Rivian R1T in World’s Toughest Towing Test on Ike Gauntlet [by TFL]

[Chadx]

@Chadx, much appreciate your opposing view here and comparison to engine braking in an ICE truck which is a great continuation to the discussion. Thinking through this, I'm only adamant about not turning the brake controller to zero or off on the R1T or any vehicle on these kind of grades.

I cannot recall in off season away from our tow rig, but also believe that on higher speed 65MPH descents like the IKE, that it is difficult to find the right gear to keep constant higher downhill speed with a heavy unbraked load. Not sure I've ever been able to run the IKE downhill without using the brake pedal frequently, in any gear, or any higher speed. Lookout Pass on the I90 Wyoming/ID border causes me similar downhill pucker factor with our boat tow, especially when slick. High passes with a bunch of big curves and at slower speeds are much more easily navigated with engine downshift braking.

Regardless, your comments resonate about only Rivian knowing how their regen braking is controlled. Frankly I don't know enough about the difference between EV regen braking vs computer controlled "downshifts" akin to your correct ICE example. Curious about any insight to these questions, as well as how many times the R1T's brake lights were lit up during the IKE descents, and how and what that means in Rivianese regen speak.

Cheers.

I totally agree with your comment about never turning brake controller to zero. That leaves one no ability to activate the trailer brakes.

There are definitely many factors that impact the need for brake applications while performing steep downhill towing. Grade, trailer weight, how the regen or ICE engine braking perform, etc.

Different BEV have different regen capability, but it's telling that on this TFL test, the Rivian mechanical brakes were never needed. I don't know how BEV manufactures determine when to apply brake lights during regen braking, but I submit that it should NOT be tied to how much regen braking is occurring. It should only be based on momentum change. Following traffic need not know that regen is keeping you from increasing speed just like when ICE engine braking. It is when the vehicle starts to slow down (a momentum decrease) that it's appropriate to indicate that by illuminating the brake lights to inform following traffic. I've not seen the technical details from Rivian or other manufactures on when/how they determine when regen should trigger brake lights. For example, if regen is holding back the load as much as it can but the vehicle is maintaining it's speed or even speeding up slightly, triggering brake lights is inappropriate. Should only indicate when the vehicle is slowing so following traffic can be forewarned.

On ICE pickups, the trend towards smaller displacement, forced induction engines is reducing the amount of engine braking available. In contrast, transmissions with more gears (10speeds) are helping since one can take smaller rpm "bites" to keep rpms up within a 1,000 rpm of redline , where engine braking is the greatest, vs being forced to brake or jump to a higher gear that is much lower rpm and little engine braking (for example, in a 6 speed).

While pickups are getting smarter and will downshift when in tow mode, that usually requires a brake application. Leaving a transmission in automatic mode (D) and relying on automatic downshifts doesn't perform nearly as well as manually downshifting. That could easily prove out if TFL (or other reviewers) would run the same downhill towing tests in automatic (D) mode and then re-run it my manually downshifting and letting the engine sit up near redline to compare number of brake applications needed.

In the end, the fact that the Rivian required zero mechanical brake applications towing that weight down that grade, is outstanding and ideal. That it didn't recharge the battery much, I'm not too worried about. Lots of things could have contributed and in the end, the performance (needing no brake applications) is much more important to me than how much battery recharge occurred.

On another note, an important R1T use case for us will be driving remote mountain forest service roads (for clarification, with no trailer). We typically creep along in our current ICE pickup in 4-Low range and manually limit transmission to the first three gears of our 6 speed transmission. This allows us to descend the slow, steep trails, which can be miles long, with few to no brake applications. I don't have Hill Descent Mode. I adjust speed by shifting between first and third gears.

Our hope is the regen on the Rivian is strong enough to do the same. A regen that is strong enough to single-pedal drive down these steep trails would be great. Having a steering wheel paddle to quickly control the amount of regen, all the way up to completely stopping, would be even better (to give feet and legs a break on these long drives). Unlike shifting gears to control speed in our current pickup, a BEV would require me to use either the brake pedal or accelerator pedal unless they have a regen paddle or an "offroad hill descent mode" that would allow the drive to set a low speed cruise control in 1/2 mph increments and it would automatically modulate with regen only.

