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I GOT IT DOWN TO 1 MILE LEFT....!!

I WAS DRIVING BACK FROM VEGAS TODAY AND HAD ONLY 1 MILE LEFT, AS I REACHED THE BARSTOW SUPERCHARGE STATION.. IT WASN'T INTENTIONAL, BUT THERE WERE SOME INCREDIBLE HIGH WINDS THAT REALLY DRAGGED THE BATTERY DOWN. I HAVE A P85 AND GLAD I DID OR I WOULD HAVE BEEN STUCK IN THE 15 FREEWAY..THEY ARE BUILDING 2 NEW STATIONS IN BARSTOW FOR A TOTAL OF 4 THERE NOW... MY QUESTION IS: HAS ANYBODY HEARD OR KNOW OF, ANYONE GOING PAST ZERO, AND IS THERE A RESERVE CHARGE, OR ANY KIND OF WARNING FROM THE CAR?? THE CAR DIDN'T WARN ME ABOUT ANYTHING WITH ONLY THE 1 MILE LEFT, I WAS KIND OF CONCERNED AND WAS HOPING FOR SOME KIND OF WARNING. I WOULD HOPE THE CAR HAS AT LEAST 10 OR MORE MILES LEFT IN IT WHEN IT HIT ZERO, AND THAT SOME KIND OF WARNING WOULD HAPPEN, BECAUSE RUNNING OUT IN THE MIDDLE OF THE FREEWAY WOULD NOT BE A LOT OF FUN.

YES THERE IS A RESERVE, AS BRODER PROVED!! I THINK HE DROVE SOME 15 OR 20 MILES PAST THE 0 MILES LEFT. I RECALL MUSK MENTIONED THIS IN THE BLOG POST ON THAT REVIEW.

Now that the excitement is over, can we stop yelling?

yes i have and "0" mean zero for me and the car turns off. It took 4 hours with 110 outlet to get it to move again

that is not true it would not go more than 1 mile for me after zero.

Good to know about the headwinds. Creeping in to Barstow on electronic fumes - one more reason to get additional charging stations in the desert between LV and Barstool.

Yes, there is some kind of warning. In the middle of the speedometer is a number in large type. It represents approximately how many miles you have left. ;)

In my experience the 85 has about a 10 mi reserve. I think the easiest way to gauge how much you really have is to watch the dotted orange line on the instrument cluster... it slowly moves down as the battery depletes, limiting your acceleration/power consumption.

I think as long as you are driving the car will not stop when you approach/pass zero. But, if you get out of the car or have your foot off the brake long enough for it to fall asleep when it is at or past zero, it will not restart again until it has been charged (not sure how much). Also, it will not even start charging (seems completely dead) until the battery is at the right temp. My guess is that it can't regulate the temp on it's own cause it doesn't have enough power.

BTW, don't test this out as it is not at all good for the battery. I was lucky.

Learned all this driving back to San Diego from the Factory :/, I underestimated the effect of terrain and temperature and didn't charge as much as I should have at the supercharger (i.e., pulled a Broder!... except I can admit MY mistakes).

also, if you are on the freeway, I assume the car will decelerate slowly in accordance with the dotted orange line mentioned above (giving you ample "notification" that you need to get off the freeway).

Did you maintain speed during the last 10/100 miles? If so, you were asking for it.

Nope, I reduced speed to 10 under the I-5 speed limit. But I WAS asking for it though, since I could have stopped at multiple public charging stations... it was 4 am, so I guess I didn't care. It was an interesting experience though.

I should also mention it has to be 10+, because I made it to my garage without the dotted line limiting me past normal driving acceleration. I only found out about the non-charging due to temp after I got out of the car and it wouldn't charge until the next day when it was warmer.

My green rated-mile bar would turn red when it goes down to about 30.

The effects of headwinds can be very large.

