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How do Hybrids work? Newbie questions encouraged!

2

Comments

  • xcelxcel Member Posts: 1,025
    Hi Robertsmx:

     

    We're talking about tiny fractions of a second. You're not going "to feel it" simply by driving a vehicle. System is much faster than we humans can perceive/experience things.

     

    ___The answer then is that you obviously haven’t driven a hybrid and you haven’t read reviews on hybrids closely enough in the past. The non-linearity of Regen is one of the most striking items about hybrids and yes, you can and do in fact feel it. The AH not withstanding because I haven’t read of a non-std. braking feel or driven it personally.

     

    ___Good Luck

     

    ___Wayne R. Gerdes
  • robertsmxrobertsmx Member Posts: 5,525
    I will repeat myself… you’re not going to feel how current flows. Could you? The point simply lies in understanding in drawbacks of a hydraulics based system when coupled to a much faster/responsive electrical system. The problem isn’t electrical systems here! Or is it? Let me know what you think. Reading reviews and sitting behind the wheel isn’t going to get you this answer.
  • xcelxcel Member Posts: 1,025
    Hi Robertsmx:

     

    I will repeat myself …

     

    ___Why? You haven’t driven a hybrid so you have never felt a hybrid’s braking non-linearity’s. Until the AH and I have not driven it yet, hybrid’s do not have a smooth interaction between light and strong regen and release let alone the transition between regen and the mechanicals. You are not switching electrons through a PC board, you are attempting to switch a rather large electro-mechanical MG/Set on and off at tens of times a second if need be and all the Hybrids I have driven are not capable of this feat to date. Conclusion, no MG/Set emergency braking capabilities on any hybrid today that I know of although I have not read much on the details of the Escape HEV to say with 100% certainty that all hybrids emergency braking/control are handed off to an electro-mechanical safety system that all automobile manufacturers use in non-hybrid’s today.

     

    ___Good Luck

     

    ___Wayne R. Gerdes
  • SylviaSylvia Member Posts: 1,636
    Let's call a truce guys. Let's not go another round.

     

    Thanks.
  • electrictroyelectrictroy Member Posts: 564
    If I were about to rear-end another car or hit a pole, I'd want REAL brakes operating, not regenerative. ***Saving my LIFE & stopping as fast as possible*** is more important to me than recovering an extra 1 or 2 watts. 1 or 2 watts is trivial, and I'm willing to let it go, in order to save my life. Give me REAL brakes.

     

    .

     

    The answers provided here were for the Toyota. Honda works differently:

    - press the brake ~1/2 inch & it's pure generator braking

    - press the brake ~1 inch & it's friction braking

    - generator braking works down to ~10 mph & then turns off

     

    So my approach is this:

    - Lightly press the brake for pure generator braking

    - Until I hit 10 mph

    - Use friction braking to slow from 10 to 0.

     

    troy
  • robertsmxrobertsmx Member Posts: 5,525
    What makes you blame non-linearity in braking in hybrids to the electrical system? You didn’t respond as to which you think will be quicker to respond: an electrical system, or a hydraulics based system. The answer lies there, and believe it or not, it may be a matter of time before we see electrical systems replacing many hydraulic components in our vehicles. Speed matters.

     

    I don’t care about whether or not these systems exist today. In current hybrids, it is more about following the safer/conventional route. It is a part of the lesson in economics.
  • larsblarsb Member Posts: 8,204
    The "regen" feature of the Hybrid braking systems "DO NOT" (I repeat, do not) make the brakes less effective or more unsafe.

     

    The systems are basically just like "regular brakes" in that they use pads and rotors and discs/drums.

     

    All that makes them different is that they have additional components to recapture the energy wasted by braking.
  • robertsmxrobertsmx Member Posts: 5,525
    That is a point largely being missed here. People are assuming that regenerative braking takes away something from actual braking, where as it is really using vehicle's inertia to generate electricity (on top of braking effort by the driver).
  • xcelxcel Member Posts: 1,025
    Hi Robertsmx:

     

    That is a point largely being missed here. People are assuming that regenerative braking takes away something from actual braking, where as it is really using vehicle's inertia to generate electricity (on top of braking effort by the driver).

     

    ___No one is missing anything here except for you. Regenerative braking is good for one thing to date, regen. Why didn’t Toyota, Ford, and Honda just remove the mechanicals to save on costs? It is in the future after all. Because the regenerative action of release to engage and back again is far to slow by comparison to the electro-hydraulic-mechanicals that are in use in most of our automobiles today.

