Hybrid Tips Optimizing mileage

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Comments

  • blueiedgodblueiedgod Member Posts: 2,798
    Yes, I admit, I did not engineer either of the hybrids. But, electric motor is there to assist the gas engine. Which means that at some point you are running on gas alone. Charging batteries is still an additional load on the engine. I don't have a hybrid, but I have a Civic Si, the alternator disconnects itself when the battery is between 90% and 100% charged. The alternator is not physically disconnected, but by taking it out of the "grid" it becomes just a pulley, since the circuit is not complete. All if the cars electric functions run off the battery. The A/C dis-engages the clutches at 5000 RPM, I have no power steering pump (purely electric steering via servo like motor assist), all this was done to bring as much power to the wheels as possible.
    Hybrid technology has limits, even the fuel cell technology is not perfect. It requires more energy to produce (either via lowering temperature, compression, or fisison of water) Hydrogen that it is capable to give out.
  • john1701ajohn1701a Member Posts: 1,897
    > motor is there to assist the gas engine.

    You are describing a "mild" hybrid, not a "full".

    With a "full" hybrid, the electric motor gets help from the engine. In fact, the electric motor propels the vehicle all by itself sometimes. For me, there's a 3 mile stretch that I drive at 35 MPH with the engine off almost (dang stoplights) the entire time.

    In Prius, a "full" hybrid, the A/C and steering are fully electric too. There is no connection at all to the engine, only the electrical system.

    JOHN
  • stevedebistevedebi LAMember Posts: 4,098
    It is my understanding that the Prius can end up depleting the batteries and running on engine only.

    This road has been traveled before on this forum, with people insisting that the engine can generate the electricity to power the electric motors, describing it as if the ICE was only there to generate electricity. If that were true, there would be no need for the ICE to drive the wheels - just route the power to the electric motors. And, there would be no "turtle" icon on the display... The Prius doesn't do this, because it requires the ICE to provide the primary power to the vehicle.

    The electrical propulsion is an assist mechanism (above 15 MPH or so, though if the battery pack is somehow depeleted, the engine will run at low speeds as well). The vehicle is still primarily an ICE, with electrical assist. Hence the fact that a small ICE only vehicle will get mid to high 40's MPG on the highway, but not in town - because it is the start/stop cycles that kill MPG in town.
  • john1701ajohn1701a Member Posts: 1,897
    > It is my understanding that the Prius can end up depleting the batteries and running on engine only.

    That is a sensible misconception.

    The point of misunderstanding is assuming that the motor & electricty are no longer available when the battery-pack is low. There are. It's no big deal. Far more power is always available than many believe... hence the misconception.

    > If that were true...

    It is true!

    However, that is not the most efficient way of propelling the car. So it is avoided almost entirely. Reverse is the only situation where that actually is allowed.

    And there is no such thing as a "turtle" anymore. Depletion is nothing but an extremely rare memory from the previous generation.

    > The electrical propulsion is an assist mechanism (above 15 MPH or so... because it is the start/stop cycles that kill MPG in town.

    It is quite obvious that HSD is not understood here. That description is filled with several misconceptions.

    15 MPH is totally, completely false. The actual limit is electric draw, not speed. That amount is 10kW.

    The "kill MPG" is town is a total mystery. My in town driving skyrockets. It's the ability to drive with the engine totally off, something you just can't seem to accept is even possible, that allows the fantastic efficiency.

    JOHN
  • stevedebistevedebi LAMember Posts: 4,098
    " It's the ability to drive with the engine totally off, something you just can't seem to accept is possible, that allows the fantastic efficiency."

    I don't recall saying you can't drive with the engine off, just that you can't drive without the engine if the battery is depleted. if you care to say you can, please demonstrate by driving 20 miles without stopping at 12 MPH, and show us that the ICE won't come on. Of course, it will come on, because the batteries aren't capable of supporting that length of driving without being recharged. And while they are being recharged, what is keeping the Prius moving? Yup, you guessed it, the good 'ol ICE.
  • john1701ajohn1701a Member Posts: 1,897
    No one claimed the engine won't *EVER* start back up.

    No one claimed the source of energy is not gas.

    No one claimed you could drive 20 miles using just the batteries.

