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Model S Range Estimates Based on What Speed?

Anyone care to offer an opinion on what speed the range for the various battery options is based on? I couldn't find anything on the T website about this.

In case you are wondering why I ask, range decreases at an exponential rate with reference to speed. An easy to remember example of this is: if you drive at 50mph you use almost exactly half the power (and therefore fuel) that you do driving at 70mph. I am talking about true 50mph and 70mph here, not what your speedo says as there are notoriously unreliable at higher speeds - and on a level road with no wind.

If you want to test this theory, use a GPS based speedo at least and one with a good signal. Or have a look here... http://www.evconvert.com/tools/evcalc/ ...and you can play with the numbers to your hearts content.

Incidentally, this exponential decrease in range is almost entirely dependent on the frontal area of the vehicle - the area you would get if you took a front (or rear) elevation drawing of the vehicle and measured the total area of the vehicle including wheels and wing mirrors but excluding the space below the vehicle, between the wheels. The formula is... Drag force = 0.5 X density of air X speed squared (the exponential bit) X coefficient of drag (Cd) X frontal area.

One way the Model S minimises the Cd is to have a very smooth belly pan. 99% of vehicles have a very rough one and this induces a good 10% increase in drag ie reduces the miles per gallon performance by 10%.

Regards, MW

yes we all know that speed affects range, so I think it would be nice to be able to limit the power usage
if there is X kWH on the battery and you need to travel Y miles, limit the top speed to Z

the faster batteries can be charged quickly, without causing damage to the cells, the better. In a few years or by the end of the decade, there shouldn't be a reason why driving across country in an EV is any more difficult than doing it in any other vehicle.

I know a good amount of people who do regularly drive more than 300 miles in a single day(especially alot of people who live near new york that drive up to boston for a day, and vice versa), and when you consider that not all cars will be ordered with that 300mile pack, even short trips can become complicated.

For EV's to truly become mass market, they will need to overcome that gap, as long as it exists, it can be used as a reason to NOT buy them. Most people may only drive that distance very infrequently, but at the same time, most people buy insurance beyond what is legally required to use it very infrequently or never.

Since Tesla has shown the drive train technology is mature enough for mass marketing, it looks like its mostly an issue of batteries for those occasional long distance trips.

Whistle;
consider the % of the market that has those 300 mi./day requirements. It's so small you'd have a hard time measuring it accurately. Not a concern for a company opening up the market to the most buyers possible. And later, the battery boys will solve the problem on their own.

I.e., this is not a serious concern for Tesla for the foreseeable (practical) future.

Thats basically what I was getting at, but when those long hauls do come up, potential buyers will feel alot more comfortable when they know they won't have to sit around for a long time to recharge. I imagine it wouldn't be as much of a problem for hte Model S as it doesn't seemed to have really deterred any real number of people based on the pre-order numbers, but with bluestar, that could possibly be a bigger problem. I imagine electric cars will be used more in urban or dense suburban areas as opposed to rural areas based on infrastructure though.

Considering that preorder is now going somewhere close to 4000, and Tesla doesn't even have prototype ready yet, that number is rather high. I expect it to raise *fast* after they get the real Model S drivable prototype ready and production running.

I'm pretty sure the % of people driving over 300 miles regularly and own only one car is quite a bit higher in Europe than in US. Not a niche market. My sisters husband will be doing trip like that every weekend, maybe even more frequently. Though most of the Europe is quite a bit more densely populated than Finland, so maybe my point of view is a bit biased. Then again, owning car here costs a lot more than in US, so single car families are way more common.

Even if 99.9% of annual driving is done less than 300 miles (which I believe is overestimate) that doesn't mean that 99.9% of car owners don't need that range. It only takes 1/3 of the potential drivers doing that trip once a year to get that figure. 33% is not a small number.

I myself tend to rent a car when I am driving for very long distances since I can get one for about $30 a day with unlimited miles and save the wear and tear on my other cars.

Does this even matter? I drive a Roadster daily, and I don't think about the range. It's simply not a factor; I have a "full tank" every morning, and I have rarely used half of it.

For road trips it is more of a factor, but as long as you have a place to stop for lunch and charge up, a 400 mile trip is trivially easy.

Currently I'm keeping my SUV just for winter driving (we get serious snow here, salt, sand, etc., and I want to keep my Roadster pretty). When the Model S arrives I will sell the SUV and go fully electric. If I need to go on a 2000 mile road trip where it's not convenient to charge, I'll just rent an ICE car. It's cheaper and less trouble than having a rarely-used car depreciating in my garage.

Douglas3: You know that the Roadster's largely carbon fibre right? That stuff doesn't rust you know :)

LOL! Of course I know it's carbon fibre body and aluminum frame. Rust isn't the any part of the reason for parking it during the worst of the winter.

They pour gobs of sand on the roads here, which includes nasty little stone nuggets that put holes in your paint when kicked up by the car in front of you. I doubt the paint armor will stop that.

The roads are also covered in salt, which gets all over everything, and it's especially hard on the carpets. (It inevitably gets all over the inside of the car, carried on your boots.)

That salt and sand will end up plastered all over the ledge underneath the door, and will probably get all over your clothes.

Hand washing. At -20 degrees C. No thanks. I'd freeze my butt, and the driveway would turn into a skating rink.

Once the snow banks start building up, you have trouble seeing around corners in an SUV. It'll be much worse in a Roadster.

I've heard that the Roadster is quite good in snow. But we get snowstorms that accumulate significantly higher than the bottom of the Roadster. Trust me, if the snow gets so high the bottom of the car is sitting on it, it's not gonna move. On big snowstorms they do the side streets last, which means the last 1/2 km of my trip home is sometimes on a nice deep unplowed street. That means there's a pretty good chance I won't be able to get it home.

