Advanced Course in Hybrid Engineering

13

Comments

  • larsblarsb Member Posts: 8,204
    That's just it - if ALL a person cares about is "getting to work" and they still want high MPG, they need to be in a Honda Insight, where you can still get 50+ MPG by COMPLETELY ignoring the MPG efficiency tools.

    If you care only about "driving to work" and do not want to put in the effort to drive for max MPG, then you really have no business buying a hybrid at all.

    Actually, pre-programmed efficiency is a good idea, but I wonder how it could be made practical?

    Does the car come with several settings that will vary the efficiency? Do you have settings based on how fast you want to get somewhere? Or do you have settings based on MPG that you want to achieve? And how about when traffic disallows a setting to proceed and puts the car into "manual override?"

    It's an idea with potential, but a lot of kinks would have to be worked out for it to become a usable idea....
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaMember Posts: 64,482
    "
    If you care only about "driving to work" and do not want to put in the effort to drive for max MPG, then you really have no business buying a hybrid at all. "

    Exactly, which is the basic effect of "feel good marketing" upon people who only want to feel good without actually trying to DO good.

    Stretching fuel mileage for the "national good" requires effort and sacrifice, which really (let's be honest) is not the strong suit of the American public right now.

    Wearing flattering fashions is so much easier than losing weight ;)
  • toyolla2toyolla2 Member Posts: 158
    gagrice wrote One of the downsides of the Prius for me was the 30 MPG on the first few miles. I can get that with a small gas or diesel car and not add the complexity or the additional cost

    I agree, in my post I stated that the poor utility of present day mechanical power conditioning systems causes overly large engines. Another downside to this, which I hadn't got to but which you just pointed out, is that it takes significant time to warm up even engines of just 1.5L . So even in an efficient system like the Prius HSD, the engine cannot raise the temperature of its mass to running temperature within two or three miles - the length of an average mission. That certainly is a problem if it impacts efficiency by 33% and those missions happen to be frequent in your usage. Hybrid development is reaching an impasse, I agree.

    If I may digress a significant part of annual running costs from those short missions was muffler pipes which deserve mention also. In later years my old Corolla developed a healthy appetite for these. "It's short trips" the Toyota garage was often wont to tell me. My current vehicles have stainless steel. We'll see.

    To get back to business, an engine of but one quarter the size should warm up more rapidly although I would hasten to add no engine should be expected to reach 10k RPM from cold right away. Some temperature/timer function should be invoked after the ignition key is inserted to protect the system from driver misuse.

    Compliance is a problem for achieving good mileage figures. I suggest that a new control is needed so that the driver can dial in the desired mpg and the car will do the rest with some sort of rolling average algorithm. But does someone who purchased an HAH want to find themselves suddenly driving a vehicle with the performance of a Yugo ?

    And let me pose this question which is more a propos to the forum. Supposing an advanced series hybrid was built with a 400cc engine of 80 HP installed into a Corolla sized vehicle would you consider buying it ? I am curious to know your thoughts regarding market resistance to smaller engines. Because if so, look no further, you've got impasse right there - at the consumer.
    T2
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaMember Posts: 64,482
    I think if the car performs well and looks decent, a small engine is not an obstacle to sales in America; however, a very small CAR is an obstacle. I'm not sure how a Corolla sized car is going to perform with 80 HP. It would have to be very light indeed, well under 2,000 lbs and probably closer to 1,600.
  • toyolla2toyolla2 Member Posts: 158
    ........with a series hybrid or HSD you wouldn't need to go to 1600lbs.
    You are thinking along coventional lines. Allow me to guess your train of thought, if a 100Hp 1800lb vehicle can do an 8 second 0-60mph ramp then an 80Hp vehicle will probably need to be around 1600lbs.
    I appreciate you're tracking 500 forums Mr_Shiftright_Host but stay with this and you'll get it. I'll compare a standard transmission with 100Hp with the 80Hp Prius :

    If the 100Hp vehicle was driving torque through a conventional M/T probably in 2nd gear (1000rpm per 10mph). It reached 60mph at 6000rpm where the Hp peaked out at 100Hp. Then foot off the gas and cruise in fifth pulling about 7Hp from the engine.

    Doing a quick analysis here. I will assume the driver changed into 2nd gear at 10mph at which point the engine was producing one sixth of 100Hp (16Hp say) so the power during the acceleration ramp at full throttle varied at the start between 16Hp at 10mph to the finish at 100Hp at 60mph. The average power for the duration would be (100+16) / 2. Which is 58Hp wouldn't you agree? Question is where did the other 42 Hp you paid for go ? That's like half an engines' worth isn't it ?

    That is the problem with mechanical power conditioning it may be mechanically efficient but it's not good at what it does.

    The HSD system, used by Prius and increasingly now other vehicles, uses electromechanical power conditioning which allows the driver to 'fireball' this 78Hp engine at only 20mph. About 28Hp is removed by MG1 which forces the other 50Hp to leave the HSD mechanically via the wheels of the car. Question is where does the 28Hp go. Well it is sent to MG2 which is directly connected to the wheels. Consequently the full 78Hp gets to the road at 20mph.

    The engine continues to 'fireball' (with rpms close to 6000rpm) as the vehicle continues to accelerate. MG1 continues to remove enough power to prevent the engine over-revving (the throttle has been jammed wide open). MG1 continues to dump this energy into MG2. At 60mph the driver lifts his foot and engine revs fall causing MG1 to speed up again. But MG1 only absorbs about 2Hp while cruising which it can feed to MG2 or to the battery if MG2 is turned off.

    Let's analyze again what happened. We picked up the action at 20mph at which speed the Prius engine was beginning to 'fireball'. And we saw how 78Hp was delivered to the wheels. A short time later at 60mph at the end of the acceleration ramp the engine, still in 'fireball' mode was delivering 78Hp to the road wheels at which point the driver throttled back to cruise.

    So the power during the acceleration ramp at full throttle varied between 78Hp at 20mph to finish at 78Hp at 60mph. The average power for the duration would be (78+78) / 2. Which is 78Hp. So you got all the engine you paid for.

    We saw how a 100Hp engine netted 58Hp overall. So what conventional engine power would be needed to compete with the Prius ?

    An engine with (78 / 58) x 100 = 134 Horse power

    So that is the effective power of the Prius that its 78Hp engine provides and why the 1600lbs you predicted was generous. I would guess that theoretically 2300lbs would give an 8 second timing. The heavier Prius gives around 10 seconds which would be consistent by my figures.