    Your replies are clearly insincere. Goodbye.

    JOHN
  • blueiedgodblueiedgod Member Posts: 2,798
    God, I opened a can of worms. I say with 95% assurance that "gas only" 1.3 liter VTEC-E engine (or whatever they have in HCH and Prius) will achieve same if not better fuel economy with a CVT transmission. All because gas only car will be at least 200 lbs lighter, and will not put additional engine load by trying to recharge the batteries. I don't care what you say, the 2nd law of thermodynamics says "there is no free lunch." Unless you can prove that the current concept of energy flow is wrong, the batteries are getting their juice form somewhere, and since you can not always drive downhill to capture and convert the gravitational energy into electric, you are using gasoline to generate electricity. The ICE/Generator/batteris all have their inefficiencies, and thus multiply the inefficiency of the vehicle. ICE being the most inefficient.
  • gagricegagrice Pahrump, NevadaMember Posts: 31,450
    You are absolutely correct. In 1986-87 Honda built the civic HF that was rated 52/57 mpg with a 1.5 liter engine. According to some on this forum the CVT is more efficient than a manual shift, therefore that same civic with the CVT drive would get in the 60+ mpg range. It would not need all the expensive gobbledegook electronics to go with it. Of course then Toyota would not get all the glory for saving the world's oil supply. I remember that little Civic CRX HF and it ran like a scaulded ape. I thought it was a great little car. Almost 20 years later we are catching up to the cars of the late 80s, that's progress folks.
  • stevedebistevedebi LAMember Posts: 4,098
    Probably should stop trying, but let me quote you in a previous post (italics are mine):

    "There is NO SUCH THING as "gasoline only" mode in a full hybrid. 100% of the time the engine is providing thrust to the wheels it is also creating electricity. So there is ALWAYS a benefit from the greater efficiency of electric, enough to provide an overall reduced loss. In other words, it is still more efficient than a gas engine alone."

    This statement indicates that the Prius Hybrid will not drive in pure ICE mode. My point was that it will use pure ICE when the battery is depleted. Granted, the ICE will still be generating electricity (which incidentally reduces it's ICE effectiveness - a power drain is a power drain and there is no free lunch here).

    "No one claimed the engine won't *EVER* start back up."

    Uhhh, agree with you there, I never claimed it either.

    "No one claimed the source of energy is not gas."

    Sorry, I don't get this one, I don't recall ever saying that either.

    "No one claimed you could drive 20 miles using just the batteries."

    Thank you for agreeing with me that the ICE will be used when the batteries are depleted. I was citing an hypotheical example that would cause battery depletion.

    "Your replies are clearly insincere. Goodbye."

    In general people stoop to personal attacks when they have nothing logical to say. Sincerity has nothing to do with facts...
  • john1701ajohn1701a Member Posts: 1,897
    I'm still not sure why you choose to counter my sharing of facts, but it is quite clear the fact that a full hybrid OFFSETS energy to more effecient opportunities is not understood.

    The motors & battery-pack take advantage of those opportunities.

    The switch from one to another or both happens as much as 30 times a minutes too, far more often than people realize or could ever possibly calculate on paper. That obviously isn't understood either.

    That switching takes advantage of effecient opportunities too.

    Don't argue and it won't be personal. State facts instead.

    JOHN
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    "electric motor is there to assist the gas engine. Which means that at some point you are running on gas alone."

    Remember that Prius is a full hybrid powered by the Hybrid Synergy Drive which features E-CVT. Electricity is generated at all time. Not too many understand the concept of how the E-CVT works.

    Traditional transmissions, even mechanical CVT, works by the idea of changing the size of two (inter)connected spinning gears or cones to change the spin ratio. In the low gear, the thrust at the wheel is greater than in the high gear.

    HSD's E-CVT works fundamentally different. In HSD, ICE and two electric motor/generators are permanently engaged through the Power Split Device. At low speed, HSD relies more on the electric motor's 295 lbs-ft torque to increase thrust at the wheel. There are no shifting involved to increase thrust as in traditional tranny.

