Towing Capacity and Range?

[Ogre]

Tesla believes it's safer to back into parking spaces.

-Crissa

Pull thru is safest, backing in is next safest.

I like that Tesla has back in where space is limited.

They also tend to have one pull in stall at most Supercharger locations. People who tow can usually get into that space so long as they can get in and out of the area.

Sponsored

 

[Challeco]

Regen isn't energy loss?

-Crissa

regen? Wrong side of the equation. Regen takes the kinetic energy from the wheels and generates electricity. The inertia I was referring to was from a stop to a roll.

 

[pagesix1536]

It depends. Towing around town will be great. Long distance towing of most trailers will require a willingness to spend significantly more time than a ICE truck. If range is cut by half, not only do you have to charge twice as often, you also likely have to charge into the top half of the battery which will be a much slower charging speeds. Having to drop a trailer also adds time. My little utility trailer takes about 5 minutes to hook up and 3-4 minutes to unhook. My pop up trailer took a bit longer and my Dad's camping trailer with a weight distributing hitch took 10-15 minutes to hook up and a bit less to unhook. Doing any of those things in inclement weather is not my idea of a good time. Having to drop a trailer every hour and half to three hours, it will make for a challenging trip. It will be doable, but it is a real consideration. It will be fine for infrequent towing or towing from campground to another campground with the ability to charge overnight, but it really won't be practical for frequent, long distance towing unless the trailer is very aerodynamic.

Sounds like a CT is not a good fit for you then.

 

[Challeco]

I think there a misunderstanding here. Let me try to clarify.

Gears are not used for braking or to slow a vehicle down or to reduce its interia. (Which are all the same thing). Either in a ICE or a electric vehicle.

Gears are used to increase "leverage" or torque by using a something that goes a further distance with less force to create something that goes a shorter distance but with more force. Or the other way around as needed.

What gears do for a ICE/electric motor is to allow the propulsion to operate in its best efficiency range for the task at hand. For example a low gear to climb hills at low speeds but high rpm, and a high speeds on the flat at low rpm.

The difference is that a ICE does not have a very good torque curve, meaning in particular, that at 0 rpm it has also zero torque. In comparison a electric motor has about 60-90% of torque at 0 rpm. This means that typical EV cars only need a single speed gear ratio to drive and it doesn't have gears you can change.

(PS A second gear is sometimes used on performance EVs so that they can reach higher top speeds, like the Porsche Taycan)

So with Teslas they have a single gear ratio that matches the motor rpm with the wheel rpm, so that it matches the efficiency island of the motor when at certain highway speeds. This results in the lowest energy consumption possible and the longest range.

When most EV's brake to slow down they also use the electric motor to do this. But unlike with an ICE this does not consume energy, instead it produces energy that is sent to charge the batteries back up. This is called regenitive braking and nearly all currently available EV's use this method. There is however a limit to how much braking can be regenerated, and this depends on various factors including battery charge rate, battery state, temperature etc.

If however you need to brake more than your regenerative braking can do through the electric motor, then the normal "friction brakes" are used. These are the same type of brakes on ICE vehicles. In typical use, and if you try to brake softly but early, you might never use your EVs friction brakes, to the point some vehicles periodically engage them to ensure they remain rust and debris free and ready to use.

I hope this clarifies things.

You use the same physics to both prove and disprove your own statements. Manual gears, Automatic gears, differential gears, and the gears in a transfer case are all fixed rotational connections within the drive train. As such, these are all available for both deceleration and acceleration. The leverage they provide is simply an amplifier of force. Regenerative braking utilizes the kinetic energy of the vehicle in motion to drive the rotor in the stator instead of the stator driving the rotor. As the permanent magnets in the rotor rotate within the windings of the stator, the magnetic field stimulates the movement of electrons within the wiring... turning a motor into a generator.

My impression of your explanation is that you feel I need educated in electro-mechanics. I may not have a PhD but I do have intimate knowledge of vehicles and the associated applied physics.

As for your explanation of torque at 0 rpm, you are wrong. Just flat wrong. The torque curve of an electric motor is "generally" between 0 and 500 rpm based on time. Time being the the y axis and rpm being the x axis on a graph. The torque cannot be anything but 0 at 0 rpm, no matter how fearfully capable the motor is. The torque and horsepower curves of an internal combustion engine are not calculated any differently. The ability of an I.C.E. to produce torque and horsepower are a function of the RPM, volume and quality of the combustion, the reciprocating mass, and the rotating mass. I am sure I am missing a few factors, but you all don't need this lesson.
The point that I was trying to make by referring to the VW gear reduction is that the energy requirement to motivate a vehicle from a dead stop is greater than it is to maintain the motivation. By amplifying the electric motor's output with gear reduction the energy requirement would be reduced. This gear reduction would only be necessary for heavy loads during the first moments of motivation.

