[ardit33]

Number 1 problem is battery weight though. Not electric motors.

I have a 84 w123 300D, and would love to add some more power to it. Lightweight hub motors would be great, but any decent size battery would be at least 200lbs+, which is hard to do on a old chasy.

[tonyarkles]

Something to keep in mind with hub motors is that they’re unsprung weight, vs the battery pack is pretty much always sprung. While that’s not a huge differentiator for efficiency, it sure cuts down on the abuse the wheels and hub motors will experience

[serf]

its less hard than you'd think unless you're really going for long range.

for my sailboat I am getting rid of a 300lbs diesel and a 30gallon fuel tank with a 45lbs PMAC.

That means I have opened up about 465lbs for batteries.

Now, with a sailboat you're never truly out of range -- but the point stands : these things are so much lighter than ICEs on average that there is a lot of opportunity even with battery weight as it is (and it's getting better daily).

[kpil]

I guess there's always the risk for a rig failure.

I looked a bit on doing the same, but came to the conclusion that it will be expensive to fulfil racing rules requiring the boat to be able to maintain speed for 5 hours ie around 25-30 NM range.

As it is now, I have about 500 NM diesel range on my boat, which is basically 3-4 days continuous runtime. Cutting it down to 25nm and 5 hours requires minimally 100kWh.

For a blue water boat, 500 NM is not quite acceptable, but can be fixed with jerrycans for a couple of dollars. An all electric blue water boat would clock in at an unrealistic 2MWh of batteries with a weight at least 20 metric tonnes. 10x the load capacity of my boat.

[dieselgate]

> there's always the risk for a rig failure.

Don't forget rudder and keel - especially if sailing off the coast of western europe...

[BobaFloutist]

This is silly, but I've also wondered if you could make a boat that can anchor and recharge batteries from ambient current, sort of like stationary regenerative braking. I'm sure it would take way too long to be worth it, but it was a fun idle thought.

[dieselgate]

Perhaps the paddle wheel[0] will interest you, the spinning is used to calculate the velocity of the boat. Probably some other propeller or similar would be more practical - like a kicker motor that's easily lowered over the side. Just spitballing. I don't think it'd be worth it considering solar options. Even wind generators are not "super efficient" in comparison but I don't have data.

[0] https://www.westmarine.com/bg-h3000-paddlewheel-sensor-w-pla...

[BobaFloutist]

I'm sure it wouldn't be worth it, because otherwise people would be doing it, it just seemed like a cool way to supplement solar or even to allow for indefinite underwater drones. Like, imagine a deep-sea research drone that could spit out an anchor and recharge whenever the battery got low. Almost certainly a case of "Cool, wouldn't really work well"

[lazide]

Uh, car batteries are much heavier than most ICE’s. The curb weight on teslas’s are crazy high.

BYD can be lighter because they skip on safety gear and proper structural elements - in my experience.

[dotancohen]

  > BYD can be lighter because they skip on safety gear and proper structural elements - in my experience.

I'd love to hear more about your experience with BYD. The ex just bought one and my kids ride in it daily. I helped negotiate the sale - I drive a Tesla and I'm very happy with the BYD.

[lazide]

Brazilians got a bunch of them and they are super common in Brazil. Also common - broken suspension parts from driving them in Brazil.

Also, the only cars I’ve ever ridden on that the top of my head literally touches the headliner while sitting in the back seat. Other than that, they seem good?

[dotancohen]

Great to know, thanks. Israeli roads are typically well maintained, but I'll keep an eye out for suspension damage.

In this Atto 3, I've ridden in the back a few times and my head does not touch the headliner. I'm 170cm.

[lazide]

Yeah, I’m 182+ cm, so a bit bigger. It still surprised me. BYD Dolphin if I remember was the worse.

The suspension issues seem like a common theme though, they aren’t built as sturdily as most cars on that front.

[cyberax]

Top-of-the-line NMC cells have energy density around 250Wh/kg at the pack level. The newer solid-state batteries can reportedly increase this to 400Wh/kg.

So a reasonable 75kWh battery pack is going to weigh around 300kg and in future around 200kg. This is... not a lot, actually. To a point where shaving off 20-30 kg from the electric motor weight is going to result in a noticeable performance/price difference.

Teslas also don't have "crazy" weight. Model 3 is 1700kg and a comparable (in size) Ford Focus is 1300kg.

[lazide]

If you stop cherry picking the lightest Tesla, you’ll see what I mean.

400 kg == 881 lbs, and that is their lightest model with lowest range.

[cyberax]

Model 3 LR with 360 miles of range is 1820 kg. Still nothing crazy.

[lazide]

That is over 4K lbs, and more than an older model full sized Toyota Tundra.

Newer model Tundras are over 5k lbs, but that is also crazy.

[bjelkeman-again]

BMW M3. Curb Weight: 3988 lb [1]

Tesla Model 3. Curb Weight: 3721 lb [2]

[1] https://www.caranddriver.com/bmw/3-series

[2] https://www.caranddriver.com/tesla/model-3

[lazide]

The Model 3 performance model (more equivalent to the M3) weighs over 4K lbs. The model you are quoting is the lowest range and lightest of all Teslas.

