how does weight affect range?

[abirozy]

Good afternoon everyone

This may have been answered, but i want to ask again and i hope i don't sound idiotic for asking. How does weight affect range in the R1T? By that, i mean, when i add accessories to the truck how will that affect the range?

1). i have put a heavy duty bed mat in by black armor. It is great, but adds about 100 lbs i think.
2). I want to add sliders. i am leaning towards the DCE at this time since i can go look at them in Anaheim and they seem very well made, but I assume they add quite a bit of weight.

i know that is like carrying an extra person around all the time, but will that affect the range greatly? if so, that may affect my decision slightly.

Best

Adam

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[Zoidz]

I recall seeing this article. This test claims to have been done empty and with a full rated payload.

"For comparison, the Rivian R1T averaged an impressive 2 miles per kWh during the same hauling efficiency test, which was only a 0.15 mile per kWh reduction (about 7 percent) compared to the previous test during which the truck wasn't carrying any weight."

 

[kylealden]

The short answer is "barely." Small differences to aero (roof mounted cargo, bike racks, etc.) will nuke your range; big swings to weight will be mostly imperceptible, within 10% or so of rated even at max payload.

The significant exception is wheels, which have a rotational component and are unsprung.

But in general, don't sweat it. Not worth worrying about for day to day driving.

If you want to set a coast to coast hypermiling record, yeah, leave the lead bricks at home (and consider pulling some seats).

 

[abirozy]

The short answer is "barely." Small differences to aero (roof mounted cargo, bike racks, etc.) will nuke your range; big swings to weight will be mostly imperceptible, within 10% or so of rated even at max payload.

The significant exception is wheels, which have a rotational component and are unsprung.

But in general, don't sweat it. Not worth worrying about for day to day driving.

If you want to set a coast to coast hypermiling record, yeah, leave the lead bricks at home (and consider pulling some seats).

Thanks for that answer...

 

[Redmond Chad]

When most people ask about "range", they mean highway range as few people try to drive over 300 miles in city traffic. kylealden's answer is perfect for them - weight means little on the highway, where aero reigns supreme.

But weight does make a difference if you do a lot of speed changes - such as in city traffic. If you have notably more weight and do a lot of city driving, you will notice an efficiency drop.

 

[VSG]

But weight does make a difference if you do a lot of speed changes - such as in city traffic. If you have notably more weight and do a lot of city driving, you will notice an efficiency drop.

I'm not so sure about that. With a greater weight regenerative braking will recover more energy as well, which will mostly offset the additional energy required for acceleration. (It is this energy recovery which makes city driving more efficient than highway driving for EVs.) I think the conclusion of "not much effect" is still correct.

 

[Singletracker]

Weight is not a huge issue, unless constantly going uphill. But, what goes up, must come down ? Aerodynamics (especially higher speed) and more aggressive tires (additional rotating mass and higher rolling resistance) are the biggies, IMHO.

 

[Redmond Chad]

I'm not so sure about that. With a greater weight regenerative braking will recover more energy as well, which will mostly offset the additional energy required for acceleration. (It is this energy recovery which makes city driving more efficient than highway driving for EVs.) I think the conclusion of "not much effect" is still correct.

I agree that regen does indeed recover some of that lost energy. Sometimes quite a bit, up to about 2/3 in fairly ideal cases. Whether what remains lost is "not much effect" or not is open to interpretation, but after driving EVs since 2008 I've found it to have enough of an effect that I notice. For example, in addition to aero losses, going up 1,000' costs 7 extra miles of range in a Model 3, and 10 miles in a Model S. Yes, you'll gain more in regen on the S (assuming you go downhill the same amount before you next charge), but you're still out more because of the extra weight. I find that the weight really matters if you are making calculations about range, which is what the OP asked. As you pointed out it does make less difference to overall efficiency (because that's when "what goes up must come down" comes into effect - it's averaged over all driving, not just one charging leg).

Lower revs in city driving (only down to a point, somewhere between 18 and 30mph in motor efficiency graphs I have seen) make the motor more efficient, and going slower means you don't have that efficiency-sucking aero to deal with. Those make city driving more efficient in some EVs (not all - for example my wife's 2017 Tesla X 100 is rated at 86 city, 89 highway).

When you have to slow down, using regen instead of braking means you lose less efficiency to brake pad heat. That's great, but it doesn't make that type of driving more efficient; it just cuts losses. If you were able to keep a constant speed through the city, you would do better than if you have to speed up and slow down.

 

[goldburger]

BUMP on a related weight note--how much does the weight of a TIRE have on efficiency? Is 10lbs significant? 20? Or is it almost all about tread/rolling resistance?

 

[mikehmb]

BUMP on a related weight note--how much does the weight of a TIRE have on efficiency? Is 10lbs significant? 20? Or is it almost all about tread/rolling resistance?

There’s a great Engineering Explained somewhere about the impacts of rotational, unsprung mass on inertia and range. Both play a considerable role. Rivian’s OE 20” tire is the same tread as the standard Pirellis Scorpion AT, but lighter (116 vs 126 load rating).

I would love to see a side-by-side test of the 20” OE tire vs the same tire in the 126 load rating. That should tell us a lot.

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