What would you like to see on your new Rivian or from the Rivian company??

[hola29]

I am merely trying to educate someone with some academic knowledge of the topic to understand the practical application of that knowledge.

I am not sure how long you have been on the internet, but those are the last words of someone taking a thread about "What would you like to see on your new Rivian or from the Rivian company??" quickly down the drain...It's all good

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[ajdelange]

Because you are having trouble understanding this let's walk through your numbers

Let’s say that Is 1 gallon an hour, and in cruise at 60 mph you are using 3 gph total, or 2 gph to actually move the truck. If you get half the gas mileage when towing that means you are using 6 gph or 5 gph to move the truck and trailer.

Without the trailer you are losing 1/3 of the energy and so your efficiency is 2/3 or 66.7%. When you add the trailer you are losing 1/6 and so your efficiency is now 5/6 or 83.3%. Here's your first error. If you had any experience with Otto or Diesel engines you would know that there aren't any out there with 66% efficiency and you would also know that changing the load does not improve efficiency by 16%. Efficiency may change by a couple of percent with load but not 16%. This isn't actually that relevant to the discussion because, as I pointed out earlier, the range reduction factor does not depend on the actual efficiencies.

You went from 2 to 5 which is a 150% increase, so the EV would see a 150% increase in power consumption for the same conditions and not just a 100% increase.

You didn't go from 2 to 5. You went from 3 to 6. Your traction power consumption went from 2 to 4 gph and your thermal loss consumption from 1 to 2 gph. Both doubled. This is, of course, the major error: assuming that the losses stay constant when the load goes up. You may not have had any practical experience with things mechanical and/or electrical and might not be aware of this but losses are like taxes - they are determined as a percentage of the useful energy. That percentage may vary with conditions. See the Wikipedia article https://en.wikipedia.org/wiki/Energy_conversion_efficiency for further insight.

 

[CappyJax]

WHAT???? I don't even know what to do with your level of stupid.

You aren't losing 1/3rd of the energy, because the engine itself is still at best only 30% efficient. So, at idle, you are using a gallon, and only 30% of that is being used to generate the power needed to keep the engine running. In other words, .3 gallons is used to keep it running. At 60 MPH and 3 gallons per hour, you would be using around .6 gallons to actually move the vehicle if that 30% efficiency is maintained. .6 of 3 gallons is 20% which is what you said, genius!!! At 6 gallons an hour while towing, you now have 25% efficiency. The overall efficiency goes up because you have increased the volumetric efficiency of the engine. And load can actually have a huge effect on efficiency. An engine with no load has a 0% efficiency. An engine running all out will have its highest efficiency of around 30%.

"You didn't go from 2 to 5. You went from 3 to 6. Your traction power consumption went from 2 to 4 gph and your thermal loss consumption from 1 to 2 gph. Both doubled."

Um no. Thermal loss doesn't even factor in here because we are talking about the efficiency of the vehicle, ie MPG, not the thermal efficiency of the engine which would already be factored in when considering MPG.

"You may not have had any practical experience with things mechanical and/or electrical"

I make a living with my practical experience.

 

[electruck]

Guys, let's take the engineering offline. Please.

 

[ajdelange]

Guys, let's take the engineering offline. Please.

I do think that there is some room for engineering information here as these vehicles are nothing if not engineering marvels and I can't believe I'm the only techie on here. But I agree there is no point in offering it to people who cannot benefit from it. Clearly in terms of the current "discussion" the kind thing to do is go silent but I don't want to discourage anyone who wants to know more about the graph in No 156, for example, from asking.

 

[electruck]

I was simply being polite. I'm not opposed to engineering discussions but this one was both massively off topic and turning personal.

 

[CappyJax]

...I can't believe I'm the only techie on here.

HA!

 

[ajdelange]

Trailering is definitely a hot topic just at the moment, more so on the CT forum than here perhaps but it should be of interest to potential Rivian owners too. With this is mind I'd like to add to the wish list a strain gauge on the trailer hitch. Knowing the towing force and the speed the truck's computer can calculate the power going to the trailer and I am assuming it will be displaying the total power consumption as a matter of course since I don't know any BEV that doesn't display power consumption. One also gets the Wh/mi consumed by the trailer from this which is the key to range prediction and would be very helpful in educating the driver on the implications of load, terrain, weather etc. on trailering operations. And, to a tech geek, it would be really, really cool.

Another application of a strain gauge is that as soon as you pull away the truck gets a rough estimate of the trailer's gross weight. This may be valuable from the safety perspective and could be used to improve range prediction algorithms that include elevation (ABRP and the Tesla navigation system both do this).

 

[ajdelange]

While posting this idea on the CT forum it occurred to me that a second strain gauge on the hitch would allow display of tongue weight so I want that too!

 

[electruck]

Another application of a strain gauge is that as soon as you pull away the truck gets a rough estimate of the trailer's gross weight. This may be valuable from the safety perspective and could be used to improve range prediction algorithms that include elevation (ABRP and the Tesla navigation system both do this).

I suspect automous driving algorithms could also make good use of that data if they are going to support any kind of towing in that mode. Although, they can probably also infer that info from the current draw on the motors.

 

[eltrkadvntrr]

Adding a strain gauge for towing is a cool idea, but it comes at a cost. I am sure that a ton of people who say they want it will cry and complain at the cost of it.

 

[ajdelange]

You could say the same about the spare tyre or the second charging port or the 120V outlets or the compressor or.... This is, of course, easily managed, should they think this a potential problem, by offering it as part of "the advanced towing package" or something like that. Now I don't think they will offer it because so few people would appreciate what it could do for them that they wouldn't sell many under any scheme. But this is a fantasy thread. I can dream and ask for a relativity condenser if I want to.

 

[ElectricTrucking]

Some times a thread needs to be closed. This is one of them.

 

[ajdelange]

Wonder why you say that. Though over 6 months old it continues to yield some interesting ideas.

 

[hola29]

And back to our regularly scheduled program...

This may already be a feature, but some sort of sync w/ an alarm clock on iOS/Android, or time to leavee to get the car warmed up or cooled down. Getting in to a pre-warmed, cooled car every time would be awesome. Has that been discussed? I don't have a Tesla (or a modern car really) so maybe that is common?

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