    So 134Hp, that's the power you need to compete with against the Prius without the HV battery. Since the HV battery assists somewhat, add 15 Hp to that figure.

    You might have noticed I didn't mention the role played by the HV battery much. That's because it's not essential to the operation.

    The HV battery is the reason why MG2 is sized for 50Hp. Although MG2 can only get 28Hp from MG1 the missing 22Hp can be supplied by the battery for power assist while accelerating but I am not sure if MG2 can actually accept the full 50Hp at the initial 20mph because it is rotating too slowly (1150rpm) but by 40mph it probably can.
    Doing away with the HV battery gives up a few features but offers advantages of reducing the weight and cost of the hybrid car. It also removes the worry of replacement and simplifies operation of the system. And if we can encourage more people into hybrids without it then that's a good thing.

    One last thing - start the commercial - Series Hybrids take the concept one stage further with full electrical power conditioning which allows the engine size, but not the engine power, to be downsized by running at higher rpms not practical with the HSD. But you might get away with a two cylinder for further weight and cost savings. Perhaps higher rpms with a tiny engine may be slightly less efficient, who knows, but it is an upgrade path worth tracing IMO - end of commercial.
    T2
  • mistermemisterme Member Posts: 407
    "if the product requires a lot of study or constant manipulation to achieve efficiency, it simply isn't going to perform to factory specs because of the tendency of humans to ignore complex directions."

    It really isn't rocket science if I were to say that the more you press the gas pedal, the faster you'll consume fuel. It all boils down to that, plain and simple no matter what you drive. I'm not sure why one might think Hybrids would/should be exempt from that rule.

    You can't get any dumber than letting your car run on cruise control. Using almost pure cruise control I can get upper 50's on the highway and mid 50's going 60-65 freeway. When my wife drives my car around the city she gets mid 40's, and you can't get any more "real world" than a typical wife driving. No hypermiling necessary.

    If one would say that "real world" numbers only reflect those driven by a careless driver with no thought of FE then that in itself is skewed, as I see a great number of people on the road especially today who obviously have efficiency in mind in all classes of vehicles.
    Would these drivers like to squeeze another 7-10MPG out of their vehicles? You bet they would. We've gained almost 9MPG from our Grand Caravan simply by not gassing it all the time and driving sensibly.

    If a wasteful driver would be able to get 60MPG, then us hypermilers should easily clear 200MPG or more from the same vehicle. (Since only he is "real world")

    Many folks here only glorify poor results like was had under CR stress tests, or focus and highlight the few who complain about their hybrid cars, and even claim that the average HCH owner can expect a mere 41 MPG.

    It's very convenient to ignore the overwhelmingly vast majority of satisfied hybrid owners, isn't it?.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaMember Posts: 64,482
    One doesn't ignore satisfied hybrid owners by pointing out the real world gas mileage I don't think. Many can be quite satisfied with 44 mpg and in fact most seem to think that's just fine.

    My point was that the mpg claimed on the window sticker is not realistic...obviously not....because in fleet service in auto magazines none of them realize those mileages.

    This doesn't mean that you or I can't realize them. I can get 24 mpg out of a V-8 Porsche but most other owners of the same car don't get that. No one has taught them how to do that.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaMember Posts: 64,482
    wrong forum. Cut and paste your question here:

    Real World Values
  • toyolla2toyolla2 Member Posts: 158
    Here are some details I cribbed from the 2007 Camry board

    CAMRY HYBRID PRELIMINARY SPECIFICATIONS ENGINE

    Gasoline Engine Type 2.4-liter, 4-cylinder, aluminum alloy block with aluminum alloy head Bore and Stroke 3.48 x 3.78 inches

    Displacement 2,362 cc Expansion Ratio 12.5:1

    Valve Train Twin-cam, 4-valve/cylinder with VVT-i Horsepower (SAE Net)* 147 horsepower 6,000 rpm

    Torque* 138 lb-ft 4,400 rpm Recommended Fuel Regular unleaded

    Emission Control AT-PZEV ELECTRIC MOTOR/GENERATOR/POWER STORAGE

    Motor Type Permanent Magnet Synchronous Motor Electric Motor Power Output 105 kW/4,500 RPM

    Torque 199 lb.-ft. 0-1,500 RPM Battery Type Nickel-Metal Hydride (150 lbs)

    Nominal Voltage 244.8 V (204 cells, 1.2V/cells) Transmission Electronic Controlled Continuously variable transmission

    Capacity 6.5 ampere hour Battery Peak Horsepower Rating 45 horsepower

    System Voltage 650 volts maximum COMBINED

    Ok let's start with the battery

    Clearly Toyota is still continuing its policy of making the battery a component of the system rather than a system in its own right. It just increases inventory problems later on. The Camry is going for power so I suppose that the battery would be doubled even though there is not a great difference in vehicle weight to the Prius. Consequently joining packs of 228 (Gen1 Prius)and 168 (GenII Prius) cells we now have one of 204 cells (34modules). If these were the original 1300W/kg cells they would weigh 75lbs collectively. The Camry pack weighs in at twice that so I assume the new cells are similarly larger which would give them a capacity of 360 amps. The 45kw battery will need to supply 180 amps so these will have similar reserve margin as those on the Gen II Prius. Toyota isn't taking chances here. Both systems have a capacity of about 2 minutes at FLC to reach 50% SOC.

    Personally I would have used same number of of these larger cells as the Gen II Prius has then they could be made plug compatible and the sizeable market that seems to want more stealth could be satisfied. On the other hand these packs may have commonality with the RX400H and HL.
    T2
  • toyolla2toyolla2 Member Posts: 158
    I have now checked over on the RX400H and HHL site and it appears that these are using a different battery again from the hybrid Camry. It seems they are both fitted out with 30 modules, each containing 8 cells, to give a total of 288 volts. Perhaps Toyota is not worried about standardisation at present because this is early days in the SOTA for hybrids. Who knows, there are rumours Li-ion cells may be coming to replace NiMh cells in a couple of years and become the dominant technology.
    But to get back to the car as a general comment the Hybrid 2007 Camry will be testing the waters of the power hybrid in the mainstream and is not likely to threaten survival of the Prius. Its success will send a message to the car company whether consumer demand is really going in that direction. It has been said that HHLs and RX400Hs are not setting the world on fire with their sales figures and the 2006 HAH is conspicuous by its absence. Its appearance not yet confirmed for mid season delivery.
    It's difficult to make sense of the figures for MG2 on the Camry. Only 200lbs-ft instead of the 295 lbs-ft that the Prius gets ? Even at the 1500 rpm base speed quoted this computes to only 57 Hp. While the equivalent MG2 on the Prius puts out a more useful 67Hp at just 1200 rpm.
    To make my point the prius mg2 is able to pull a constant 67hp as the vehicle accelerates from 15mph to 46mph. It appears that the Camry has to be travelling at 70mph before its MG2 can supply 105kw (140hp) if gearing similar to prius. Looks like some more computing is in order.
    T2
  • dancarddancard Member Posts: 1
    I created a wikipedia article on the Camry Hybrid. Would be nice if you added more technical battery info:
    http://en.wikipedia.org/wiki/Toyota_Camry_Hybrid
  • toyolla2toyolla2 Member Posts: 158
    Recently I was informed of a li-ion battery to arrive on the market for the Prius. Scanning the website for edrivesystems, I learned that plug compatibility was going to be available in the $10,000-12,000 range. It will provide storage up to 34 miles when replacing the OEM pack. It comes with its own smart charging system for plug-in. Here was my response to someone considering this deal.