Here is a bit of physics....
Assume that one drives fast enough on a level road so that wind resistance is the dominant component of all resistive forces. This is true for typical highway speeds in excess of say 65 mph.

The force created by wind resistance is given by

F = 1/2 rho A Cd V*V

where rho is the air density , A the frontal cross section of the car, Cd is the coefficient of drag (around 0.24 for the MS, I think) and V is the velocity of the car in still air.

The power P(V) consumed by the car while driving at velocity V is therefore

P(V) = F * V = 1/2 rho A Cd V*V*V (i.e. proportional to the cube of the speed V^3)

Now let's assume a headwind component W, so the car sees an effective speed of V+W instead of V.
Let us further assume that W << V (not necessarily true!) then we can expand this as follows

(V+W)^3 = V^3 (1 + W/V)^3 = V^3(1+3 W/V + higher order terms)

therefore P(V+W) = P(V)* (1 + 3 W/V + ... )
and the energy E expended to drive a fixed distance against the wind W goes up by the same factor 1 + 3 W/V +... since the velocity over the ground is still V.

In other words, if the headwind component were just 30% of the traveling speed (assuming typical highway speeds on flat roads), THE RANGE IS ABOUT CUT IN HALF if the driver continues to drive the same indicated speed as if there were no headwind.
Slowing down greatly helps in this scenario.

Every year several GA planes crash because the pilots underestimated the impact of headwinds and run out of fuel.

@vinnimo - Don't depleted batteries regain some of their energy if they are allowed to rest? Perhaps that is why you were able to charge the following day. I doubt that your battery could have been cold when you first returned from your trip.

Solution to headwinds - get behind a semi trailer, leave a 2 second buffer for safety, crank up the music and cruise.

@Tam +1

@DouglasR

Not sure if they regain energy, that could be why. Outside temp was around 35 F when I pulled in, but I imagine you are right in thinking it would have already been warm enough from the drive.

@dbfish

at least 2 sec buffer is a must... gotta always look out for those pesky rocks and random projectiles from trucks too.

@steadicamp

Just curious what was your charge leaving vegas?
Could you guesstimate the head winds mph?
Lastly, how fast were you going?

I havent made the trip to vegas yet so i'm preping.

@winfriedwilcke Great nums, thanks.

In the case of headwinds on an airplane's range, it is not an exponential effect, but simply arithmetic. A headwind automatically decreases the plane's forward velocity (with respect to the ground). A 20 mph headwind, on a one-hour flight, would decrease the ground range by just 20 miles - enough to crash, perhaps, but a linear effect.

As you have shown, the loss would be far more for the Tesla at 65 mph.

So why not have an air speed indicator? That way if you are driving 80 with a 10 mph headwind, you'd see 90, and you'd understand where your power is going.

OTOH, if you are going 80 with a 10 MPH tailwind, you'd see 70, and you'd be a happy camper.

I am not sure how many drivers are willing to adjust their speed as a function of wind. I do it fairly regularly if wind is strong.

R3dStang66

I made the trip back from Vegas as well on Monday. Did a max charge before leaving the Venetian. Arrive at SC in Barstow with around 38 miles of range. I used 400 w/mi. Same distance to Vegas only used 338w/mi. Could not guess wind speed but they were howling big time. I also did not push my speed. Probably average 65 MPH since traffic was moving a little slow due to the winds and sand blowing.

@steadicamp
It was nice meeting you at he SC,
I am glad to hear you made it home safely.

I did find out it is the person who plugs in first that gets the larger charging rate.
After you left i was still getting only 70mph charge. I had to unplug and replug then it moved up to 170mph.

C

Some of you guys have bigger kahonas then I ever hope to have... how do you sit?

I went 11 miles with my P85's gauge on 0 while looking for a charging station. I found the station but discovered it hadn't been put online yet. Long night but at no point did I every run out completely out of power.

Still...I would recommend you at least start 'thinking' about your next charge when you drop below 40 or 50 miles of range. Just as you might with an ICE engine when you get down to an eighth of a tank of fuel.