I think that's all the reasons...

I will take it out on nice days during the winter, but I doubt I'll be driving it anything like daily. Like I am now.

"I myself tend to rent a car when I am driving for very long distances since I can get one for about $30 a day with unlimited miles and save the wear and tear on my other cars."

You canæt rent a car at that rate in Europe. In Norway, it'll cost you at least $220/day if you want to put many miles on it, and that's not for a large car like the Model S, more like a Ford Focus 1.6L.

One factor I have not seen addressed is traffic. If I sit in traffic averaging 15 mph for 30% of my 60 mile commute how does that affect my range? Is 300 mile range still 300 miles? I live in New England, traffic around Boston is a very real concern, especially in the winter when temperatures tend to average below freezing. Does anyone know if Tesla has tested their batteries in cold climates?

The slower you go the more range you have. A roadster can get over 300 miles traveling less than 35 mph. Teslas battery packs are temp controlled so no worries there. You will use a little more power in extreme temperatures, but not enough to worry about.

In fact with that speed (15-25mph) Roadster theoretical range is over 400 miles. It is just the optimal speed for maximum range.

I'd say look at blog http://www.teslamotors.com/blog/roadster-efficiency-and-range, but that seems to behave weirdly, almost always the charts that belong in that blog do not show up. There are several of those, Wh/mile / speed, losses / speed, miles / speed at least. Tried to reload it several times and at max I got two of those.

Got it to finally show that range vs speed chart after zillion reloads (but not the other two at the same time), and with 25mph range is a bit less than 400 miles. Optimal range is between 15 and 20 mph.

"One factor I have not seen addressed is traffic. If I sit in traffic averaging 15 mph for 30% of my 60 mile commute how does that affect my range? Is 300 mile range still 300 miles? I live in New England, traffic around Boston is a very real concern, especially in the winter when temperatures tend to average below freezing. Does anyone know if Tesla has tested their batteries in cold climates? "

Theres something about the combination of use and the battery giving off some heat in use and the built in battery temp control that should keep it working fine, I haven't seen any specific cold weather reviews, but to my understanding it works fine in those conditions

Roadster battery is fine even over -20C cold. Just not for near empty left outside for storage at that temperature. Somewhere in older blogs there is a video where they test Roadster winter handling in Sweden. Pretty cool video.

There is actually some optimal temperature where battery cooling/heating system needs least power to keep them at the right temperature and I bet it is pretty close to zero Celsius (which is the freezing point, in case people using Fahrenheit don't know it).

Range = speed X runtime hours

Speed = 5, 10, 20, 35 etc etc……(miles /km)….whatever….

Run time hours = Kwh (battery pack) / Kw (power required)

Kwh (battery pack) = 42Kwh(5000-cells), 65Kwh(8000 cells), 85Kwh(8000 cells)

Kw (power required) = (Air resistance + rolling resistance) X speed / % efficiency

Air resistance = Fair = 1/2 Cd A p v2

Rolling resistance = μ (r+ brake and steering) x GWV x g
_________________________________________________________________
NOTE: the range will vary according to the acceleration also.....

because more the acceleration more (pulse) power is required.
Thus more C-rate from the 18650 cell........so the over-all "Ah"
decreases........

Kw (power required) = (Air resistance + rolling resistance) X speed / % efficiency

Those are main losses, bun ancillary losses are not small either, AC on/off, lights, radio etc. draw enough power that it is significant, but small, fraction of the losses in slow speeds.

You have one excess "speed" in that calculation (both rolling and air resistance formulas already include it).

@ time: my friend i don't have a excess "speed" in the formula..!

because my aero: i have used v square not v cube,

and there is no v in my rolling resistance....

which i later added it...........

The slower you go, the more mileage you get. I'd expect that time spent at 15mph to extend your range. The specifics would be hard to figger. Note also that stop-start traffic is actually good for EV range, since the regen recovers much of your kinetic energy.

Sounds to me like you should see an extra 25-50 miles on that max, just a WAG.

I really appreciate the thoroughness of the posts addressing the re-charge practicality of long distance driving.. However in a truly practical assessment the energy needs of car/driver combo have thus far been incomplete.
Average US highway driving ranges between 60-80 MPH which puts the Tesla S at 3-4.5 hours of driving before requiring a recharge assuming that there will be some loss and nobody wants to leave themselves without a fuel buffer, before re-fueling! Personally as an Italian with healthy metabolism I , similar to the Tesla S, prefer eating every 4-5 hours..

If indeed the recharge can be accomplished in 45 min, assuming you can access 3-phase at a lunch stop, this model of car/driver refuel seems to work quite well. Undoubtedly, battery technology will improve faster human nutrition evolution.

In the healthy driver scenario, slow Mediterranean meal and a short nap, while the Tesla slowly sips on electrons, the Tesla S range is quite perfect. Remember that sleepy drivers cause more accidents than drunk and reckless combined, so re-charging body and car is critical aspect of long range driving.

How common are 400V connections? Is it considered 3-phase? and what will it cost at home, or at a good hotel to recharge per hour on that 400V, or 240V, or 110V connection? Southern California residencial KWHrs are about 13 cents including taxes, until the minumim allowance is exceeded, then rates may double several times.

Ugh. CA is whacked. Here in BC rates are half that, no limits on amount drawn.

Pray for the success of Focus Fusion. Your rates could ultimately drop by a factor of 50 (98% reduction). Unlimited usage.


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