Will Tesla Semi decelerate quicker than ICE semis?

[Silent Ludicrosy]

The battery packs handling it isn't a concern. You see, there will be a giant Tesla brand Tesla Coil to handle the discharge of excess energy preferably generating music.

 

[Kacey Green]

View attachment 330058

Mad Max prop?

 

[nwdiver]

Although the generator might not overheat, the battery getting hot or filling up is a real concern. Although I suppose with the rumored 1MW charging rate it’d take quite a bit to overwhelm that battery!

If limited Regen due to a full battery was ever a concern they could just add a bank of resistive dump heaters like trains have.

 

[EVSteve]

Trucker here... biggest advantage in stopping time and distance is the instant light switch reaction the regen system provides. Air brakes have a long delay from pedal application to pad engagement. Engine braking takes even longer to engage and only provides meaningful push back at high RPM. Most truckers don’t highway cruise at those revs to conserve fuel. It’s really only used for decending long grades instead of snub braking.

I would like to see Tesla implement regen braking application in a similar way Chevrolet handles the Volt. Letting off the accelerator applies some regen, brake application activates progressively more agressive regen and then the final travel on the brake pedal applying friction braking.

At the end of the day driver strategy is to use braking as a last resort to avoid a collision especially when loaded. It simply takes too long to stop. I’ve also seen van trailers have freight punch through the nose and strike the back of the cab after a sudden stop. Safety training encourages drivers to always have a way around potential hazards. I hope the AP system takes this into consideration. The current fleet of trucks employ a very dangerous method of a forward sensor applying full braking much like Tesla’s TACC. Full braking uses up all available traction making any steering input an almost guaranteed jackknife.

Tires are the limiting factor. Most companies will run hard compound for mileage and eco tread patterns for fuel savings. The super single drive tires Tesla has on the Semi provide less grip vs duals. Having driven a day cab with super rain traction is extremely limited and snow is impossible.

Lots of factors to co wider both inside and outside of Tesla’s control.

 

[WannabeOwner]

Letting off the accelerator applies some regen, brake application activates progressively more aggressive regen and then the final travel on the brake pedal applying friction braking

I'd like that on the Car, let alone a Truck In particular balanced so that lift off accelerator is always same effect (i.e. use friction brakes if necessary), even if battery cold or 100% SoC. And if Brake Pedal could have initial travel providing even-more-regen, as you describe, I'd prefer that to using friction brakes

 

[GWord]

Initial question is a month old but I didn't see anyone doing the math so here goes:

Assumptions:
Height - 1000m (rounding from 3000ft)
Distance - 7mi
Speed 40mph
Weight 80,000lb

Work:
Change in potential energy of 1000m @ 80,000lb = 356Mj
Convert to kWh = 99kWh
Time to travel 7 mi @ 40mph = 10.5min
99kWh over 10.5min = 565kW

So regen would need to be able to bank 565kW if you assumed the truck was going 40mph. This assumes frictionless / lossless systems, so any wiring or CD conversion losses or driveline losses are helpful in reducing the 565kW number. Even with reasonable losses, it seems aggressive, even if divided over 4 motors. Probably would need to slow down or use actual friction brakes.

Edit: Never mind! Saw that @mongo already did the math at 18mph.

 

[Big Earl]

I'd like that on the Car, let alone a Truck In particular balanced so that lift off accelerator is always same effect (i.e. use friction brakes if necessary), even if battery cold or 100% SoC. And if Brake Pedal could have initial travel providing even-more-regen, as you describe, I'd prefer that to using friction brakes

Having three EVs with three different approaches to regenerative braking, I prefer Tesla by a wide margin.

Our Fiat 500e has regenerative braking blended into the brake pedal (starts off as regen and adds friction brakes if your request exceeds what regen can provide). It's okay but not as smooth as the Tesla and not always consistent. They friction brakes end up being very grabby in wet weather, which is annoying every time you approach a stop sign.

Our Cadillac ELR has regenerative braking blended into the brake pedal as well as a low gear mode that adds about 20 kW of regen to the accelerator pedal as well as a steering wheel paddle that adds full regen. The problem is that none of it is smooth. The smoothest method of operation is regular drive mode (not low) and using the brake blending. Low mode has a very touchy transition from regen to power and the regen paddle is all-or-nothing with no ability to dial in the right amount of regen.

Tesla's regen on the accelerator pedal is very smooth and allows you to not move your foot back and forth in most driving situations. The regen is strong enough to slow the vehicle down smoothly in most situations. When stronger braking is required, you simply use the brake pedal. In my opinion, this is the smoothest and most consistent operation of any EV I've driven (I haven't driven an i3 yet).

The edge cases come in during high states of charge and cold temperatures. All of our EVs exhibit similar limited regen during these conditions. I've found that I'm able to adapt quickly to the limited regen in all of the vehicles.

I haven't driven a semi truck, but I have driven a 40+ foot RV with air brakes and a big Caterpillar diesel with jake brakes (not a transmission retarder). This particular arrangement behaves very similar to Tesla, as the take brake activates any time you release the accelerator (unless you switch it off). This provides a fixed amount of deceleration (based on engine speed) and you simply apply the friction brakes if you want stronger deceleration. The main difference is that most jake brakes have limited variability, ranging from none to three stages, while Tesla is infinitely variable.

Sorry for the long-winded post. To summarize, I support Tesla's status quo.

 

[gjunky]

reading all this, I think to solve the regen problem on hills for the semi (and any EV really), only drive in nice weather and always charge at the bottom of a hill

 

[SigNC]

Having read through this thread I have to wonder, are there any plans to optionally have drive motors in the trailers that are being pulled? Seems like it would not only up what could be moved but importantly it would also provide regen braking on the trailers helping keep them in line.

 

[Big Earl]

Having read through this thread I have to wonder, are there any plans to optionally have drive motors in the trailers that are being pulled? Seems like it would not only up what could be moved but importantly it would also provide regen braking on the trailers helping keep them in line.

I think that was discussed earlier. The problem with doing that is trailers sit around for a long time being loaded and unloaded, so the battery and motor investment is best spent on the tractors themselves. Additionally, trailers are pulled by different trucks, so all tractors would need the capability to pull battery-powered trailers in order for it to work.

 

[SigNC]

Yeah i wasn't even really thinking about having batteries on the trailers but more so just motors so they could assist in the drive and regen. They certainly would be tied to a tesla only tractor though if you did that.

 

[jgs]

Having read through this thread I have to wonder, are there any plans to optionally have drive motors in the trailers that are being pulled?

Bosch to show electrified semitrailer axles at IAA

 

[jgs]

They certainly would be tied to a tesla only tractor though if you did that.

The Bosch system posted just above doesn’t seem to be.

 

[Big Earl]

Bosch to show electrified semitrailer axles at IAA

That's a pretty good solution for refrigerated trailers.