    At high speed, HSD relies more on the gas ICE to maintain constant speed. Electricity is still being generated at high speed in order for the ICE to be at the most efficient state(RPM). In another word, variable amount of electricity generation can achieve the same functionality as a CVT while taking the most advantage of the ICE. The amount of electric generated are either routed to the electric motor(to power the wheel) or the battery(for later more beneficiary use). Electric power boost is also useful for those sudden burst of power for passing on the highway, which gas ICE is inefficient at.

    Dennis
  • john1701ajohn1701a Member Posts: 1,897
    The fact that even the slightest decline in the road will result in recharging while driving baffles most people. We're talking changes it pitch so subtle you wouldn't normally even notice them. Fortunately, the Multi-Display makes it very easy; the sudden +30 MPG jump in efficiency is a rather blatant clue. So owners catch on quickly. Skeptics reading about Prius on paper don't. Their arguments are based on fundamentals that don't apply, like those from mild hybrids (with a mechanical CVT, rather than electric) and the antiqued battery-only vehicles.

    I wish I had a decent method available for explaining to people how the carriers of the PSD (Power Split Device, aka: Planetary-CVT) can rapidly alter the flow of electricity without anything else happening. Those carriers keep right on spinning the same way they were a fraction of a second earlier, but now the system is capturing electricity rather than consuming it. Then a second later, it switches back to consuming. Then a second after that, it the system is both capturing & consuming at the same time. Then a second later, all electrical activity halts entirely. Then a second later, it starts consuming again.

    And of course, there is absolutely no consistency between the switching of modes and the timing of those switches. It is extraordinarily dynamic, taking a wide variety of factors into account... so many that I wonder how the other automakers will be able to get their software to work as well as Toyota's quick enough to be able to compete on the same level. The concept model of Prius came out in 1995. That's a rather significant lead. Every tiny programming tweak makes a difference, and Toyota has had a heck of a lot of time to make revisions. Several MPG can easily be lost by the system not being capable of both detecting and responding to certain criteria fast enough. Not choosing the right engine size, motor size, battery-pack size, carrier size, peak RPM, combined RPM, peak voltage, etc. have an effect on efficiency too. Taking all that into account, you realize so many efficiency opportunities could be missed that the MPG may be no better than a traditional vehicle. And that doesn't even take into account the fact that Toyota also went to great lengths to make sure the battery-pack isn't ever stressed, to always maintain a moderate charge-level... since deep-discharging shortens the life of a battery.

    Needless to say, the system is far more "complex" than most people realize. But then again, all that complexity is in the electronics. The hardware itself is actually extraordinarily simple. Very little happens physically to achieve the remarkable MPG.

    JOHN
  • eheadingeheading Member Posts: 26
    Dennis. First let me say that as an owner of a 2003 Prius, I love it, and am thrilled with the way it operates. To a great extend I think I understand and agree with your statements about the energy switching. But it seems to me that you are saying the CVT in the Prius does not vary engine speed with load, merely switches to more electrical power. But if this is so, why does my engine pick up RPM if I go to accelerate or go up a modest grade. It seems to me that the CVT does function somehow like a tradional CVT in addition to switching energy sources.

    Ed Headington
  • gagricegagrice Pahrump, NevadaMember Posts: 31,450
    I can see by both your descriptions of the HSD system that this would be difficult or impossible to duplicate in an ICE alone. My question is do you think it can work in any size platform, up to a Land Cruiser size? Question two, with so much of this technology riding on the computer is it totally redundant? And is the program all on EPROM or Flash memory? Those simple explanations make it easier to understand how the system works.
    Thank you, Gary
  • blueiedgodblueiedgod Member Posts: 2,798
    At high speed, HSD relies more on the gas ICE to maintain constant speed. Electricity is still being generated at high speed in order for the ICE to be at the most efficient state(RPM). in other words it puts an added resitance to the ICE to generate electricity.
    In another word, variable amount of electricity generation can achieve the same functionality as a CVT while taking the most advantage of the ICE. The amount of electric generated are either routed to the electric motor(to power the wheel) or the battery(for later more beneficiary use). while each of the system has its own loss, you are combining the loss for each system.

