Navigation is a lying liar

From your example, I would say Nav was a "truth-telling liar"...accruing to your benefit.

That is, although -

A. It first told you there would be 32% remaining by the next SpC (demonstrably not true, although it would be instructive to know (1) your Speed Made Good over the distance; (2) headwinds; (3) temperatures - so that's the "liar" portion of it);

BUT

B. It placed you at the next SpC at the charge-optimal 10%. This means it had kept your time at the previous SpC to the very minimum AND it also meant you would be charging at the next SpC at the highest possible speed - minimizing your time there, too.

So all in all, you made out, other than the anxiety level. Does this make sense to you?

Also, you can watch the trip graph and adjust your speed accordingly so you'll arrive with sufficient buffer.

Tesla Nav is OK at very basic stuff like getting you from A to B, exceptionally poor at anything with regards to energy use planning, trip planning, or avoiding traffic. V7.1 was supposed to correct some of these but from my experience (1800 cross country miles with 7.1) does not.

EV Trip Planner is the solution for now until Tesla engineers catch up. It is well done and generally reliable. That a high school kid has outdone Elon is sad but that's that.

AudubonB said:

From your example, I would say Nav was a "truth-telling liar"...accruing to your benefit.

That is, although -

A. It first told you there would be 32% remaining by the next SpC (demonstrably not true, although it would be instructive to know (1) your Speed Made Good over the distance; (2) headwinds; (3) temperatures - so that's the "liar" portion of it);

BUT

B. It placed you at the next SpC at the charge-optimal 10%. This means it had kept your time at the previous SpC to the very minimum AND it also meant you would be charging at the next SpC at the highest possible speed - minimizing your time there, too.

So all in all, you made out, other than the anxiety level. Does this make sense to you?

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Trip planner does need work, but pulling in with 10% is about perfect to optimize time but still leave some safety margin.

Yep.... my Nav and I often disagree. I'm pretty sure it's trying to kill me... it insists it isn't.

Has anyone else had their dash nav and touch screen nav disagree?

Interesting to note that Ben, the evtripplanner guy, lists himself on LinkedIn as an intern at Tesla over the last 6 months - so there is hope!

I've given this subject quite a bit of thought because most of the mileage we do in our Model S is long distance, and quite a bit of that is done in remote areas where our margin for error and charging opportunities is very slim indeed.

The navigation and energy display system gives estimates of the performance of the car based on a specific set of conditions which may or may not exist at the time you are doing your drive.

If the navigation system tells you its going to take you 2 hours to drive 120 miles, and you end up doing it in 90 minutes, did the navigation system lie? No, you drove faster than 60 mph for those 120 miles.

If the system says you have enough energy to get from point A to point B, and you run out short of your destination, did the system lie? Probably not, you most likely used the battery's electricity at a faster rate than what the system calculated you to use.

These systems are predictions, and just like all predictions, they are based on assumptions of certain variables, many of which (temperature, weather, weight, tire pressure, tire type, presence of roof racks, etc) all can substantially affect the outcome of the prediction.

Its the same as just accepting the navigation route without verifying it for yourself. How many stories have people laughed at where a driver turned off a bridge or when off the road because their navigation system told them to "Turn Left Now!" and they blindly obeyed?

Please, people, verify your trip yourself. Please take responsibility for yourself and do your own thinking. Please don't make Tesla plaster warning labels, CYA statements and Terms of Services agreements all over the Model S systems.

nwdiver said:

Yep.... my Nav and I often disagree. I'm pretty sure it's trying to kill me... it insists it isn't.
Has anyone else had their dash nav and touch screen nav disagree?

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Yes, a couple of times. One time was hilarious - the IC was telling to go left and the CID was telling to go right. It was on a T-intersection with roads merging again together after a couple of blocks.

The trip planner is weird in general, but I've found the energy use estimates to be extremely accurate, usually within 1% on long drives. It definitely does not assume 55MPH. I drive at approximately the speed of traffic (typically 70-80MPH on interstates) and the estimated SoC at arrival is bang on. The system definitely not only accounts for higher speeds, but real-world speeds driven by actual drivers, not just official speed limits.

Without knowing more, it's hard to know about the source of your trouble. Perhaps the car is misinformed about the speeds on those roads? Or you drove extremely fast? Cold weather will do this, but I doubt that was a factor.

Suffice to say, it can and usually does work properly. If it's not working for you then you need to look for what might be causing that. The good news is that this may mean you can fix it and get better results the next time.

Mike K said:

... as soon as I continued on my trip the estimated state of charge on arrival dropped significantly both times. From the first supercharger we went from the car estimating itself to have a 32% charge at the next supercharger to 20% in a matter of 10 minutes. We pulled in with 10%.
...
I get that the EPA ratings are based on a certain speed but the navigation doesn't need to be and if it's basing state of charge on a 55mph assumption then it should give you the option of inputing your speed so it can tell you how long you really need to charge to be able to continue on at your desired speed.

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Yes and no. I'd guess your point is that it should allow you to input your planned speed yourself, or at least inform you of the expected speed and with that I agree. BTW, I think it uses Google's data for average speed in those segments in calculating energy usage.