But, as Tesla's engineering is so gloriously far ahead of any other manufacturer, I doubt this issue will affect Tesla's semi tractor or the Cybertruck... rendering my suggestion entirely moot.

 

[Ogre]

The torque cannot be anything but 0 at 0 rpm, no matter how fearfully capable the motor is.

(I’m not dug into your argument here so forgive me a bit, but this statement is a bit weird to me)

I think a better way of looking at this is electric cars are self-starting. You can have an electric car at 0 RPMs and as soon as you apply power, they are pushing against the load. An ICE engine literally cannot run below a certain RPM and provides very little power at low RPMs. This is why ICE vehicles have electric starters. It is also why ICE vehicles have a clutch or torque converter. Without absurdly low gearing or some kind of transmission that slips, you could not really start an ICE vehicle.



One thing Tesla has done in the past is run 2 different gear rations on the front and rear drivetrains. The rear axel is geared for low speed acceleration and power, the front axel for higher speed acceleration and power. The car intelligently shifts how much power is poured into which drivetrain at various speeds and shuts off the rear drivetrain at highway speeds.

(Forgive me if the above was covered already)

 

[JBee]

You use the same physics to both prove and disprove your own statements. Manual gears, Automatic gears, differential gears, and the gears in a transfer case are all fixed rotational connections within the drive train. As such, these are all available for both deceleration and acceleration. The leverage they provide is simply an amplifier of force. Regenerative braking utilizes the kinetic energy of the vehicle in motion to drive the rotor in the stator instead of the stator driving the rotor. As the permanent magnets in the rotor rotate within the windings of the stator, the magnetic field stimulates the movement of electrons within the wiring... turning a motor into a generator.

My impression of your explanation is that you feel I need educated in electro-mechanics. I may not have a PhD but I do have intimate knowledge of vehicles and the associated applied physics.

As for your explanation of torque at 0 rpm, you are wrong. Just flat wrong. The torque curve of an electric motor is "generally" between 0 and 500 rpm based on time. Time being the the y axis and rpm being the x axis on a graph. The torque cannot be anything but 0 at 0 rpm, no matter how fearfully capable the motor is. The torque and horsepower curves of an internal combustion engine are not calculated any differently. The ability of an I.C.E. to produce torque and horsepower are a function of the RPM, volume and quality of the combustion, the reciprocating mass, and the rotating mass. I am sure I am missing a few factors, but you all don't need this lesson.
The point that I was trying to make by referring to the VW gear reduction is that the energy requirement to motivate a vehicle from a dead stop is greater than it is to maintain the motivation. By amplifying the electric motor's output with gear reduction the energy requirement would be reduced. This gear reduction would only be necessary for heavy loads during the first moments of motivation.

But, as Tesla's engineering is so gloriously far ahead of any other manufacturer, I doubt this issue will affect Tesla's semi tractor or the Cybertruck... rendering my suggestion entirely moot.

Hey Challeco!

Sorry I wasn't trying to imply anything, rather I was trying to understand what you were saying, and correct the things that didn't make sense to me in relation to how it works physically, and for anyone else that might be interested to learn.

Seeing you have some competence let me adress what I see as the misunderstanding directly.

Remember torque is a moment and does not have a temporal coordinate measured in seconds. Energy does however have a temporal component. For movement to occur time must pass meaning there is an energy transfer. However, a gear or lever can exert a force without moving, and as such does not have a time component therefore no change of energy state.

Imagine a old fashioned water well with a bucket and winch. Pulling up a full bucket can be done by hand and requires energy to change its height. You can stop the bucket in the middle and lock the pulley with a pin. In this stationary position no energy is required because it doesn't move, but a torque force is still applied to the pin that stops it from falling.

Hope this helps.

 

[Crissa]

regen? Wrong side of the equation. Regen takes the kinetic energy from the wheels and generates electricity. The inertia I was referring to was from a stop to a roll.

Oh, well, you can vary regen, I don't believe Tesla gives the driver this level of control, though.

PS, with an electric motor, you do not need rpm to generate torque. The motors' rotational resistance or push is tightly controlled by the electric field within it. The field is constantly changing and Tesla in fact uses this as a heater in some modes.