    Wouldn't it make more sence to make a Diesel hybrid and make it run on Crisco, or biodiesel?
  • john1701ajohn1701a Member Posts: 1,897
    > Wouldn't it make more sence to make a Diesel hybrid

    Diesel has limitations. The start/stop abilities are impaired by the fuels need to have a hot system available. Gas is much more dynamic in that respect.

    Emissions are a huge problem too. Right now, they are so dirty 45 states limit sales quantities and 5 states prohibit sales entirely of passenger vehicles that use diesel.

    Later on, when battery-packs size/density grow (and/or ultra-capcitors are added), the engine size is reduced, and the SULEV emission levels can finally be achieved, diesel will then get an opportunity to be a practical alternative.

    JOHN
  • john1701ajohn1701a Member Posts: 1,897
    > But it seems to me that you are saying the CVT in the Prius does not vary engine speed with load, merely switches to more electrical power.

    That is true... to an extent.

    It's that software decision-making I was talking about. At some point it is advantageous to adjust the RPM. But before that, how would you ever sense the variation of electricity flow? There is no physical aspect of that to detect... without a scanning device, of course.

    JOHN
  • stevedebistevedebi LAMember Posts: 4,098
    Dennis-
    I always understood that the Prius is constantly generating electricity; my question is using that electricity.

    Your post raised a question in my mind. If the Prius goes us a very long hill, will the battery become depeleted and the car revert to ICE only while the battery is charged?

    It seems to me that I have read that the Prius can end up ICE only under certain (generally rare) occasions. Assuming the battery can be depleted (and I see no reason for a 40% discharge battery cutout otherwise), I see two possibilities:

    1. Battery gets depleted, ICE only takes over while battery is recharged sufficient to resume electrical assist. Prius loses full HP/Torque.

    2. Battery gets depleted, ICE generates electiricity and electrical assist is used, while battery is not recharged until the uphill or whatever caused the battery depeletion is finished. ICE loses HP/Torque due to load (or increases fuel use to compensate), but Prius retains nearly full HP/Torque.

    Does one of these descriptions fit?
  • john1701ajohn1701a Member Posts: 1,897
    Ah! Now the thought-provoking discussions have began. Great!

    Unfortunately, none of the above are what actually happens (with HSD).

    Stop thinking "take over" and you'll be fine.

    While climbing long hills, the battery-pack is rarely used anyway. In fact, most of the time there is so much electricity being generated that the thrust-motor doesn't need it all. So recharging takes place at the same time.

    When I climb out of the river valley (a 2-mile highway stretch, steep enough to require a truck lane) after work everyday, the battery-pack is almost always at a charge-level *HIGHER* at the top than when I started at the bottom.

    The battery-pack doesn't *EVER* get depleted in virtually all driving situations, except those few really steep mountains. But even then the engine still provides enough electricity to keep you going at a good clip.

    The drain you keep imagining simply doesn't happen. There is much, much more electricity available then you realize. The "revert" situation you believe will happen won't *EVER* occur. Instead, the engine will continue to generate on-the-fly electricity and you'll keep right on climbing up the mountain. The battery-pack will simply remain low. The only indication you'll sense is the RPM increasing. That's it!

     
    Your misconceptions do raise a very important point. Other hybrid designs are not as flexible/capable as HSD. So the belief that all hybrids react the same way under stressful conditions is a very real PR problem.

    Any suggestions to clarify the confusion?

    JOHN
  • gagricegagrice Pahrump, NevadaMember Posts: 31,450
    A good real world review of the 2004 Prius.

    It had been a stunning performance: real-world highway power which, even after driving the Prius for over 2000 kilometres, I simply hadn't expected.

    http://www.autospeed.com/cms/A_2036/printArticle.html
  • stevedebistevedebi LAMember Posts: 4,098
    Thanks for your reply. I see this as a modified version of option 2, where the engine has higher RPM to provide more power to the electric components.
  • mistermemisterme Member Posts: 407
    "the ICE will still be generating electricity (which incidentally reduces it's ICE effectiveness - a power drain is a power drain and there is no free lunch here)"

    Truly there is no free lunch whether HSD is consuming electrical energy in all electric mode, or the ICE is replacing what electricity is consumed by its motors.
    While it is true that the motors turn to replace the electricity, something is consuming extra energy to turn those motors that otherwise could be used to propel the car.