    Let's say you are motivated by saving money. Greed works for me too ! And let us also say that you have $8000 ( I negotiated the price down for us ) burning a hole in your pocket.

    Then I guess how much worth this system will be to you will depend eventually on the amount of electricity
    you are able to purchase for it. And for 10hrs on charge @ 10c/kwhr that will be $1. A buck a day. Or $365 per year. The absolute best case.

    But there are many ifs associated with that. For instance, you must be able to get the car back to a garage everyday with the battery depleted. Some of you know well that the Prius is not forgiving in that regard. Its internal
    software is vigilant in looking for any opportunity to recharge a depleting battery. You may be tailgated causing you to exceed 42 mph momentarily or any other reason. Bingo the engine starts up. Actually, I would be surprised if you could even manage to consume $100/year of electricity. For this exercise your local electricity supplier may even find you an old de-commissioned electric meter for free to hook up if you tell them what you're doing.

    But what about the numbers. Yeah, tell us about the numbers ! Well let's say Prius will do 52mpg if driven non aggressively, so we will get 17 miles for $1 of gas.
    Edrivesystems website says 34 miles (up to/ per charge)

    So, if you've been paying attention so far, on a 34 mile trip you'll get $1 of electrical mileage replacing the $2 of gas miles so you will make a profit of 1 buck a day best case. $365 per year.

    But $8000 invested at 5% will bring in $400. So you are out of pocket there with the carrying charge for the loan. And we haven't even talked about depreciation of this asset yet. Ask yourself will you be able to sell the vehicle in 8 years for $8000 extra because you fitted this special battery in it?

    What is $8000 really worth ? Here's an easier way to look at it -- at $1/ day that amount of money will spread over nearly 24 years. Even if the electricity was free and if you are prepared to accept the loss of investment income from that $8000 over 24 years. Are you going to keep your Prius that long ? Phew.

    Let me find my soapbox now. It can't be repeated enough that many power systems like wind,solar,tidal,hydro,corn attract interest by their low commodity cost and availability ( the wind is always blowing somewhere
    and the sun isn't going anywhere soon). But implementation costs are always astronomic and only feasible on the mega scale. Boutique storage systems which is what Li-ion batteries are, are great for personal storage lap-tops, ipods, hearing aids, watches etc. Solar PV's are great
    also for a radio relay on a mountain top, or if you happen to be in a geosynchronous orbit around a planet but for you and me - there are better low hanging fruit. How about using natural gas for home generation of electricity, for instance, we could then be heating
    our homes for practically free with the waste heat.

    The li-ion is merely a container for energy. I have a red plastic container for carrying about the same amount of energy in the form of gasoline for my lawnmower but this container costs tens of thousands less. I hope you had fun reading this. Well it was good for me anyway.
  • gagricegagrice Pahrump, NevadaMember Posts: 31,450
    Well it was good for me anyway.

    I agree. It is this kind of logical thinking that will make the plug-in hybrid a very small niche market. Unless they can get Li-ion batteries to about 10% of current cost, it is a losing proposition. I thought the EV-1 was great until I started counting all the costs.

    Thanks again for a well thought out post...
  • peraltaperalta Member Posts: 94
    This topic has been started by me at Prius 2004+. I know toyolla2 do not think this can be done but I am trying to explain that this is doable and adds only minimal weight and minmal production cost.

    Another benifit is AWD capability (not off-roadable) for bad weather driving.

    To simplify my explanation, I used MB 4matic 4ETS system as my analogy.

    I will start with MB 4matic. It has a 40:60 center diffrential. All 3 diff's front, center and rear are open (not limited slip). Wheel spin is controlled by ETS by application of brakes thus redirecting power to the nonspinning wheels.

    In contrast, the PSD in HSD can act as the center diff sending 72% torque to the front. The remaining 28% goes to MG1 and then to the MG2. The MG2 in this case will be relocated to the rear instead of being fused with the first output of the PSD (72%) before connecting to the front diff.

    The limitation, of course, is that any wheel that spins (eg on ice) will drain all the power there, just like the 4matic. However, MB has 4ETS that brakes the spinning wheels. Toyota has VCM which can be programmed similar to 4 ETS to address the problem.

    I am saying that HSD can be built as AWD without the need of additional motor (MG3 or MGr). This is accomplished by the MG2 being translocated the rear resulting to minimal penalty to weight and cost but with added drivability to adverse weather conditions.

    I think this is another option to HSD set up that toyota might have overlooked.

    Please post your thoughts.
  • toyolla2toyolla2 Member Posts: 158
    Hi Peralta,
    I have to correct a post I made in Toyota-Prius 2004+ board in answer to your suggestion of Toyota's VCM.

    In your proposal - to use braking action similar to MB's Electronic Traction Control is not quite the same thing as shutting down MG2's controller as I had suggested in the event that the rear wheels lose traction and start to spin uncontrollably.

    Shutting down a controller means zero power and I assumed the wheel rpms would fall quickly into line with road speed. However a braking action as you proposed is actually dissipating power by slowing the wheels down with brakes. OK, with that scenario you have provided a mechanical load for MG2 that the icy road surface was not able to supply. That looks better for this AWD Prius idea.

    Let's look at some numbers. At 10mph assume the Prius engine is outputting max torque. Then 6.6hp will find its way to the front wheels, if, and only if, the 22lbs-ft can be exerted on MG1. The slowest we can make the ICE is 1200rpm which produces the slowest MG1 speed of 2760rpm at 10 mph. With 22lbs-ft MG1 produces 11.6hp of electrical power for MG2. Of course if the battery could absorb this, all would be good and well. However , assuming the battery is fully charged already, it will rely on MG2 to use this power and if MG2 on the rear wheels can't, due to excessive slippage, then the rear brakes will have to turn on as you suggested. And then I agree, your system will work.

