My experience with the Tesla Model 3

[Cdnfireman]

Every time you step on the brakes in a traditional vehicle you throw away energy, every time a semi uses the jake brakes they also throw away energy, with electric motors this energy is recaptured and put back in the battery. Saying you lose longevity in hilly terrain or stop and go traffic is old school thinking. With an electric if all the energy of stopping can be recovered in the motors hilly terrrain or stop and go makes little difference. If you travel a route through hilly terrain as long as the start and end point elevations are the same the energy used will be similar to that of the truck on flat ground, because every-time the vehicle is slowed going down hill the energy is captured to use on the next uphill, the only loses are those of the motor and battery transforming this energy, each of which should have efficiencies of over 90%. This is exactly where an electric trucks wins over diesel, the diesel will take considerably more additional energy in these circumstances.

Inrush current makes little difference to battery life as this is such a small portion of the total energy used. That's like saying you loose a huge amount of fuel economy in a pickup when idling at a stoplight because the gauge maxes out at 99L/100km, it's not that energy consumption goes up, its because the small amount of energy being used is doing not work, so the efficiency is 0%

You're making quite a few assumptions.....like that if your start and finish elevation is the same that the energy used is replaced by the regenerative braking. That would only be true if the regenerative braking was input back into the battery at its most efficient rate, and ignores motor/battery temperature concerns. Imagine you have a very hard pull up a steep hill that requires close to maximum output of the motor and battery. Then immediately had a steep downhill that required maximum braking effort to maintain a safe speed. The motor and battery would be screaming hot at the end of the uphill pull, and then would be required to absorb more heat on the downhill. I’m betting that they both would be close to an over temperature situation and would have to de-rate via the control systems to prevent damage, or the regenerative braking system would be disabled altogether due to motor and battery temperature, requiring the use of the regular service brakes.
And inrush current is a huge factor in an electric motor. Because a DC motor has an essentially flat torque curve, the motor pulls maximum current at start up, but because all that energy can’t be instantly converted to physical work, some of the energy is wasted in the form of heat. Do this repeatedly with a big load in heavy traffic and watch what happens to your battery condition and motor temperatures.
Put a heavy, low speed load on your battery drill and watch what happens. It and the battery get hot quickly and the battery is dead quickly as well. Same principle.

 

[Cdnfireman]

And pulling the same amount of weight up the same hill the diesel truck will use the same amount of energy as the electric truck. Going down the other side, the electric gets to recover some of its energy through regenerative braking, but the diesel is also using very little fuel as well, since with the jake operating, the fuel is shut off to the injectors....so the increase in efficiency isn’t as big as it appears.

 

[lilduke]

Its hard to find specs on this tesla semi, its not even on the road yet.

But I imagine it will use traction motors like a train. It will have gear reduction built onto the motor.

Pretty sure they have that on the Tesla cars as well.


Its not really a direct drive in the way you're thinking it is.

Model S drive train. notice the gear box..

 

[jhurkot]

It’s on the road.

https://youtu.be/_WElH0yzeT4

 

[Stompin Tom]

https://www.meritor.com/technology/

here is the meritor eAxle. The only thing missing are ujoints, other than that, allot of moving parts, not a direct to wheel drive.

 

[Stg2Suby]

Just to clarify Peterbilt is experimenting with a couple different approaches. The Class 8 579 is using a conventional transmission/driveshaft/axles etc. The smaller 220EV is using an E-axle with the electric motor integrated right to the axle. Here's some info on the smaller 220EV https://www.truckinginfo.com/322454/a-closer-look-at-peterbilts-electric-model-220ev

 

[lilduke]

It’s on the road.

https://youtu.be/_WElH0yzeT4

that looks like cgi? haha

 

[jhurkot]

You're making quite a few assumptions.....like that if your start and finish elevation is the same that the energy used is replaced by the regenerative braking. That would only be true if the regenerative braking was input back into the battery at its most efficient rate, and ignores motor/battery temperature concerns. Imagine you have a very hard pull up a steep hill that requires close to maximum output of the motor and battery. Then immediately had a steep downhill that required maximum braking effort to maintain a safe speed. The motor and battery would be screaming hot at the end of the uphill pull, and then would be required to absorb more heat on the downhill. I’m betting that they both would be close to an over temperature situation and would have to de-rate via the control systems to prevent damage, or the regenerative braking system would be disabled altogether due to motor and battery temperature, requiring the use of the regular service brakes.
And inrush current is a huge factor in an electric motor. Because a DC motor has an essentially flat torque curve, the motor pulls maximum current at start up, but because all that energy can’t be instantly converted to physical work, some of the energy is wasted in the form of heat. Do this repeatedly with a big load in heavy traffic and watch what happens to your battery condition and motor temperatures.
Put a heavy, low speed load on your battery drill and watch what happens. It and the battery get hot quickly and the battery is dead quickly as well. Same principle.

