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300 mile range based on 55mph

300 mile range based on 55mph

I am eagerly awaiting my Performance Model S, but last weekend got me thinking. I drove from Los Angeles to Solvange to play golf(244 miles round trip). I thought wow, I am going to make it on a single charge. I am not sure that is true. On the trip, I never once was below 75 MPH. What is the real range when driving under real conditions? To think you can drive 55 on CA highways is crazy and dangerous.

Jason S | 11 aprile 2012

Assuming you aren't getting the Aero wheels, I'd say the 244 would be very close to the full battery range at 75.

Tesla should have more info in the coming weeks. There has been an app shown on sales floors with range @ mph estimates, but I haven't seen it on the teslamotors.com site yet.

Brant | 11 aprile 2012

The range estimator in the store only goes up to 60mph
Weird, huh?

ddruz | 11 aprile 2012

Engles' great pictures from the Santana Row event show examples of the range estimator going up to 65 if that is helpful:

https://plus.google.com/photos/117433471618932049710/albums/572080445134...

h8young | 11 aprile 2012

Daxz posted this from the TMC forum:

Max Range (miles)
Speed 40kWh 60kWh 85kWh
55mph 160 230 300
60mph 150 213 283
65mph 136 197 260
70mph 128 182 245
75mph 116 169 225
80mph 109 156 213

Link: http://www.teslamotorsclub.com/showthread.php/8070-Suggested-Supercharge...

gjunky | 11 aprile 2012

Aren't all these numbers based on the car being range charged (charged to 100% capacity)?

In most cases, we would have to subtract 20% from the range unless I am mistaken.

Just noticed that the TMC thread link also shows the 80% ranges.

jbunn | 11 aprile 2012

Double you speed, quadruple your wind resistance. Drag racks up very fast.

EdG | 12 aprile 2012

A thought: the Aero wheels suggest about a 5% increase in range. I assume that's at 55 MPH, and only because of reduced drag. So that would be more like (approximate calculation based on 5.00%) 4.33% at 65 MPH, and 3.75% at 75MPH.

My conclusion: if I'm running to the end of my range, I'm going to have to slow down. Specifying the Aero wheels will do something, but not much for my decision points. I'll only get them if I like their looks.

BYT | 12 aprile 2012

Every version I have seen of the aero wheels look horrible to me. I have seen better hubcaps I am afraid... :(

TikiMan | 12 aprile 2012

I wonder how much loss is added on with the A/C or Heat on?

stephen.pace | 12 aprile 2012

@BYT: Have there been any real photos yet of the aero wheels? As far as I understand, all of the photos shown so far including the Design Studio have been Photoshopped as placeholders until the final aero wheels are ready. Don't get me wrong, I still expect them to look worse than the fan wheels, but I don't think we've seen the final result yet.

BYT | 12 aprile 2012

Actually the ones at the Tesla Stores on display look exactly like those I'm afraid.

Volker.Berlin | 13 aprile 2012

A thought: the Aero wheels suggest about a 5% increase in range. I assume that's at 55 MPH, and only because of reduced drag. So that would be more like (approximate calculation based on 5.00%) 4.33% at 65 MPH, and 3.75% at 75MPH. (EdG)

I am pretty sure you've got this one backwards. The aero wheels have no effect on weight or drivetrain or rolling resistance (idealized). They merely affect aerodynamic drag. Aerodynamic drag is the only range determining factor that changes with speed (again, idealized but very close to reality), and as we all know, two-fold speed means four-fold aero drag. Therefore, the effect of an improved Cd value (i.e., "aero wheels") should be greater at higher speeds. Of course, even with those magic wheels, range will decrease at higher speeds -- but the difference between range w/ aero wheels and range w/o aero wheels will grow with speed, not shrink.

EdG | 13 aprile 2012

Good point. Poor thinking on my part. Still, 5% or 7% is so close to the norm that it probably won't overtly affect most ride decisions. Only once in a rare while would it make any difference.