    Motor A turning and generating power for Motor B while re charging the battery is all wonderful, except something has to turn Motor A first.

    If it is ICE then more gas is consumed.
    If it is Kinetic energy then the car is slowing down and not coasting as it otherwise freely would.
  • john1701ajohn1701a Member Posts: 1,897
    > no free lunch

    We already all know I'm getting 53 MPG, not 999,999,999 MPG.

    What is your point?

    JOHN
  • mistermemisterme Member Posts: 407
    My point:

    "Motor A turning and generating power for Motor B while re charging the battery is all wonderful, except something has to turn Motor A first"

    I was really only chiming in here...wasn't directed specifically to John.
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    "But it seems to me that you are saying the CVT in the Prius does not vary engine speed with load, merely switches to more electrical power. But if this is so, why does my engine pick up RPM if I go to accelerate or go up a modest grade."

    The ICE RPM can vary with the load while switching to more electrical power. HSD can do it with the use of PSD. Electric power does not have to come from just the battery pack. The extra horsepower created by the ICE can be converted to the electricity. How much HSD generate electricity depends on other conditions such as current speed, accelerator pedal position, slope of the road, battery SOC, etc... For example, at low speed, the extra hp created by ICE would be split more into electricity than to the wheels. This creates more torque, therefore, more thrust at the wheel(equivalent
    of a low gear).

    Most of the ICE horsepower is split into the wheel instead of generating electricity, in most of the situations. One situation I can think of that generates the most electricity is when you floor the Prius from a stop. In order for E-CVT to "simulate" the first gear, about 43hp from the ICE must go into generating electricity to provide 29kW(with 10%loss in conversion) of electricity to the main 50kW motor. The remaining 21kW is provided by the battery. By knowing this, you can take steps to minimize conversion loss to increase MPG. Avoid situations when ICE and battery are powering the main electric motor! I don't own a Prius so, you can test out if it is also true in practice. ;)

    The loss in conversion that we are talking about is about only 4.3hp or about 5.6% of max 76 hp that Prius ICE can output. If you max out the A/C, it'll take about 4hp as well. Atkinson ICE is 15% more efficient than comparable Otto cycle ICE therefore, there is still overall gain from HSD design even in this condition.

    Dennis
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    "My question is do you think it can work in any size platform, up to a Land Cruiser size?"

    Yes, Toyota has shown the concept HSD FXT full size pickup truck.

    "Question two, with so much of this technology riding on the computer is it totally redundant?"

    I believe there are more than 16 computers(ECUs) in 04 Prius. Each ECU dedicated to individual task such as batter management, regen brake, steering, etc... They all are connect with CAN. Yup, you guessed it right, Car Area Network. There is a main ECU that "decides" what to do in case of minor to major failures reported by other ECUs.

    "And is the program all on EPROM or Flash memory?"

    I would say Flash memory or some other type that is rewritable since there are service campaigns to update 04 Prii already. EPROMs are read-only.

    Dennis
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    "If the Prius goes us a very long hill, will the battery become depleted and the car revert to ICE only while the battery is charged?"

    If the battery become depleted, the car would only be powered by the ICE. It does not mean that all the mechanical power from ICE would go into the wheel. Some ICE horsepower would be split to generate electricity to recharge the battery(HSD would do this way before near depletion) and/or to power the electric motor.

    ICE hp powering the 50kW motor is important because in this high load situation, the car will be going at lower speed. If you are climbing a very steep hill, you want to go slower. If you are towing, you want to go slower. etc... HSD would be generating more electricity to increase thrust at the wheel as explained before.

    Remember, a fully charged Prius battery is capable of delivering 21kW(28hp) for 135 seconds. For normal drivers(not race car drivers), it is sufficient to overcome most, if not all, high load situations.

    Dennis
  • gagricegagrice Pahrump, NevadaMember Posts: 31,450
    I don't think it would be a problem unless you were racing up Pike's Peak.
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    Thanks for the link. It was a great read. This is my favorite part. :)

    "On the way there was a very steep climb - Willunga Hill. The road is wide and dual lane each way and the speed limit is 100 km/h(62 mph). Many cars struggle up it - it's amongst the steepest main road hills that you'll find. I was intensely curious to see how the Prius would climb it - by now carrying only one occupant and perhaps 20kg(44 lbs) of luggage.