     

    ___Have you driven a hybrid yet? Until you have, you have no idea as to how fast the transition is between Regen, release, and back to regen in another gear actually is. With that, you can definitely feel how [b]slow[/b] the process is after a few taps of the pedals vs. locking up the binders and feeling the pulsation of ABS or TCS in a fast but slick corner from a particular wheel. There isn’t a maybe about it, it just is. Do you know why Hybrid’s have mechanical brakes with safety overrides in which Regen is locked out? You can argue whatever you want but the 1000’s of engineers at Ford, Honda, and Toyota know more about it then what you obviously think because they have overridden regen for the respective automobiles safety functions on every Hybrid other then possibly the Escape HEV (I haven’t read up enough about it just yet to say one way or the other).

     

    ___Good Luck

     

    ___Wayne R. Gerdes
  • robertsmxrobertsmx Member Posts: 5,525
    Why didn’t Toyota, Ford, and Honda just remove the mechanicals to save on costs?

     

    Remove what mechanicals? Specify. Also elaborate on “electro-hydraulic” mechanicals you’re talking about. If you still believe hydraulics in any way are more responsive than electrical systems, I will try to dig up some links for you.

     

    For time being you go with what you've got. This does not mean forever.
  • electrictroyelectrictroy Member Posts: 564
    My Insight's regenerative braking slows at ~1 mph per second. If I'm about to slam into a pole at 60 miles an hour, I want faster slowing than 1 mph/second (a full minute to stop).

     

    I want the old-fashioned but highly effective friction brakes.

     

    Troy
  • robertsmxrobertsmx Member Posts: 5,525
    I’m not sure how you could measure how regenerative braking is translating to deceleration (down to mph). I have my doubts on common understanding of what regenerative braking really is.

     

    Electric motors transform potential energy (electric charge) to kinetic energy and when they are run in reverse (i.e. as electric generator), they can capture kinetic energy to store potential energy. That’s all there is to the bottom line of regenerative braking.

     

    Vehicle is already moving, and when driver applies brakes, the controller knows to switch to generator mode and starts to capture whatever kinetic energy it can and before the vehicle comes to a complete stop (due to braking by the driver). Since some of the kinetic energy is being transformed into electric charge, there is lower loss to the atmosphere by way of transformation of the kinetic energy into heat energy.

     

    I’ve yet to understand why it is being assumed here that regenerative brakes is actually stopping the vehicle by itself (well it is but only in conjunction actual braking action by the driver, pretty much like engine braking except for the fact that there is less energy lost in translation).
  • stevewastevewa Member Posts: 203
    Consider the railroads which have used electric motors to brake trains for about 80 years. They still use friction brakes. The reason is simple. Regenerative (or dynamic braking in the case of Diesel/Electric locomotives) is only effective over a certain speed range. Once the vehicle is moving too fast or too slowly it doesn't work. In the case of the Prius regenerative braking stops working below about 6MPH. There just isn't enough kinetic energy left to resist the magnetism of the field. If you wanted to completely stop using just the motor, you'd have to apply so much field current that you'd defeat the purpose of rhe regenerative brakes (i.e. recharging the HV battery).

    There is another consideration which you need to consider w.r.t. use of regeneration during ABS conditions. There's a friction brake at each wheel, while there's only one electric motor/generator set. Since the regenerative brakes have to transmit force through the differential/transaxle, there's no way to modulate the braking force between the drive wheels (and no way at all to brake the rear wheels in a FWD system). One could remedy this by placing a traction motor at each wheel, but that would add weight and complexity to the system far more than having conventional brakes (which you'd still need because of the limitations mentioned above).

     

    Hope this helps to further clarify things.

     

    btw, the FEH is no different from the others w.r.t. overriding regen braking...
  • electrictroyelectrictroy Member Posts: 564
    "I’m not sure how you could measure how regenerative braking is translating to deceleration [1 mph per second]"

     

    .

     

    Because I have a brain? It's not that difficult to observe my Insight's deceleration with generator braking is about 1 mph per second.