Robert.Boston | 13 aprile 2012

There are 6 J1772 chargers in Solvang, so charging wouldn't be too much of an issue, especially if you're playing the River Course. If you're playing the main course, you should convince the Alisal Ranch owners that good hoteliers should have EV charging for their guests!

Also, are you really sure that your average speed is 75mph? I'll accept that the highway miles are, but if you're taking CA-154 off at Goleta, aren't speeds along there slower? You could even pop over to CA-1 west of Ventura and enjoy a slightly more leisurely drive.

DallasTXModelS | 28 aprile 2012

How is the range determined anyway? Has anyone at Tesla actually driven a fully charge 85kWh battery until it was at the critical recharge level and recorded the actual mileage or is this strictly an unproven estimated mileage based on a math calculation?

Also, is the increased range for the aerodynamic wheels and tires actual or only calculated?

BYT | 29 aprile 2012

@DallasTXModelS, I have seen and have photo's of Model S Vin #000001 and it has over 20k miles on it so I think we can safely say they are well aware of the real world battery limits. The car did NOT however have aerodynamic wheels on it.

Brian H | 29 aprile 2012

Dallas;
Supposedly, the beta "real-world" users were finding the range estimates were conservative; they were doing up to 15% better.

DallasTXModelS | 29 aprile 2012

Brian H;
That's great to hear, considering the unrealistic numbers usually found on ICE window sticker which are usually obtained by professional drivers that coast alot and don't jackrabbit start.

Also, there is the regenerative braking feature that gives back some battery charge during braking. I've always been able to get better than reported mpg due to my driving habits. I very rarely brake though which makes me wonder if I am going to benefit any from the regenerative braking.

I saw in a beta test drive video the driver saying that he doesn't brake very much either because the electric motor slows down the vehicle when letting up on the accelerator pedal. I'm wondering if regenerative braking also happens when the car is slowing without the brake pedal being depressed or does the brake pedal actually have to be depressed to cause the regeneration.

ggr | 29 aprile 2012

In both the roadster and the Model S, the brake pedal is for brakes, and the regeneration happens when you back off the accelerator. It feels like strong engine braking on a manual transmission ICE, except it goes all the way down to nearly stopped. It's wonderful: one foot driving much of the time.

jerry3 | 29 aprile 2012

Regenerative braking is only better than wasting heat the way friction brakes do. It recovers, at best, 50% of the kinetic energy of the vehicle but in most instances it's probably more like 33%. The exact amount depends on the maximum amount regeneration is allowed to give the batteries and the state of charge of the batteries. Not using regeneration and letting the car glide down without regeneration is usually the most efficient because all the kinetic energy--other than tire rolling resistance, wind resistance and bearing losses--is used for forward motion. There is also probably some speed above which it's a wash or negative but for normal urban and suburban driving gliding is much better than regeneration whenever there is a choice.

I can understand why Tesla did put the regeneration on the gas pedal rather than on the brakes: It's far less complex than a system that has regenerative brakes (like the Toyota system). However, in my opinion, the most efficient way is to have no regeneration on the accelerator and all the regeneration on the brakes. That way gliding is automatic rather than requiring foot education to always press at the sweet spot.

Mark E | 29 aprile 2012

@Jerry3:
I can't stand the way that automatics coast - its awful to drive an automatic for that reason. Having driven the roadster around 600km the regen on the throttle is fantastic. You can control the car as well as with a manual transmission, making spirited driving on winding roads a real pleasure.

The Toyota regen on the brake has generated quite a lot of negative response from drivers because you end up with a strange braking response.

With regen on the throttle you can still coast to a stop - you have even greater control than lifting off and applying the brake - it takes about 5 minutes to get used to it.

If the Tesla coasted like an automatic it would totally wreck the driving experience and I would never have been as keen on going EV.

jkirkebo | 30 aprile 2012

Agree. This is why I always drive the Leaf in eco-mode, more regen on the accelerator pedal. Having it on the brake pedal just makes it difficult to get max regen braking with no mechanical braking.

