NYT article: Stalled on the EV Highway

[brianman]

It's easier to drive "casually" with the flow of (light) traffic, meaning that you can use cruise control and/or drive in a way that's similar to cruise control. I suppose there might also be some drafting / peleton affects of staying with (light) traffic.

In contrast, when I go slower than traffic I tend to be self-conscious about it and "get up to speed" periodically which effectively kills off some of the efficiency gain I am attempting. Additionally if you camp out in the right lane due to the lower speed, you have to deal with traffic entry/exit in your lage more often which causes you to adjust rather than coast.

Just some thoughts. Nothing definitive here.

 

[stevezzzz]

This extra cost does not exist. Holding the car stationary against gravitational force does not require energy: you could do this with the friction brakes (as you do when parked on a slope). Energy is expended to achieve motion against that force (energy = force * distance), but that is the constant energy we've already counted above.

The 10kW you measure holding the car against the slope with the motor is simply because motors become extremely inefficient as you approach zero speed (in fact, 0% efficient when stopped). That 10kW is going entirely into heat in the motor/battery/power electronics.

I think GeekGirls had it right the first time. Just because you could use the friction brakes to hold position on a slope without using battery power doesn't mean that you don't use energy when the motor has to provide that same force to oppose gravity and prevent rolling backward. You're right that at zero mph all that energy (10kW reported on GeekGirls' steep driveway) is wasted, in that none of it is used to produce forward motion to or increase potential energy through altitude gain. But unless I'm mistaken, it's not correct to state that an electric motor is using more energy at zero rpm than it would be at a higher rpm to generate the same torque: as we learned in high school science class, an electric motor generates full torque at zero rpm. Does it require significantly less current to generate the same torque at 1000rpm? 3000rpm? I don't think so, though I'm no electric motor expert. So I'm standing with GeekGirls on this one: the 10kW drain she experienced would be there at any speed (to a first approximation, at any rate) and I claim that only the application of additional torque (from drawing additional current) contributes to forward motion (and altitude gain).

 

[GeekGirls]

This extra cost does not exist. Holding the car stationary against gravitational force does not require energy: you could do this with the friction brakes (as you do when parked on a slope).

You can hold the car stationary at no energy cost, but not with the electric motor. It's not my field of expertise so I'd like someone familiar enough with the physics to explain how to model it, but I can assure you it doesn't take 10kW to "idle" on a flat surface - but I could expend that much all day on my driveway and make zero forward progress. Applying friction is fundamentally different from applying an equal and opposite force against the effects of gravity.

 

[vfx]

I've written a featured OpEd at the Times of Israel ...

I regard Tesla’s Superchargers as more of a marketing tool than a serious option for mobility.

JB was just qouted saying that the money for Superchargers comes out of the Marketing budget.

 

[rolosrevenge]

I seriously doubt that this will have any effect on the stock prices. Did the whole "bricking" scandal drop the stock prices, even in the short term? So they got one piece of bad press. How much other good press have they had?

 

[dennis]

We've dealt with bad press before, and a reporter who doesn't know how to use the vehicle really isn't in the same league with all the problems Fisker has. I'm afraid your gloating will be short lived.

I know you don't keep up to date with the problems/reliability of the Karma, but @pythagorus and I do since we both own one. Since my Karma was last updated in early October, it has been 100% reliable and glitch-free. Other owners report the same on the Fisker forum. Reminds me of how the installation of 4.2 recently stabilized my Model S experience.

 

[brianman]

I know you don't keep up to date with the problems/reliability of the Karma, but @pythagorus and I do since we both own one. Since my Karma was last updated in early October, it has been 100% reliable and glitch-free. Other owners report the same on the Fisker forum.

That's great news.

 

[JRP3]

I was actually talking about Fisker as a whole, the company problems and the car problems. I'm glad the car issues have stabilized, but the flaming Fiskers have unfortunately become something of a legend. I don't know how many times I have to correct people who claim the lithium pack is exploding and burning up the cars

 

[dennis]

I was actually talking about Fisker as a whole, the company problems and the car problems. I'm glad the car issues have stabilized, but the flaming Fiskers have unfortunately become something of a legend. I don't know how many times I have to correct people who claim the lithium pack is exploding and burning up the cars

Yes, it is a shame that two fires caused by a cooling fan and one fire caused by cars submerged in sea water got morphed by the EV/Obama haters and the self-styled online "journalists" into massive battery fires. But to me it illustrates how fragile perception is when you are an early market entrant, and why Tesla needs to go out of its way to make sure that the experience of this NYT reporter is not repeated.

 

[doug]

You can hold the car stationary at no energy cost, but not with the electric motor. It's not my field of expertise so I'd like someone familiar enough with the physics to explain how to model it, but I can assure you it doesn't take 10kW to "idle" on a flat surface - but I could expend that much all day on my driveway and make zero forward progress. Applying friction is fundamentally different from applying an equal and opposite force against the effects of gravity.

There's a more appropriate thread on hill holding where I probably went more in depth about this some years ago. But picture an electromagnetic crane, of the type used to move cars at a junk yard, holding a car stationary suspended above the ground. Now consider the Joule losses in that electromagnet. You could say something similar is going on in a stationary motor under load.