     

    troy
  • robertsmxrobertsmx Member Posts: 5,525
    Are you sure it is not 0.8 or 1.2? ;-)

     

    What you experience is similar to engine braking in a conventionally powered vehicle except that in this case you're recapturing some of the energy to recharge the batteries. When you apply brakes, the electric generator continues to convert mechanical energy to electrical energy in the background (in a way, assisting your conventional braking effort), again something similar to engine braking used in conjunction with driver applying brakes.
  • electrictroyelectrictroy Member Posts: 564
    You are still missing my point. Let me repeat it:

    - my insight's regenerative braking slows me at ~1 mph per second

     

    - my insight has slid off the road & is about to slam into a pole at 60 miles an hour

     

    - do I want to slow my car at only ~1 mph/second?

     

    - heck no! I want the old-fashioned friction braking to stop me. I'm perfectly happy with Honda's decision to disable regen & use only friction brakes for the emergency ABS stop.

     

    troy
  • robertsmxrobertsmx Member Posts: 5,525
    Don’t forget, you HAVE old fashioned brakes at your disposal. You’ve got issues with a system that is basically recouping some (otherwise) lost energy and works on the backside.

     

    Pike’s Peak Highway in Colorado is a good example to be brought up here. When you start your vehicle downhill from the 14K ft elevation, would you follow warning signs that ask you to use engine braking instead of applying brakes, or no? After all, engine braking isn’t going to “stop” your car.

     

    As far as ABS versus regen goes, the issue is largely with “speed” of hydraulics than anything else. Someday, we should see faster ABS systems, potentially integrated with regen braking. I have already read a few technical papers on the subject.
  • electrictroyelectrictroy Member Posts: 564
    Someone complained that regen is disabled during ABS, and they don't understand why.

     

    MY point is that if I'm about to DIE, I don't give a darn about regen. I support Honda's decision to disable it during emergency ABS braking.

     

    troy
  • mistermemisterme Member Posts: 407
    I think ABS is currently applied where it needs to be....right at the wheel.

     

    If you were to depend on IMA or HSD systems to pulse the wheels then you are going through differential, gears, bearings, belts and would work against the inertia of all the associated spinning parts and any wear and tear slop that may develop over time.

     

    The only way I can see for this to work is to also pulse right at the wheel, which would require traction motors at each axle. I think this could be a vastly better way but we don't have it yet.

     

    If you want regen at the same time as ABS, then regen might render ABS useless because the regen load on the wheel might keep the wheel sliding when it should be in its rolling cycle.
  • robertsmxrobertsmx Member Posts: 5,525
    Engineers may or may not have deliberately disabled regenerative braking during situations where other accessories like ABS or stability control take over. If they did attempt to keep them exclusive, reason could be reliability and effectiveness of the overall system (a situation I can imagine is lack of a good feedback system from the hydraulics based pumps that controls ABS could leave the controller undecided as it tries to switch between motor and generator modes).

     

    The other issue may be “automatic”. ABS triggers on loss of traction, an instance where wheel slips rather than rotates (regenerative braking requires wheel rotation). No rotation, no regen.
  • patpat Member Posts: 10,421
    Consider buying a hybrid? Reconsider after you learned about the long wait? Whether or not you chose to add your name to the waiting list, a reporter is hoping to hear your perspective. Please respond to jfallon@edmunds.com with your daytime contact info by May 27, 2005.
    Thanks,
    Jeannine Fallon
    Corporate Communications
    Edmunds.com
  • shadow11shadow11 Member Posts: 4
    I originally posted this in "Hybrid Tips: Optimizing mileage", but then found this forum and thought the post might be more appropriate here.

    I have read a lot of posts talking about how to drive to ensure that the electric motors only are on (referring to the Prius and other "full hybrids" that can drive on electric motors only), and I am a little confused about how that helps mileage. After all, the energy to power the batteries ultimately comes from the gasoline that is put into the car.

    From my understanding of how hybrids work, one of the main ways they get better fuel economy is by having smaller engines, and by running those engines more efficiently.

    However, whenever energy is converted from one form to another, I would assume that the conversion is not 100% efficient. If the gas engine was running at a similar efficiency when powering the car as when it charges the battery, wouldn't you get better mileage when the gas engine only is powering the car?

    I would think that when travelling at a constant speed, and with the CVT allowing the gas engine to operate at peak efficiency, you would get better mileage when using gas only. The electric motor helps mileage by providing extra power / acceleration when necessary while allowing the gas engine to operate at peak efficiency, and also by storing the kinetic energy from braking / coasting.