Also the CC in the Leaf won't use more regen than what you get with no pedal pressure at all. Thus, in steep downhills, the CC is not able to hold the speed and I have to feather the brake. The additional regen on the brake pedal is usually enough, but it's very hard to find the point of max regen/no mechanical braking. It is MUCH easier to find the "coast" point on the accelerator.

So in conclusion, I wish the Leaf had all it's regen on the accelerator pedal and none on the brake pedal like Tesla.

Mark E | 30 aprile 2012

@jkirkebo:

That's a major design problem with the leaf CC - if you touch the brake you should cancel the cruise, so you'd have to reset it again at the bottom of the hill. How annoying!

Timo | 30 aprile 2012

@jerry3 It recovers, at best, 50% of the kinetic energy of the vehicle but in most instances it's probably more like 33%.

That's not entirely true. Regen is really efficient, you get more like 70% real recovery for strong regen, maybe even more, as long as rate of deceleration doesn't go too high and speed itself doesn't make huge impact on deceleration rate (aero drag and rolling resistances). There are very few losses on the way from wheels to back in battery, engine=90%, PEM=95%, Battery itself=95%. 0.90*0.95*0.95 = 0.81225 ~= 80%.

Of course if you slow down slower than you would with coasting you are actually using energy to produce slight acceleration so that all is just relative. Regen losses themselves are quite small, you get that approx 80% back no matter which rate you are decelerating, but only from the portion of the kinetic energy that would be otherwise lost on braking. You wont get anything back if you match the coasting speed, and losses are always there.

(same 80% from getting into speed and again 80% from regen makes 0.80*0.80 = 0.64: which means you wont ever get more than approx 60% of the energy you used back into pack even if there were no other losses than just drivetrain losses)

Vawlkus | 30 aprile 2012

I prefer to look at the regen in the accelerator pedal as a safety feature. If I ever loose my brakes, I can still use the regen to slow down. Safety first children :P

Beaker | 30 aprile 2012

+1 for regen on the accelerator pedal.

foto | 30 aprile 2012

So what is the best way to slow down to a halt when the light just turned amber? And is it always better to take roads with more traffic lights vs. ones with less with regenerative braking?

ggr | 30 aprile 2012

By far the best efficiency is to set the cruise control, and neither accelerate nor slow.

BYT | 30 aprile 2012

And to do it by saying in your own voice, "Set CC to 55 Tessy"

jerry3 | 30 aprile 2012

Mark E,

- I can't stand the way that automatics coast - its awful to drive an automatic for that reason. Having driven the roadster around 600km the regen on the throttle is fantastic. You can control the car as well as with a manual transmission, making spirited driving on winding roads a real pleasure.

Yes, I don't like the way an automatic coasts either. Toyota's attempt to simulate one means you have to have an educated foot to get around it. After a lot of practice I can do it pretty consistently, but it would be so much easier if I didn't have to.

As far as the "strange braking behaviour" goes, it's like any other car. You have to get used to each car's idiosyncrasies (Though it was kind of hard to get used to the VW TDI's habit of shorting out the battery every year and requiring a tow). Other than that you can feel the transition from mostly regen to mostly friction braking if you really try hard, there's no other effect.

jerry3 | 30 aprile 2012

Timo,

- That's not entirely true. Regen is really efficient, you get more like 70% real recovery for strong regen,

Tesla's regeneration must be much more efficient than the Prius' regeneration. I've never seen anyone submit numbers higher than 50% on a Prius and 33% is more common.

jerry3 | 30 aprile 2012

bfadewole,

- So what is the best way to slow down to a halt when the light just turned amber?

Depends on where you are in relation to the light. Generally the longer you take to stop the more efficient you are.