The "offroad hill descent" modes in ICE pickups are getting better, but they do it all with mechanical brake application and are still noisy and apply needless wear and tear compared to simply driving in 4-Low and controlling descent with gear selection and engine braking. My hope is there are, or will be, advanced enough hill climb and hill descent modes in the Rivian so the motors and software can manage slow, trail speed ascents and descents better than I can with my current ICE pickup.

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[Chadx]

The brake lights always come on during deceleration on any EV since you are essentially stopping w/o brakes.

The key part to what you are saying is "deceleration". There is no need for brake lights to come on during regen if the vehicle is maintaining it's current speed or even accelerating (such as towing down a steep grade). Brake lights should be tied to a change in momentum (slowing down) and not how much regen the vehicle is applying. This would be the same and engine braking down a hill in an ICE tow vehicle. No reason for brake lights to come on if there is not a significant slowing of the vehicle. I'd even argue that illuminating brake lights when there is no slowing of the vehicle is conditioning following traffic to not take the brake lights seriously. Following traffic really only needs be notified is there the vehicle is slowing which was not the case with the Rivian in the TFL towing segment. Though regen was active, the vehicle was at a constant speed yet the brake lights were coming on.

 

[SANZC02]

The key part to what you are saying is "deceleration". There is no need for brake lights to come on during regen if the vehicle is maintaining it's current speed or even accelerating (such as towing down a steep grade). Brake lights should be tied to a change in momentum (slowing down) and not how much regen the vehicle is applying. This would be the same and engine braking down a hill in an ICE tow vehicle. No reason for brake lights to come on if there is not a significant slowing of the vehicle. I'd even argue that illuminating brake lights when there is no slowing of the vehicle is conditioning following traffic to not take the brake lights seriously. Following traffic really only needs be notified is there the vehicle is slowing which was not the case with the Rivian in the TFL towing segment. Though regen was active, the vehicle was at a constant speed yet the brake lights were coming on.

This is the regulation for lights being triggered

Vehicle decelerations	Signal generation
≤ 0.7 m/s²	The signal shall not be generated
> 0.7 m/s² and ≤ 1.3 m/s²	The signal may be generated
> 1.3 m/s²	The signal shall be generated

 

[Trandall]

Yikes. I knew the towing range up the mountain would be horrid, but I was not expecting just abysmal regen on the way down. Rivian regen must be pathetically inefficient. Tesla has orders of magnitude better regen than the Rivian in this test.

Also, that Electrify America charging on with the Rivian was abysmal. This definitely is making me pause to proceed from a Tesla to a R1S.

You are obviously trolling but I'll play along. Their is no Tesla at any price that could even complete this test so how is that orders of magnitude better? We don't even know what was happening on this unscientific test. Could have been trailer brakes diminishing regen and charging throttled by EA. It is just an interesting anecdotal single data point NOT evidence of Tesla's superiority. Tesla makes some very advanced vehicles they just don't make anything that can do what the R1's can do. In Tesla's defense they haven't yet tried.

 

[Chadx]

This is the regulation for lights being triggered

Vehicle decelerations	Signal generation
≤ 0.7 m/s²	The signal shall not be generated
> 0.7 m/s² and ≤ 1.3 m/s²	The signal may be generated
> 1.3 m/s²	The signal shall be generated

Good info. Thanks for posting! Those numbers are hard to translate conceptually, but, that article gave numbers a bit easier to comprehend....
--------------
1.3 m/s² is 2.9 mph/sec (4.7kph/sec) deceleration.
Some BEV regen are up to 3m/s² (6.8 mph/sec or 11 kph/sec) deceleration.
A hard brake is about 10mph/sec. deceleration.
Skilled drivers can do 14mph/sec. deceleration.
Vehicles tend to top out at about 15mph/sec. deceleration.
--------------

That middle "may generate illumination" category is fairly wide, but happy to see there is a threshold where manufacturers are not to trigger brake light illumination.
The "shall not generate brake signal" threshold of ≤ 0.7 m/s² (about 1.3 mph/sec) deceleration seems like it should be higher as that rate would trigger a lot of unnecessary brake illumination., but then, that rate 1.3mph/sec decel seems similar to an ICE vehicle deceleration when lifting off the pedal and coasting so perhaps there is why it was chosen. Interestingly, I decelerate at a higher rate than that when manually downshifting my ICE pickup which I regularly do around town even when not towing.