    I admit that I am not very knowledgeable about hybrids, so I was wondering if any of the experts could provide me more insight.
  • stevewastevewa Member Posts: 203
    You are correct. The reason people driving to maximize EV mode get better mileage is that they are using less torque as a result of their driving strategy. In theory the most efficient driving mode is when all the power from the gas engine is going to the road while at the same time the gas engine is working at its most efficient load. There are only a limited number of situations where this can occur, however. My Escape seems to do its best at about 45 MPH on level ground, this is just above the speed where the gas engine _has_ to be spinning to protect the electric motor from overspeeding...but it can operate with very little throttle.
  • midnightcowboymidnightcowboy Member Posts: 1,978
    Shadow11,

    Here is a simple answer.

    You are right conversion is not 100% efficient.

    In a normal car none (0%) of braking energy is recovered.

    In a hybrid with regenerative braking some of the enegry is recovered and used to charge the batteries.

    Later the batteries use this recovered energy to run electic motors to provide some of the car's power.

    Essentially this electric power is free.

    That reduces the power need from the gas engine and in some case also the size of the gas engine needed.

    This effectively increases the miles per gallon of hybrid cars.

    YMMV (Your mileage may vary),

    MidCow
  • shadow11shadow11 Member Posts: 4
    Hi MidCow,

    Thanks for the response.

    I realize that the electric power generated by braking is one way that hybrids become more efficient. I believe the battery also charges when you let the engine do the breaking by coasting to a stop. However, I was under the impression that the majority of charging of the battery was performed by the ICE.

    Is this not the case?
  • midnightcowboymidnightcowboy Member Posts: 1,978
    Shadow11,

    Most of the charging comes from regenerative braking.

    In the Prius and other cars/vehicles that use the HSD system from Toyota, there is a small motor/generator ( MG1) which also charges the battery when you are driving because it is always spinning. Many critics say this is inefficinet in that it continues to take some power away from the ICE and try to charge fully charged batteries.

    The Hondas ( Accord Hybrid, Civic Hybrid, Insight) use an IMA (intergrated Motor Assist) and it primarily provides battery charging through regenerative braking.

    In both cases you will also obtain some charging when you let off the gas and coast in your vechicle. . However, in both cases this amounts to only a small amount of charging.

    Good Luck,

    MidCow

    P.S. -For what it is worth I think the Prius is probably the best hybrid car. The primary reason I didn't get one was because it doesn't ot have a manual shift transmission and I really like to shift :)
  • john1701ajohn1701a Member Posts: 1,897
    > Most of the charging comes from regenerative braking.

    That blanket statement doesn't apply to Prius and other HSD vehicles. They are hybrids with *PERSISTENT* electrical systems. Regenerative braking only contributes a small amount of electricity with respect to how much the generator creates... which is far from small. It is 10kW, which is the same size as the current Civic-Hybrid uses for its thrust motor. With the 2006 Civic-Hybrid, that increases to 15kW... which is still considerably smaller than the 50kW Prius currently uses.

    Civic-Hybrid and the other IMA vehicles are hybrids with *PASSIVE* electrical systems. With them, the regenerative braking is the primary source of electricity.

    JOHN
  • john1701ajohn1701a Member Posts: 1,897
    > try to charge fully charged batteries

    That is a misconception.

    In reality, the electricity is simply directed back to the thrust motor immediately, rather than using it to recharge the battery-pack.

    This is surprisingly efficient, due to the way the Planetary-CVT is designed. The reason for the misconception is that people don't realize how frequently this happens. 10 times per minute is quite common, which is fast enough to take advantage of an efficiency opportunity without allowing the penalty of charging to take place. In other words, their are inefficiencies with the gas engine that it prevents from occuring.

    JOHN
  • midnightcowboymidnightcowboy Member Posts: 1,978
    Actually you are wrong! why confuse people with incorrect answers electric motors provide high torque at low RPM to help intitial acceleration.

    This is one of the primary reasons the highway mileage on the Prius and other Toyota HSD deriviative hybrid systems is lower than the city mileage. EPA Prius 60/51 60=city mileage 51=highway mileage.
  • midnightcowboymidnightcowboy Member Posts: 1,978
    Actually you are wrong again! This has been a critcism of the Toyota HSD system all along. The small motor generator (MG1) always spins. It serves to top off the battery, but when the battery is full and when MG2 can no longer supply power and torque to the car becuase the car is going too fast, the energy is wasted.