    At the base of the hill the LCD display (able to be configured to show a variety of data including exactly how the hybrid system is operating at any moment) showed its normal 'half' level for the battery - would that be enough, I wondered? I booted the electronic throttle and from a starting speed of 100 km/h(62 mph), watched the nose rise and the climb begin.

    Here's where the go-slow starts, I thought.

    The LCD showed the electric motor working to assist the petrol engine... and the car accelerated. Yes, accelerated up this very steep climb. 110 km/h(68mph), 115, 120, 125(78mph). I turned on the headlights and watched the sparse traffic pulling to the side to let me through. At 128 km/h(80mph) the Prius was giving its all: periodically the drive to the electric motor halted for an instant (perhaps to allow it to cool) as we raced upwards at full throttle, my eyes watching the battery level draining away. But well before the battery was empty and the electric assist exhausted, we'd reached the top of the hill and I again returned to the speed limit.

    It had been a stunning performance: real-world highway power which, even after driving the Prius for over 2000 kilometres(1,243 miles), I simply hadn't expected.

    When I lived in South Australia, Willunga Hill had been one of my litmus test roads. And any car that can get 5.3 litres/100 km(44.4 mpg), has the potential to comfortably carry four people and their luggage, and can rocket me up that steep incline at 128 km/h(80mph) is A Good Thing."


    Dennis
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    "...misconceptions do raise a very important point. Other hybrid designs are not as flexible/capable as HSD. So the belief that all hybrids react the same way under stressful conditions is a very real PR problem.

    Any suggestions to clarify the confusion?"


    What do you think about the following explanation?

    There are many types of hybrids. The full hybrid with E-CVT works by the way of generating electricity instead of shifting into different gear ratios. HSD E-CVT twin motor/generator design eliminates the need for the battery to propel with gas-electric hybrid powertrain. Battery pack is just an optional device for extra performance and efficiency.

    Dennis
  • gagricegagrice Pahrump, NevadaMember Posts: 31,450
    I was impressed also.. Glad you liked the review.. Gary
  • quasar4quasar4 Member Posts: 110
    --Sorry to be a kill-joy, but what do the last umpteen posts have to do with tips for optimizing mileage?
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    The discussion led to a tip to improve Prius' fuel economy by reducing conversion loss in msg#89. The other posts are related to the discussion about high load situations and how E-CVT is amazing at providing available power to maximum extend without depleting the battery pack, in the real world situations(not on race track).

    Dennis
  • stevedebistevedebi LAMember Posts: 4,098
    ...my eyes watching the battery level draining away. But well before the battery was empty and the electric assist exhausted, we'd reached the top of the hill and I again returned to the speed limit.

    That is what I was referring to. On the road from LA to Abququerque (I40 east bound), there are a couple of hills that take about 8 minutes to climb at 75 MPH. I suspect the battery might get depleted on this stretch of road. Any Prius owners driven this route yet?
  • stevedebistevedebi LAMember Posts: 4,098
    "If the battery become depleted, the car would only be powered by the ICE. It does not mean that all the mechanical power from ICE would go into the wheel. Some ICE horsepower would be split to generate electricity to recharge the battery(HSD would do this way before near depletion) and/or to power the electric motor."

    This is a variance with other posts (not necessarily by yourself) which indicate that power goes directly from the ICE power generators to the wheels. Your post indicates the power is generated into and out of the battery pack, and from there to the wheels. Makes sense to me.

    People should keep in mind that this depletion situation is quite rare in normal driving...

    The issue is relevent to MPG (and this board), because if that battery pack goes depeleted, your MPG reverts to ICE (until the battery charge picks up).
  • john1701ajohn1701a Member Posts: 1,897
    > and from there to the wheels

    That is not correct.

    The electricity does not pass through the battery-pack (in Prius anyway).

    Electricity generated from the engine is sent *DIRECTLY* to the thrust-motor. There is no conversion from 500V to 206V and no conversion from AC to DC. It remains intact and is consumed immediately when needed. When not needed, they is is converted to recharge the battery-pack.