    Of course the rear brakes will just have to absorb the 11.6 hp (8.7kw) until the rear wheels 'bite'. I think this would need road testing to see how much brake heating and wear this produces. As you may know brake wear on Prius is practically zero, you might have seen the impressive images on the web that appear to back that statement.
    Your proposal may change that.

    As a point of interest to readers who may not have the time, I have worked on numbers which show the direct thru' power to the front wheels to increase linearly to 65.8hp @ 100mph, a rate of 6.6hp per 10mph. Meanwhile assuming a good battery. MG2 comes up to its peak 67hp @ 20mph, continues to 51.28mph at constant power, then declines to 38.2hp @ 100mph. Of course the 38.2hp will drop to 10.2hp when the battery depletes. However having a constant power of 104hp from 51mph to 100mph should get you there in 45 secs. Does anyone have that benchmark ?

    The AWD would vary from 13.2/67 @ 20mph
    33.8/67 @ 51mph
    52.7/51 @ 80mph
    65.8/38 @ 100mph
    These are the estimated front/back hp at full acceleration that I came up with. MG2's controller on the rear wheels can remove up to 28hp-the battery's contribution -in order to balance the f/b ratio more evenly - but only an AWD afficinado could tell us the advantage in that.

    As Peralta wrote, we could use input from others. Thoughts from anyone else from this fading republic would be welcome.
    T2
  • peraltaperalta Member Posts: 94
    The beauty about this is that there is practically no sacrifice in fuel economy. AWD is very attractive especially to places with 4 seasons (winter included) but a lot of people does not want it due to poor fuel economy, sacrificed performance, excess weight, and is more expensive. The above proposed set up could change that.
  • peraltaperalta Member Posts: 94
    For max economy, at highway cruising the MG1 can be braked to zero speed channeling all the power to 72% output of PSD (all mechanical drive). Resulting to ultra overdrive gear ratio.

    The translocated rear MG2 will have 3 modes, low gear, direct drive and neutral (single planetary gear drive), each mode choice is selected for maximum economy and max regeneration. (the Japanese estima hybrid has rear motor with belt driven CVT).

    For maximum acceleration, the PSD can be clutched to locked position, increasing the direct mechanical torque factor of the engine towards the final drive from 0.72 to 1.00. On top of that, the MG1 will act as a booster motor (instead of the regular generator).

    For low speed all electric mode (on the proposed AWD set up), the MG1 can rotate in reverse with the engine shut off to power the front wheels forward while the relocated MG2 powers the rear wheels.

    Just a thought.

    Peace
  • peraltaperalta Member Posts: 94
    "The AWD would vary from
    13.2/67 20mph
    33.8/67 51mph
    52.7/51 80mph
    65.8/38 100mph

    These are the estimated front/back hp at full acceleration that I came up with. MG2's controller on the rear wheels can remove up to 28hp-the battery's contribution -in order to balance the f/b ratio more evenly - but only an AWD afficinado could tell us the advantage in that."

    I am totally impressed on how quickly you can come up with the numbers. By the way, those numbers shows that at low speed, there is rear bias and then the bias is gradually switched to front at high speed.

    That power biasing front to rear is good. When lamborghini AWD was made, the front torque bias was increased at high speed because it made the car more stable. This is a very good coincidence.
  • peraltaperalta Member Posts: 94
    I am going to correct my statements...

    The CVT belt drive in Estima is located in the front and not at the rear motor.
  • midnightcowboymidnightcowboy Member Posts: 1,978
    The HSD systme already has application fro AWD. It adds a 3rd Motor-Generator , MG3, which solves the front/rear differential problem.

    Whay try to re-invent the wheel when the Toyota design engineers already have a production solution.

    LOL,

    MidCow
  • peraltaperalta Member Posts: 94
    "Whay try to re-invent the wheel when the Toyota design engineers already have a production solution. "

    Here are my answers:

    - Less number of motor/genrator (minus 1)
    - less weight = better acceleration = better Fuel Economy
    - cheaper to build
    - Better weight distribution
    - Free up more space under the hood

    This sounds like a good commercial!!!

    Peace
  • devsiennadevsienna Member Posts: 70
    I think you're ignoring what it would take to make a transaxle that runs the length of the car, plus the various linkages that would be necessary to move MG2 to the rear. On a larger car, like the Highlander, you might have the necessary clearances under the car to do such a thing, but I'm guessing that the added weight of the transaxle and linkages is more than the weight of MG2, or in the case of the Highlander and Lexus RX400h, MG3.
  • peraltaperalta Member Posts: 94
    As I mentioned before, there is additional weight on relocation of MG2, but minimal. My guess is about 75 lbs max. and that consist of a single planetary gear drive with integral differential and two half shafts. The connection of MG2 to the front are electrical cables and wirings. There are no propeller shafts that tunnels from the front to the rear.
  • devsiennadevsienna Member Posts: 70
    Are you forgetting that MG2 is mechanically tied to the outer ring of the PSD? The ICE, MG1 and MG2 are all mechanically tied to eachother and the drive wheels. You can't just move MG2 to the rear without having a transaxle that runs the length of the car. Otherwise yer not talking about just moving MG2 to the rear, but re-engineering the HSD system completely.

    I suggest that you look at one of the prius planetary gear simulators to get a better idea of why they are all tied together and how they work with eachother to provide optimal gearing for keeping the ICE running in it's most effcient range.

    Also keep in mind that if you relocate MG2 to the rear, and mechanically disconnect it from the PSD/front wheels, that you lose the ability to drive in reverse. MG1 isn't powerful enough to move the car, and the ICE only spins in one direction...
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    devsienna is right. peralta's suggestion would turn HSD into something else (series dominant) -- generate electricity in the front (MG1) and feed that electricity to the back (MG2). Some mechanical power can go to the front wheels through PSD. Front wheels will be partially powered by ICE and rear wheels powered by electric motor (MG2). To control the power split between front and rear, you'll need to manage MG1 speed and Battery pack. The more MG1 generates electricity, the less power goes to the front wheels. MG1 electricity can charge the battery and/or power the rear wheels.

    Like devsienna pointed out, front wheel will be only able to turn one direction (forward). For the car to go backward, your design will need to depend on the pure battery power -- in order for MG2 to spin backward. If the battery SOC runs low, the ICE will be forced to turn on. The front wheels will want to go forward and rear wheels will want to go backward -- not pretty or efficient.

