Rivian towing efficiency

[Groover]

Long Rivian towing test

Bottom line, the Rivian range was reduced by 62% when towing a Mustang on a car hauler.

The route was from Detroit to LA so it was plenty long but other than that not a whole lot details.

62% range reduction sounds like much more than would expect if I were towing the rig with my F150 but as a Tesla owner I expected towing to hit an EV harder than an ICE powered one for several reasons.

1) Most EVs have great aerodynamics to extend their range so they will be affected more by a not very aerodynamic trailer than the average pickups already on the road.

2) EVs benefit from regeneration during stopping but in most cases the regen is sized to handle the base vehicle weight. Extra weight may have required the use of mechanical braking more frequently resulting in lost energy. Batteries don't absorb energy as well as they provide it so their is limit to how strong the regen circuit can be. Also, the regen circuit is different from the drive circuit so putting in a stronger regen circuit would add cost and weight to the vehicle.

3) Electric circuits lose efficiency according to the square of the amount of power being pushed through them so there may have been a major efficiency drop from the higher currents.

Anyway, this is just one piece of data and the results will be different for every trailer. I am impressed that they found enough chargers to let them make the trip so this proves that it can be done. And more charging stations are being built every day. The photos show that tow vehicles are not accommodated well. That will become more important as EVs become more prevalent.

I would love to see a similar test replicated by an ICE powered truck to compare the losses. Some graphs on drivetrain efficiency vs power to the ground for various drivetrains would be interesting too.

[valhalla360]

pianotuna wrote:

Groover wrote:

pianotuna wrote:
Grover,

I think it may be the square of the voltage--not "power".

Example

120 x 120 = 14,400

100 x 100 = 10,000

10,000 / 14,400 = 69%

So a 31% drop in wattage.

.
The voltage of a lithium ion battery is essentially fixed for any given vehicle. Since power is volts times amps and voltage is fixed the amps vary with power. So the I squared R losses do apply.

Afraid not. There may be less voltage drop--but there is still some.

And what about voltage drop in the wiring? If the motor is pulling twice the power for towing, the amperage in the wiring will roughly double (more with a bit of voltage drop). Double the amperage and you increase voltage drop in the cables which in turn increases the amperage.

I realize they are short thick cables but it's also a lot of power they are putting thru them (one of the reasons they generally use high voltage battery banks vs old fashioned 12v).

But 100miles between charging seems like a deal breaker for 99% of RV buyers.

I think something like Ford's plug-in-hybrid makes far more sense. Normal commuting, you can run almost exclusively on battery power (charging overnight in the garage) but when you need to make a longer run, the engine kicks in and you don't see the limitations.

[1320Fastback]

Sounds like less than 50 miles pulling a parachute. Right now EV just isn't there for towing long distance imo. Stopping often to top off the batteries to go 500 miles in total is a joke.

[philh]

aero drag on that trailer is nothing compared to a travel trailer that is shaped like a brick. I guessed a 2/3 drop in range with a full height travel trailer. Looks like I may have underestimated the impact.

[Wishin]

I think one of the big issues towing (or any long distance driving with an EV) is that the fastest charging takes place up to about 80% of the battery capacity. If you want to wait around to bring it from 80% to 100% of charge you might be at the charge station a really long time. So when they were typically charging up to 80% and stopping around 16% state of charge, you don't get much range.

I watched the TFL truck video and it was pretty good. They did a lot of digging to get as much info. as possible.

[pianotuna]

Groover wrote:

pianotuna wrote:
Grover,

I think it may be the square of the voltage--not "power".

Example

120 x 120 = 14,400

100 x 100 = 10,000

10,000 / 14,400 = 69%

So a 31% drop in wattage.

.
The voltage of a lithium ion battery is essentially fixed for any given vehicle. Since power is volts times amps and voltage is fixed the amps vary with power. So the I squared R losses do apply.

Afraid not. There may be less voltage drop--but there is still some.

[blt2ski]

Grover,
Based on my 40 years towing etc. Going from a potential high of 26 to 16 mpg and getting 10 towing, is not totally out of the ballpark.
I've gotten upwards of 25-26 with my current 1500 4.3 V6 empty, as low as 11-12 towing. An older GM 6.5 TD 16-18 down into the 11-12 typical, low of 9 best 14 towing multiple factors involved. My Duramax was a bit better than 6.5. BB V8 12 down to 7-8. SB V8's similar to 6.5 TD mpgs. Maybe 1mpg less.