Electric motors are more like muscle in their operation than like ICE driven motors because they are controlled by electrical impulses, not mechanical gears. So if torque drops below rolling resistance it doesn't actually drop to zero, the motor can still produce that force without moving. (No work gets done that way, but heat is generated)

Heck, these magnetic fields don't even need the motor controller to be powered, since rotating the motor pushes against those fields and creates power. Which is how you get the situation where an EV malfunctions and literally cannot be towed because the motors are magnetically locked into a rotational position with a huge amount of rotation resistance.

-Crissa

 

[JBee]

Oh, well, you can vary regen, I don't believe Tesla gives the driver this level of control, though.

-Crissa

You can vary regen with how hard you press the brake pedal. My 2001 Prius already did this.

 

[Crissa]

You can vary regen with how hard you press the brake pedal. My 2001 Prius already did this.

Yes, but Tesla isn't Toyota.

Tesla doesn't, as far as I know, they only have throttle regen.

-Crissa

 

[Challeco]

Oh, well, you can vary regen, I don't believe Tesla gives the driver this level of control, though.

PS, with an electric motor, you do not need rpm to generate torque. The motors' rotational resistance or push is tightly controlled by the electric field within it. The field is constantly changing and Tesla in fact uses this as a heater in some modes.

I agree with you about the way an electric motor works. But I understand torque is a calculation based on time, force, leverage, and motion. Zero is zero. But, this is semantics, because the major advantage of electrics over I.C.E. is the persistent potential of the charged fields against the rotor, like you explained.

I've used the example of the diesel electric rail engines for how persistently powerful electric is. Thousands of metric tons of weight from a dead stop that only steam was comparable.

 

[Challeco]

Yes, but Tesla isn't Toyota.

Tesla doesn't, as far as I know, they only have throttle regen.

-Crissa

My Ford fusion has the brake pedal regen like the Toyota. It sucks. The more I drive the Model 3 and the Fusion hybrid, the less I value the hybrid as an electric. The best hybrids have to offer is assistance from a dead stop. Otherwise, the batteries are woefully inadequate, the electric motors are weak, and the total weight drops the fuel economy to where a regular 4 cylinder I.C.E. can beat them for fuel efficiency. Hybrids are training wheels for people who have never driven a Tesla.

 

[Bitmaster]

Tesla believes it's safer to back into parking spaces.

-Crissa

Why is this? I have a Volt with the port in front of the drivers door and it is super convenient to charge.

 

[Bill906]

Why is this? I have a Volt with the port in front of the drivers door and it is super convenient to charge.

It is generally safer to back into a parking spot and drive out forward.

Before you enter a parking spot you can see all traffic, pedestrians etc. in the lane of traffic. There isn't a problem or safety issue when you are pulling into the spot. Backing into or pulling in forward are pretty much equally safe. The issue is when leaving the parking spot.

If you pulled into the spot forward, you'll have to back out to leave. Assuming you can't pull through forward and assuming vehicles parked on either side of you, you cannot see if any traffic is in the traffic lane until your vehicle is mostly in the lane. And you have to turn your head over each shoulder to see if anything is coming. If you backed into the spot you are looking forward and although you still have to enter the cross traffic area a little bit to see if anything is coming it'll be less than if you backed in, plus your facing forward, it's much easier to look left and right.

Now when I'm shopping (Grocery, Target, etc.) I pull into parking spots forward because I want access to the back hatch of my SUV to load groceries etc. So there is that.

I have a detached garage behind my house that is accessed by an alley. There's about 2 feet from the threshold of my garage door to alley traffic. I learned to back into the garage so I could pull out forward very soon after moving into this house. Backing out is a little nerve racking. You just have to blindly back out slowly until you can see if anything is coming and hope my neighbors are going slow and are being attentive.

 

[Ogre]

Backing into a parking space or charging stall means you are backing into a small area with very little dynamics. You have 2 cars and the back of the stall. These things usually aren’t moving and are easily accounted for.

Backing out of a stall you have pedestrians walking, other cars driving, and sometimes other cars backing up. Lots of things out of your control and in motion. I think people like that big open space when they are backing out of a stall, but that space can quickly get filled in ways which are hard to notice.

 

[TomGriff]

Sounds like a CT is not a good fit for you then.

I'm not planning to do distance towing and CT will be good for my needs, a bed, good charging curve (presumably), can seat six around town and seats 4 comfortably for long trips and will have Autopilot. Just reading the forums and it is pretty clear that quite a few people talk about towing and based on their comments they haven't towed and underestimate the time to drop and hook large trailers. It will also be interesting to see if Tesla breaks with their other cars and puts the charge port on the front which would allow charging without dropping the trailer in some of the superchargers I've been to.

Sponsored