    I think this design can work but the HV battery might need to be bigger. Regen braking might not be able to capture as much because the weight shifts to front and MG2 is in the rear wheels. You will also need to worry about cooling MG2 in the back. Will it be all worth it to have AWD? I am not sure.

    Dennis
  • peraltaperalta Member Posts: 94
    Let me simplify how HSD works. ICE power is split 72/28 at the PSD. The 72 part goes to a shaft that powers the differental (via a chain drive). The 28 part goes to MG1 to generate current and then goes to MG2 to convert back to mechanical energy. The MG2 and the output shaft from 72 part joins together to drive the front differential. My suggestion is that the MG2 does not have to join the front output shaft but power the rear instead. No need for transaxle that runs the lenght of the car.

    As I mentioned in "more bags of tricks", it can be more flexible and can run on all mechanical mode for max economy at steady cruising or it can have max acceleration by reprograming the MG! as a second booster.

    I haven't seen the estima HSD system but I guess that it has similar system as my suggestion since has enough room to accomodate the belt drive CVT and it has a standard AWD set up.
  • toyolla2toyolla2 Member Posts: 158
    Welcome to the board devsienna,

    actually the redesign would not be necessary if MG2's gearing of 4.13:1 was preserved and the braking system was able to prevent the rear overspinning when traction was lost. However, I think you killed peralta's suggestion stone dead when you brought up the small matter of driving in reverse.

    Of course the 59lbs-ft from the front wheels in the forward direction (assume the engine was started because of a depleted battery) would be opposed by the 259 lbs-ft from MG2 in reverse applied to the rear wheels. However (playing devil's advocate here) should the rear lose traction then the rear braking system will not save the day and the vehicle will take off in the forwards direction. Good luck defending an accident from that one in court ! You might argue that the braking system could go to work on the front wheels and block any forwards motion when the drivers intention is to move backwards. Any conscientious designer would walk away from that one. I can see now why Toyota included both MG2 nd MG3. But it was a good attempt to produce an AWD-lite. Knowing what won't work and why helps in exploring for the better solutions. My personal opinion is that it is difficult enough to diagnose problems with HSD's interconnected electrical and mechanical system without bringing in the braking system as well - as peralta has suggested.
    T2
  • toyolla2toyolla2 Member Posts: 158
    You wrote : -
    "As I mentioned in "more bags of tricks", it can be more flexible and can run on all mechanical mode for max economy at steady cruising or it can have max acceleration by re programing the MG1 as a second booster."

    Since there is only 28Hp of battery available MG1 can never be a power booster unless you can tell me where the 67Hp of electricity for MG2 is coming from at the same time ?

    Peralta, take a minute and look at the electrical power flowing. That 28% of torque split that you quote often is actually 22lbs-ft (28% of 80lbs-ft) and it is able to propel MG1 at 10,000rpm at least until the vehicle reaches 51.28mph. At which time MG1's rpm must begin steadily reducing because the ICE has maxxed out at 5000 rpm and the vehicle is still needing to go faster. Because remember the equation I stated over on the 2004+ board ?

    But what has MG1 been generating during this time ?
    Well, 22lbs-ft @ 10,000rpm = 304v @ 100 amps = 42.2 Hp. It is this power added to 25Hp from the battery which is able to give MG2 its full power of 67Hp. It is able to do this only from 20mph to 51.28mph. Beyond 51.28mph MG1 is still permitted 22lbs-ft but at steadily reducing rpms as I just mentioned, until at 100mph and 2400rpm it can produce barely 10.2 Hp which is sent over to MG2 along with 28Hp from the battery. In the unlikely event that more than two minutes were to elapse then only MG1 would still be in business continuing to feed MG2 with 10.2 Hp.

    Since the Prius will not require its full ICE power of 76Hp to cruise at 100mph. The ICE will have slowed down considerably and so will MG1, in fact MG1 may now be going backwards as a motor with power generated by MG2 operating in the so-called heretical mode in order to depress the ICE speed to a suitable low level for cruising. See Yahoo toyota prius site c. August 2001 for discussions. A scan tool showed in later postings that 35% of a particular commute was actually spent in this mode.

    By the way there is no useful mechanical mode, 59lbs ft of direct thru' mechanical torque requires MG1 to act as a generator with 22lbs-ft. But let's say we were to freeze MG1's rotor as you suggested then ICE rpm will equal 2.6/3.6 MG2.

    At 60mph MG2=3600rpm therefore ICE=2600rpm. Since the ICE likes to run at close to full torque at all times in order to reduce needless mechanical engine motion, this rpm would appear to be racing the engine albeit 38hp would be instantly available on tap if needed, which with the HSD is a useless advantage since the HSD can instantly invent whatever gear it needs to be in. Again scan tools show the ICE settles at 1211 rpm mostly until more than 8.5kw is desired. This order of power will cruise the Prius on level road at 60mph. Using MG1 and MG2 at all times is probably the most efficient way to run this vehicle as Toyota engineers intended. Did I just agree with MidCow ?
    T2
  • peraltaperalta Member Posts: 94
    toyolla2,

    I agree with almost all of your statements. There is no need for my suggested "bags of tricks" since the THS is well engineered, well thought, and very much optimized and my suggestions were not mathematically based.

    There is one thing that I do not totally agree since I see a solution to it. You mentioned;

    "Of course the 59lbs-ft from the front wheels in the forward direction (assume the engine was started because of a depleted battery) would be opposed by the 259 lbs-ft from MG2 in reverse applied to the rear wheels. However (playing devil's advocate here) should the rear lose traction then the rear braking system will not save the day and the vehicle will take off in the forwards direction. Good luck defending an accident from that one in court !"

    The prius engine is not running when in reverse and it is almost always in that case since reversing usually takes only a few feet (it rarely depletes your battery). Another reason is that it is weaker with the engine running since there is an opposing forward torque from the engine. When reversing, you are not using full power, you are inching to your destination. Just a very short warm up after starting the engine should be good enough charge to use for reversing.

    Other problem is that you lose the AWD in reversing. Yes, but there is a fix. With the engine not running and braked, the MG1 can rotate forward pushing the final drive in reverse and multiplying the MG1's torque by 2.57 (72/28). Remember, you reverse by inches at a time, not at full power.

    Peace
  • peraltaperalta Member Posts: 94
    By retaining the original computer logic plus the addition of 4ETS-like program, I guess the rear mounted MG2 is viable.

