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Advanced Course in Hybrid Engineering

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  • tpetpe Posts: 2,342
    Thanks for the info. 100 lbs still seems like a lot of weight for a 1.3 kWh battery pack. I wonder if its another one of those Cobasys/Chevron issues where they were no longer allowed to use batteries of the same energy density that Panasonic had manufactured for the RAV4 EV.
  • toyolla2toyolla2 Posts: 158
    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.

    I agree, I think the original poster just allocated the share borne by the 100lb battery to be 200watts as a fraction of total losses at speed assuming the 'Prius I' total weight was 2950lbs (1340kg).

    But let's say you bring an '03 Prius and its 540kJ of kinetic energy down to rest in 4 seconds. You would have to remove 135kJ per second. With the 201v battery that represents a current of 675 amps. The battery controller will only allow 50 amps of charging current. So if you want to recapture all that energy you better slow down in about 52 seconds ! You see why I am against the battery idea ?

    The battery is quite large just for storing KE even if you had allowed a 300% manufacturing margin.

    6.5Ah is 23400 amp-secs, which multiplied by 201v = 4.7MJ.

    Why is the battery so big ? Well, you are going to pull 100 amp during full bore acceleration (21kw) which is the 16C rate. In comparison cranking 500 amps out of your car's 72AH lead acid is about 7C . As heavy as that HV battery is, it takes quite a bit of stress in the Prius - and you think it should be smaller ?

    I've already suggested the use of a dynamic braking resistor. But there are other options on board Prius. One idea is that, having cut the fuel to the engine then taking MG1 up to 10,000rpm to keep the engine revs high while the car slows, a kind of enhanced engine braking.

    Then again, in summer whenever your foot comes off the accelerator, while moving, the inverter for the A/C compressor ( 2kw ? ) could be made to turn on full. Providing this temporary overide of the cabin thermostat (done transparently in the software) would be a good use of existing hardware and with hypermiling techniques has potential for recouping quite a bit of energy in the hot season ! Don't laugh, you've just seen the math.

    Devsienna seems to have answered your other questions, tpe, guess I can go early :-)

    T2
  • dhanleydhanley Posts: 1,531
    This is all very interesting!

    Out of curiosity: have you looked into how the math work out for ultracapacitors? In this case, the charge doesn't persist as long, but the weight is much less, and potentially the next "go" after the "stop" can be largely supplies by the stored energy from braking.
  • tpetpe Posts: 2,342
    The battery controller will only allow 50 amps of charging current. So if you want to recapture all that energy you better slow down in about 52 seconds ! You see why I am against the battery idea ?

    New Li-ion battery chemistries allow for much faster charge/discharge rates (A123 Systems, Altair Nanotechnologies). These batteries are also in the neighborhood of 1 kWh per 10 kg. So even with the packaging they should be significantly lighter than 100 lbs. This should be good news for hybrids.
  • goodcrdgoodcrd Posts: 253
    Don't be narrow minded. All I am hearing in these posts are old technology and old news. For traction motors just check out whats been going on in Electric Mass transit for the past 60+ years. High torque low speed you use frequency modulation 0 to 100 Hz after reaching your base speed you use Pulse width modulation for low torque high speed operation. Now what about Hydraulic Hybrid vehicles. Check out Eaton and Fords prototypes and let the discussions fly. You can't create energy out of nothing. Hybrids use energy derived from whatever the source more efficiently and it's all good. So fix the emissions problems with diesel engines and use whatever technology which best fits the application.
  • tpetpe Posts: 2,342
    So fix the emissions problems with diesel engines

    I thought that one of the problems with diesel hybrids is the engine's inability to shutdown and startup quickly, e.g. at stoplights. While that doesn't really amount to hybrid technology it is a gas saving technique that most hybrids employ. Is this a problem that's been solved?
  • gagricegagrice San DiegoPosts: 28,890
    I am questioning the shutting down of the engine as a fuel savings. Studies have shown that unless the stop is lengthy there is a fuel hit starting the engine. I think the fact that the Prius city mileage is so poor compared to the estimates would back up those studies. I have auto-stop on my Hybrid Sierra and do a lot of stop and go driving on short trips. I don't see that I have gained anything over the non hybrid PU with the same engine.
  • grandtotalgrandtotal Posts: 1,207
    Studies have shown that unless the stop is lengthy there is a fuel hit starting the engine.

    Other studies have shown that there is a fuel saving. In the case of the Prius the engine is spun up to approximately 1000 RPM. Once oil pressure is established fuel and ignition are supplied. It's not like starting an engine in the regular way.
  • gagricegagrice San DiegoPosts: 28,890
    That is all nice but it does not seem to be paying off as planned. It does not get the 60 MPG advertised in city stop and go application. It does take energy to spin that engine to 1000 RPMS just as you get a surge of fuel on start up. No free lunch.
  • tpetpe Posts: 2,342
    It does not get the 60 MPG advertised in city stop and go application.