 

[doug]

Let's try to keep this thread on topic. I believe there are existing threads for more in depth discussions about cruise control, hill holding, Fisker's problems, and Better Place. If not, feel free to make one.

 

[dennis]

Let's try to keep this thread on topic. I believe there are existing threads for more in depth discussions about cruise control, hill holding, Fisker's problems, and Better Place. If not, feel free to make one.

C'mon Doug, can't I get a little credit for bringing the Fisker discussion back on topic? :biggrin:

Yes, it is a shame that two fires caused by a cooling fan and one fire caused by cars submerged in sea water got morphed by the EV/Obama haters and the self-styled online "journalists" into massive battery fires. But to me it illustrates how fragile perception is when you are an early market entrant, and why Tesla needs to go out of its way to make sure that the experience of this NYT reporter is not repeated.

 

[dpeilow]

Indeed, not to mention BP is in real trouble and has pulled out of the US, not that it was really ever here. Of course in Israel a Model S could do almost any trip on a single charge, and certainly could do anything reasonable with maybe 3 supercharger locations. Battery swapping is a good "idea" but a poor reality. Funny that as BP continues to have problems and Tesla continues to be successful Brian thinks BP has the answer

Well, this is another variant of the 'just buy a Model S' argument, which assumes they grow on trees. What you have missed out is that Brian said the cars are 1/4 the price, i.e. accessible to the mass market. Whether BP tried to expand too quickly is other debate and the coup was worrying (guy with an oil background), but their infrastructure investment wasn't that great and the idea is to spread that across thousands of users. I hope by concentrating on Israel they can regroup.

Of course if the NYT journalist had access to a battery swap with full charge, we probably wouldn't be having this discussion.

 

[brianoflondon]

Well, this is another variant of the 'just buy a Model S' argument, which assumes they grow on trees. What you have missed out is that Brian said the cars are 1/4 the price, i.e. accessible to the mass market. Whether BP tried to expand too quickly is other debate and the coup was worrying (guy with an oil background), but their infrastructure investment wasn't that great and the idea is to spread that across thousands of users. I hope by concentrating on Israel they can regroup.

Of course if the NYT journalist had access to a battery swap with full charge, we probably wouldn't be having this discussion.

Exactly my point. If Tesla can replicate the Model S down to a $20,000 market all's fine.

I'm really not a Tesla hater, I really would love one of the cars, it's just that 20,000 cars per year in the US is not going to change ANYTHING for the wider world. It certainly isn't going to drive mass adoption and back down in the real world of 24kWh batteries, trying to say that an electric vehicle can drive from DC to upstate New York is just STUPID.

Whoever at Tesla gave this journalist the OK to attempt such a trip is a muppet of the highest order. They should have said no, please borrow the car and use it for commuting 50 miles each way every day around the Beltway and into DC. That's what its built for.

And next week I shall be calling Lamborghini and asking if I can take one of their cars (not a tractor) and attempt the Paris Dakar rally in it.

I've looked at buying more Better Place cars for my staff but, as travelling salesmen, it turns out they're just not a fit for the car's capabilities. Better Place actually are discriminating and will vehemently dissuade people from taking the car if it doesn't suit their use pattern: that's what Tesla's marketing department should have done here with the NYT or at least told him to wait till May when this trip would have been easy.

For the record shutting Australia and the US is a good move IMHO. They have to make a success in the only two places they've built all the kit: Denmark and Israel. The US is a long way off for mass EV adoption because of the distances, density and the low cost of liquid fuel.

 

[Norbert]

Well, this is another variant of the 'just buy a Model S' argument, which assumes they grow on trees. What you have missed out is that Brian said the cars are 1/4 the price, i.e. accessible to the mass market. Whether BP tried to expand too quickly is other debate and the coup was worrying (guy with an oil background), but their infrastructure investment wasn't that great and the idea is to spread that across thousands of users. I hope by concentrating on Israel they can regroup.

Of course if the NYT journalist had access to a battery swap with full charge, we probably wouldn't be having this discussion.

You can't make that argument without showing that Better Place is making a profit. (We can assume Tesla will be able to make a profit, based on the available information.)

BTW, How much is the subscription (and the car)? How much would it be if they covered their costs?

Whoever at Tesla gave this journalist the OK to attempt such a trip is a muppet of the highest order.

That's an invalid extrapolation of a single incident. In general Superchargers are received well. All he would have needed to do is charge more where he was already charging.

 

[smorgasbord]

When coasting down hill NO additional energy is used for aero, tires, or drivetrain.

Let me try again, since I'm not being clear.

Climbing a hill at 50MPH takes more power than going on a flat road at 50MPH. However, the drag effects from aerodynamics and from tires are exactly the same. I'll argue that drivetrain efficiency is also about the same with an EV (not so with an ICE) - the graph I posted shows that drivetrain losses are pretty flat. Thus, the extra power you put in to climb the hill is almost all captured as Potential Energy when you're at the top of the hill. With me so far?

