Which, given the 20% larger battery on the "truck", is quite a difference.

The "truck" weighs around 20% more (CT @ 6,000 lbs vs X @ 5000 lbs), so the larger battery pack effect is nullified and cancels out.

It’s more likely about aerodynamics (unless you’re going uphill with no regen, or doing a lot of stop/start)

That's not how these calculations work at all. Weight (if it doesn't change the size or shape) really only has an effect on rolling resistance, which is a small portion of overall losses.

The extra weight should make a marginal difference in efficiency. Just expect more tire wear.

That seems to be a rather simplified view, as if stemming from the world of frictionless pulleys and rope that does not stretch.

These are self-propelled electric vehicles that have regenerative braking. Regen is miles ahead of just dumping momentum as heat [as conventional brakes must] but it can never be 100% efficient -- and it may not even be able to begin to try to capture 100% of that momentum in the first place, depending on the particular braking circumstance.

These characteristics weigh heavily on how such vehicles perform in the real world, especially when the terrain is not flat. (And in this test, the terrain was not flat.)

It is a pretty simplified view.

I wrote an electric vehicle power / efficiency / range estimation program back in college when I was very into building electric bikes. (More advanced version of the ebikes.ca calculator for an example). There were a whole lot of parameters that went into actually estimating the performance, but the general rule of thumb was rolling resistance is pretty much worth ignoring (for efficiency) until you have spent time optimizing aero and drivetrain losses.

It was pretty damn close to real world measurements.

I'm going to use rules of thumb rather than exactly calculating things for a colloquial conversation online.

Doesn’t weight have a massive effect on power needed for acceleration ? To go from A to B You need to get up to speed but also acceleration for regulating your speed after taking a turn, crossing a traffic light, passing someone over…

If we ignore air resistance, then weight and time are the only variables needed to determine the power needed for a given acceleration. Force is related to mass through "F=ma", and power is effectively force over time.

Though, neglecting air resistance is a huge deal. A cyclist traveling over 20mph is spending something like 90% of their energy at that point overcoming air resistance. For objects travelling faster, it's a square low of how much more power is needed. Air resistance is a very huge effect. With that said, if travel is dominated by accelerating and decelerating (eg: urban or mountainous environments), then yeah - weight is a huge big deal.

Newton's laws of motion would like to have a talk with you about those statements. A heavier vehicle absolutely needs more energy than a lighter one when all other factors stay the same.

The majority of energy expenditure is not acceleration and deceleration (especially on an EV with regen braking). At moderate and high speeds wind resistance dominates. At slower speeds rolling resistance is a largish factor.

And what does Newton say about regenerative braking? Does the energy you put into the system just go puff?

I hate when people make smart-ass claims with surface level knowledge at best.

> Does the energy you put into the system just go puff?

Yes, actually. The most common example of this is drivetrain power loss, which EVs are not immune to. Tesla engineers have stated that they are ~15% which is about the same as with ICE vehicles.

While a heavier vehicle at times needs more energy - trains are a counter example to consider. Magnitudes heavier, but do not need magnitudes more fuel.

Which comes to Newton's laws of motion, the two concepts of inertia and Newton's second law: "F=ma", come into play. If the course is a straight 100 mile segment with no elevation gain - then the dominant fuel expenditure will be counter-acting aerodynamic drag. When trains haul many cars, the train cars are drafting behind one another, meaning those cars do not need any force to overcome drag, just the lead car needs to do that.

So, places where trains do badly, will be places where weight matters. Urban environments when stopping/starting a lot - trains will keep it slow. Very hilly/mountainous courses - trains "nope" that and require shallow grades. Which goes to show, if you're spending most of your time fighting gravity - then weight is really important, if most of the time is fighting aerodynamic drag, then weight becomes less important as aerodynamic drag decreases. For example, it does not matter as much how heavy a bullet train is, the drag coefficient is a better indicator of overall fuel cost rather than carry weight.

I'd love to see how you derive that from Newton's Laws of Motion, which are all about acceleration. All other things being equal, it takes no more or less energy to keep a heavy object in motion than a light one. After all, a pendulum's period is proportional to its length, and not its weight.

There’s a 600ft climb involved too. It’s not an enormous difference, but lifting that extra 1200lbs still adds up to about 0.3 kWh.

And then you have a good percentage of that .3 kWh available as extra energy to recapture as regen.

Is that a good thing to have a very heavy car ?

Yes, it decrease range, increase road wear, increase tire/brake pollution, decrease road safety

I can't think of a single negative thing

Bigger and heavier cars are more expensive, thus they are worth more and they must be better.

Ok, I get it, there is more metal, so the scrap value is higher. Makes sense.

And it has a much higher tow capacity