    The EPA city mpg rating is grossly overstated for hybrids. They plan on addressing this in a year or two. I think you will see something like a 42 city mpg rating for the Prius. Still very good but someone that expected 60 was probably disappointed.
  • toyolla2toyolla2 Posts: 158
    My calculations on ultracapacitors, perhaps not including the latest components, showed they have an effective power density the same as NiMH batteries which makes them just as heavy.

    Power density is the most important parameter to Toyota.
    The earlier model of Prius had 38 7.2v cellpacks of 800w/kg power capability. When the the newer Prismatic cells became available with 1300w/kg they were able to trim the number of cell packs down to 28, at least that is my take.

    Since both types of cellpacks weighed in around 1050 gms, and both had energy storage of 46Wh/kg this meant the lighter '03 battery also stored less energy, but its ampacity was much greater which was the major interest to Toyota. On paper this computes to 180 amps, up from 110amp. In practice a maximum of 100 amps seems to be used.

    I was just on the Maxwell.com Ultracap site browsing their interesting products with 10Kw/kg power densities but they didn't give the weight of their 650F 2.7v , for example, so I couldn't compute how many amps they could deliver. Of course if it weighed 1kg then 4000amps, but then what is the ESR ? I am not sure I trust their 10kw/kg figure just yet - they are holding too much back. A scalability issue perhaps.

    see yhoo prius_stuff #1071,#1165 and #17142 for ultras and regen they could be useful posts, but posts like #1068 refer to the earlier Prius which I think we should keep out of Edmunds to deal with the latest technology here. Also they are not so warm to non owners cluttering their site with speculative postings, these days. Never mind that talk of plunking down $12000 for an EEstor Li-ion, doesn't seem to phase them at all! Buying a Prius is on my horizon but I want the 'right' technology. Small engine, lightweight and no HV battery. In a few words my Prius has to be quick, simple and cheap. A pure series hybrid. I see the HSD as heavy and complicated right now. And rather expensive too I might add.

    T2
  • goodcrdgoodcrd Posts: 253
    Lets expand on the engine stop question. A diesel engine is torque heavy. It doesn't relie on horse power. If you allow the engine to operate at a low enough rpm to keep the needed compression to ignite the fuel you can store the excess energy produced as stored energy in the form of compressed hydraulic fluid in the high pressure accumulator. You can also valve the engine to allow the pistons to move under no load until engine power is needed again after the stored fluid energy has been depleted. Diesel engines need heat of compression to ignite the fuel. It is not the re starting of the engine as much as getting the engine up to operating temperature which gives rise to the poor fuel saving with shutting off the diesel engine. Also storing energy in the form of a high pressure fluid gives specific power from 3kw/kg to 7kw/kg at a much lower cost then batteries available today.
  • goodcrdgoodcrd Posts: 253
    I forgot. If you can lower the compression of a diesel engine you won't burn your fuel as completely. So with the CRD engine by increasing the injection pressures and lowering the amount you get much better distribution of fuel into the cylinder to make up for the lower compression which compensates somewhat with the incomplete burn. This also lowers the NOx output. (Combustion at lower temperatures) They are very close to balancing the compression with the fuel burn issue to lowering the NOx output of the diesel engine without after engine treatments.
  • toyolla2toyolla2 Posts: 158
    I just visited Altair nano's site and saw that the power density of the nanosafe cell is qoted at 4000w/Kg which is three times that of the Prius NiMH. But though the theoretical limit is 180 amps for the Panasonic cell I see that Toyota doesn't risk more than a 50 amp charge (sic) and 100 amp discharge (via scanner).

    For the nano cell if we choose a more conservative 2000W/Kg that would infer about a 300 amp charge which would get you a regenerative stop of 60mph to rest in roughly 8 seconds. More interesting just 25kg could provide 50kw for acceleration which should definitely impact engine size needed. Right now, if I may remind you, Prius has 28Hp/76Hp battery/ICE ratio. Toyota doesn't have a smaller engine than the 1.5litre which would work well with this powerful a battery.

    As other posters have observed the car companies aren't seeming to follow this mantra, we'll all just be sitting ducks when the next spike in oil price occurs. The Prius is going to maintain its sales but I believe there is interest in a vehicle size below that. This battery could certainly change the dynamic if it became available.

    The fast plug-in charge of a 100Wh/Kg battery at the 2000w/Kg level would take 100*3600/2000 or 180 secs with a 50kw supply for 25Kg. For BEV enthusiasts the best charger for this system would probably be another nano battery on permanent trickle charge.