So 40-60% in mpg/driving range is pretty typical. SWAG based on my numbers, some that have posted in last couple hours, a 40-50% drop is more typical for most most of us, with the 45% I mentioned earlier being a reasonable ave drop overall.

Marty

[IdaD]

JRscooby wrote:
How much does the trailer shorten the per tank range of your ICE?

2015 Ram CTD, 4wd/CC.

Empty highway is generally 18-19 at towing speeds.

An 11k lb fifth wheel or 10-14k lb gooseneck stock trailer drops me to 9-11, although I've seen 12. A lot more weight and wind drag than the setup on the Rivian test, obviously.

I've towed low profile and lighter trailers with this truck too. While I can't honestly say I've run the numbers, I can say I noticed far less impact on fuel use compared to towing larger trailers. I have to think the aerodynamic impact of a low profile trailer behind a brick shaped truck is a lot less vs the Rivian.

[goducks10]

I get my best mpg's cruising the net.

[Reisender]

JRscooby wrote:

fj12ryder wrote:

JRscooby wrote:
Am I getting the numbers about right? Comparing ICE that gets 10 MPG while towing, unhook the trailer and mileage jumps to 16.2?

Sounds more than reasonable. My Dodge gets about 10 mpg towing, and about 19 solo.

My little V6, the few trips made without trailer and long enough to check mileage, always ran 19-20.5. Running around town, 16-18. Towing my popup, under 62 MPH, 16-18. Never hauled a Mustang, but a '53 Chevy on a trailer took me down to less than 10.
My 3406E would average around 6, but bobtailing home from Florida Mississippi, or Minnesota after dropping Red Cross trailers, she would crowd 12.
What I really wonder is how many people that are bad mouthing the loss of range when towing have run the numbers; How much does the trailer shorten the per tank range of your ICE?

Bingo. Our grand cherokee easily lost half its range towing well within its spec. Max range of about 250 kilometres towing.

[JRscooby]

fj12ryder wrote:

JRscooby wrote:
Am I getting the numbers about right? Comparing ICE that gets 10 MPG while towing, unhook the trailer and mileage jumps to 16.2?

Sounds more than reasonable. My Dodge gets about 10 mpg towing, and about 19 solo.

My little V6, the few trips made without trailer and long enough to check mileage, always ran 19-20.5. Running around town, 16-18. Towing my popup, under 62 MPH, 16-18. Never hauled a Mustang, but a '53 Chevy on a trailer took me down to less than 10.
My 3406E would average around 6, but bobtailing home from Florida Mississippi, or Minnesota after dropping Red Cross trailers, she would crowd 12.
What I really wonder is how many people that are bad mouthing the loss of range when towing have run the numbers; How much does the trailer shorten the per tank range of your ICE?

[fj12ryder]

JRscooby wrote:
Am I getting the numbers about right? Comparing ICE that gets 10 MPG while towing, unhook the trailer and mileage jumps to 16.2?

Sounds more than reasonable. My Dodge gets about 10 mpg towing, and about 19 solo.

[Groover]

blt2ski wrote:

JRscooby wrote:
Am I getting the numbers about right? Comparing ICE that gets 10 MPG while towing, unhook the trailer and mileage jumps to 16.2?

That's a plus minus of towing with current V6. And similar to the diesels I've had.

I would not say that increase is absolute, but on par.

Marty

You are not using percentages correctly. If you had towing mileage you would multiply it by .62 to get the decrease in mileage. Or you could take a short cut and multiply it by .38 (1-.62) to get towing mileage. Working the problem backwards starting with towing mileage you would divide towing mileage by .38 to get non-towing. 10mpg divided by .38 is 26.3mpg.

To check it
26.3 X .62 = 16.3mpg reduction
26.3-16.3 = 10mpg

I don't think that you would see that much drop towing that trailer with a gasoline engine.

[Groover]

Better written article by TFL truck

[blt2ski]

JRscooby wrote:
Am I getting the numbers about right? Comparing ICE that gets 10 MPG while towing, unhook the trailer and mileage jumps to 16.2?

That's a plus minus of towing with current V6. And similar to the diesels I've had.

I would not say that increase is absolute, but on par.

Marty