7 ms·

I always thought the problem with hybrids was the complexity of the drive train, but this video is challenging that notion. It argues that the hybrid pack (minu

by chem83 4mo ago

I always thought the problem with hybrids was the complexity of the drive train, but this video is challenging that notion. It argues that the hybrid pack (minus the battery, perhaps?) is more compact and simpler than a manual gearbox, even. It consists of two electric motors and a planetary gear set, which is seemingly simpler than clutch packs, gear sets and belts of regular transmissions, including CVTs. Time codes 3:06, 37:07, 43:57, 43:36 (note on the eCVT naming), and 44:17.

entropi 4mo ago
There are other, more focused (also arguably better at explaining) videos on explaining how it works. Here is one: https://youtu.be/dxmxIsoV_Xo https://youtu.be/dxmxIsoV_Xo It took a while and several explanations for it to completely click for me. The e-cvt mechanism does seem to be quite clever and simpler (at least mechanically).
xattt 4mo ago
Interestingly, iForceMax drivetrains in Toyotas seen in Tundras and derivatives are the “other” kind with conventional transmissions. This does not appear to be a packaging issue, as the late 2000s LS 600h had a V8 with rear-wheel drive (and then AWD) with an “eCVT” in a “conventional” longitudinal package.
roelschroeven 4mo ago
Yes, but specifically about the Toyota's hybrid system. Other systems are more complex, they have a traditional engine and transmission and an electrical system on top.
- phkahler 4mo ago
  Ford has been making very similar hybrids for 20+ years. The old Escape, the Fusion, CMax, Maverick. These are all the same general layout as the Prius.
  - roelschroeven 4mo ago
    I probably should have said Toyota-like hybrid system, to include manufacturers that either licensed Toyota's system or developed something similar themselves.
mtsr 4mo ago
This is why there have been Prius taxis that were in service for 1 million km.
bee_rider 4mo ago
On a completely tangential note, has anyone ever tried a hybrid that was like a diesel-electric train? The engine just charges the battery. IIRC it can be much simpler, no need for gearing at all, the engine just runs at a constant speed and the battery handles delivering variable amounts of power.
- avel 4mo ago
  Related: Honda's 2 Motor Hybrid System Explained. https://www.youtube.com/watch?v=-P_VChtMGK8 https://www.youtube.com/watch?v=-P_VChtMGK8
- deleted 4mo ago
  [deleted]
- adgjlsfhk1 4mo ago
  one of the primary arguments of the video is that ecvt is a strictly superior solution. (and that diesel electric exists for massive torque conversion in trains, but loses efficiency)
  - deleted 4mo ago
    [deleted]
- bluGill 4mo ago
  Called a series hybrid, and it has been done. However gears are more efficient than a generator -> motor, and charging a battery adds even more losses. Thus if the engine is running anyway you are better off just mechanically connecting it to the wheels. Trains don't do the above in large parts because the gears needed either wouldn't fit in the allowed space. (we may not be able to make them large enough either - that problem is solvable but may not be worth it)
  - wat10000 4mo ago
    I wonder if fuel efficiency just doesn't matter enough for trains, since they're already so efficient at turning motive energy into motion. Other costs may dominate.
nisegami 4mo ago
There's so much variety in hybrids that's hard to discuss as a single category. I think the most important question is whether the system requires a regular automatic/manual transmission or forgoes one entirely. The Toyota planetary gear system forgoes one, as does the modern Honda and Nissan approaches. Not having a transmission in the traditional sense saves so much complexity that the overall system is net simpler imo even with the additional complexity from having a motor and engine. Then there are systems that have a full automatic drivetrain and some extra clutches to couple to a motor-generator. And there's even systems with an electronically controlled manual transmission instead. Those systems are going to be incredibly complex and fragile.
caminanteblanco 4mo ago
Well for quite a while, this has been a Toyota specific design, per their patents, but they ceded all royalties to those a few years ago [0], and to me, this seems like such a fundementally elegant design. [0] https://global.toyota/en/newsroom/corporate/27512455.html https://global.toyota/en/newsroom/corporate/27512455.html
jeffbee 4mo ago
There's a lot of memes about how dumb it is to have all of the ICE moving parts, but they're just memes. We know how to make engines and they are cheap to mass produce. The complexity argument is aesthetic.
- fhdkweig 4mo ago
  I don't know much about cars, but I have to assume that fewer moving parts means less wear and repairs.
  - jeffbee 4mo ago
    That's a fair assumption that doesn't prove itself in practice. In practice, a Prius engine lasts forever. Someone will jump in to complain about some anecdotal failure but the fleet statistics are strong. They even outlast other non-hybrid Toyotas. There are a lot of reasons for this but a significant one is the lack of belt-driven accessories, lack of friction clutches, and ability to avoid high-stress operation because of the electric side of the power train.
    - asa400 4mo ago
      This is exactly correct, and I can't count how many times I've had to have this argument, thank you for pointing it out. My hybrid (not a Prius, actually) doesn't have a dedicated starter motor, the traction motor starts the ICE engine. The climate control is electric and powered by the hybrid battery (with the added benefit of being able to run the A/C while the ICE engine is off). The power steering is electric so there's no hydraulic power steering pump to fail. I'm sure there's more I'm forgetting. Mechanically, it's just simpler than an ICE engine alone. > ability to avoid high-stress operation because of the electric side of the power train. This one is huge, also, and people always forget about it, so thank you for raising it. ICE hate being heavily loaded at low RPMs (also known as "lugging"), and the electric motors alleviate a lot of that low-end workload. It's a big win not just for efficiency, but also drivability, as almost all non-diesel engines make terrible torque low in their RPM range.
phkahler 4mo ago
>> It argues that the hybrid pack (minus the battery, perhaps?) is more compact and simpler than a manual gearbox, even. Having worked in the field I've been of that opinion for 15 years or more. Two motors and a planetary gear are simpler than a regular transmission. More efficient also, and more reliable. The inverter and small battery may add some cost, but the MPG improvement is more than worth it. Hybrids are an awesome improvement over plain old ICE, but they tend to get an unnecessary price premium due to their advantages.
simondotau 4mo ago
It might be simpler than a regular gearbox, but so what? That tech is already commoditised, and generally very reliable. The engine - not the transmission - is the biggest pain point with ICE vehicles. It’s what needs constant maintenance and fluid changes.
- Tor3 4mo ago
  > The engine [...] neds constant maintenance and fluid changes. I drive my ICE to the dealership once a year, and one hour later the above is all done (in the meantime I drink coffee and read a book nearby). Once a year. I wouldn't call that "constant maintenance and fluid changes". It's "yearly", as in "once a year". I will be getting an EV in the future (we're setting up our house with solar and a V2H system - Vehicle To House), but that's not because an ICE needs constant engine maintenance. It doesn't.

