (mentally) to slow down when you're in a "hurry" to get charged (gas).

 

[scaesare]

I agree on several fronts with previous comments:

• You should not count on range below 0 (even if it was available for some folks previous, it may have been due to algorithm/calibration issues, and or firmware changes may have changed the landscape)
• As much as we'd like it to be, usable power capacity estimation of a battery at any instant isn't an exact science. The presentation of range down to the exact mile may make it seem so, but it ain't (nor is gasoline tank level either...)
• If there was indeed a >0 amount of range remaining when the car shut down, I'd like to see that remedied. However, I'd avoid trying to drive it "down to the wire" regardless.
• The state of EV's is that environmental factors still effect range more than we are used to with ICE vehicles (or more than we cared about anyway). Thus paying attention to speed, elevation, wind, etc... makes enough of a difference that it pays to educate yourself about them.

An additional note about that last: folks have advised slowing down. This is more significant than many people realize. Losses due to wind resistance go up with the square of speed. Thus driving 80 rather than 60 incurs ~45% more drag. Air drag is the single largest contributor to energy consumption on flat roads.

Slowing down early when you realize you might be strained for range helps.

 

[UberEV1]

If we know, or at least if the experts tell us, that running the battery to Zero accelerates degradation of the cells, why would we want to do that, at least very often? Yes, we paid for it and the car should give us everything promised down to the last mile. But this sounds like Bad x 2 . . . running the risk of being stranded + potentially reducing future battery capacity. We are pioneers in a new era, so this is all part of the learning curve.

 

[roblab]

I agree on several fronts with previous comments:

Slowing down early when you realize you might be strained for range helps.

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.

 

[FlasherZ]

We're dealing with several generations of understanding that there are "2 gallons below E". It's going to take a while to change that behavior.

I once owned a bucket truck with a defective gas tank sender. When the needle finally dropped away from "Full" you had about 5-7 miles to make it to a gas station. Perhaps anyone who runs the car out of range thinking there's a buffer should be sentenced to drive that for a while.

 

[AB4EJ]

FWIW, I recall a very similar thread in the LEAF forum, about the inaccuracies in the range estimate (which they call the "guess-o-meter"), especially when the battery is low. So this is by no means a Tesla problem; rather it is about something that is inherently difficult (if not impossible) to do, which is to know how much range a vehicle really has remaining, given all the variables (plus some things you can't measure that happen internally in the individual battery cells). Each car is going to have its own "personality" due to variances in battery condition and aging, how it has been used, etc. The advice about allowing plenty of reserve and also knowing the locations of "emergency" charging spots along the way is the best way I have seen on how to avoid getting stuck.

 

[apacheguy]

For example the Canion app for the Miev shows a lower voltage for cell #10 of the 88 total. This pack was subsequently replaced under warranty.


View attachment 91040

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