We're still not at the point where weight savings from motor offsets battery. Tesla cars are all extremely heavy for their size

Not by much. The Model 3 is approximately 1 person heavier than a comparable BMW 3 series. The Model 3 Long Range is about one person heavier than a 3 series wagon.

The BMW 330i is about 660lbs lighter according to some questionable internet sources for curb weight

Base Model 3 is 1611kg vs 1545kg for a 330i. I'm looking at both a 330e and a Model 3 at the moment or maybe an M340i xdrive touring.

The mass is a problem of you don't t recuperate braking energy. Tesla's do recuperate braking energy. A heavy ICE driven vehicle in contrast just loses braking energy as heat.

Edit: typo

Energy recovery from regen is minimal unless you're stuck in stop and go traffic. Usually less than 5%.

The argument made wasn't so much about getting more range from regen as about regen lessening the impact of added mass: with perfect regenerative braking, a ten ton vehicle wouldn't use much more energy than a one ton vehicle if they shared the same outer hull.

Real life doesn't have perfect regen, but on the other side of the equation real life ICE cars actually lose more efficiency to added weight than just what is converted to heat while breaking because they tend to compensate worth a bigger engine to get comparable (or better even) acceleration than a lighter counterpart and that means that during cruise where the mass is irrelevant the engine is running at all an even worse load point in terms of efficiency. ICE are terribly inefficient at partial load and when your engine is sized to get decent acceleration despite high total mass you simply can't gear long enough to get the engine to a reasonable load point in a moderate speed cruise. Electric motors don't have this problem (or a much, much smaller version of it), so they wouldn't suffer quite as hard from added mass as ICE even worth no regen at all.

> ICE are terribly inefficient at partial load

Yes, but this doesn't happen much anymore. Torque converter, electronic throttle control, variable valves, and 6+ speed gearboxes means the engine is usually near full throttle even if your foot is barely on the gas.

Turbochargers also help, along with cylinder deactivation for some V8s.

Modern engines are nearly always at a relatively efficient load point. This wasn't true until about a decade ago though.

A Prius or Ford Fusion hybrid get better MPG in city driving than highway. That's because regenerative braking recovers most of the energy needed to get back up to speed. The improved MPG has more to do with higher drag at high speeds which reduces efficiency.

Unless you're stuck in stop&go traffic, the extra energy needed to move the extra mass isn't particularly large either.

It highly, highly depends on motor setup.

Tesla low gearing induction motor is by far not the best here.

Synchronous motors have much better regen capability.

There's just not that much power available for regen. I've done a lot of dicking around with E-scooters. Even at their low speeds with lots of stop and go, regen is less than 10%.

It's only used because dumping excess energy back to batteries is cheaper than including brake hardware. The math may work out the same for EV's. Regen just to decrease the cost of brakes rather than increase range significantly. In the e-scooter world, the cheap ones use regen and more expensive models have traditional disc brakes.

Air resistance burns a ton of energy at any speeds over 20mph.

How much RPM were you getting at your scooter, and what was the vehicle mass?

You say 5% at most... The difference in between, say, 5% and 10%, a bad and good regen is huge.

The RPM's are huge. Like 16k, because smaller motors are lighter for same power. Mass is generally 40lb + rider.

The RPM doesn't matter much though. Regen efficiency is around 80% from wheel to battery. With cars you get much less regen because you lose tons of energy to air at the speeds they travel.

Mass also increases braking distance and reduces handling, no?

First off, 48 volt systems doing regen is already taking off, and there are already many new cars doing it (not just ones that have a hybrid sticker on them either: https://en.wikipedia.org/wiki/Mild_hybrid#Examples)

Second, as other comment says, the idea that braking regen is going to make up for an extra half a ton of batteries is pretty laughable

Also the ice is only 30 percent efficient, where the electric is around 95. So take the energy density /3 for starters.

While your point is arguable what is not arguable is that the weight in a Tesla is very much evenly distributed across the chassis and has a very low center of mass which leads to excellent handling. Whereas an ICE typically has a big heavy engine up high and at the front of the vehicle which puts the vehicle's center of mass way out of whack.

> the equivalent ICE would be 500+

It's not quite that heavy. An LT1 makes 500 horsepower and weighs less than 500 pounds.

It definitely varies, though under 400 lbs would be tough to find....it takes a significant amount of effort to make a light, high power engine. Electric motors OTOH are well understood, and relatively easily engineered.

The point still stands though. You're savings a few hundred pounds compared to an ICE, but you're losing more than in battery weight. An x2 (or maybe even x1.5) increase in battery density, and a (ground up) electric vehicle will almost always be lighter than a similar conventional car with a full tank of gas.

Are you including the transmission?

Teslas have a transmission, but it's not in the same league of complexity or weight.

Forgot about that on my longer reply. EV engines are _tiny_ and incredibly efficient.

However you are ignoring that while you can spin the blades more efficiently, however scaling an electric motor to that size may end up with even more weight, you also have to replace the turbojet portion of these motors. So you will need even more engine. That turbo jet is more efficient at speed while the fan is better at lower speed.

In the end we would have slower planes but we will eventually reach a point where we can do it.

Someone can probably explain it better and my understanding is rough and not current; jets were cool when I was kid

Your speculation about motors is incorrect; motors are actually more efficient the larger you build them. It's a property of the goodness factor: https://en.wikipedia.org/wiki/Goodness_factor

It is profoundly foolish to compare motors and heat engines on first principles like this, obviously. Still, here's a turbine that handles 30x the power of a jet engine, running a generator that is about the same size as a jet engine: https://www.ge.com/news/sites/default/files/Reports/uploads/...

generator is in the upper left. Obviously not at all optimized for size or weight- there aren't even any magnets in that thing.

You're making the parent comment's point, ICE != ICE

Mercedes is selling cars with an engine that weighs 354 lbs, with just 2 liters of volume. Now 354 lbs is still pretty heavy, but it's 354 lbs with fluids and accessories.

Some (many even) of those accessories have equivalents on a Tesla that aren't included in saying it weighs 75lbs, like pumps for coolant and the AC compressor

But the two aren't at odds, o e could use an electric engine and still burn gasoline to produce the electricity, sort of like ships do.