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@dhrivnak: I once went to an EV event about 90 mi away, a little 110v charging while there, and mostly highway 65mph. I used less than half my range going to the event so I turned up the heat and headed home. Suddenly I ran into an unexpected snow squall -not in the forecast - that lasted about 20 miles. I slowed down to 40mph but wh/mi increased to over 400 driving through heavy slush! Got home OK but couldn't help but start thinking about who I knew in the towns ahead that would let me plug in for an hour!
NigelM
Recovering Member
Tyl
Active Member
70mph travel speed with 20mph headwinds on the nose is really like traveling along at 90mph for energy use. So the minute you know you are in a strong headwind and going to be in it for a while, watch your mileage very carefully! Don't wait to slow down..... DO IT NOW!! unless you have the energy (battery range) to easily make it to your destination or closest charger/supercharger. Yes, that means going 50mph or slower, if not on an interstate! Getting behind a slow moving semi truck works well too, especially because the semi's usually go along a little faster ..55 or 60mph! I have been caught in headwinds many times and really need to slap myself to follow slowdown procedures immediately!! I seem to think the headwinds effect is not really there! What the heck am I thinking?? It IS really there an can put you in a bind in no time at all! Now here is the fun part.... if the winds are sustained tailwinds!!! It seems like you can go forever! ... but that can bite you too!! Sometimes those tailwinds die out suddenly and your energy planning goes out the window!!!!! Good to know! The main thing I wanted to stress is DO NOT WAIT TO SLOW DOWN!!! My experience is Palm Springs CA area along where all the windmills are located. When traveling westbound.
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Roadster or MS: just keep energy indicator arm/needle at or below the first mark. Either car will perform more or less equally, maybe Tesla calibrated it that way. If there is no wind (or a tailwind), the speed will approximate the 'rated mile' rate, i.e. one rated mile per mile travelled (or better). With a headwind you will be going slower of course, but starting out across a 30 mile flat it is good to hold it to the first mark until you've figured out 'which way the wind is blowing'. Then you can add more accelerator or less depending on how lucky you feel. If you set CC you can measure gusting winds by observing the delta of the needle. All this can be resolved by an algorithm I've perfected, available here: <[oops, got carried away!]> :smile:
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I tried this when I first got my S. I had a really hard time getting my pitot in an area without crazy air turbulence. I mounted it out in front of my front spoiler area and the readings I was getting were just crazy and made no sense. I tried to push it out in front pretty far on a carbon fiver rod and it just didn't work.
it was an RC eagle tree data logger that I was messing with - elevations work great. I even bought a little a LCD panel I planned on mounting left of the dash w/ airspeed and elevation...
The power being consumed at a given speed is affected by the road gradient as well as the wind speed. A very modest grade of 1 or 2 % is difficult to notice, but it could have a larger impact than a 10 mph wind. The GPS should have access to the elevation profile for the route, from which the grade can be derived. The smoothness of the road and the tire pressure are also important factors, but the smoothness is not easily sensed, so subtracting all these out to get the wind speed would have considerable error.
I believe a wind speed indicator would be very useful additional sensor to improve range estimation, but we need the range profile first. EVTripplanner has this, so it can be done, but it needs to be in the car.
The wind sensor method I propose would add zero extra drag, the readings should be stable, and it would yield readings on direction as well as magnitude. I would install a strain gauge in the mountings of both side mirrors so that they sense the drag pressure on each side of the car. Driving the car at a range of speeds in zero wind would allow simple calibration. if the readings are equal, there is no side component to the wind vector. If the right mirror pressure is higher, the wind is from the right, and an average of the two readings would indicate the net head wind.
Even if all this range calculation is not available, having a separate wind speed reading would be very useful to warn you of a headwind that could reduce your range below your prediction.
> I believe a wind speed indicator would be very useful [tbleakne]
The best indicator would be the car itself since that is what you are trying to get from point A to point B thru a swirling air mass. Unlike an airplane your car has a direct connection to mother earth so: ground speed (accurate), rate of energy consumption (accurate), temperature (accurate). Until someone comes up with a program to resolve these inputs to a single result, the best you can do is set your Tesla Cruise Control to a speed that uses energy at a rate you can afford at that particular point in your trip. Its a crap shoot but thats what makes it fun.
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The best indicator would be the car itself since that is what you are trying to get from point A to point B thru a swirling air mass. Unlike an airplane your car has a direct connection to mother earth so: ground speed (accurate), rate of energy consumption (accurate), temperature (accurate). Until someone comes up with a program to resolve these inputs to a single result, the best you can do is set your Tesla Cruise Control to a speed that uses energy at a rate you can afford at that particular point in your trip. Its a crap shoot but thats what makes it fun.
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That brings up an interesting idea for a cruise control that maintains a particular Wh/mile (within upper and lower bounds).
Rogallo
Member
In gliding and hang gliding we have Speeds to Fly to maximize glides over the ground to get the farthest distance, developed originally by Dr. Paul MacCready. Would be nice to have a fairly simple chart that would show rough speeds to drive in different wind conditions to maximize range.