    This has been discussed over and over. You might want to look at some of the early discussions in the Prius 2004+ thread

    This is one of the primary reasons the highway mileage on the Prius and other Toyota HSD deriviative hybrid systems is lower than the city mileage. EPA Prius 60/51 60=city mileage 51=highway mileage.
  • sinepmansinepman Member Posts: 137
    It is so weird how I get the opposite of what the EPA states. First off, the EPA testing is ancient and we all know that. If I drive in city traffic I get lower than I get on the highway. I am currently averaging 47.3 but I drive 75-80 all the time. To me, that's great.
  • john1701ajohn1701a Member Posts: 1,897
    What are you talking about?

    That most certainly is not how HSD works!

    JOHN
  • midnightcowboymidnightcowboy Member Posts: 1,978
    John Fargunat (John1701a) said:

    "What are you talking about?

    That most certainly is not how HSD works!

    JOHN"

    The EPA on a Prius is 60/51 The first number means the expected miles per gallon in the City, 60 miles per gallon. The second number is the highway miles per gallon, 51 miles per gallon. The City miles per gallon is 9 miles higher than the highway. All cars are more efficient on the highway, but the Prius and other HSD based vehicles are not. One wonders why the little motor generator MG1 spins and spins needlessly converting ICE to electrical at the penalty of energy conversion loss when the traction battery is fully charged!

    Have a good day,

    MidCow
  • john1701ajohn1701a Member Posts: 1,897
    First, you grossly misspelled my name.

    Second, that reasoning is based on common assumptions... not how the system actually works.

    There are far more efficiency savings opportunities in city type driving than there are when cruising on an open highway. The HSD system takes full advantage of them by preventing the inefficiencies that would normally occur, hence the MPG observation.

    And where the heck did that "fully charged" claim come from? That isn't even close to correct. The Multi-Display very clearly shows 6 bars (68.57%) almost all of the time. I've personally only seen it up to 8 bars (80.00%) briefly 3 times over the past 40,600 miles. That's not full by any definition.

    JOHN
  • ctcmoctcmo Member Posts: 1
    Here's a newbie question for you:

    How does regenerative braking actually work?

    I've heard again and again that it converts kinetic energy, but I don't know by what means. Where on a hybrid vehicle is the actual mechanism that converts braking energy, and how does it do so?
  • toyolla2toyolla2 Member Posts: 158
    Hi midcow,
    on post # 88 you stated the following

    " One wonders why the little motor generator MG1 spins and spins needlessly converting ICE to electrical at the penalty of energy conversion loss when the traction battery is fully charged!

    It is first necessary to to have a clear idea of what the Toyota HSD is. It is a power split device and takes the form of a planetary gearbox except that unlike conventional planetary gears where the the outer ring gear is fastened to the gearbox casing and is therefore stationary, in the HSD this gear is allowed to rotate (upto 6000rpm @100mph) and is connected to the drive wheels via a 5:1 ratio.
    MG1 is connected to the central sun gear and though it may appear to be spinning needlessly to midcow and others, it is in fact splitting off some power which it must do (about which more later )
    The engine is connected to the planetary carrier and of course provides the power which gets split. The three planet gears are distributed and held symmetrically around the carrier and make contact with the internal teeth of the ring gear. Clearly (I'm hoping it's clear!) if the sun gear was removed there would be nothing for these three gears to 'bite' on and the engine would be rotating easily while those three planet gears would be spun around by the internal teeth of the ring gear as they passed by. So almost no torque would be imparted to the ring gear and the car would sit still. If now the sun gear and MG1 assembly is mounted there would still be no torque if the sun gear with MG1 were allowed to start flying off in the opposite direction. At this point the engine cannot put any useful power into the system so there is no power to split and MG1 would - in midcow's words - spin needlessly.
    But supposing the electronics to MG1 are turned on. And the electronics says "I am going to continue to allow MG1 to be pushed backwards at 6000rpm but I will not allow it to be pushed backwards at 6001rpm." Of course with a little more engine throttle you know this is bound to happen. But the electronics are probably measuring the shaft speed about 100 times/sec with great accuracy at this time and when this tries to happen will change the electrical conditions to make MG1 start to regenerate probably as much 22kw. This will have the effect of applying a restraining force of up to 20lb-ft on the sun gear. The planet gears will pass this force on from the sun gear to the ring gear which due to the 2.6 ratio between sun and ring will exert a torque of 50lb-ft. This example pertains close to full throttle. It shows how quickly torque can be generated and it attempts to explain the power splitting process and how a small torque at the sun gear can control a much larger torque from the HSD output. It should be mentioned that the engine is effectively supplying both these torques . At lower throttle openings the same strategy applies with MG1 always extracting power from the sun gear in order for the HSD output (the ring gear) to be able send power to the wheels.
    So MG1 never spins needlessly.

