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

[Chadx]

Rivian should be able to confirm it’s behavior but they are lacking in communication with its upcoming customers. Perhaps you could ask them. If my speculation is correct then it would be an easy fix in the software to allow the gain to be tuned properly and only have the trailer brakes engage with brake pedal activation to maintain towing safety.

This would be ideal and would be identical to how an ICE Pickup functions. When one uses ICE engine braking, the electric trailer brakes do not engage and I disagree with others that have said a Rivian should initiate braking with the trailer brakes while regen braking. Brake lights perhaps, but there should never be trailer brakes triggered by regen braking. That would be like a ICE pickup sending signal to trailer brakes when you are engine braking. No reason for that. Trailer brakes should only be activated from applying brake pedal (or the manual override button on steering wheel).

I always manually downshift my ICE transmission to engine brake (rather than relying on the pickup to downshift like on typical towing reviews). With conscientious driving (such as not starting ones decent down a mountain pass already at 75mph), I rarely use mechanical brakes driving down mountain passes while towing.

It is absolutely not dangerous for a Rivian to be programmed to not engage electric trailer brakes until the brake pedal is pushed as that is exactly how ICE pickups work. Regen on an BEV pickup is no different than engine braking on an ICE pickup. When one pushes the brake pedal, the typical inertia-based (proportional) brake controller sends increasingly higher voltage, and more trailer braking force, based on an accelerometer that senses the decrease in momentum (unless using a time-delayed brake controller). The quicker the vehicle is slowing, the harder the trailer brakes are applied all the way up to the max voltage the brake controller is set to. Having the trailer brake override button on the Rivian steering wheel is fine and no different than leaning forward to the dash and manually squeezing a typical ICE pickup brake controller to apply the trailer brakes to stop a wagging trailer or in other situations where it's needed. More to it than that, but that the simplified version.

Only Rivian knows how they have the trailer brake controller programmed, but they should program it to only send voltage to the trailer brakes when the pickup brake pedal is depressed or the steering wheel gain in pressed. They should never be sending braking signal to the trailer on regen. That would cause unnecessary wear on a trailer brake pads and potentially excessive heat for absolutely no reason. A pickup should not apply trailer brakes unless the driver presses the brake pedal (or the override button). Period. Just like an ICE pickup brake controller.

Note that trailers with surge brakes are entirely different than electric brakes and the pickup brake controller (Rivian or otherwise) has no communication or impact on trailer surge brakes. Surge brakes engage when the trailer tongue compresses the brake cylinder (read: When the trailer pushes into the pickup when the pickup is slowing faster than the trailer). The harder it pushes, the more pressure that is applied to the trailer brakes. Driving mountain passes often is one reason why I much prefer electric brakes over surge brakes because I only want the trailer brakes to engage when I step on the brake pedal (or apply with brake controller) and not when engine braking like surge brakes will sometimes do. Electric brakes will also engage if a trailer separates from the tow vehicle (small onboard emergency battery activates electric trailer brakes) vs a surge brakes not doing so.

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[the long way downunder]

It is interesting, especially for those that want a "camping" option other than the Yakima tent. I'd still like to see a trailer specifically tailored to using regen braking to augment an EV's own regen braking to add even more energy return to the vehicle for people that want to have a tow trailer option and not have it bogged down by the significant weight additional battery storage will add.

Check out the Airstream eStream
https://www.thorindustries.com/innovation-estream
I'd like to see Rivian work with Airstream and have the trailer connected V2V, while towing, for regen and for the trailer to be a "booster" power source for the R1 and the R1 be a campsite generator for the trailer.

 

[Chadx]

@moosehead and others:

I'm relatively new to towing - I have a 6,500 pound boat I tow a short distance 2 times a year (in/out of storage and water). Nothing crazy, and not very far. The trailer is brake system (as far as I know) is activated by the pressure of the weight of the trailer when the vehicle slows down (and the trailer moves closer to the vehicle). What's that called?

Anyway, I'm intrigued by this notion of a brake controller. Does every trailer have the ability to communicate with the vehicles brake controller - or only some (and the others have a mechanical braking system)? I have a brake controller in the used Sequoia I purchased, but never gave it much thought thinking it didn't do anything..... hmmm

Also, what is meant by "gain"? I get it's some sort of 'sensitivity' control - but exactly how should I think about it and the scale I can select from (e.g, is a 5 really half of 10, or is it not linear)?