    I did notice Altair included footnotes regarding "forwardlooking statements" - Safe Harbour language.

    T2
  • tpetpe Posts: 2,342
    This battery could certainly change the dynamic if it became available.

    This battery is available, somewhat. Altairnano has a $750,000 order for their battery packs from Phoenix Motorcars. They've already delivered at least one 35 kWh pack and its installed in an SUV that's currently making the rounds at the alternative energy shows. My understanding is they are contracted to deliver 10 of these packs by year end. Not exactly high volume. Some company with a lot of manufacturing capacity needs to pay Altairnano a licensing fee and start churning these things out.
  • toyolla2toyolla2 Posts: 158
    "100 lbs still seems like a lot of weight for a 1.3 kWh battery pack"

    You mean compared to the 72Ahr battery in your car ?

    But that oldtech commodity battery weighs but 50lbs and holds just 0.9 kwh and costs a hundred dollars.
    Why, if you made one twice as heavy it'd store 1.8 kwh and set you back a whopping two hundred bucks.

    Why on earth would you do that when for $2000+ you could pick up one of those hi fallutin' NiMHs with 1.3 kwh ?

    Don't take me seriously. It's Friday.

    I'm just fooling around, that's all !

    T2
  • tpetpe Posts: 2,342
    I think we're in agreement here.

    On one of your previous posts you gave the altairnano battery 2000W/kg. I think that their claimed 4000W/kg has been demonstrated so you can go with that. This type of technology allows for a stupidly fast series hybrid that has no more than a 80 kg battery pack. There's guys like Richard Branson, founder of Virgin Airlines, donating 1 billion dollars to green causes. If I was in his position I would contract to build a high performance series hybrid with the Altairnano battery coupled with a highly efficient diesel generator. I don't think it would be that expensive.
  • larsblarsb Posts: 8,204
    This is a pretty technical article about the HSD system versus other types of hybrid systems.

    Even has MATH equations.....how nerdy !!! :shades:

    A tale of two hybrids
  • toyolla2toyolla2 Posts: 158
    larsb, welcome it's great someone in this fading republic has found time to contribute to the technical side of things. We can't complain about our North American domestic manufacturers being systematically dismantled because of the advanced engineering prowess of the Japanese products if we can't even support a scientific technical thread in one of the major automobile web sites, possibly the major automobile website in the USA, here at Edmunds.

    Oh, this just in - Magna International, an auto supplier like Delphi but unlike Delphi not in chapter 11, just announced it is looking to partner with three equity firms to takeover Chrysler in order to protect its order book. Didn't waste any time did they ?
    Two thirds of their business is with the big three and with $2Bn in cash and $2Bn in reserves, I guess Magna can be a player. They might even pick this time to go after their rival so over at Delphi they better start putting broomhandles in those doors !

    The posted article seems to be riddled with inaccuracies, starting with : -

    "ICE: Internal Combustion Engine - The standard drivetrain of cars way back in the 20th Century."

    History will no doubt recall the ICE as a prime mover.
    The standard drivetrain of cars way back in the 20th century would of course include the ICE plus a clutching arrangement controlling a multistage gearbox.

    Since the author is going to go on to describe systems which don't have some of those things mention of them should have been included at the get go.

    I've learned that it is important to describe the architecture very accurately otherwise you can find yourself inadvertantly making statements that are BS.

    Take the Prius, for instance, the writer omitted to point out that the transaxle that delivers power to the differential via two intermediary spindles is only 82% efficient. Account was taken of the losses in the PSD caused mainly by churning electrical power between MG1 and MG2 but what were those 95% transmissions ? I would also like to see those 95% efficient transmissions, sadly not on this planet charlie, a 1:1 ratio might be 95% but anything above 1:3 and you're looking at 93% and that's just for a single mesh.

    Also the Power Split Device is actually a torque split device a more knowledgeable writer would have pointed out.
    However the writer did conclude that the series hybrid may become the predominant architecture in the future. However I would have to take issue with his description of what a series hybrid is. There is more than one type you know. The writer's version is essentially an EV with a back up generator to provide enough energy to cruise. Let's say at 70mph, about 20Hp I suppose.

    An entirely different direction which I have been refining over the past thirty years not including a couple of concentrated years on the internet suggests a unique version which rarely gets mention. In this version the battery and ICE roles are reversed. The prime mover would now be a powerful but small engine (600cc or less) driving a hi-speed generator at up to 12,000rpm when 100kw or 120Hp is needed for those short periods of extreme acceleration. This version would have no high voltage 'boutique' energy pack of expensive dubious chemistry either. The keynotes for this idea being simplicity, low mass and cost.