I vote for a wind indicator. I made the following trip with no thoughts of windspeed and looked them up after this event. On April 11 I drove from Berkeley, CA to the Harris Ranch Supercharger. I left with 270 miles on the car and arrived with 68 remaining. Actual distance 185. On April 16 I charged up to 260 miles for the 185 miles drive home. I hit 0 miles about 3 miles from my house. Thankfully the last 2.5 miles were all downhill. I generally drive 80 on the 5 but coming back, as I watched the actual miles approach the predicted miles I modified my speed to the limit. Going down There was a considerable tail wind, gusting to 23mph. Coming back head winds were gusting to 28mph. Obviously elevation is also a factor here as well. Is the on board computer sophisticated enough to handle the wind/elevation calculation. It seems there needs to be this consideration.

I wonder for time like this and there is no where to charge and all you have is a portable generator would it work for extra few miles? I know some of these portable generator can stay on for 4.5 hours. I think 110v that would give you 30 miles.

Heres my trip planing so that I don't end up Brodering. Let's say I have a 210 mile trip planned. I do a standard charge to 76500watts (90% of 85kw) divided by 210 miles I get 364wh per mile. As a buffer I want a 5% cushion, so that comes out to 346wh per mile. When I hit the road I watch my wh per mile and every 30 miles or so I adjust my driving to stay below 346wh per mile. This should compensate for headwinds, elevation changes and climate control usage. Of course if there is a significant elevation gain near the end of the trip one would need to plan for that.

This should be more useful/accurate than an airspeed indicator (I have one in my truck).

Anyone see any flaws in this plan?

My average over the 1600 miles I have on my P85 so far is 335whm.

@Pricee2

+1

I was going to say that also.

I think that in addition to watching speed, we will start to watch the whm as our usual mode of driving.

If you start now, you will get an idea of what to expect for each driving situation (condition).

Glad we are all looking at trip management.
We just took a small trip from Menlo Park to Rancho Murieta, about 135 miles or so. We had to include some 28 miles jaunts from Pine Grove to Rancho each day.
So on the way up, we stopped for dinner at Folsom and SC so we started again at 240 mile range. Then after landing in Pine Grove, hooked up to what was available, 110V slow charge of about 3mph. We did this every time we got to our "home base" This sort of covered our trips back and forth to Rancho.
Then each time we got to the venue, I asked as I arrived where I could charge my electric car. No one had any idea and was sure there was no such facility. So I changed my question to is there a 110V outlet I could use. I was immediately directed to an available 110V outlet. Plugged in and started to get my 3 miles per hour charge.
So changing the question got results.

One small charge for my MS, one giant leap to be able to drive home with no stops needed and 40 miles to spare on arrival.

Ask for 110 outlet vs electric car charger. Slow, but often will get you home.

And carry a 110V extension- no telling where the outlet will be.
We have even run extension cords from motel windows, which works if the manager agrees not to look for the extension "hazard".

Hope this helps
Any other "tricks" discovered are most welcome.

Great discussion of working with so many variables driving cross country. I've drafted on the trucks and prefer private buses because they cruise faster. Reducing speed is always an option. But I would like to share an option I've only heard reference to by those crazy enough to drive beyond the limits of Superchargers: RV park 50 amp RV hookups. Just got off the phone with the operator of Clark's Mobile Home Park in Baker, 65 miles east of Barstow. They said they would be willing to charge a reasonable fee, I suggested $5 for an hour charge.

I'm planning a road trip from Long Beach, CA to Glacier Nat'l Park in the Fall. 1500 miles the first 600 supported by Superchargers. Been contacting the RV Parks along the route to see what the charge would be for 4-6 hours or an overnight stay. Some are reasonable (11-20 cents/Kw) others want to charge the full day RV hookup ($25-40). It would be great to see a network of cooperative and reasonable park operators familiar with our needs.


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