That’s true, but don’t forget that the battery pack has coolant running through it.

 

[skegpro]

Sounds like everyone in Vancouver will be driving electric.

https://www.revelstokereview.com/ne...0-cheaper-to-fuel-than-gas-vehicles-bc-hydro/

 

[doorfx]

That’s true, but don’t forget that the battery pack has coolant running through it.

Roflmao. Too funny.
I guess it pays to do research and not tell the guy that owns one how it works.

 

[Stompin Tom]

Roflmao. Too funny.
I guess it pays to do research and not tell the guy that owns one how it works.

If you watch the Peterbilt video they show the radiator positioned in the same spot as a diesel, much smaller, but still there. Also should be noted that the electronics dont just drive the wheels, they also power a compressor for the brakes and a hydraulic motor for steering.

 

[Caper11]

Model S drive train. notice the gear box..


http://d2ojs0xoob7fg0.cloudfront.net/evtv-word-press/wp-content/uploads/2014/07/IMG_3988.jpg

That just looks like a transaxle, same as bolting a electric motor to your rear end in your pickup.

Still a direct drive.

 

[Stompin Tom]

That just looks like a transaxle, same as bolting a electric motor to your rear end in your pickup.

Still a direct drive.

I guess that depends on your definition of direct drive

https://www.magneticinnovations.com/products/direct-drive-motor/

"A Direct Drive Motor, is a type of permanent-magnet synchronous motor which directly drives the load. As a result, the use of a transmission or gearbox is eliminated"

 

[lilduke]

That just looks like a transaxle, same as bolting a electric motor to your rear end in your pickup.

Still a direct drive.

no direct drive would be the motor bolted directly to the tires...

 

[Caper11]

Well I spose it’s semantics, and a view of the definition. A direct drive in a industrial application would be the definition that stomping tom gave us, even if the electric motor is bolted directly to a speed reduction or speed increasing gear box, i still would call it a direct drive. Now in the same application mentioned above, instead of a ridged coupling, install a torque converter, its no longer a direct drive.

In a automotive example like the one shown thats a transaxle and its needed to differentiate the wheels to allow the car or truck to turn.

Tesla looks like they use a variable frequency motor drive bolted directly to a transaxle or independently on each wheel like mentioned in the tesla truck.

 

[lilduke]

all I know is that it has a gear box, axle shafts ext.
there is your fusible link.

guses I could call my dodge direct drive because the motor is bolted directly to the transmission

 

[Cdnfireman]

Roflmao. Too funny.
I guess it pays to do research and not tell the guy that owns one how it works.

he owns a Tesla semi? Not....

 

[jhurkot]

he owns a Tesla semi? Not....

Not yet

 

[Stompin Tom]

Not yet

my dad always told me never say never. But in this case I feel quite confident that I can say I will never own an electric semi. I am to old and the technology to far off for me think it will be a viable option before I retire.

 

[ABMax24]

And pulling the same amount of weight up the same hill the diesel truck will use the same amount of energy as the electric truck. Going down the other side, the electric gets to recover some of its energy through regenerative braking, but the diesel is also using very little fuel as well, since with the jake operating, the fuel is shut off to the injectors....so the increase in efficiency isn’t as big as it appears.

No, the increase is exactly as big as it appears, the energy recovered from regenerative braking goes back to the battery.

The amount of energy a jake brake can dissipate is huge, the cummins X15 being up to 600hp of retarding power, the same it produces. For example say there is a long grade where an X15 truck runs downhill with the jake brake maxed out for 5 minutes, that engine has dissipated the equivalent of 37kwh of energy. That would power the Tesla semi at worst case 2 kwh/km for 18.5 km, I'd consider that significant. Or to put that in terms of diesel, if a truck uses 40 L/100km that truck lost the equivalent of 7.4 liters of diesel in energy dissipated through the jake brake.

Trucking contracts are often won and lost in cents per kilometer, Tesla trucks will catch on big if they can improve even slightly over current equipment.