The Tesla model S (actually more equivalent to the M3) is over 4500 lbs [https://www.edmunds.com/tesla/model-s/2026/features-specs/].

No one is realistically saving weight by switching to batteries. Because batteries are heavy for the energy and gasoline is hella energy dense.

[parpfish]

i know series hybrids aren't as efficient as parallel hybrids (thanks technology connections!), but i wonder if they'd be a good candidate for fun restomods.

drop in a tiny, powerful electric motor and a small battery (crammed in whatever location is best for weight distribution), and then wire up a little genny powered off your existing fuel tank that can jump in as a range extender

[coderenegade]

Series hybrids can compete with parallel hybrids, because the full decoupling of the engine from the wheels claws back some of the efficiency you lose through the energy conversion. It's series-parallel hybrids they can't really compete with, because those are able to do the same trick, but they also lose less energy in conversion, because the engine does some of the heavy lifting.

Series hybrids are great for packaging, though. Parallel and series-parallel commit to certain packaging decisions like having a transmission, or a long, monolithic unit, because it's the mechanical coupling that buys them smaller motors and potentially better efficiency. Series hybrids don't care about any of that, so even though you have bigger motors and potentially higher losses, you have more freedom over where things go.

Personally, I think there's a massive untapped market in converting old cars to hybrid engines. You wouldn't try to upgrade the old engine, you'd design a smaller and more power dense package and rip all of the original gear out. Because electrification lets you cut the size of the engine down so aggressively, this is probably a feasible strategy. As you pointed out, series hybrids are probably best suited to this because of their packaging flexibility. As others have pointed out, there's tremendous potential there for replicating original driving characteristics using software and the electric motor. And if we're being honest, off-road vehicles probably should get rid of the transmission and low range, because electric motor torque is just better. As is, the potential for cars is enormous, but we're getting the worst possible outcomes thanks to legislation.

[WillAdams]

Jeep/Stellantis certainly had problems trying to do this:

https://www.thedrive.com/news/jeep-tells-4xe-hybrid-owners-t...

[tclancy]

Yeah, my comment was hand-waving away a bit of the reality of it, but swap the Fiero engine for a battery and some of these and it's got to be close to achieving full lift.

[dotancohen]

Reducing the motor mass by 200 kg means you've just removed 10% of the weight of the vehicle. You could theoretically now reduce the battery pack by 10% as well.

[N1H1L]

Not true. The CdA (coefficient of drag multiplied by frontal area) matters far more for range than the weight for range. That is a smaller EV, which may very well be heavier can have a higher range and efficiency.

[dotancohen]

The Cd matters for highway driving, but weight is the dominating factor for city driving.

[xethos]

As efficiency improves across motors and inverters, wouldn't regen make CoD matter more, possibly tilting it to the dominant factor again?

[dotancohen]

Regen recoups about 80% of the kinetic energy, and it is already up close to the theoretical physical limit without switching to exotic materials.

Cd will never be the dominating factor at speeds which do not produce significant aerodynamic drag.

[xethos]

> Cd will never be the dominating factor at speeds which do not produce significant aerodynamic drag

That helped it sink in, thank you

[anonymars]

Remember also that tires (deformation) and the like sap energy too

[thfuran]

I don’t think there’s a whole lot of room for improvement there.

[dredmorbius]

Unsprung mass is a concern, though, and being able to put motors in the wheel has benefits.

[j_maffe]

I think the cited weight loss comes from energy efficiency gains leading to less battery capacity needed.

[FabHK]

Electric engines are already very efficient (particularly compared to internal combustion). If you go from 90% to 95% efficiency, you don't save much in terms of battery.

ETA: Internal combustion engines half a century ago had an efficiency of 20%, now they're at 40%. That cuts the fuel you need to carry in half. Electric engines are near 100%, and as I said, going from 90% to 95% efficiency cuts required battery by a bit more than 5%, so peanuts.

[ajuc]

Going from 90% to 95% efficiency you're halving the thermal loses, thus reducing the need for cooling by half. It's a big deal.

Same with going from 99% to 99.5% efficiency. It still reduces the cooling needed by half.

[testdelacc1]

> reducing the need for cooling by half

But the motor is not the only thing that needs to be cooled. It’s mainly the battery, which has a narrow operating range. The power electronics that convert AC to DC also need to be cooled.

So you’re halving the cooling needs of the motor, which is nice but small compared to the other two. And even then, total cooling doesn’t impact range that much compared to warming the battery in cold climates.

I think you’ve overstated your case.

[ssl-3]

Half is half.

If we halve waste-heat generation for a practical widget enough times, then we won't need liquid cooling for that widget at all. If the trend continues and gets good enough, then maybe we can get all the way to a complete passive-cooling snoozefest.

That's pretty boring, but boring is good. The systems we use every day without a thought because they boringly Just Work are, perhaps, our greatest successes.

[FabHK]

I was responding to

> I think the cited weight loss comes from energy efficiency gains leading to less battery capacity needed.

So, no, the efficiency gains of electrical engines do not lead to significantly less battery capacity needed.

[HDThoreaun]

In the video the yasa guy said most of the weight loss is from getting rid of the yoke.