    BTW where does the generated power go?, it goes to the electronic inverter which powers MG2. MG2 is made to devour all the electrical energy brought in by MG1 unless the battery happens to need charging in which case it cuts back to allow the battery to absorb the excess. MG2 happens to be conveniently connected to the ring gear where it drives the wheels by the same 5:1 reduction as previously mentioned.

    Why is MG2 twice as big as MG1 ? The answer is because during acceleration MG2 not only has to absorb all the power from MG1 but also absorb up to 20kw from the battery as well.

    But what's the point of all this ? A very good question, I'm glad I asked !

    The Prius is capable of a lot more things than has been mentioned here. To get through everything would take half a dozen posts at least. And some involve speculation because not many people play with synchronous motors and inverters. And, I might add, those that do utilise industrial servos do so without needing to understand the why. Getting two servos with the same inverter bus when either can be called on to motor or generate under a wide range of speeds particularly when mechanically coupled with a planetary gear and with the addition of a prime mover in the mix is something that needs a write up from the designers themselves. And this is what we are not getting.

    The real point of a spinning MG1 is to form a CVT function. The so called Continuously Variable gear ratio Transmission. Toyota chooses to use an electro-mechanical implementation while Honda have chosen to use a wholly mechanical implementation as found in the 2006 HCH. I have to say that now that Honda have dispensed with the manual transmission option on the Civic hybrid it is to be hoped they can concentrate their resources to really nail this device and improve its reliability. Something that industrial CVTs were lacking when they were discarded years ago.

    The reason for the CVT was originally for it to be an alternative to automatic three speed transmissions which were no more efficient than now particularly on subcompact cars. Today the reason is to allow a much smaller engine perform as if it were a larger engine when needed but to have that fuel consumption of the smaller engine most of the time.
    When using a manual transmission, the power profile of a constant torque engine is triangular, power increases with rpm. The area under the curve represents the energy delivered over time.
    The power profile of the output after an engine goes through a CVT, however is closely rectangular - at low revs the torque is much higher than in the previous case dropping slowly until at high revs the torque will become the same. The area under the CVT's rectangular profile will be almost double that area found under the manual transmission therefore the CVT will have delivered twice the energy in the same time.
    This can be played two ways by doubling the road performance of an existing engine or accepting the same performance from a weaker engine.
    The Toyota Prius and HCH obviously go for the latter and the fuel economy it brings. I would say that CVT's can provide fuel economy approaching double that of the manual transmission car and then that's it folks ! There will have to be another shift in thinking.
    T2
  • mistermemisterme Member Posts: 407
    "Civic-Hybrid and the other IMA vehicles are hybrids with *PASSIVE* electrical systems. With them, the regenerative braking is the primary source of electricity"

    Regen accounts for 5-10% recharge, the other 90% comes from the gasoline engine.

    Either you don't know the IMA system or are just spreading misinformation about it.
    Hybrid vehicles don't need more misinformation spread about than already is.
  • midnightcowboymidnightcowboy Member Posts: 1,978
    Wow that was pretty interesting explanation but it still didn't explain why the MG1 keeps on providing a charge even when it is not needed. It you could put a centrifical electric operated cluth on MG1 then it would have to dump excess power when the MG2 didn't need it the PSP didn't need it and the battery was at it optimum charge ( 80% according to JOHN).

    It seems to me that the wider the CVT range the better. With the palnetray CVT concept is is practical to be able to get a very low equivalaent first gear and a very high evivalent high gear. Typically a apread of 5-6 is considered very wide. This afford the best acceleration and the best no load mileage. However, with the torque of the electric motor the lwo end is already sufficient.

