8 ms·

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 wo

by ardit33 3mo ago

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.

j_maffe 3mo ago
I think the cited weight loss comes from energy efficiency gains leading to less battery capacity needed.
- FabHK 3mo ago
  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 3mo ago
    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 3mo ago
      > 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 3mo ago
        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 3mo ago
      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 3mo ago
  In the video the yasa guy said most of the weight loss is from getting rid of the yoke.
parpfish 3mo ago
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 3mo ago
  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.
tclancy 3mo ago
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.
serf 3mo ago
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).
- lazide 3mo ago
  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 3mo ago
    > 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 3mo ago
      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 3mo ago
        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.
tonyarkles 3mo ago
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
WillAdams 3mo ago
Jeep/Stellantis certainly had problems trying to do this: https://www.thedrive.com/news/jeep-tells-4xe-hybrid-owners-to-park-outside-and-quit-charging-to-avoid-fires https://www.thedrive.com/news/jeep-tells-4xe-hybrid-owners-t...
dotancohen 3mo ago
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 3mo ago
  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 3mo ago
    The Cd matters for highway driving, but weight is the dominating factor for city driving.
    - xethos 3mo ago
      As efficiency improves across motors and inverters, wouldn't regen make CoD matter more, possibly tilting it to the dominant factor again?
      - thfuran 3mo ago
        I don’t think there’s a whole lot of room for improvement there.
      - dotancohen 3mo ago
        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 3mo ago
        > Cd will never be the dominating factor at speeds which do not produce significant aerodynamic drag That helped it sink in, thank you
dredmorbius 3mo ago
Unsprung mass is a concern, though, and being able to put motors in the wheel has benefits.

by ardit33 3mo ago

j_maffe 3mo ago

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

FabHK 3mo ago
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 3mo ago
  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 3mo ago
    > 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 3mo ago
      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 3mo ago
    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 3mo ago
In the video the yasa guy said most of the weight loss is from getting rid of the yoke.

parpfish 3mo ago

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 3mo ago
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.

tclancy 3mo ago

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.

serf 3mo ago

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).

lazide 3mo ago
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 3mo ago
  > 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 3mo ago
    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 3mo ago
      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.

tonyarkles 3mo ago

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

WillAdams 3mo ago

Jeep/Stellantis certainly had problems trying to do this: https://www.thedrive.com/news/jeep-tells-4xe-hybrid-owners-to-park-outside-and-quit-charging-to-avoid-fires https://www.thedrive.com/news/jeep-tells-4xe-hybrid-owners-t...

dotancohen 3mo ago

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 3mo ago
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 3mo ago
  The Cd matters for highway driving, but weight is the dominating factor for city driving.
  - xethos 3mo ago
    As efficiency improves across motors and inverters, wouldn't regen make CoD matter more, possibly tilting it to the dominant factor again?
    - thfuran 3mo ago
      I don’t think there’s a whole lot of room for improvement there.
    - dotancohen 3mo ago
      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 3mo ago
        > Cd will never be the dominating factor at speeds which do not produce significant aerodynamic drag That helped it sink in, thank you

dredmorbius 3mo ago

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