    Backing up, it needs some minor mods as mentioned above but is still doable, reversing in all electric AWD mode. I am assuming that battery SOC is not a concern since the THS's logic on battery SOC is full charge at zero or low speed and partial charge at high speed. And you only back up few feet most of the time (not miles).
  • peraltaperalta Member Posts: 94
    It looks like my suggestion has already been used by toyota in the THS-C. After researching, I found out that toyota has gone to great lenght in different combinations of hybrid system.

    These were the ff;

    THS-I,
    THS-II (current prius),
    THS-M (mild hybrid, non-US),
    THS-C (Estima hybrid)

    There may be other iterations that I am not aware of.

    The THS-C is similar to my suggestion except that it went the extra mile of putting a denso belt drive CVT at the front. It has one motor in the front and one motor at the rear.

    http://metropolis.japantoday.com/carsbikes/389/carsbikesinc.htm

    http://www.hybrid-vehicles.net/toyota-estima-hybrid-minivan.htm

    My suggestion is not novel anymore but I was right all along that it works.
  • peraltaperalta Member Posts: 94
    http://www.electrifyingtimes.com/mini.html

    Enjoy...

    Toyota started producing Hybrid estima (AWD) with THS-C in 2001.

    It is puzzling since they have a different AWD later in 2005 in the form of RH/HH with MG-rear.

    However, the gossip is still on that there may be a sienna hybrid in 2007 having a 2.4L engine similar to that of the Estima.

    By the way, the C stands for CVT (belt drive) and the M stands for mild (similar to saturn hybrid).
  • devsiennadevsienna Member Posts: 70
    The prius engine is not running when in reverse and it is almost always in that case since reversing usually takes only a few feet (it rarely depletes your battery). Another reason is that it is weaker with the engine running since there is an opposing forward torque from the engine. When reversing, you are not using full power, you are inching to your destination. Just a very short warm up after starting the engine should be good enough charge to use for reversing.

    This is not true. I frequently have my engine come on while I'm reversing out of the driveway or a parking spot. With the current HSD system, there is nothing that prevents the engine from being on while in reverse.
  • devsiennadevsienna Member Posts: 70
    http://www.electrifyingtimes.com/mini.html

    Enjoy...

    Toyota started producing Hybrid estima (AWD) with THS-C in 2001.

    It is puzzling since they have a different AWD later in 2005 in the form of RH/HH with MG-rear.

    However, the gossip is still on that there may be a sienna hybrid in 2007 having a 2.4L engine similar to that of the Estima.

    By the way, the C stands for CVT (belt drive) and the M stands for mild (similar to saturn hybrid).


    From what I can tell, Toyota has abandoned the THS-C design for the Estima. The new Estima in Japan uses THS-II now.

    Why they abandonded THS-C is anybody's guess. My guess is the added complexity of the cone/belt CVT plus the clutch that was being used in the front drive system wasn't very efficient or cost effective. The link you provided unfortunately lacks suffcient details about the system to make a determination.
  • stevedebistevedebi LAMember Posts: 4,098
    "With the current HSD system, there is nothing that prevents the engine from being on while in reverse."

    I think some people get confused on this issue. The ICE is not used in reverse, but will run if the battery needs charging.
  • peraltaperalta Member Posts: 94
    Can you site any source that says alphard/estima abandoned the THS-C and now uses THS-II?

    From what I found, a 2005 version of Alphard have been reviewed at "Japan Today" and it still uses THS-C.

    http://www.theautochannel.com/news/2003/11/09/172502.html
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    "I think some people get confused on this issue. The ICE is not used in reverse, but will run if the battery needs charging."

    Prius can go reverse without using battery. PSD will allow ICE to spin forward while the wheel spinning backward (negative gear ratio). MG1 has to spin very fast in order to achieve this. Play with the THS simulator below. Note that the Classic Prius (THS) MG1 max out at 6,500 RPM while HSD allows up to 10,000 RPM.

    http://homepage.mac.com/inachan/prius/planet_e.html

    If you set the ICE(engine) to 1,000 RPM and MG2 (motor) to -1,100 RPM, you can see the car is going in reverse at -30 km/h. Effective transmission ratio is -0.91. Cool huh?

    Dennis
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    "Can you site any source that says alphard/estima abandoned the THS-C and now uses THS-II?"

    Here you go: http://www.toyota.co.jp/en/news/05/1011_1.html

    The ESTIMA HYBRID CONCEPT
    A new generation of stylish minivan that combines the latest hybrid system, THS II, with electric 4WD to achieve both environmental and driving performance

    ▪ The refined exterior is designed to evoke the identity of the Estima Hybrid in a sophisticated one-motion form.
    ▪ The interior feels clean and open. It is accented by a high-tech-looking central panel and is equipped with comfortable second-row seats with built-in footrests and power foldaway third-row seats that allow you to transform the space to your liking. Electrical appliances can be run on the provided 1,500-watt power supply system.
    ▪ From the perspective of environmental performance, the ESTIMA HYBRID CONCEPT is equipped with the THS II, Toyota's latest, highly efficient hybrid system, and an exhaust heat recovery system in the pursuit of low CO2 and other emissions.
    ▪ In addition to the quiet and smooth acceleration indicative of a hybrid vehicle, the ESTIMA HYBRID CONCEPT achieves increased driving pleasure through VDIM—a system that seamlessly supports the vehicle operations of running, turning and stopping for all conditions from normal through to extreme driving. The combination of VDIM with E-Four (electric four-wheel drive) provides even higher levels of drivability.
  • stevedebistevedebi LAMember Posts: 4,098
    "If you set the ICE(engine) to 1,000 RPM and MG2 (motor) to -1,100 RPM, you can see the car is going in reverse at -30 km/h. Effective transmission ratio is -0.91. Cool huh?"

    Simulators are not real life. Unless the software engineer was privy to Toyota software code, it would include items that did not represent actual Prius programming. For one thing, I suspect that the ECU would limit reverse speed to well below 30 kmph.

    Two questions:

    1. Has anyone actually done this in real life?

    2. Why would anyone want to do this in real life?

    I suppose I should have said that the electric motor is used in reverse "under normal conditions".
  • hot_georgiahot_georgia Member Posts: 51
    Anybody going to hybridfest?
    http://www.hybridfest.com/

    Sounds like a big event and include advanced engineering demonstrations on the hybrid drivetrain by representatives of the hybrid venders themselves.
    Lots of things to do and see, people are attending from all around the country.