    JOHN
  • stevedebistevedebi LAMember Posts: 4,098
    "The electricity does not pass through the battery-pack (in Prius anyway).

    Electricity generated from the engine is sent *DIRECTLY* to the thrust-motor. There is no conversion from 500V to 206V and no conversion from AC to DC. It remains intact and is consumed immediately when needed. When not needed, they is is converted to recharge the battery-pack."


    1. Hey, take it up with Dennis, it was his statement not mine. I would like to know the correct and accepted answer.

    2. Your statement would indicate that there is no need for the battery pack when climbing a large, long hill, and that when the pack is depleted, the electrical components will still power the wheels. Only one of the two statements can be correct. Either the Prius will go ICE only on battery pack depletion, or it won't go ICE only. Big difference in MPG.

    3. Question about AC? Why would the engineers use Alternating Current anyway, since electric motors run on DC, and batteries put out DC? Or are you just saying that there is no Alternating Current in the Prius?
  • john1701ajohn1701a Member Posts: 1,897
    > 1. Hey, take it up with Dennis

    His statement is correct. Your interpretation of it isn't.

     
    > 2. Your statement would indicate that there is no need for the battery pack...

    YES!!!

    THAT'S WHAT I HAVE BEEN TRYING TO TELL YOU ALL ALONG.

    Your repeated attempt to somehow factor in the battery-pack getting depleted is the source of your confusion. IT DOES NOT! In fact, it is usually recharged on the way up. So you typically end up with more stored electricity available at the top than when you began the climb at the bottom.

    > 3. Why would the engineers use Alternating Current

    There's no contest, AC is a far better choice when it comes to power & durability.

    JOHN
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    "1. Hey, take it up with Dennis, it was his statement not mine. I would like to know the correct and accepted answer."

    John said that same thing that I said. From analyzing your post, I think I know where you get off-track to come to misunderstanding.

    You'll need to clear up what the two powertrains in a gas-electric hybrid. For the gas powertrain, you'll need just the gasoline Internal Combustion Engine. For the electric powertrain, you'll need something to generate electricity; diesel ICE, Fuel Cell, Rotary ICE, Steam engine, Gas ICE, etc.... For Prius, the same gas ICE is reuse(simplicity) to generate electricity by splitting power from the ICE. Battery is not the original source of energy for electricity; the electric generator is. It is just there to cache electricity for demanding situations.

    So, even if the battery isn't there, Prius is still powered by gasoline and electric powertrains because HSD always split power to both paths. How much to which path decides the amount of thrust to the wheel. The power that split to the electric generally suggests low speed, high torque and thrust to the wheel. The power split from ICE straight to the wheel generally suggests high and constant speed, low thrust(just enough to maintain the same speed), etc..

    The battery power increases total horsepower available and fuel economy because the electricity in the battery is mostly "free lunch" received from regenerative braking, in reference to traditional cars. I hope that clears it up. If not, let us know what you find inconsistent.

    "3. Question about AC? Why would the engineers use Alternating Current anyway, since electric motors run on DC, and batteries put out DC?"

    Because only AC current can be transformed into higher or lower voltages.

    Dennis
  • mistermemisterme Member Posts: 407
    "The battery power increases total horsepower available and fuel economy because the electricity in the battery is mostly "free lunch" received from regenerative braking, in reference to traditional cars."
    ___Is most of the battery charge really due to regen braking?

    "Because only AC current can be transformed into higher or lower voltages"
    ___Both AC and DC can be lowered.

    Question:
    If the battery is taken out of the equasion and ICE is providing power for one motor to generate electricity for the other motor, is there a loss of power in conversion there?
    I understand that one motor (I forget MG1 or MG2) can't spin freely for output to the wheels but wouldn't it make more sense to mechanically lock this motor so ICE isn't loaded down by the generator in these circumstances?
  • john1701ajohn1701a Member Posts: 1,897
    > is there a loss of power in conversion there?

    Step back and look at the ENTIRE equation.

    The existence of the 2 electric motors (and PSD) allow the gas engine (which is smaller in the first place) to run at a more efficient RPM than normal. Also, the engine uses the Atkinson-Miller cycle instead of Otto (which isn't as powerful, but is clearly more efficient).