Now, let's say the hill is steep enough that in neutral you'd hit 75 MPH and stay there. A hypermiler in an ICE would say that's the way to go. However, at 75MPH you are still encountering aerodynamic drag and tire drag. My contention is that if you engage enough regen to slow you down to 50 MPH, instead of losing power to high aerodynamic drag, you'd capture it in regen. You wouldn't capture it all, but you'd capture some - and any you capture is better than nothing, as you end up in the same spot but with a bit more juice in the battery.

Am I making sense now?

 

[medved]

I've written a featured OpEd at the Times of Israel replying to this today drawing on my experience driving the battery switch capable Renault Fluence ZE in Israel.

It may be of interest to some here....

I personally like more owning the battery and getting free supercharge than paying for the lease of a battery. As the energy storage keeps improving I think, in the future, there will be no need to swap batteries. Just my opinion. Therefore, I am happy that Tesla is doing it the way they do.

 

[Ben W]

[FONT=arial, sans-serif]It's very weird because the author got significantly more mileage out of the Model S when he drove normally, not at 45 miles an hour in the right lane. Counterintuitive [/FONT]

Not necessarily. As noted, the heating costs at extreme cold temperature can be quite significant. Driving half as fast may be aerodynamically more efficient, but it also means the cabin and battery heater run twice as long. (At higher speeds, with more power output, the battery heater may not have to run at all; the batteries will simply heat themselves.) In other words, the "optimal" cruising speed increases substantially as the temperature gets colder.

Similarly, the "optimal" cross-country speed increases with the performance of the superchargers. With superchargers spaced every 80 miles, say, the fastest way to get cross-country in a Model S is probably to floor it at maximum speed from one supercharger to the next. The only limiting factor would running out of juice before reaching the charger; that alone is a good reason for Tesla to add more chargers at frequent intervals along heavily traveled corridors. I remember doing this calculation with the Roadster, based the slower 70a/240v charger; the optimal speed in that case turned out to be about 55mph. E.g. if you drive slightly faster to get to the next charger 5 minutes sooner, it'll take an extra 6 minutes of charging to recover the energy you wasted driving faster. This goes out the window with the superchargers; if they're spaced closely enough, the only limiting factor is how often you want to be pulled over

Back to the article: The author clearly did a lot of things wrong. At the same time, Tesla could do a lot to guide users to better outcomes. Simply displaying the optimal driving speed for the given auxiliary load (heater etc.) would be highly useful information. When parking in cold temperatures, a prompt: "How long until you expect to drive the car again?" would allow the car to optimize battery temperature over that span. Even for a few hours, this could massively reduce power losses of the type described in the article. The ability to preemptively "wake up" the car from the iPhone app, if needed sooner, would be an added bonus.

 

[Norbert]

Not necessarily. As noted, the heating costs at extreme cold temperature can be quite significant. Driving half as fast may be aerodynamically more efficient, but it also means the cabin and battery heater run twice as long. (At higher speeds, with more power output, the battery heater may not have to run at all; the batteries will simply heat themselves.) In other words, the "optimal" cruising speed increases substantially as the temperature gets colder.

Good point.

Back to the article: The author clearly did a lot of things wrong. At the same time, Tesla could do a lot to guide users to better outcomes. Simply displaying the optimal driving speed for the given auxiliary load (heater etc.) would be highly useful information. When parking in cold temperatures, a prompt: "How long until you expect to drive the car again?" would allow the car to optimize battery temperature over that span. Even for a few hours, this could massively reduce power losses of the type described in the article. The ability to preemptively "wake up" the car from the iPhone app, if needed sooner, would be an added bonus.

I was thinking about this already. The achievable savings would need to justify the more complicated UI.

- - - Updated - - -

... My contention is that if you engage enough regen to slow you down to 50 MPH, instead of losing power to high aerodynamic drag, you'd capture it in regen. You wouldn't capture it all, but you'd capture some - and any you capture is better than nothing, as you end up in the same spot but with a bit more juice in the battery.

Am I making sense now?

That does appear to make sense. It shouldn't be too difficult to measure the difference between the driving techniques by driving the same route twice (in the same total time, to be comparable). Perhaps an open question is whether the regen-efficiency itself depends on the speed.

 

[JRP3]

Exactly my point. If Tesla can replicate the Model S down to a $20,000 market all's fine.

Eventually they will get close enough I suspect. In the mean time there are other EV and hybrid options. I just don't see the BP model as being an answer in the interim when it will likely soon be irrelevant.

I'm really not a Tesla hater, I really would love one of the cars, it's just that 20,000 cars per year in the US is not going to change ANYTHING for the wider world. It certainly isn't going to drive mass adoption and back down in the real world of 24kWh batteries, trying to say that an electric vehicle can drive from DC to upstate New York is just STUPID.

Except that the trip could have been completed successfully with some minor effort. I would agree that sending an untrained reporter off on such a journey would not be a good idea.

I've looked at buying more Better Place cars for my staff but, as travelling salesmen, it turns out they're just not a fit for the car's capabilities. Better Place actually are discriminating and will vehemently dissuade people from taking the car if it doesn't suit their use pattern

That seems to point out the failure of the entire BP model which supposedly promises unrestricted driving.