If you are somehow expressing that your speed shouldn't have an effect on your charging time, that's not the way physics works.

Mike K said:

We just took a trip from LA to Phoenix. On the way we made two stops at superchargers. Both times the car told me I had enough charge to move on with my trip despite the fact that it projected me having 10% battery charge when I got to my destination, basically no buffer. That wouldn't be so bad were it not for the fact that as soon as I continued on my trip the estimated state of charge on arrival dropped significantly both times. From the first supercharger we went from the car estimating itself to have a 32% charge at the next supercharger to 20% in a matter of 10 minutes. We pulled in with 10%.

Then we left that supercharger and it said we'd have 20% charge left when we got to our destination. We pulled in with 4 miles.

I get that the EPA ratings are based on a certain speed but the navigation doesn't need to be and if it's basing state of charge on a 55mph assumption then it should give you the option of inputing your speed so it can tell you how long you really need to charge to be able to continue on at your desired speed. I'd rather hang out at the supercharger for another 10 minutes and be able to drive 75mph than rush out and have to drive 55mph to putter into the next station.

In either case had I departed the supercharger when the car told me I had enough charge to continue, I would have ended up dead on the side of the road or completing a large portion of the trip at 55mph in the right lane. No bueno.

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If you have the trip planner on turn it off. It's a disaster. I just do calculations myself on the fly based on my own experience and judgment. That produces much better results than the trip planner.

nwdiver said:

Yep.... my Nav and I often disagree. I'm pretty sure it's trying to kill me... it insists it isn't.

Has anyone else had their dash nav and touch screen nav disagree?

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I've had it disagree with each other, other map apps and my own common sense. Approximately 6 out of 10 times it will circle the destination with a series of left, right or u-turns seemingly lost. I know this is a regional thing since many people find it accurate but for me it's the worst nav I have ever used.

nwdiver said:

Yep.... my Nav and I often disagree. I'm pretty sure it's trying to kill me... it insists it isn't.

Has anyone else had their dash nav and touch screen nav disagree?

Click to expand...

The reason for this is that the touch screen maps are Google maps with up to date data. On the other hand, the "dash" nav maps are over 2 years out of date. They need to be desperately updated soon.

artsci said:

If you have the trip planner on turn it off. It's a disaster. I just do calculations myself on the fly based on my own experience and judgment. That produces much better results than the trip planner.

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I typically input the destination to see if I agree with the selection of Superchargers and to get an estimate of my SoC as well as the overall mileage to the stop. I have the nice google lady silenced as she is... overly enthusiastic about telling me to not exit the highway I'm on.

Most of my life has been "get in and drive" and I've settled back into that after the novelty of "my car has GPS navigation!" wore off.

mrElbe said:

The reason for this is that the touch screen maps are Google maps with up to date data. On the other hand, the "dash" nav maps are over 2 years out of date. They need to be desperately updated soon.

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No, they both are Navigon data. The 17" just overlays the Google Maps with Navigon.

Mike K said:

It might be misinformed but it's the 10 freeway so I doubt that. My speed was 75mph and there was no headwind really. While I can appreciate that 75mph isn't going to yield ideal range, it was the speed limit for the road and it's reasonable to expect someone to be driving between 75 - 85mph on that stretch.

Around town it's generally spot on. I think it just doesn't know what to do with higher speeds.

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It's worked well at higher speeds for me, so it's something more than just the speed.

Do you happen to have the rated range at the times you set off, and the corresponding start and end points for each leg of the trip? That would tell us what sort of efficiency it was projecting, what you actually got, and whether this was a colossal failure of the projection, or a colossal failure of efficiency on the way.

I don't know this for a fact, but having made dozens of long distance trips in two Model S', I think that the navigation/range estimate is based on driving the speed limit, but not faster.

I believe in California the maximum is 70 mph even for rural interstates like I-5 and I-10. There is a huge difference in doing 80 or 85 mph over 70 mph, and this will materially decrease range from the original estimate. Even where the speed limit is 75, doing 85 or more will really cut down your range, regardless of whether that is the "flow" of traffic.

Finally, wind is the most underestimated variable that is very hard to predict, and that alone is worth adding a 10-15% buffer if you're traveling in a remote stretch where making the Supercharger is all or nothing and you want to drive at a faster speed. And unless you're positive you're traveling downwind (like, for example, 99% of the time traveling south on 101 through the Salinas Valley), if there's even a mild breeze, add in a little more.

I also agree with others who posted that EV Trip Planner is a great tool that allows you to estimate based on whatever speed you want to travel.

If you really want to know what's happening and what to expect with the wind, download Windfinder - wind, wave & weather reports, forecasts & statistics worldwide and save it as a favorite on your MS's browser. I learned of this app last year at Tesla Connect and we used it to our advantage driving from Minneapolis to Spokane and back. 30 mile headwinds and 100+ temps at 75-80mph=about 485 wh/mile so we had to slow down. Not fun getting passed by big pick up trucks in S Dakota, but at least Windfinder helped us anticipate temps, wind speed, wind direction and apparent wind.