 

[EarlyAdptr]

Your fishing boat trailer, like most fishing boat trailers, likely has Surge brakes; not electric. As you describe, it is the weight of the trailer pushing into the tow vehicle that applies the trailer brakes and the more the force, the harder the trailer brakes are applied. The vehicle tow controller plays no part in how surge brakes operation. Only electric trailer brakes.

Thanks @Chadx !

So, with a weight of ~6,500 pounds (boat + trailer) and no "electronic" brake control, is this inherently dangerous (towing only using the Surge brake 'controller')? Do I have a higher risk of jack-knife or some other horrible outcome without that electronic controller?

PS Not that it matters, but it's a surf boat

 

[Chadx]

Thanks @Chadx !

So, with a weight of ~6,500 pounds (boat + trailer) and no "electronic" brake control, is this inherently dangerous (towing only using the Surge brake 'controller')? Do I have a higher risk of jack-knife or some other horrible outcome without that electronic controller?

PS Not that it matters, but it's a surf boat

Surge brakes are not dangerous and they are the standard brake type for boat trailers. Electric and surge trailer brakes perform similarly (trailer braking force increases the quicker the towing-vehicle decelerates). Surge brakes work better on trailers that are submerged regularly. There are aftermarket conversion boxes that can be retrofitted to boat trailers to make a hybrid electric/surge system. Those conversions sit on the boat trailer tongue, where the surge brake cylinder sits, and replaces the mechanism that mechanically compresses the surge brake cylinder with an electrically activated unit. That unit plugs into your vehicle and the electric brake controller in your vehicle now triggers the retrofitted unit to compress the brake cylinder rather than the compression of the trailer tongue doing so. The primary advantage is the ability to electrically activate the brakes while driving, but boat trailers rarely sway and there is major safety advantage to such a conversion.

Most surge trailers still have a brake activation cable to activate the brakes if the trailer becomes separated from the tow vehicle. Always ensure that cable is attached securely (and not to the hook of your safety chains; but directly to the receiver or someplace on the tow vehicle).

With surge brakes, as with any type of trailer brakes, you'll want to ensure they are maintained and adjusted correctly. There are adjustment procedures to ensure they are providing enough braking force when activated but not dragging while driving.

Small to medium surge brake boat trailers typically also have an physical accessory pin (a "backup" pin) that prevents the trailer brake cylinder from getting compressed when you back up. If the brakes are adjusted correctly, you'd normally feel a lot of resistance when backing up with the pin not in place if the brake cylinder on the tongue compresses enough as you back up. typically not an issue on flat asphalt, but backing into an inclined driveway, etc. would activate the surge brakes. Of note, there are some surge brakes trailers, typically larger trailers like your size and up, that electronically do this for you. It requires the trailer harness to be plugged into the tow vehicle because it reads the backup light signal to know when you are driving in reverse and so automatically keeps the surge brake cylinder from compressing. Quick way to identify that you do NOT have this feature is if your boat plus is a flat 4. Since this setup requires backup light wire, it will either have a flat-5 plug or a 7pin round.

Note that an electric backup lockout will not prevent the surge brakes from activating if the boat wiring harness is not plugged into the tow vehicle and would then require you to use a physical pin to lockout the brakes while backing up. If you have automatic/electric type, make sure you also have the physical pin and know how to use it so you'll be able to back up the trailer in situations where the wiring harness can't be attached to the tow vehicle (wire harness damaged, adapter stolen, someone elses pickup or a tow truck doesn't have a compatible light plug, etc.).

 

[kylealden]

Tesla has orders of magnitude better regen than the Rivian in this test.

This is a wild exaggeration. The Tesla got 4% compared to the Rivian's 2%. The Rivian has a significantly larger pack, so at best the Tesla got slightly more energy, not "orders of magnitude." There are tons of confounding variables, including the ambient temperature, the fact that the Rivian had just towed uphill, brake controllers and trailer brake configuration, software rounding of the SoC indicator, etc. You literally can't draw meaningful conclusions from the comparison.