    For replacement of the HV battery the existing 12v lead acid would be just slightly beefed up and equipped with a step up converter in order to perform the 'virtual HV battery' role. This would facilitate engine starting via the generator's feed_thru inverter and at other times allow low speed "electric only" operations to 10mph. 10mph since a single general purpose battery would not have the power capability to put out more than 1500W on a continuous basis.

    T2
  • lensmanlensman Posts: 5
    Edit: I see now that the previous post to mine by toyolla2 talks about exactly this same idea, I apologise if my post reads like this is my original idea, it was you who first mentioned this idea to me...

    I will try and post a sane distillation of whats in my head!
    ....whilst I catch up on what Ive missed since my last visit here!

    I know the major thing holding back all electric vehicles per se is battery technology, we can't get enough juice for the given size/weight to make an electric car go the distance we would want out of a family car (about 350 miles on a tank) I also know that even the latest li-poly batteries are prohibitively expensive, still take a while to charge and suffer from charge loss over time, ie they have some way to go before we reach the holy grail of a lossless, high concentration electrical energy store...

    I also know that if we all made a slight change in our driving habits and if our workplaces would provide sockets for charging your car whilst at work and our respective governments help put in place the infastructure for charging your car at home(I live in an appartment without a garage, so running an extension cord out to the car would get me loads of more headache! ) we could all live with and love the current best of breed electric cars (tesla roadster is an example of the right technology, but, too expensive for most of us)

    That said I also think a better more gradual change involves, hybrid cars that still run on petrol, but, eek out the most efficiency out of the fossil fuel and as a by product lower emissions drastically. Which brings me to the meat of my post, Ive posted some of this here before, but talked about a diesel engine powering a generator that charges an onboard battery and drives an electric motor that drives the wheels (a serial hybrid). I realise that by adding the conversion from fossil fuel to electricity and storing most if it in lossy battery then converting it back to motive power to the wheels involves quite a few losses of efficiency.

    Ive been thinking about something said to me a while back be either toyolla2 or goodcrd ???, sorry folks if I've got this wrong it was a while back. It was essentially that of whther we need a large battery store at all!?

    In essence the gasoline engine powers a generator that drives an electric motor directly... Lets talk efficency of such a setup, how much energy loss are we talking here?

    Im going to make some assumptions here: (these is just guess work)
    Typical motor electricity to motive power efficiency: 85-90%
    Typical generator motive to electricity efficiency: 80-90%

    So a simple scenario where we replace the drive train (gearbox, clutch, drive shafts) with a generator coupled directly to our gasonline engine, which then powers a motor driving the wheels, would net us a lower estimate of about 68% of the engine output (85% * 80%).

    With the original clutch/gearbox in place I know you lose some of the engine power too, what is this roughly, about 10-15%? Would this electric drivetrain be any lighter than the equivalent mechanical drive train(gearbox, clutch) I know drive shafts would be needed for the electric motor too, but with in wheel motors being talked about this too might not be needed!

    How much loss in efficiency in using this electric drive train are we a talking about over the mechanical drive train? My of the top of the head guess would put it about 20%.

    Now couldnt this be efficiency loss be made up in using a smaller lighter gasoline engine (3 cylinder, lean burn, 1-1.5 litre capacity if not smaller like a motorbike engine!) that has been tuned to run at a high rpm with turbo charging if necassary (would this be even needed!)?

    Wouldnt focusing on a smaller lighter more efficient gasoline engine be the way to go. It wouldnt need to provide a wide power band, just a very small highly efficient band of power producing electricity to power the motor. (you could even include some ultracapicators that could soak up the excess electricity produced if the car is moving too slowly for amount of electrical power the gasoline engine/generator combo is producing and if you were to use regenarative braking, this could then be used to provide extra power to the motor when needed, or when restarting the gasoline engine if its been shutdown)

    Another benefit over a standard ICE mechanical drive train setup would be the internal passenger cabin layout options provided by the space saving of not having a large engine/gearbox, drive shafts/tunnel to the rear wheels.

    Sorry that this post is long, but, Im fascinated by all of this, should have been an engineer instead of the desk bound computer programmer that I am !!!!

    Any ideas, criticism is welcome as is any kind soul that can point out any huge holes in my understanding or concept.

    Its all gone very quiet on this board of late!
  • toyolla2toyolla2 Posts: 158
    I wrote this about the suitability of 10 : 1 chain reduction drives needed in a SHEV to reduce speed of the traction motor to a value suitable for the wheel axle.