    All that combined provides a greater MPG savings than the loss from the power conversion. That's an overall benefit. But only looking at a single part, you'll never see that.

    JOHN
  • mistermemisterme Member Posts: 407
    Thanks John for the clarification.
    I thought I read a post somewhere the Prius driver observed higher ICE RPM's when he stepped on it.

    I actually was looking at 5 parts: ICE, 2 electric motor/generators, PSD, and output to wheels.
    Perhaps a future version will address the conversion loss.
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    "Is most of the battery charge really due to regen braking?"

    In the city, yes. On the highway, probably no.

    "If the battery is taken out of the equasion and ICE is providing power for one motor to generate electricity for the other motor, is there a loss of power in conversion there?"

    Sure there is. It is necessary for HSD to achieve E-CVT with much precise control and at the speed of electricity. All type of transmissions waste energy by generating heat either in the clutch, torque converter, or belt/cone.

    "I understand that one motor (I forget MG1 or MG2) can't spin freely for output to the wheels but wouldn't it make more sense to mechanically lock this motor so ICE isn't loaded down by the generator in these circumstances?"

    It is the generator(MG1) that adjust engine RPM to wheel ratio by generating variable amount of electricity. Sometimes, very rarely and shortly, it needs to stop because it is the ideal condition for a given moment. Since MG1 RPM range has 20,000 different outcomes, 0 RPM is just one of the many possibility. Locking MG1 will force the ICE to adjust it's RPM to the car's speed; which will be like a car with a single gear ratio(no transmission). Power delivery range will be short and fuel economy will drop.

    Dennis
  • stevedebistevedebi LAMember Posts: 4,098
    Dennis-
    Can you please point me to some links for the Prius electrical system? The material on how-stuff-works is for the older Prius, and indicates a battery is required for operation. I have yet to see a diagram that shows a power connection directly from the ICE to the electrical propulsion system. It's not a question of the HSD, but rather how the electricity gets to the HSD.

    I'm trying to get a grip on this, since I have read posts in which the 2004 Prius battey has become depleted, and the vehicle lost a lot of zip.

    Thanks
  • stevedebistevedebi LAMember Posts: 4,098
    I did a web search and found an article about emergency response which indicates that the battery powers the electric motor, i.e., there is no way for the ICE to directly power the electric motor. According to this Toyota documentation, the ICE is used to recharge the battery. This would indicate that the HSD will not run without the battery pack, or if the battery pack is depleted. It will have to recharge.

    http://techinfo.toyota.com/public/main/2ndprius.pdf

    See pages 4 and 13 for descriptions of the battery and it's functions.

    However, I can see how some desciptions of the MG1 and MG2 can lead one to believe that the ICE will directly power the MG2 system. Anyone have some good links on this issue?
  • stevedebistevedebi LAMember Posts: 4,098
    OK, I think I found a link. This is from the press kit on the first generation Prius (but should still apply to 2004 models), which indicates the ICE can power the electric motors with part of it's energy (I suppose when at lower RPMs the power would be better used via electrical path):

    http://www.pressroom.com.au/pressroom/sample/presskits/priuskit.h- tm#7

    Thanks for all your help in explaining this issue...
  • john1701ajohn1701a Member Posts: 1,897
    YES! That proves it!!!

    That "Higher Speeds" animation showed *EXACTLY* what I've been saying all along. There were *NO* arrows to or from the battery-pack.

    The engine fed the generator-motor which fed the thrust-motor, a direct path without battery-pack interaction at all.

    JOHN
  • john1701ajohn1701a Member Posts: 1,897
    It proved that oversimplification of "gas engine only" was too vague. Thank you for providing the detail we needed to clarify that.

    When watching that animation and it is easy to observe how the PSD interacts, you can clearly see how electricity is created on-the-fly and sent directly to the other motor for immediate use.

    JOHN
  • stevedebistevedebi LAMember Posts: 4,098
    Well, where should I have looked - everywhere BUT the Toyota website - Duh!

    It also explains the stories I have heard about those rare times when the battery gets depleted. The electric is still engaged, but the full power only comes with the use of the battery pack. So if it happens to go down, the car will lack energy until the battery pack is charged again.

    Always nice to have a full understanding of a topic...
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