Thanks in advance.

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.

For trailers with electric brakes, the gain is set depending on each trailer and how much load you have in that trailer as well as road conditions. You may have a trailer where, when loaded, the gain is set to 7, but if you leave it at 7 when the trailer is empty (read: lighter weight), that same setting will have the trailer brakes locking up. So you may set the gain down to 4 or so when running that same trailer empty. Same with slippery conditions where the trailer brakes have less traction and so may lock up unless the gain is set lower.

The process to setup the appropriate gain for each trailer and how it's loaded at the time is available online, but the short version is one drives a slow speed on dry pavement and uses the trailer controllers manual override to force the controller to push it's current max gain setting to the trailer (without you stepping on the brake pedal) and the trailer reaction is observed (locking tires and you should set it lower. Not enough braking force, set gain it higher).

 

[the long way downunder]

It is absolutely not dangerous for a Rivian to be programmed to not engage electric trailer brakes until the brake pedal is pushed

That's the gist of it. So long as the brake pedal pressure was in "regen" range, with no friction braking in the R1, the trailer should not brake unless there's a stability intervention.
Once the regen is max'd out and the vehicle starts using the friction brakes, the trailer should participate to share the work (avoid vehicle brakes overheating) as well as enhance the stability by having the trailer "pull the vehicle straight."

 

[E.S.]

Check out the Airstream eStream
https://www.thorindustries.com/innovation-estream
I'd like to see Rivian work with Airstream and have the trailer connected V2V, while towing, for regen and for the trailer to be a "booster" power source for the R1 and the R1 be a campsite generator for the trailer.

As mentioned above, the Airstream eStream is a good camping option for those that want something bigger than the Yakima tent. What I mentioned was a towing trailer that heavily used brake regen (like an EV) to work in tandem with an EV's own brake regen and not be bogged down by the additional weight of the extra batteries on said trailer.

 

[Trekkie]

The DC charging speed is my biggest concern with Rivian. My Audi E-tron (2019) will hold 150kW all the way to 80%. It's battery is 83.5kWh, about 40% smaller than the Rivian. So the Audi charges at a higher speed and has less capacity to refill. There is no excuse for the Rivian to not hold at least 150kWh all the way to 80%. Even without towing, it will turn my 20 minute charging stop in the Audi to almost 40 minutes in the Rivian.

I'm getting a 2022 S model while waiting for my Max Pack

keep in mind, Audi (and VW) do some cool things/not cool things depending on your point of view. The battery is really 95 (i think) and you get 83.5 of it, so they can charger harder/faster/longer but at the trade off of not getting to use the whole thing.

I kinda like that design, because it makes charging so nice as you point out.

 

[moosehead]

This would be ideal and would be identical to how an ICE Pickup functions. When one uses ICE engine braking, the electric trailer brakes do not engage and I disagree with others that have said a Rivian should initiate braking with the trailer brakes while regen braking. Brake lights perhaps, but there should never be trailer brakes triggered by regen braking. That would be like a ICE pickup sending signal to trailer brakes when you are engine braking. No reason for that. Trailer brakes should only be activated from applying brake pedal (or the manual override button on steering wheel).

I always manually downshift my ICE transmission to engine brake (rather than relying on the pickup to downshift like on typical towing reviews). With conscientious driving (such as not starting ones decent down a mountain pass already at 75mph), I rarely use mechanical brakes driving down mountain passes while towing.

It is absolutely not dangerous for a Rivian to be programmed to not engage electric trailer brakes until the brake pedal is pushed as that is exactly how ICE pickups work. Regen on an BEV pickup is no different than engine braking on an ICE pickup. When one pushes the brake pedal, the typical inertia-based (proportional) brake controller sends increasingly higher voltage, and more trailer braking force, based on an accelerometer that senses the decrease in momentum (unless using a time-delayed brake controller). The quicker the vehicle is slowing, the harder the trailer brakes are applied all the way up to the max voltage the brake controller is set to. Having the trailer brake override button on the Rivian steering wheel is fine and no different than leaning forward to the dash and manually squeezing a typical ICE pickup brake controller to apply the trailer brakes to stop a wagging trailer or in other situations where it's needed. More to it than that, but that the simplified version.