    Secondly the sprocket speeds of 200 revs/min under consideration (for a bicycle) are also quite removed from the 200 revs/sec encountered with the induction motor in the SHEV. In this environment the chain speed with a 12" circumference drive sprocket would be around 200'/sec.
    Of course as we know a motorcycle chain doesn't go anywhere near this velocity because primary gear reduction has already been accomplished inside its transmission.

    And you responded

    I can tell you from motorcycle experience that chain drive is more efficient than drive shafts for power transfer to the rear wheel, and more efficient than direct gearing for camshaft/crankshaft synchronization. But I don't know how this translates to automotive uses."

    After spending this weekend studying a Haynes manual for the Kawasaki KZ400-550 series quad cyl motorcycles, I have to say I stand corrected about the use of chain at hi speeds ( > 10,000 RPM).

    The primary drive internal to the engine, in Kawasaki's design does in fact include a Hy Vo chain with an approx 1:1 ratio driving the secondary shaft from the main crankshaft at speeds to 10500 RPM. However the reduction needed to the gearbox of 2.935 is accomplished by gearing in the following manner: From the secondary shaft a 26 tooth gear drives a 65 tooth gear on the clutch assembly.

    You referred to the chain used in the "Final drive" for power transfer to the rear wheel from the gearbox external sprocket. Yes, this setup provides a 2.5 step down ratio to the wheel but with the more modest speeds of around 3500rpm at the drive sprocket.
    And one other thing owing to the length of the chain back to the wheel on a motorcycle, geometry allows a good wrap on the sprockets at both ends.

    Using a similar system for the 1 : 10 single stage reduction needed by the traction motor on that SHEV transaxle could be marginal since the wrap angle on the smaller sprocket would be significantly diminished due to the proximity of the two sprockets.

    I did some calculations of the primary drive chain speed for the Kawasaki. The 23T sprocket on the crankshaft using 3/8" per link Hy Vo chain will have a 2.5" dia. pitch circle and rotating at 10500 RPM will yield a chain velocity of 7500ft/min or 90 mph !

    The chain on the final drive to the wheel, for comparison, is driven by a 16 tooth sprocket that rotating at 3500 max rpm will yield only about a 30mph chain velocity.

    T2
  • toyolla2toyolla2 Posts: 158
    This is another sack cloth and ashes post about some speculation I made close to the beginning of this forum that inverters for automobile usage may approach 1000vDC.

    In the US most industrial inverters are run on 660vDC because diode input bridges on 3-phase 460vac will produce this voltage across the main bus. In Canada the powers that be because they generated so much electrical power looked into the future and advocated a 575vac system. Although the higher voltage would seem to allow savings with thinner copper conductors savings were nefarious at best. It certainly made equipment, switchgear etc, more expensive because of the smaller market in Canada to meet this new standard. It also did not forsee that the day of specifying large electric motors would be over.

    Today the trend is towards multiple smaller machine drives simultaneously controlled through digital comm. links. Inside these smaller drives higher voltages have become more of a problem than a virtue. Low cost 575vac inverters available off-shelf, assuming they are not front ended with a 3-phase SCR half-bridge soft start, will have their IGBT devices working off an 800vDC bus. The problem is that these relatively new inverters have not been found to be as reliable as the established 460vac inverters used previously. It turns out that maybe, just maybe, 650vDC may turn out to be the sweet spot for silicon IGBT technology after all and that going forward, the use of voltages above 650vDC should be avoided if possible.

    This was triggered by seeing a inverter die posted on the Yahoo prius_stuff board. There was a query on the terminations and I suggested to them that this would appear to be a SENSEFET fabrication on the internals of an IGBT !
    There are donuts on two of the power leads, but sensefet outputs are likely to be much faster than current TXFMRS and may be a way that Toyota is making their circuits more secure. This will be probably be checked out soon. ORNL (Oak Ridge National Lab) also mislabeled the polarity on their pic.
    I hope they don't make mistakes like that with other stuff they work on up there. :)

    T2

    Sensefet is a Motorola trademark name
  • larsblarsb Posts: 8,204
    This explains why heavier Hybrid SUVs suffer less from the extra weight of hybridization than one might think:

    link title

    Hybrids are getting heavier, but they seem to bear their weight better than conventional vehicles when it comes to fuel efficiency, according to a recent study. In the study, the scientists found that the trend toward higher-performing hybrid-electric vehicles (HEVs) in the North American market is eroding the fuel consumption benefit of hybrid technology.

    However, the gain in vehicle weight and power is not necessarily surprising or discouraging, as researchers Conor Reynolds and Milind Kandlikar explain. HEVs are new in the market and, as such, are diversifying from the compact cars that first appeared in 1999, such as the relatively light, low-power Honda Insight.