    Actually you are really trying to simplify it too much to call the torque cure triangular and the power outpiut profile retangular.While it might approxiamte to that on an occiliscope it is actually closer to a standard bell curve and inverted "U" . Actually an ideal engine would always run at the most efficient output maxiumm torque , WOT. The with CVT you just adjust the effective gear ratio to the desires speed. But once you have charege the battery and are at the desired speed what do you do with the excess power. You could back off the engine speed but then you reduce the eficiency of the engine, which an ICE has low effciency to start with or you could pulse the engine, but there is a startup lag time.

    I am sure you realize the torque curve of an electric brushless motor , It is almost maximu torque from 0 to approximately 1000 rpm after that is significantly falls off. The HSD system effectively extends this by mutiplying the efective rpm through gearing.

    If you need more explanation please let me know, but you have pretty well written most of the information written in the Prius technical manual. Let me guess, you are an engineering student just getting ready to graduate. Good luck with your futre job search. Again thanks for your efforts to explain the Prius CVT system.

    YMMV,

    MidCow
  • toyolla2toyolla2 Member Posts: 158
    Hi midcow,
    too bad you couldn't follow my explanation. I tried hard to put up the best post I could. I even used spell check, something that you could use also if you don't mind my saying.

    Perhaps this is the bit that you, or the person reading for you, may have missed.

    MG1 is always extracting power from the sun gear in order for the HSD output (the ring gear) to be able send power to the wheels.
    So MG1 never spins needlessly.

    BTW where does the generated power go?, it goes to the electronic inverter which powers MG2. MG2 is made to devour all the electrical energy brought in by MG1 unless the battery happens to need charging in which case it cuts back to allow the battery to absorb the excess. MG2 happens to be conveniently connected to the ring gear where it drives the wheels (through the 3.95 : 1 reduction)

    Of course when the cruise speed is reached, accelerating torque will no longer be needed and power will drop considerably. MG1 must still act as a generator albeit at a much lower level in order to maintain control of the sun gear speed. Remember the car still needs torque transfer from the engine's planetary to the ring gear and it can only do that with an (dare I use this word with you midcow) "obstinate" sun gear. If a sun gear were to offer no resistance you may as well not have it there at that time. Now in that circumstance can you tell me where the torque would be coming from to continue to propel the vehicle. ?

    BTW If you going to reply spare me the remarks that appeared in the last paragraph of your previous post please and thankyou.
    T2
  • stevewastevewa Member Posts: 203
    Just because MG1 is spinning doesn't mean it's generating power.

    By the way, this is NOT an electric brushless (DC) motor. It's a permanent-magnet, 3-phase AC motor. Same for MG2. IMA uses a brushless DC motor. Easier to wire but more complicated mechanically and electrically.

    The rate of rotation of MG1 is controlled by the computer to deliver the ideal "effective gear ratio" for the ICE. Depending on conditions that could mean that MG1 is acting as a generator, acting as a motor, or being forced back-EMF to provide a braking effect against it's input shaft. When acting as a generator, the power from MG1 can go to either MG2, the battery, or both.

    Oh, and internal combustion engines have their maximum POWER at or near redline, not their maximum TORQUE.

    I would not dismiss John out of hand, he's probably more knowledgable about THS and HSD than most Toyota dealership staffs.
  • midnightcowboymidnightcowboy Member Posts: 1,978
    Hey Toyolla2,

    You didn't like my spelling; sorry I didn't go back an spell check or reread! I am bad about that sometimes and yes I am a crummy typist and I don't always spell the words correctly. It is just that the spell check on Edmunds doesn't suggest the correct spelling and sometimes I am too lazy to look it up.

    Let's see you didn't like my last paragraph but yet you said "...or the person reading for you." Actually, you don't know anything about my intelligence, experience or abilities or if I read it myself or had someone read it too me. My implication was that you gave a rather long drawn-out engineering oriented answer that really didn't answer the question. Maybe, it would have been appropriate in the "advanced engineering" thread. But assuming that I was a Newbie, it was out of place, too complicated of an answer, but interesting to me! That was the intent of my point, sorry if it offened you.

    The MG1 spins all of the time. Sometimes it supplies the MG2 and sometime it supplies the battery when acting as a generator. And sometimes receives power form the battery and acts as a motor. It is debatable whether or not it spins needlessly. But let me explain further ....

