Dual motor real life efficiency?

[Zorg]

So, what is the real world efficiency at highway speed (70-75) for a dual motor R1S with 21" wheels?

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[ads75]

I would assume Rivians range estimate methodology is the same for all of their trims/models, so whatever percentage of rated range verse real world range you have seen for the quad motor, I would apply the same for rated range verse real world range of the dual motor.

Customers supplying there own estimates probably won't be very accurate, most don't have dual motor verse quad motor to test, some live in cold climates, some have heavy foot syndrome some live in hill areas.

 

[Golfer04]

Supposedly is 10-12 percent better than a quad in conserve on the highway. A friend of mine has one and a couple of other people have reported on forums. Wish Kyle Connor would test one.

 

[Zorg]

Are we talking 2.4 miles per KWh?

 

[Electrified Outdoors]

Its a great question honestly. Dual motor is slightly better than quad motor in conserve mode.

DM in all purpose is basically driving around in conserve mode all the time when its going more than 20 mph. Unless your accelerating hard or there are traction issues. The rear motor can engage or disengage on the fly.

Quad large rated up to 347 mile on a full charge in conserve mode. DM in all purpose is rated at 352.

So to your question at 70-75 significantly less than that depending on conditions.

I like the quad motor for its capabilities and am fine with dropping into conserve when i need max range. Others prefer the DM which is extremely capable, slightly more efficient, and at a lower price point.

Rivian had some folks out to test them up against each other but efficiency wasn't one of the metrics.

 

[Zorg]

I am curious. Our R1T with 20" AT and quad motors got 2.0 miles per KWh over a 1500 miles road trip with freeway speeds around 80 ish in Conserve.

 

[zefram47]

I am curious. Our R1T with 20" AT and quad motors got 2.0 miles per KWh over a 1500 miles road trip with freeway speeds around 80 ish in Conserve.

At highway speeds wind resistance is going to dominate in the efficiency equation followed by rolling resistance of the tires. Just switching off a motor or two isn't going to significantly affect things.

 

[mkg3]

There's more to it.

Since all 4 motors are equal motors, each motor has 208.75 HP and 227 ft-lbf of torque. By going to conserve mode, only two are active. That means that to maintain any speed over given range, the total capability of the two motors are:

417.5 HP and 454 ft-lbf torque

For the Dual Motor (standard/performance), each motor has 266.5/332.5 HP, and 305/414.5 ft-lbf torque. It too goes to FWD mode in conserve so only one motor is active. So for the same conditions as the quad, it has:

265.5 HP and 305 ft-lbf torque

The DM performance is a software change to feed current and/or voltage to increase the HP so in the conserve mode, it drops down to be the same as the standard DM ratings.

One can easily see that DM uses much less HP and torque motor, which equates to lower Watts (amps x volts) so the consumption is less than QM. (1 hp = 745.7 watts)

At 80mph (or any speed but its more impactful at higher speeds), the drag, rolling resistance and the weight are nearly equal between the DM and QM (drag force is the same, both rolling resistance force, and weight are slightly better in DM since its lighter weight); hence, DM results in better range because it simply uses less Watts to maintain the same speed.

 

[sub]

There's more to it.

Since all 4 motors are equal motors, each motor has 208.75 HP and 227 ft-lbf of torque. By going to conserve mode, only two are active. That means that to maintain any speed over given range, the total capability of the two motors are:

417.5 HP and 454 ft-lbf torque

For the Dual Motor (standard/performance), each motor has 266.5/332.5 HP, and 305/414.5 ft-lbf torque. It too goes to FWD mode in conserve so only one motor is active. So for the same conditions as the quad, it has:

265.5 HP and 305 ft-lbf torque

The DM performance is a software change to feed current and/or voltage to increase the HP so in the conserve mode, it drops down to be the same as the standard DM ratings.

One can easily see that DM uses much less HP and torque motor, which equates to lower Watts (amps x volts) so the consumption is less than QM. (1 hp = 745.7 watts)

That isn't how motors it work.

The motors are not generating 417.5 HP and 454 ft-lbf torque when you are rolling down the highway at a constant speed.