    “In our analysis, we found that changes in weight and power affect HEVs differently than ICEVs [conventional internal combustion engine vehicles],” Reynolds explained to PhysOrg.com. “For example, we found that added weight doesn’t matter as much for hybrids as for conventional vehicles, a comparison that reinforces the fuel benefits of hybrid technology.”

    The study by the University of British Columbia scientists is the first to account for all nine light-duty HEV models on the North American market in 2007 (a number expected to double in the next two to three years). While HEVs made up about 1.6% of the total vehicle sales in the U.S. in 2006, nearly 30% of these HEVs were SUVs. Further, HEV cars in the second generation hybrid wave (2004 and later model years) exhibit higher performance levels across the board: an overall 30% weight increase and 60% power increase.
  • toyolla2toyolla2 Posts: 158
    What sort of scientists can get funded to ride around in upscale vehicles and produce a report of use to nobody ?

    POLITICAL SCIENTISTS that's who
    T2
  • toyolla2toyolla2 Posts: 158
    Hi Lensman, in Jun'06 DIESEL HYBRIDS ?
    You wrote

    " This is obviously leading to my personal theory that a series hybrid design with a small very efficient diesel engine running at a constant RPM turning a generator which charges up a battery/electric motor and all the associated regenerative braking/turning off when the battery is fully charged etc... would be the most efficient design. Lensman"

    Let's see "small very efficient diesel engine running at a constant RPM turning a generator"
    Operating strategy - Always to run at full rated power.

    The difficulty with this approach is that you would have to specify the performance required of the drivetrain so that your diesel can be sized correctly.

    "There can be no ideal. No technology is perfect, and you’ve to deal with compromises. It is all about getting the job done with simplicity and minimum overhead. robertsmx"

    If we were to target a top speed of 100mph as they did with the Prius you will need to continuously rate your diesel for about 50Hp. It will need something like a 1.2L tdi to deliver that at 2400rpm most efficiently, but that engine will be a long way from the low cost single cylinder engine that you may have envisioned, more approaching a 3 or 4cyl. Perhaps an engine consisting of just one single cylinder of that same engine could deliver 12.5Hp and maintain 65mph on a level surface etc, etc.but you will need around 80kw of NiMH/Li-ion to get it up there in 10 secs and that energy source could weigh more than 115kgs (260lbs) roughly four times the capacity of the '04 NWH20 Prius.

    If we selected the Prismatic cells from Prius, each 7.2v cell pack weighs 1040g and is rated @ 1300W/kg in that package and should be 180Amp capable. Toyota uses an electronic current limit of 100amps for longevity, let's do same. Each pack should be good for 720W. 80kw will need 115kgs worth. Four times more powerful than existing Prius pack although not necessarily four times the weight since some ancillary included hardware to support the battery will not need to be scaled up at the same rate.

    100mph with a fully charged pack, but for how long can you go? Assume 50Hp is total needed then subtracting 12.5Hp diesel power requires additional continuous 37.5 Hp or 28Kw will be needed.
    The Prismatics rated at 46Wh/kg means the 7.2v cell packs will rate at 6.5AHrs. But that's too much information. All we need to do is multiply the energy density by the amount of battery material we have and then divide that heap of energy by the required consumption rate. 46 x 115/ 28k = 0.1889hrs or 680 secs.


    So there you have it. A compromise. You can have your ten minutes at maximum altitude then you're dropping from the sky. On the other hand Prius could do this all day and produce 50Hp at around 3300rpm. ( interpolating 76Hp for 5000rpm). [mg1= -3720rpm for Prius fans]

    It's not such a depressing result however if there is indeed a market for people who would accept these limitations on an 80mpg car. Since very few people drive beyond 90mph it's always been a want rather than a need. Its always been difficult to limit top speeds in the past because taller gears and overdrive meant for fuel economy allowed manufacturers to offer speeds well beyond 100mph free of charge, after all it's the superior 0 to 60mph in the lower gears that you're basically after. Whether manufacturers can get away with ( i.e. maintain good sales) a car with excellent acceleration and throttle response second to none but with an "inverse time" specification on speeds above 65mph remains to be seen.

    There are some other pros to the idea. A small engine will warm up sooner and become efficient after a mile rather than three miles or more. It's emission will also be better for the initial part of those trips as well. Tell me who doesn't make sure their car is well warmed up before submitting it for exhaust emission testing. It is difficult to put a dollar figure on that. But then I read a poster (maybe on Priuschat I can't remember) who reported that his mileage readout improved following a spell with a block heater and it seemed to have a useful effect whatever the weather. Half the time, of course, that will not be possible. I am particularly warm to the idea of being able to get the ice melted quickly in those remote parking lots because you have a few kilowatts electrically installed inside the heater vents.