    When one form of energy is converted to another, there is always a loss of efficiency. No conversion is 100% efficient. I think it is a poor design to always spin the MG1. Why in the world would someone design something where the ICE power is converted into electrical power of the MG1 which is immediately converted into supply power for the MG2. Then the MG2 acts as a motor further converting power with additional energy loss. Why not use the power directly from the ICE? Double and triple conversion of energy is just not an efficient design.

    Lets look at two designs the Honda Insight 5-speed and the Prius

    The Insight doesn't needlessly spin a MG1 and double/triple convert nenrgy and it has an EPA rating of 60 City and 66 highway. The Prius always spins the MG1 ( it is up in the air whether it is needless or not) and it has an EPA rating of 60 City and 51 highway.

    In my higher math, before calculus of several variables, I thought that 66 was greater than 51. Why is the highway mileage of the Prius less than the City mileage while the Insight is higher ?

    Okay, some would save the HSD full hybrid uses electric power to gain City efficincy and higher City EPA. Perhaps a ICE only Prius would have mileage in the range 35/48 with a gain of 25 mpg City and 3 mpg Highway because of HSD. Man that sounds like a whole lot of regenerative braking to get that +25 City. I just don't by it.

    True is could be the CD. However the Prius has a low CD of 0.29 which isn't htat much higher than the Insight's 0.25. There there is the weight difference, but then we digress ...

    Back to my hypothesis: The Prius has lower highway mileage than city becuase the MG1 spins needlessly and wastes energy by double/triple converting enegy and/or charging fully charged batteries.

    Cheers,

    MidCow

    P.S. Oh by the way you notice I did not mention anything derrogatory about you driving an Echo :)

    P.S.S. - I was a member of Eta Kappa Nu and Sigma Tau. Then later with my MBA, Beta Gamma Sigma. But, hey who's counting.
  • falcononefalconone Member Posts: 1,726
    Did you know that Einstein was not a good speller. If someone doesn't spell right it is RUDE to point it out to them. Hope your feelings weren't too hurt.
  • PF_FlyerPF_Flyer Member Posts: 9,372
    Let's drop the personal comments and stick to the topics please.
  • stevedebistevedebi Member Posts: 4,098
    "Did you know that Einstein was not a good speller. If someone doesn't spell right it is RUDE to point it out to them. Hope your feelings weren't too hurt."

    Actually, Einstein wasn't that good at basic math either, which I find even more interesting. His forte was theoretical physics. But math and spelling are not necessary for proper logic...
  • midnightcowboymidnightcowboy Member Posts: 1,978
    Einstein is my hero. Did you know that he didn't think is was important enough to remember his own home phone number; he could always look it up.

    I wonder, what kind of hybrid enhancements Albert would make today if he were still alive. That man had vision :)

    I would low to see what kind of transmission he could design.

    6-speed manual Prius, (the best of all worlds)

    MidCow

    P.S.- With Mod to allow MG1 to idle when not need on highway cruising have gotten MPG specs up to 60/55 thats a 4 mpg improvement
  • zodiac2004zodiac2004 Member Posts: 458
    I wonder, what kind of hybrid enhancements Albert would make today if he were still alive. That man had vision

    He probably would see it for what it's worth and not bother with it...LOL
  • larsblarsb Member Posts: 8,204
    quote zodiac2004-"He probably would see it for what it's worth and not bother with it...LOL"-end quote

    Albert, being frugal, would have loved to only spend $32.86 for 31 days of driving like I did in my last fillup. :shades:
  • zodiac2004zodiac2004 Member Posts: 458
    Albert, being frugal, would have loved to only spend $32.86 for 31 days of driving like I did in my last fillup.

    And being smart, he wouldn't have forgotten about the $450 monthly payment coming out his bank account either.
  • larsblarsb Member Posts: 8,204
    quote Z04-"And being smart, he wouldn't have forgotten about the $450 monthly payment coming out his bank account either."-end quote

    If Albert did not pay cash for his vehicle, then he would have a monthly car payment ANYWAY, whether he owned a Hummer or a Hybrid. Might as well have low fuel costs if the car payment is there REGARDLESS of the vehicle type. :shades:
  • zodiac2004zodiac2004 Member Posts: 458
    If Albert did not pay cash for his vehicle, then he would have a monthly car payment ANYWAY, whether he owned a Hummer or a Hybrid

    Let's not have the exact same comparisons we've had before in the name of Albert, shall we.
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