I've driven all five of the Model X, Model S, Model 3, Model Y, and R1T. The R1T had easily the strongest regen of the five (as in, most aggressively decelerating with no mechanical brakes). That should correspond to more power returned to the pack in a like-for-like situation. We just don't have a like-for-like situation to compare yet.

We'd need an identical test in similar conditions and actual energy numbers using a trip meter or other instrumentation (not guessing based on the % SoC) to draw any conclusions.

 

[Kenshaka]

I've towed a wide variety of agricultural equipment, a lot of it pretty heavy, with both half-ton and one-ton pickups. I also have a lighter weight aluminum trailer I tow all the time with my Honda Pilot and sometimes pull heavier rented trailers with the Pilot. Overall, I'm impressed with what I saw from the test, putting the range issues aside for a moment. Normally, pulling an 8000 load or anything close to it with a half-ton pickup up a steep grade would have the truck engine roaring like crazy, the transmission hunting gears, and in the steepest parts speed would drop below the optimum. On the downhill, it would be a bit nerve-racking to keep the brakes from over-heating. The Rivian aced all of that and did it quietly and comfortably. Also, the fact that the Rivian is able to self-level with the air suspension is a nice feature. I've had half-ton trucks with a heavy trailer really squatting down in the rear, which affects their stability while driving. So lots of things to like about this TFL report on how the Rivian did towing a heavy load.

Now I totally get the range issue could be a deal breaker for some people that need to tow really heavy loads frequently and for long distances, like a maxed out big RV. But most people don't haul all that far, or can take time to stop, the Rivian should work very well.

Like some others have commented, I have to believe regular gas stations will start adding EV charging at some point. Will that take 10% market penetration by EV vehicles, or something less? Hopefully one of the national chains, maybe BP (now stands for Beyond Petroleum after all) will show some foresight and start converting one gas island per station to electric, or add them at the side of the station lot where a truck and trailer can pull in easily without blocking traffic. As someone pointed out, the electric vehicle would need to sit there somewhat longer than a gas vehicle, but a lot of people in gas vehicles are inside the gas station for 15 minutes or more by the time they hit the restroom, meander the shopping isles, stand in line for awhile, etc. So a 30 minute partial charge stop might only be displacing two gas vehicles. Hopefully Rivian trucks will be able to charge more quickly than what was shown today as Rivian improves it's software and battery technology.

The Shell station by my house in Sacramento has has had two EV chargers for over a year now

 

[EarlyAdptr]

Surge brakes are not dangerous and they are the standard brake type for boat trailers. Electric and surge trailer brakes perform similarly (trailer braking force increases the quicker the towing-vehicle decelerates). Surge brakes work better on trailers that are submerged regularly. There are aftermarket conversion boxes that can be retrofitted to boat trailers to make a hybrid electric/surge system. Those conversions sit on the boat trailer tongue, where the surge brake cylinder sits, and replaces the mechanism that mechanically compresses the surge brake cylinder with an electrically activated unit. That unit plugs into your vehicle and the electric brake controller in your vehicle now triggers the retrofitted unit to compress the brake cylinder rather than the compression of the trailer tongue doing so. The primary advantage is the ability to electrically activate the brakes while driving, but boat trailers rarely sway and there is major safety advantage to such a conversion.

Most surge trailers still have a brake activation cable to activate the brakes if the trailer becomes separated from the tow vehicle. Always ensure that cable is attached securely (and not to the hook of your safety chains; but directly to the receiver or someplace on the tow vehicle).

With surge brakes, as with any type of trailer brakes, you'll want to ensure they are maintained and adjusted correctly. There are adjustment procedures to ensure they are providing enough braking force when activated but not dragging while driving.

Small to medium surge brake boat trailers typically also have an physical accessory pin (a "backup" pin) that prevents the trailer brake cylinder from getting compressed when you back up. If the brakes are adjusted correctly, you'd normally feel a lot of resistance when backing up with the pin not in place if the brake cylinder on the tongue compresses enough as you back up. typically not an issue on flat asphalt, but backing into an inclined driveway, etc. would activate the surge brakes. Of note, there are some surge brakes trailers, typically larger trailers like your size and up, that electronically do this for you. It requires the trailer harness to be plugged into the tow vehicle because it reads the backup light signal to know when you are driving in reverse and so automatically keeps the surge brake cylinder from compressing. Quick way to identify that you do NOT have this feature is if your boat plus is a flat 4. Since this setup requires backup light wire, it will either have a flat-5 plug or a 7pin round.

