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One Mile Per Second

Just placed my MS reservation - for a P85 because of the addicting acceleration and constant torque.

Now I happen to find the latest Edmund's long term test post, which says that their car loses 1 mile of range per each second of hard acceleration. Yikes.

http://www.edmunds.com/tesla/model-s/2013/long-term-road-test/2013-tesla...

For those that have the P85, how careful do you really need to be with acceleration, in daily driving around the city/suburbs, in order to maintain reasonable range?

You will get tired of acceleration before you run out of range. In the city I can push it up to about 400 - 450 W/m... that is at least 3 hours driving. If you want to spend a weekend on a closed track then you better bring your battery charger.

I go to work 27 miles each way. I drive with the flow of traffic (60-80 mph) in CA and accelerate at will like a "regular" car, often in the fast lane. Car sits at work all day, unplugged. Car typically goes from 239-242 to 172-179 rated miles at the end of the day. No range anxiety here. I also got the P for the added acceleration and torque.

As someone has pointed out in the Edmunds comments if you drive a Ferrari in a similar way then you burn 1.7mpg and end up with a total range of 39 miles. This is not a problem even vaguely isolated to electric vehicles.

In fact, the Tesla is MUCH more efficient during hard acceleration than an ICE. When you punch the ICE, the engine becomes significantly less efficient and NONE of the energy is ever recovered. Basic physics says that, neglecting energy that is recovered later, if you accelerate twice as fast then it takes about 4x the total energy to get to a given speed. Even if efficiency (i.e. torque out vs. kW in) goes down, it still isn't really that big of a penalty. The 5 miles per second is bogus math - I'm wondering if they're using the instantaneous remaining range in the Energy App...that shows how many miles are left if you keep driving just like you are at that moment.

I get about 12 MPG in my M3 sedan. If I floor it ill probably go 50 miles per refuel. I only get 200 miles per 15 gallon tank now!!

Thanks guys, for the real word info and proper perspective.

In my non-performance model I can hit max speed in 25.8 seconds, so you won't be losing 1 mile per second for long! ;-)

@cliff - not that it matters to the discussion, but basic physics says that it takes the same amount of energy to go between two speeds, regardless of the acceleration rates. Not true in real life due to nonlinear effects present in mechanical and electromechanical systems.

Edmunds statement is hot air for the reasons already discussed.

It is not unusual for a genuinely disruptive technology to provoke those affected to claim smoking guns where none are to be found.

When riding a materially inferior horse, the only shot is to spark FUD about the newcomer that is kicking your a**.

By any measure, the energy cost of drag-race driving in a Model S is far better than any gas counterpart.

" their car loses 1 mile of range per each second of hard acceleration. Yikes."

Yikes? why? The only CEO with a reality distortion field is not anymore amongst us and Elon doesn't seem to have such a thing.

Simple newtonian physics say that accelerating a 2100 kg car from 0 to 30 m/s takes 0.5 * 2100 * 30^2 = 945 kJ = 262 Wh. If you include some losses in the drive train and energy lost in rolling/air resistance, then there is nothing 'Yikes' about it, just inevitable real world physics.

Oops, shame on me.

I made a huge error there. Acceleration from 0-30 m/s is not done in 1 s, but rather 5 s and according to should lose 5 miles of range. Hmmm, further research needed, or just sensationalism from Edmunds?

So 262Wh / 4s = 65.5Wh / second. Assuming 265 miles with 85kWh you get 320Wh / mile. Not even close to one mile / second...unless you burn rubber without moving much.

Electric motors generally draw 500% - 600% of normal running current when starting. This is due to the magnetizing flux required to start any motor. Under full acceleration, Model S like any motor will draw a large starting current. Inrush current can be limited in any motor with a variable frequency drive. If you start a motor slowly using a lower AC frequency you limit current inrush. Model S has a VFD. When you floor it you are applying full frequency to the motor. It will draw full starting current. If you start out feathering the accelerator you will apply a lower AC frequency to the motor and magnetizing flux will be lower. The loss is due to motor loss and is reflected in heat generated in the motor.

Have fun, but keep cool!

KRS, probably most energy is lost in the battery.

Very good 18650 cells have an internal resistance of 100 mΩ. At max power, the cells have to deliver something like 3.5C. For a 2.9 Ah cell, that is about 10 A. 10 A * 0.1 Ω = 1 V. If you lose 1 V from the 3.6 V nominal, that is more than a quarter lost in heat.

Or, seen from the other side, the battery has to deliver 33% more power (internally) than what comes out at the terminals. Couple that to further losses in the motor and electronics, and no wonder you lose so much range on full acceleration.

You can thank those thousands of little cells in your batteries! They are working very hard for you.

I average 393 Wh/mi and I flog it. So the rated range is 10-20% off just plug it in at night and forget about all this noise. You never notice the difference and can drive as hard as you want without guilt and for much less (see other posts about variance in how much less but in Texas it's 1/3-1/4 the $ of gas for my M5). Who cares if its green:) Ok I like my green car literally green...

Timo;

The 1 mps referred to range loss while goosing it.

As tempting as it may be, you won't be driving around with your Model S constantly floored. You'll be fine.

Edmunds has been fair in their reporting otherwise. I suspect this is just a case of the rated range dropping precipitously due to the algorithm assuming you will keep it floored, or that your average watt hour per mile will stay high. And if not, as others have said, so what? My previous car I floored about three times when I first got it but the gas consumption was so painful that I stopped!

@GotAmped - even more important in real world environments is aero drag and rolling resistance. In a vacuum without gravitational influences, it is correct that energy consumed under different acceleration is equal between speeds. On the road, rolling resistance and aero drag means that if you spend longer getting from speed A to B you will use more energy - this is more dominant than non-linear performance in the electric inverter, motor and drive train.


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