    Hope to see you there!
  • bkuchbkuch Member Posts: 1
    My understanding of Hybrid vehicles is limited, but I have this question. Why couldn't wind power be used to recharge batteries? All you would need is to add a wind scoupe either on the hood, front or side of the vehicle. The wind would turn turbines connected to an alternator which would in turn charge the batteries.

    A vehicle traveling at highway speeds should be almost self reliant, shouldn't it? Why not?
  • dhanleydhanley Member Posts: 1,531
    That won't work because the drag on the wind turbine would be greater than the energy the wind turbine would produce. Conservation of energy.
  • gagricegagrice Pahrump, NevadaMember Posts: 31,450
    You would have a better net gain with ultra thin low drag solar panels glued to the roof of the car. It would have the added benefit of charging the batteries while parked. As long as the sun is shining.
  • midnightcowboymidnightcowboy Member Posts: 1,978
    Because perpetual motion doesn't exist
  • toyolla2toyolla2 Member Posts: 158
    This is a redo of the earlier posts #115,6

    CAMRY HYBRID PRELIMINARY SPECIFICATIONS

    ENGINE
    Gasoline Engine Type 2.4-liter, 4-cylinder
    Aluminum alloy block with aluminum alloy head
    Bore and Stroke 3.48 x 3.78 inches
    Displacement 2,362 cc Expansion Ratio 12.5:1
    Valve Train Twin-cam, 4-valve/cylinder with VVT-i

    Max Power 147 Hp @ 6,000 rpm (129lbs-ft)
    Max Torque 138 lb-ft @ 4,400 rpm

    Recommended Fuel Regular unleaded
    Emission Control AT-PZEV

    ELECTRIC MOTOR/GENERATOR
    Motor Type Permanent Magnet Synchronous
    MG2 105 kW (141Hp) 167lbs-ft @ 4,500 RPM
    199 lb-ft 0-1,500 RPM
    MG1 72kw 36lbs-ft @14700 RPM

    POWER STORAGE
    Battery Type Nickel-Metal Hydride
    Nominal Voltage 244.8 V (204 cells, 1.2V/cells)
    Capacity 6.5 ampere hour
    Weight 150lbs
    Battery 45 Horsepower Peak Rating (33kw)
    45 because 192-147 = 45 presumably

    This is commensurate with the Prius battery weighing 100lbs
    and delivering 28.5Hp

    Max Bus voltage 650v

    Is it just me but these text windows seem to be getting smaller and smaller. Entering this post feels like I'm fitting a ship in a bottle :-)

    Anyway, doing some analysis here ; we know that the engine torque is around 129 lbs ft so IF the same PSD ratio as Prius is used here then MG1 will exert 36lbs-ft. We know also that MG2 can use 105kw at 4500rpm and above. Since the battery supplies 33kw then 72kw must come from MG1. From this we can infer that 72kw @ 36lbs-ft will require a speed of 14700rpm.

    To determine the speed at which the vehicle develops max power we use the equation

    MG1= 3.6 * ICE - 2.6 * (MG2/2.47)

    The ICE is now goes to 6000rpm which with MG1 at 14700rpm gives (MG2/2.47) = 2423 rpm

    Then IF 4.113 ring gear to wheel axle ratio is same as Prius where 1200rpm=20MPH, then 2423rpm will be 40MPH.

    This is a big improvement over the Prius which did not come up to full power until as late as 51.28MPH. MG2 will be rotating at 5984rpm which is well above the base speed of 4500rpm quoted.

    I make max speed for MG2 as 14820rpm at 100MPH. If that 4.113 figure is lower for the Camry the appropriate correction can be made.

    Someone quoted 12,400rpm max for MG2 and around 50lbs-ft less torque (on the West Virginia U. website) down from 295lbs-ft of the Prius but I make it even lower at 167Lbs-ft go figure. The spec says MG2 puts out 199 lbs-ft at 1500rpm perhaps it does, but at 4500rpm for 105kw it has to be 167lbs-ft.

    Anyway that new 2.47 planetary ratio brings it back up to a respectable 412lbs-ft. To which you must add 129-36 or 93lbs-ft of direct mechanical support.

    The interest for me is that you get 192 Hp at 40mph, a good 10mph lower than when Prius reaches its max power and then like the Prius will hold steady until you hit 100MPH !

    T2
  • toyolla2toyolla2 Member Posts: 158
    ...is the fact that it can recover the energy typically lost in braking.

    "No , that fact is not beautiful at all, gearhead_greg", I wrote.

    Regeneration, the recapture of mechanical power by converting to electric power for storage on board is a good idea if : -

    You are operating a battery electric vehicle.

    You are operating a gasoline electric hybrid upgraded to a PHEV because either
    1. gas is $15 a gallon - the economic reason.
    2. Hydro-electric power generated in your area - off oil/ anti-pollution statement
    3. Electric power derived from nuclear energy - same as above

    And is a bad idea : -

    For the current batch of hybrid cars on the market.

    It is my considered opinion that it is not an economic decision now and almost
    never will be to install a storage battery for the recapture of kinetic or potential energy on any gasoline hybrid propelled vehicle.

    To be clear - I am not against regenerative braking - I am just simply questioning the storage of reclaimed energy in a battery that you are about to install for that express purpose. Gains are modest at best and lugging 100lbs around when you didn't hafta' starts to be a big negative on prolonged hiway driving.

    For new designs a superior idea is to dissipate the power from light braking in a resistive device commonly referred to as a dynamic braking resistor, yeah no kidding. For industrial electronic drives these are the component of choice. They are low cost and compact, in this application about the size of a video cassette when mounted to a heat sink. A single transistor or relay contacts can bring them into circuit as necessary.

    The advantage of hybridisation is to extract more power from a given engine than can be done with a multi-gear gearbox. The electrical system avoids the adoption of a mechanical CVT which is not predictable over time and over the temperature fluctuations experienced in most of North America. This fact permits the current Toyota HSD system to use a 2.4 L in place of a 3.3L in the case of the Camry for example. The superior performance is not all attributable to 40 Hp of battery power. It is more to do with the fact that the Camry 140Hp engine is able to exert its full power from 40 mph all the way up to maximum speed in a seamless manner which is not interrupted by gear changes which would otherwise keep pushing the engine back down its power curve at each change.

    The other advantage of hybridisation is to reduce the frictional losses on a given engine by using the electrical system to present a load to the engine which always seems to the engine to be a higher torque but at lower RPM than the same engine would experience in a non hybrid car for whatever power happens to be be required at the time. The effect of engine friction is thereby reduced since every piston stroke generates more useful power per stroke than it would be called upon to do in the typical non hybrid application.