- And is it always better to take roads with more traffic lights vs. ones with less with regenerative braking

The most energy is used getting up to speed, so the fewer times you have to stop the better. In some case you can drive so that you hit all or most of the green lights, in other cases you can't.

jerry3 | 30 aprile 2012

ggr,

- By far the best efficiency is to set the cruise control, and neither accelerate nor slow.

I've found that cruise control increases energy use because it keeps the speed within one or two mph rather than letting the speed vary for changing terrain. Even in the Midwest, there is enough of a variance that cruise control hurts efficiency big time.

cerjor | 30 aprile 2012

In the not too distant future we will be talking about miles/kwhr like we do with mpg now. The Tesla says it gets 230 miles from its 60 kwhr battery. That's 3.8 miles/kwhr. The Leaf goes 100 miles from its 24 kwhr battery for 4.2 miles/kwhr. The Honda Fit EV advertises 123 miles with a 20 kwhr battery. That's 6.2 miles/kwhr. We really don't know the actual numbers but you get the idea.

Brian H | 30 aprile 2012

That Honda # sounds like Imperial Pucky. 4 of those batteries to get 80kwh would extrapolate to about 500 miles.

I doubt they even get that # of km., much less mi.

jerry3 | 1 maggio 2012

The speeds are different. The Honda might be using the JIS 10 mph (15 km/h) cycle. (Yeah, I know 10 mph is really 16 km/h)

Timo | 2 maggio 2012

@jerry3, it's relative. If you regen only slightly then the other losses (aero, rolling, bearings etc.) take big portion of the slowdown energy, and you end up having only small gain. Regen itself is efficient in Prius too (though less efficient than Tesla EV due to more parts on the way to battery). As I said you only get something back from that portion of energy that would be otherwise lost in braking so in order to see the real regen efficiency you would need to use max regen, but that is not the most efficient way to drive.

jerry3 | 2 maggio 2012

Timo,

- As I said you only get something back from that portion of energy that would be otherwise lost in braking so in order to see the real regen efficiency you would need to use max regen, but that is not the most efficient way to drive.

Agreed, that's certainly correct. Regeneration is better than throwing it all away as heat. My question was where the 95% efficiency came from. The MGs themselves are about that efficient (or maybe even better) but the amount of kinetic energy recaptured is far less, which was the 33% to 50% I was referring to.

perbakken | 2 maggio 2012

Please also take a look at top of page 42 in this document: http://files.shareholder.com/downloads/ABEA-4CW8X0/1779195579x0xS1193125...

Of course this will not influence on these "theoretical" drive ranges, but if this new EPA-standard is to be used, maybe Tesla (and all other EV-makers) will have to reduce the official drive range with maybe as much as 30%.

Timo | 3 maggio 2012

@jerry3, its a chain for losses. Engine turned to generator is nearly as efficient as other way around, same about PEM and same about batteries, but that's where the chain ends, it's a very short one. You get around 80% total efficiency (not 95%), because all of those three parts are over 90% efficient. Even with just 90% each that is 0.9*0.9*0.9=0.729, which makes that 70%, not 50% and definitely not 33%. Either Prius regen has quite a lot more losses or that figure you have has some other losses than just drivetrain counted as regen losses.

IIRC Tesla regen max is around 50kW, at around 60mph it requires about 15-20kW to just keep going and drivetrain losses are not very big part of that, so other losses are not insignificant factor if you count those in. If we assume 15kW for ancillary, aero and rolling then that's around 1/3 of kinetic lost to other losses before we even get to actual regen losses. That might explain why your figure is so much lower than mine.

OTOH it also means that using regen vs not using regen is not that bad, both have those "other losses" always on (otherwise your would never even slow down by just gliding).

MandL | 3 maggio 2012

Honda Fit range note:
[1] 123 city/95 highway mile range (unadjusted); 76 combined mile range (adjusted). Preliminary estimates determined by Honda using EPA methods. Your range will vary. For additional information about EPA test methods, visit http://www.fueleconomy.gov/feg/label/learn-more-electric-label.shtml.