    Although I am dead set against diesels for a number of reasons on further reflection I can't deny there are could be some attractive benefits. Utilising the contents of the fuel tank by circulating the diesel fuel as a coolant through the engine could be one of them, naturally an oil cooler rad would be needed and the engine would have to have an automatic cutoff before a minimum tank level is reached. That is not a problem assuming there would still be some electrical miles left in the battery. Then I just thought, doesn't diesel have some decent lubrication properties ? How critical would it be to use fuel for lube on a 30lbs-ft 2400rpm 300cc diesel.? I know it's become illegal in some places to dispose of old engine oil in repair shop space heaters but after running through the engine this wouldn't be old oil at all. In fact this would be almost new oil ! I was looking at the DeltaHawk site regarding their twostroke aviation 160Hp diesel. They stated they won't be certifying their machine with oil cooling but isn't it implicit that two strokes lubricate wth their own fuel ? Enquiring minds wish to know.

    Lensman when I originally answered your post, at DIESEL HYBRIDS ? I hadn't read your post thoroughly before I entered my diatribe on optimal efficiency. Looking more closely, the case you propose sidesteps this 'optimal' issue somewhat with your small diesel by employing it only at full power. At constant speed and full torque there are no variable losses, of course, to cause departure from the optimal efficiency point. Running at full torque thus ensures that the fixed losses are always a small part of the throughput.

    The question is now how often will this engine need to be started. Well with 12.5Hp or 9Kw and using the equation above
    46WHrs x 115kg / 9kw = 0.587hrs. Lets assume bibberonage of from 90 % to 10 % SOC =0.47hrs or 28 minutes. Then the engine will run for 28 minutes minimum when triggered at the 10 % level. Depending on the power being used by the vehicle it could and probably will stay on for much longer than that.
    Ideally you want it to stay on permanently as much as possible so the energy can go directly through to the traction motors and not churn through the battery a process which is only 80 % efficient.

    The problem with this system as I see it, is that with appropriate gauging available to the driver, this car will start driving you. You'll know that out on the highway you will want to be draining the batter
  • toyolla2toyolla2 Posts: 158
    The problem with this system as I see it, is that with appropriate gauging available to the driver, this car will start driving you. You'll know that out on the highway you will want to be draining the battery slowly, at least on hills, so that the engine can have some work when you reach stop and go traffic downtown, that would be my preference. Or you may want to watch your speed on the hiway so that arriving in town you can drive electric. Then again, some people might not be thrilled to leave their car parked at work with just 15 % on the SOC meter and may just hit the 'Force Charge' button when a few minutes from their destination anyway etc etc. As in the Prius the battery is there primarily to provide acceleration performance in town and to assist the engine when gradients are encountered out on the hiway and not intended for turning the vehicle into an electric car. In my view electric car drivers, in contrast, have already bought into the shortcomings in the range of their vehicle. I don't know about you but when I'm driving I want the vehicle to be as transparent as possible and not find myself pulled into hypermiling. Engines that stop and start unexpectedly could be disconcerting. I'm sure even a small diesel would make some clatter when it started. Prius owners seem to get accustomed to it.
    T2
  • lensmanlensman Posts: 5
    Thank you for your reply toyolla2, good to see some speculative figures rather than my wishy washy wordy post.

    The biggest detractor from what you write is that the petrol/diesel engine would need to run for 28 mins or so to juice up the batteries from 10% to 90% charge. You mention having a 'force charge' button on the dash somewhere. I think this is a great idea actually, it puts the onus on the driver to decide whether they are arriving at somewhere where they could charge the batteries from the mains supply or use the onboard generator/engine combo to start charging the batteries beforehand. Appologies as this is going to go slightly off topic...This could be extended 'coolified'(tm) :) by being linked into your SatNav, so if you are roughly however many minutes (it would take to recharge the battery pack to 90% charge from its current level) away from your destination it could automatically start the engine to begin force charging the battery.

    Now the obvious question is what happens if you arrive at your destination without having force charged and with only 10% charge left in the batteries without means to plug in. Well you mention around you could get ~50hp from the 1.2L diesel engine in your example configuration. The engine could run immediately you set off again, and it would be feeding the electric motor directly, only charging the batteries when the motive force required from the motor falls (you've reached your cruising speed). I am again out of my depth here, but ok you would be limited to 50hp in this situation but could this work? I mean wouldnt 50hp be plenty enough from rest and up to 30-40mph, and then you'd only need what was it, 20hp to stay at 30-40mph...