    The ability for the engine control unit to stop and start the engine can't be discounted either but the above two paragraphs are key to the main advantages of the hybrid.

    Comments welcome
    T2
  • tpetpe Member Posts: 2,342
    I am just simply questioning the storage of reclaimed energy in a battery that you are about to install for that express purpose. Gains are modest at best and lugging 100lbs around when you didn't hafta' starts to be a big negative on prolonged hiway driving.

    For the most part your post seems very knowledgeable but you are dead wrong on this point. Carrying an extra 100lbs is going to have a very, very small effect on highway mileage. Extra weight's negative impact is primarily during acceleration. However this is offset to a large extent by having this additional kinetic energy to recapture through regenerative braking. With that said if your driving consists of almost exclusive highway mileage there isn't much to be gained by going hybrid.
  • toyolla2toyolla2 Member Posts: 158
    Thanks for responding TPE, perhaps I can change your point of view.

    "Carrying an extra 100lbs is going to have a very, very small effect on highway mileage."

    That's what I thought too. It is a small effect but not insignificant as it turns out.

    Someone posted that at 60mph the rolling losses for the Prius battery were 200 watts.
    Recaptured energy from braking the Prius to rest is 540Kjoules. So if the battery was carrying this restored energy while at 60 mph it would be depleted to zero in 45 minutes.

    But even if the battery held no recaptured charge - it used it all up re-accelerating to 60mph again - this 540 KJ of energy is expended every 45 minutes. I brought this up on a Yhoo board some months ago and someone else - using a sophisticated equation punched in the numbers and came back with only 115 watts, but he was no longer a skeptic. His calculation omitted the aerodynamic loss which may have been included in the earlier 200W figure.

    "With that said if your driving consists of almost exclusive highway mileage there isn't much to be gained by going hybrid."

    The second reason to go hybrid covers just this situation. The engine is constrained to go as slow as possible at high torque by means of MG1 and the PSD. Engine frictional losses in this super overdrive are substantially lower. The engine will be kept away from actually lugging but unlike a fixed mechanical gear the servo MG1 can instantly cause the engine revs to rise quickly for more power when the need arises.

    The only problem I have with this is that in order to depress engine revs, MG1 has to become a motor obtaining its electrical power from MG2 which becomes a generator. This caused some uproar in Aug 2001 when original analysis (reverse engineering) was being done. The fact that the main traction motor MG2 could be in a generating condition when cruising at 60mph was regarded as "heretical" but was eventually accepted. Subsequently MG2 was said to be operating in "heretical mode" whenever MG1 was forced to be a motor.

    Heretical mode is when MG1 is negative from the eqn : -

    MG1 = ICE * 3.6 - MG2 * 2.6 (MG2 = 1200rpm per 20mph)

    Of course power must always be transferred between MG1 and MG2 in one direction or another while there is to be a positive torque applied to the road wheels. Direct engine to wheels power is a maximum of only 6.6 Hp per 10 mph for the Prius. But only a fraction of this is needed at 60 mph cruising so the electrical power circulating between MG1 and MG2 is similarly low probably less than 5kw, and this implies that losses will be low too.

    Hopefully the engine frictional losses that are saved by the slower running engine will swamp the electrical losses incurred by those MG1 and MG2 transfers; otherwise a tall gear manual transmission would be more efficient I agree. The fact that the HSD system has allowed a smaller than usual engine to be used should also be factored in.

    T2
  • tpetpe Member Posts: 2,342
    Someone posted that at 60mph the rolling losses for the Prius battery were 200 watts.
    Recaptured energy from braking the Prius to rest is 540Kjoules. So if the battery was carrying this restored energy while at 60 mph it would be depleted to zero in 45 minutes.


    The extra rolling friction would seem to be the only loss associated with extra weight. I don't see how it could induce an aerodynamic loss. In fact if it forced the car to sit slightly lower there might be a minute aerodynamic gain.

    200 watts is roughly equivalent to 1 mile lost every hour. With the Prius rated at 51 mpg on the highway this would come out to 1 mile for ever 1.18 gallons burned. You state that the amount recaptured from braking would be used up in 45 minutes. What if you stopped twice in this hour? Wouldn't that give you a net gain?

    Here's something that I'm not sure about. Is this battery pack the only battery on the Prius or is there a second battery that performs the function of starting the engine? If its the only battery then it really doesn't represent an additional 100 lbs because you have to consider what a traditional battery would have weighed. And I'm not entirely sure why this battery weighs that much to begin with. It only stores about 1 kWh of energy. You should be able to do that in a 20-25 lb Li-ion battery or <40 lb NiMH battery. I say that because the Toyota RAV4 EV had a battery pack that could store 27 kWh and it weighed slightly more than 900 lbs. This pack consisted of 24 12V NiMH batteries. Maybe I'm missing something but is seems like if you used just one the weight would be less than 40 lbs.

    One last point. Rolling resistance can be significantly reduced by choosing the right tires. Does the Prius come standard with low resistance tires? It probably does.
  • devsiennadevsienna Member Posts: 70
    Here's something that I'm not sure about. Is this battery pack the only battery on the Prius or is there a second battery that performs the function of starting the engine? If its the only battery then it really doesn't represent an additional 100 lbs because you have to consider what a traditional battery would have weighed. And I'm not entirely sure why this battery weighs that much to begin with. It only stores about 1 kWh of energy. You should be able to do that in a 20-25 lb Li-ion battery or <40 lb NiMH battery. I say that because the Toyota RAV4 EV had a battery pack that could store 27 kWh and it weighed slightly more than 900 lbs. This pack consisted of 24 12V NiMH batteries. Maybe I'm missing something but is seems like if you used just one the weight would be less than 40 lbs. One last point. Rolling resistance can be significantly reduced by choosing the right tires. Does the Prius come standard with low resistance tires? It probably does.</i>

    The high-voltage battery pack is indeed used to start the engine via MG1. The only other battery in the car is the small 12-volt battery which is there mostly to boot up the computers and run various 12-volt items when the main battery isn't connected (radio, lights, keyless entry, alarm, etc). When the main high-voltage battery is connected, all of those items are powered via it through an step-down transformer. MG1 is also used to generate electricty which in turn can be used to recharge the battery or provide extra electricity to run MG2, or do both at the same time.

    The battery pack is rated at 1.3kWh. The weight of the pack is listed as 45kg, or about 100 pounds.

    And yes, the car comes with low rolling resistance tires.
This discussion has been closed.