by chem83 4mo ago

entropi 4mo ago

There are other, more focused (also arguably better at explaining) videos on explaining how it works. Here is one: https://youtu.be/dxmxIsoV_Xo https://youtu.be/dxmxIsoV_Xo It took a while and several explanations for it to completely click for me. The e-cvt mechanism does seem to be quite clever and simpler (at least mechanically).

xattt 4mo ago

Interestingly, iForceMax drivetrains in Toyotas seen in Tundras and derivatives are the “other” kind with conventional transmissions. This does not appear to be a packaging issue, as the late 2000s LS 600h had a V8 with rear-wheel drive (and then AWD) with an “eCVT” in a “conventional” longitudinal package.

roelschroeven 4mo ago

Yes, but specifically about the Toyota's hybrid system. Other systems are more complex, they have a traditional engine and transmission and an electrical system on top.

phkahler 4mo ago
Ford has been making very similar hybrids for 20+ years. The old Escape, the Fusion, CMax, Maverick. These are all the same general layout as the Prius.
- roelschroeven 4mo ago
  I probably should have said Toyota-like hybrid system, to include manufacturers that either licensed Toyota's system or developed something similar themselves.

mtsr 4mo ago

This is why there have been Prius taxis that were in service for 1 million km.

bee_rider 4mo ago

On a completely tangential note, has anyone ever tried a hybrid that was like a diesel-electric train? The engine just charges the battery. IIRC it can be much simpler, no need for gearing at all, the engine just runs at a constant speed and the battery handles delivering variable amounts of power.