    I fully realise that the holy grail of all the serial hybrid would be a engine running on petrol/diesel that is of fundementally different design to extract the wasted ~60% from the fuel that current internal combustion engines give off in sound and in heating the atmosphere :) !
  • toyolla2toyolla2 Posts: 158
    The biggest detractor from what you write is that the petrol/diesel engine would need to run for 28 mins or so to juice up the batteries from 10% to 90% charge
    Take a look at my post again, I think I suggested we are going to use one cylinder of a conventional 1.2L diesel to give 12.5Hp. This is 9kw. Meanwhile an 80kw capable NiMH battery will hold 4.5kwhrs whether we like it or not !

    So at 9kw this will take roughly half an hour to charge, I said 28mins.

    If you have 10% SOC, that would be worst case, in parking lot well that's more than enough to start engine. Let's do some math. you need to exit the lot straight onto a busy major hiway, worst case again. You need 100hp for 10 secs in your battery to get to speed fast. Your 12.5 Hp engine will put that in the battery in 80 secs. Can you see how I did that ?

    Remember you only need a horsepower or two to mosey around the parking lot so you'll probably be ready to go as soon as you find the exit.

    A word of caution, although this can be done doesn't mean it should be done. This battery would cost around $8000.
    T2
  • larsblarsb Posts: 8,204
    An Engineer disassembles and examines a Prius

    Upon tearing apart a Toyota Prius—spanking new from the dealer—what strikes an engineer's eye is that this first parallel drive train gas/electric hybrid car is more like other modern vehicles than not. Ignore the large nickel-metal hydride battery tucked out of sight behind the rear seat; filter out the associated starter-motor-like heavy-gage high-voltage orange cables running along the frame to carry current to and from the electric traction motor for power and regenerative braking. Now you have a system that seems "conventional," despite the optimized hybrid-power-train architecture.

    The Prius overall appears to follow the Toyota build philosophy: standard modules, bits and pieces--from electronics to doors and other components--that readily fit in place, enabling the same vehicle model to be built to the same quality standard anywhere in the world.

    Like any modern vehicle, the Prius packs numerous electronic subsystems. Six, however, stood out: the inverter/converter, the user-interface/dash module, the engine control module, the navigation/display system, the airbag control module and the anti-skid system. The functionality, placement, electronic content and packaging of those subsystems represent the cutting edge not only in terms of technology but also in the context of reliability and power management.
  • toyolla2toyolla2 Posts: 158
    The Wall Street Journal confirmed today that the next-generation Prius will not use lithium-ion battery technology -- at least for the first few years. The lithium-ion batteries that were to be used in the Prius would have been provided by Panasonic EV Energy Company.

    From your comment in News and Views #268, I agree with you tch_titanium, this is not totally bad news to me either.

    The Toyota concept of invoking a hybrid model differs from mine and I've always felt that they were going in the wrong direction with the HSD system despite its success.
    I would say that somewhere in the mix of the two is the understanding that electric traction is involved but after that.....let me try and explain my side.

    Generally the Hybrid is defined as the act of combining two different energy sources e.g. gasoline and NiMH battery for synergism.
    And that's the HSD. In my mind, though, I have the term Hybrid defined as the act of the conversion of one energy source into another so that synergism will result.

    My model does not require an HV battery as either a major storage element or as an element able to deliver major power. In the model I propose, a conventional sized lead acid 12v battery could deliver 900W of power to the HV bus which would suffice for the type of limited low speed mobility in forward and reverse most often required.
    Otherwise the model recognises that Stealth (electric only) driving and regeneration (when stopping and hill descending) are not essential unless you are building a conventional EV. The exergy of gasoline is such that hauling a 100lb battery around to save a few drops of gas does not impress me. As to the recapture of mechanical energy then the use of an electrical resistor mat to dissipate potential and kinetic energy as heat in order to reduce disc brake maintenance has much higher efficacy, as I see it, being cheaper, simpler, lighter and able to be of higher power rating than the absorptive NiMH system currently in vogue. e.g. Prius can absorb a maximum rate of 10kw and that is if the weather is warm and the battery temperature is up, I think you would agree that most moderate braking manoevres need an absorptive ability several times that.

    You wrote :
    Advances in silicon, magnetics, and other materials has been steady (much better than batteries) and I'd have to think that's where most of the improvements are going to continue to come from.
    I second that and would add that a single cylinder performance engine such as found in Yamaha's WR450F with its 96x62mm oversquare design should be considered as a simpler prime mover to supercede the 1NZ-FXE four cylinder now in use.

    Finally the use of the existing 50kw inverter but with a low cost induction motor geared directly to the differential gear of the transaxle would be far simpler and about twice as efficient. You would be looking at a 7% reducer loss versus an 18% estimated loss of the current transaxle multistage reducer.

    T2
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