Only Rivian knows how they have the trailer brake controller programmed, but they should program it to only send voltage to the trailer brakes when the pickup brake pedal is depressed or the steering wheel gain in pressed. They should never be sending braking signal to the trailer on regen. That would cause unnecessary wear on a trailer brake pads and potentially excessive heat for absolutely no reason. A pickup should not apply trailer brakes unless the driver presses the brake pedal (or the override button). Period. Just like an ICE pickup brake controller.....

@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.

 

[Zybane]

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.

 

[ads75]

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.

Do you have a link showing a Tesla towing like this? I'd like to see the direct comparison.

 

[the long way downunder]

Do you have a link showing a Tesla towing like this? I'd like to see the direct comparison.

TFL did the Ike towing test with the X. They published a couple of videos.
https://www.youtube.com/results?search_query=tfl+tesla+ike

 

[Zybane]

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

 

[the long way downunder]

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

It would be interesting for TFL or someone to do an apples-to-apples between X and R1 (I'm disappointed they didn't have a Model X there for the R1T test, which is there normal format, to "head to head" to competitors.)
I think TFL neglected to experiment with the trailer brake controller gain and the vehicle regen settings. I would have liked to see them immediately repeat the test (after all, it's an 8 minute climb … surely they could repeat the test in the space of 30 minutes, do enough charging to get back to the same state-of-charge) and maybe accelerate more modestly to 60 mph. Also the adaptive cruise went off-line, so they should have repeated to make a pass using cruise.
I don't think the R1 is anywhere near as efficient as the Model X – aside from being a ton heavier, it's rolling on heavier, tires and was towing a heavier trailer … again, why not repeat the test at 4500lbs to compare to the Model X and repeat at max rated load?

 

[EarlyAdptr]

So am I watching these correctly, with the Tesla test, they pre-position the tesla WITHOUT towing the trailer, and then connect the trailer just before the steepest part of the test and then go down?

Versus with the Rivian, they are using a heavier load, and tow it all the way from their office to the "staging area" and then (also towing) run the final steep part and then down?

That doesn't seem very consistent to me. I can understand not towing the same load, as the X maxes out at 5,000 pounds.

 

[the long way downunder]

So am I watching these correctly, with the Tesla test, they pre-position the tesla WITHOUT towing the trailer, and then connect the trailer just before the steepest part of the test and then go down?

Versus with the Rivian, they are using a heavier load, and tow it all the way from their office to the "staging area" and then (also towing) run the final steep part and then down?

That doesn't seem very consistent to me. I can understand not towing the same load, as the X maxes out at 5,000 pounds.

Yep, they're normally consistent, but for the X they didn't repeat the usual test program. Seems to me for the X, they should have had it versus a PHEV that can tow 5000lbs.

footnote: towing 5000lbs is really limiting … the "math" of tongue weight, cargo area passenger load, and what you probably want to tow (boat, rv) makes it impractical … not forgetting 100 miles between having to find a Supercharger and then charge for an hour. I've been towing with an X since Feb 2016, usually an enclosed snowmobile trailer that also works as a sort of "van" for moving things. Between the Supercharger access with trailers and the range, it's just not practical. The "soft road" SUVs typically tow 7700lbs and that is a useful number – towing more than 7000lbs requires a tow vehicle, not a family wagon. While the R1 boasts 11,000lbs, to me what that means is it can tow 7000lbs and I don't have to futz about with tongue weight limits or GVWR. I just wish it came with the max pack (180kWh) and 300kW+ charging with a very fat, flat curve.

 

[1shadowsabre]

Many comments have been made about the lack of energy regained before this video came out. I also wondered why they didn't regain more energy via regen. It is mentioned that the brake pedal was not touched during the decent however the brake lights came on as they should when decelerating(most if not all EVs do this). I wonder if the trailer brakes are actually activating when this occurs. That could explain why they didn't recoup more energy along with possible thermal management of the battery. Paying attention to the charging, it appears that the BMS is certainly in its infancy.

@TFLtommy Did the trailer brake stay set at 5 for the entire test?

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

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