avel 4mo ago
Related: Honda's 2 Motor Hybrid System Explained. https://www.youtube.com/watch?v=-P_VChtMGK8 https://www.youtube.com/watch?v=-P_VChtMGK8
deleted 4mo ago
[deleted]
adgjlsfhk1 4mo ago
one of the primary arguments of the video is that ecvt is a strictly superior solution. (and that diesel electric exists for massive torque conversion in trains, but loses efficiency)
- deleted 4mo ago
  [deleted]
bluGill 4mo ago
Called a series hybrid, and it has been done. However gears are more efficient than a generator -> motor, and charging a battery adds even more losses. Thus if the engine is running anyway you are better off just mechanically connecting it to the wheels. Trains don't do the above in large parts because the gears needed either wouldn't fit in the allowed space. (we may not be able to make them large enough either - that problem is solvable but may not be worth it)
- wat10000 4mo ago
  I wonder if fuel efficiency just doesn't matter enough for trains, since they're already so efficient at turning motive energy into motion. Other costs may dominate.

nisegami 4mo ago

There's so much variety in hybrids that's hard to discuss as a single category. I think the most important question is whether the system requires a regular automatic/manual transmission or forgoes one entirely. The Toyota planetary gear system forgoes one, as does the modern Honda and Nissan approaches. Not having a transmission in the traditional sense saves so much complexity that the overall system is net simpler imo even with the additional complexity from having a motor and engine. Then there are systems that have a full automatic drivetrain and some extra clutches to couple to a motor-generator. And there's even systems with an electronically controlled manual transmission instead. Those systems are going to be incredibly complex and fragile.

caminanteblanco 4mo ago

Well for quite a while, this has been a Toyota specific design, per their patents, but they ceded all royalties to those a few years ago [0], and to me, this seems like such a fundementally elegant design. [0] https://global.toyota/en/newsroom/corporate/27512455.html https://global.toyota/en/newsroom/corporate/27512455.html

jeffbee 4mo ago

There's a lot of memes about how dumb it is to have all of the ICE moving parts, but they're just memes. We know how to make engines and they are cheap to mass produce. The complexity argument is aesthetic.

fhdkweig 4mo ago
I don't know much about cars, but I have to assume that fewer moving parts means less wear and repairs.
- jeffbee 4mo ago
  That's a fair assumption that doesn't prove itself in practice. In practice, a Prius engine lasts forever. Someone will jump in to complain about some anecdotal failure but the fleet statistics are strong. They even outlast other non-hybrid Toyotas. There are a lot of reasons for this but a significant one is the lack of belt-driven accessories, lack of friction clutches, and ability to avoid high-stress operation because of the electric side of the power train.
  - asa400 4mo ago
    This is exactly correct, and I can't count how many times I've had to have this argument, thank you for pointing it out. My hybrid (not a Prius, actually) doesn't have a dedicated starter motor, the traction motor starts the ICE engine. The climate control is electric and powered by the hybrid battery (with the added benefit of being able to run the A/C while the ICE engine is off). The power steering is electric so there's no hydraulic power steering pump to fail. I'm sure there's more I'm forgetting. Mechanically, it's just simpler than an ICE engine alone. > ability to avoid high-stress operation because of the electric side of the power train. This one is huge, also, and people always forget about it, so thank you for raising it. ICE hate being heavily loaded at low RPMs (also known as "lugging"), and the electric motors alleviate a lot of that low-end workload. It's a big win not just for efficiency, but also drivability, as almost all non-diesel engines make terrible torque low in their RPM range.

phkahler 4mo ago

>> It argues that the hybrid pack (minus the battery, perhaps?) is more compact and simpler than a manual gearbox, even. Having worked in the field I've been of that opinion for 15 years or more. Two motors and a planetary gear are simpler than a regular transmission. More efficient also, and more reliable. The inverter and small battery may add some cost, but the MPG improvement is more than worth it. Hybrids are an awesome improvement over plain old ICE, but they tend to get an unnecessary price premium due to their advantages.

simondotau 4mo ago

It might be simpler than a regular gearbox, but so what? That tech is already commoditised, and generally very reliable. The engine - not the transmission - is the biggest pain point with ICE vehicles. It’s what needs constant maintenance and fluid changes.

Tor3 4mo ago
> The engine [...] neds constant maintenance and fluid changes. I drive my ICE to the dealership once a year, and one hour later the above is all done (in the meantime I drink coffee and read a book nearby). Once a year. I wouldn't call that "constant maintenance and fluid changes". It's "yearly", as in "once a year". I will be getting an EV in the future (we're setting up our house with solar and a V2H system - Vehicle To House), but that's not because an ICE needs constant engine maintenance. It doesn't.