Note that an electric backup lockout will not prevent the surge brakes from activating if the boat wiring harness is not plugged into the tow vehicle and would then require you to use a physical pin to lockout the brakes while backing up. If you have automatic/electric type, make sure you also have the physical pin and know how to use it so you'll be able to back up the trailer in situations where the wiring harness can't be attached to the tow vehicle (wire harness damaged, adapter stolen, someone elses pickup or a tow truck doesn't have a compatible light plug, etc.).

THANK YOU! Answers all my questions and comports with my operation of my surge-brake trailer

 

[Zybane]

This is a wild exaggeration. The Tesla got 4% compared to the Rivian's 2%. The Rivian has a significantly larger pack, so at best the Tesla got slightly more energy, not "orders of magnitude." There are tons of confounding variables, including the ambient temperature, the fact that the Rivian had just towed uphill, brake controllers and trailer brake configuration, software rounding of the SoC indicator, etc. You literally can't draw meaningful conclusions from the comparison.

I've driven all five of the Model X, Model S, Model 3, Model Y, and R1T. The R1T had easily the strongest regen of the five (as in, most aggressively decelerating with no mechanical brakes). That should correspond to more power returned to the pack in a like-for-like situation. We just don't have a like-for-like situation to compare yet.

We'd need an identical test in similar conditions and actual energy numbers using a trip meter or other instrumentation (not guessing based on the % SoC) to draw any conclusions.

It's a real world result. The only thing of significance that could alter the regen number would be inadvertent application of the trailer brakes. But I did not see the Rivian+Trailer slow down when the brake lights occasionally tapped on. Under hard regen, my Model Y brake lights also come on, doesn't mean the brakes are actually being applied.

Any way you slice it; a 7K lb Rivian plus 8K lb trailer only getting 2% battery back on the long steep decline is really bad. That is a LOT of kinetic energy. To only get ~2.7 kWh (approx. 2% of R1T battery pack) out of that is quite laughable.

 

[JeremyP]

A quick check on an online potential energy calculator, using 15000lbs and 2000 feet of elevation change, gives around 11kwh of potential energy that could be recovered. Anyone want to make an estimate of losses over 8 miles from rolling and wind resistance, battery charging losses, etc. to see if the energy recovered was reasonable?

Edit: is it reasonable that if the consumption was about 1kwh per mile on the level(ish) beginning of their drive then you can subtract about 8kwh (8 miles) of energy due to moving losses from the 11kwh of potential energy, which would result in around 3kwh that could go back into the battery? Just so happens that 3 out of 135 kwh is 2%

 

[chopsui]

The only thing of significance that could alter the regen number would be inadvertent application of the trailer brakes.

This is simply not true as many, including the TFL guys in the video have pointed out.


You don't need to be on here trolling. Your tesla stock will be fine.

 

[garthkoyle]

So the Model X gained 4% battery back regen doing the same down the Ike Gauntlet, with a 3,500lb lighter trailer.

Remember that the model x has a 35% smaller battery. So recapturing the energy will equate to a larger %.

 

[SANZC02]

It's a real world result. The only thing of significance that could alter the regen number would be inadvertent application of the trailer brakes. But I did not see the Rivian+Trailer slow down when the brake lights occasionally tapped on. Under hard regen, my Model Y brake lights also come on, doesn't mean the brakes are actually being applied.

Any way you slice it; a 7K lb Rivian plus 8K lb trailer only getting 2% battery back on the long steep decline is really bad. That is a LOT of kinetic energy. To only get ~2.7 kWh (approx. 2% of R1T battery pack) out of that is quite laughable.

Have to be aware of decimal places in the percent display as well. 2% of 135 is 2.7 kw, 2.9% is 3.9 kw. Without the decimal point or knowing where on the downhill portion of the trip it went from 1% to 2% we do not really know how much it generated.

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