So 3.8 m/kwh is probably the number to compare. Which is surprising since it's about half the car a Model S is.

jerry3 | 3 maggio 2012

Timo,

The 95% was just for the MG, not for any other part of the drivetrain.

I understand about the multiplication--no problem with that.

The 33% and 50% is arrived at by calculating the kinetic energy--and as I recall it was done from 60 mph by group members that have a lot more instrumentation on their cars than I do--and the amount of power going into the battery from a fully regenerative stop, and then using those to numbers to come up with an energy recapture number. Note that the friction brakes are always on when braking--even if it's just a small amount like 1% or 2% of the total braking force. (At least that's what the graph in the NCF manual shows). So the real recapture amount is going to be less than just what the drivetrain calculation indicates.

Timo | 7 maggio 2012

For Model S and Roadster that is different because they do not engage brakes at all when doing regen (unless you press the brakes).

Amount of kinetic energy is very easy, it is just combination of speed and mass. If they measured how much energy was going to battery without separating which part of the car is actually creating the losses, then they counted those two which are on on gliding too (rolling and air), and figure is a bit twisted. To get that 30-50% is quite easy then, depending of how strong the regen is the rolling and air drag can produce something like 1/3 deceleration on top of that, then that remaining 66% gets multiplied few times with different parts of drivetrain losses. Using that 0.66*0.9*0.9*0.9=0.48 ~50%. If the regen is weak then relative energy gain is even weaker.

Point is that using that kind of calculation you don't get the relative efficiency compared to gliding and I think that was the question to answer here. Regen efficiency is not bad, it just isn't quite as good as just gliding.

jerry3 | 7 maggio 2012

- Regen efficiency is not bad, it just isn't quite as good as just gliding.

Agreed. Although I think in the Prius' case there needs to be one or two additional multiplications based on the amount of charge that can take place at any one time. I can see how the Tesla regen is more efficient than that of the Prius.

Here are a few actual measurements that W. Brown supplied for the 2004 model:

WB> All of the following records are data captures that occurred from 50
WB> MPH to 10 MPH. Each record is the result of the average from 3
WB> separate runs:
WB>
WB> Mode.........Amps.......Seconds........Cumulative w/h
WB> Braking.......90...........9................54.03
WB> Braking.......70..........15................64.38
WB> Braking.......60..........19................71.01
WB> D.............18..........51................59.50
WB> B.............26..........30................48.35

Volker.Berlin | 31 maggio 2012

Volvo's "road train" (or a similar concept) could provide up to 20% range increase in long distance/high speed driving:
http://green.autoblog.com/2012/05/29/volvos-sartre-road-trains-autonomou...

EdG | 31 maggio 2012

Note that Volvo's cars are all mimicking the first vehicle, and not having each car tracking the one in front of it. This is a critical difference between the "road train" and ACC (as I pointed out on April 20 at http://www.teslamotors.com/forum/forums/cruise-control?page=1 ). If each car could was programmed to follow only the one directly in front of it, the experiment would have failed well before the first few kilometers.

Brian H | 31 maggio 2012

Yes, and what an interesting demonstration of positive feedback chaos it would be! >:)

Timo | 31 maggio 2012

@EdG, not necessarily. Computers can react couple of million times faster than humans (literally) so there is practically no delay caused by reactions unlike with humans. You would need to get reliable info from car in front of you to make it work, and that's where ACC usually fails. Interpreting sensor data is the crucial factor in this. You could do a "road train" by simple LIDAR and prism system (or similar accurate distance sensor) in cars.

There are already completely robotic cars that can navigate in traffic in real world conditions, so "road train" is not far ahead.

Brian H | 31 maggio 2012

Timo;
the lags are in engine response. At the time your car sees the one ahead moving, it has to spin up the engine/motor, and then the actual accel time is on top of that.

It's like a Slinky, waves upon waves.

Leofingal | 31 maggio 2012

Sounds like bad servo tuning to me. These issues should be easily correctable through a well written PID loop.

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