As easy proof, 417.5 HP is 307 kw. If rolling along at a constant speed was using 307 kw it would only take 135 /307*60 = 11 minutes to completely drain your battery from 100% to 0%.

If you get 300 miles at 80mph that would mean that the motors are using 135 / (300/80) = 36kw of electricity. Which is about 48 horsepower.

The motors might have the ability to produce 417 HP but they are actually only producing 48 when you are going a constant speed on the highway.

This also makes sense because if it was using everything it has just to maintain it's speed it would throw you into the back of the seat when you floor it.

 

[Zorg]

Sounds like there might not be a big delta at freeway speeds between conserve mode and dual motors.

 

[R.I.P.]

Sounds like there might not be a big delta at freeway speeds between conserve mode and dual motors.

It's noticable. All else being equal, motors and inverters have a loss factor. Even if that loss is relatively small, the DM is going to have half the loss when compared to a QM running down the highway in conserve mode. Mile after mile, all the little things add up.

Probably the biggest factor, however, is that a lot of people are reluctant to run in conserve mode because of the potential for tire wear and a rear disconnect system with a less than stellar record. These problems have (hopefully) been corrected in the DM, and it all just happens automatically.

 

[mkg3]

That isn't how motors it work.

The motors are not generating 417.5 HP and 454 ft-lbf torque when you are rolling down the highway at a constant speed.

As easy proof, 417.5 HP is 307 kw. If rolling along at a constant speed was using 307 kw it would only take 135 /307*60 = 11 minutes to completely drain your battery from 100% to 0%.

If you get 300 miles at 80mph that would mean that the motors are using 135 / (300/80) = 36kw of electricity. Which is about 48 horsepower.

You the motors might have the ability to produce 417 HP but they are actually only producing 48 when you are going a constant speed on the highway.

This also makes since because if it was using everything it has just to maintain it's speed it would throw you into the back of the seat when you floor it.

Of course you're right. I wasn't implying that the motors are at full power at any given moment.

The point was that more powerful motor require more feeding. In other words, at any given power consumption rate at a constant speed, two motors with more power consumes more energy than a single motor with less power.

I didn't think I needed to explicitly state that one is not using full power when driving at a relatively constant freeway speeds. Sorry, I confused you on that part. I thought this was inherently obvious.

 

[SeaGeo]

Quad large rated up to 347 mile on a full charge in conserve mode. DM in all purpose is rated at 352.

I don't think that's an apples-apples comparison. If you dig into the EPA testing docs, DM is about 5% more efficient than QM in conserve. The range shown on the screen in conserve is not the range that the EPA test data produces in conserve.

 

[mkg3]

The best way to tell actual difference between QM and DM, is to drive at the same speed and get the actual consumption rate (kWh/mile).

One can divide the usable battery energy (~125 kWh for the long range and ~140 kWh for max pack).

It's difficult to simplify the discussion because there are so many unknown variables (e.g., loss from inverter, transmission ratio (resulting in corresponding motor RPM) and so on that all affect power consumption).

Even the actual kWh/mile displayed on the dash has a lag. It's too bad that Rivian gives data averaged over the last 15 minutes and for the odometer set. Would be much more useful if its averaged over the past 5, 15 and 30 miles, as well as instantaneous reading.

 

[sub]

Of course you're right. I wasn't implying that the motors are at full power at any given moment.

The point was that more powerful motor require more feeding. In other words, at any given power consumption rate at a constant speed, two motors with more power consumes more energy than a single motor with less power.

I didn't think I needed to explicitly state that one is not using full power when driving at a relatively constant freeway speeds. Sorry, I confused you on that part. I thought this was inherently obvious.

It also isn't obvious (or true) that a motor with a higher max output must use more energy at any given output.

As an example, if you have 2 nearly identical motors where the only difference is that one of them has a better heatsink installed the one with the better heatsink will have both a higher rated max output AND will use less energy at any given output because it will run cooler and electrical resistance increases with temperature.

While it appears that the motors on the dual motor config are more efficient, that has more to do with the how the motors are designed than what their max output is rated.

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