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Advanced Course in Hybrid Engineering

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  • toyolla2toyolla2 Posts: 158
    Hi robertsmx,
    I will get back to you re the IMA later, but I noticed that you wrote in post #36 when generally discussing mild hybrids. There is a twist to your statement when considering SHEVs that is not well known or recognized and I read something recently in a Yamaha document that supports the idea I've been proposing for SHEV engines that they be high speed.

    "However, in the world of ICE, there isn’t likely to be a big weight/packaging size differential between a 1.5L and 2.0L."

    I kinda agree but...
    Let's see what I found from reading the maintenance manual for the Yamaha 'Waverunner'. This three-seater personal watercraft employs a 1046cc 4cyl engine which produces 170Hp @ 10,000rpm (it direct drives a water pump).
    Just TWO cylinders of this marine engine would be equal in power to the atkinsonised version of the Echo 1.5L that powers the Prius. I accept that the relation between engine mass and the size and number of cylinders is not linear there's lots of fixed mass that both engines must have. It does however highlight that for this particular type of load - an impeller in a hydraulic system - marine designers have found tradeoffs to increase engine powers to levels that appear distorted alongside conventional thinking regarding the weight/packaging size versus horsepower expected from automobile engines.

    Or as I am wont to put it, you can no more make an efficient Series Hybrid Electric Vehicle using a contemporary automobile engine than you can make a successful airplane out of cast iron.
    T2
  • toyolla2toyolla2 Posts: 158
    You mentioned direct drive wheel motors,here's my take.

    The only popular uses I know for direct drives are
    disk drives; to permit compactness and avoid the speed variation problems associated with rubber belts.
    And clothes driers to replace the two step-downs to the drum and the single phase motor; the one equipped with that fault prone centrifugal start-switch. But in this application whether the three phase direct drive pancake motor with inverter will provide the improvement of a more quiet and compact machine is open to question.

    However the problem with this technology in automobiles is two-fold.
    Firstly they add significant weight to the wheels and this unsprung mass, as it is called, out on the wheels will bring a large amount of vibration back into the vehicle unless you are driving on very smooth concrete which mostly of course you don't.

    Secondly the base RPM is low (600rpm on the wheel)so the horsepower will be low also. You only get to use the magnet and copper materials 10 times per second whereas at 12,000rpm you can use the same materials 200 times a second. It can mean the difference between 10Hp and 100Hp in this context. For simplicity I have been proposing a 10:1 planetary reducer built into the end bell as they did on the original EV1 back in 1990. Take a look at my post #31.

    It can be argued that an inverter grade induction motor is not significantly less efficient than a permanent magnet synchronous machine as you mentioned. But avoiding the expense of exotic neodymium magnets should also assist reducing its cost to Walmart proportions.
    I want a $500 motor not the $4000 say, that you will find on the PRIUS. When I was involved with electric vehicles, I used to have a saying of not "sacrificing yourself on the altar of high efficiency". You can always find a place elsewhere for the same money which will provide a better improvement overall.

    Having an inboard motor makes the sharing of coolant with the ICE more secure and further reduces the frame size you can get away with on this motor. My point is that liquid cooling will allow the specific power density of the motor to be increased.

    Regarding diesels - these are slow machines - even so called high speed diesels top out at 4000rpm. They have to. The first part of the stroke is constant pressure; the fuel continues burning while the piston moves down, you have to allow time for that process to occur; sure the elevated compression ratio they use brings the Air Standard Efficiency from 36 to 44%. If the diesel were required to work at full rated power, I would be with you on diesels unfortunately the nature of motoring is to need +100Hp while accelerating for 8 seconds or so followed by a considerably longer duration when the demand is 10Hp or less. The higher rpm of the conventional ICE is much more desirable in this application IMO. This probably explains why you won't be seeing F1 cars with diesel engines anytime soon.

    Turbos, well of course, in fact I think all vehicles should be fitted with turbos. Too bad the 3 cyl on Honda's INSIGHT didn't get one.
    After I read Hugh McInnis' book on Turbochargers I was a believer.

    Unfortunately these devices need some TLC, manufacturers have not installed the sensors and the microcontroller technology needed to prevent John Q. Public from abusing them, they've got a bad rap. In the hands of sports car aficionados and SAAB they continue to survive. But you don't see enough of these cars on the road to give me the confidence that service support would not be an issue.
    I'd be a lot more enthusiastic if Corollas and Civics started championing this technology.

    I would however have no trouble being a first time buyer of a SHEV with its induction motor and inverter drive because this type of technology is now meat and potatoes in the factory automation business. Motor generator sets are no big deal either even though the automobile version would be light years from the usual Honda standby set.
    T2
  • "Yamaha 'Waverunner'. This three-seater personal watercraft employs a 1.0liter 4cyl engine which produces 170Hp @ 10,000rpm. Just TWO cylinders of this marine engine would be equal in power to the atkinsonised version of the Echo 1.5L that powers the Prius."

    .
    The Waverunner engine is spinning at 10,000 rpm! If rev-limited to 5000 like the Prius, it would only generate ~85hp... about the same as the Prius engine.

    No miracle engineering there. They simply made the waverunner spin faster (and less fuel efficient).
    troy
  • toyolla2toyolla2 Posts: 158
    TROY,
    I was just pointing out that higher speed engines are already considered doable for the consumer market and not merely some near-term project that would need big R&D dollars. I wasn't intending to suggest that it was a replacement candidate for the Prius engine just that a two cylinder version of that engine could provide the same power.

    I agree, it may not be as fuel efficient as the Prius engine while running @ 10,000rpm but it could be as much as 100lbs lighter so there would be an automatic increase in mpg for that reason alone.

    Dare I say that some of the problem lies with your obsession for efficiency. Imagine if the Prius engine was an Atkinsonised V8 3.0L it could run half the speed and so be even more efficient (using your logic) than the current 1.5L. It goes without saying (but I'm going to anyway!) that the increase in vehicle mass with the V8 would cause the mpg to take a hit. You weren't expecting to lug all that extra weight around for free were you ?

    T2
  • robertsmxrobertsmx Posts: 5,525
    When discussing efficiency, you have to realize losses not just horsepower. An engine half the size of the Yamaha engine you quote could produce half the power (85 HP) at 10K rpm assuming similar efficiencies, and ultimately match 1.5-liter Atkinson Cycle motor as used in Prius in peak power output. But to relate power and fuel efficiency, we really need to look at BSFC.

    Efficiency of a hybrid drive train is going to be determined primarily by two factors. One, how much of the energy is recycled. And the efficiency of the non-electric motor involved. Parallel versus Series isn’t going to be an issue. It is all about efficiency.

    You may have seen a Honda example of a prototype hybrid vehicle earlier from me that involves an ICE mated to electric motor in Series as well as in Parallel mode. The active mode depends on demand. For normal cruising, the vehicle ran in series mode, with ICE charging battery pack running electric motor hence the vehicle. During start up and acceleration, ICE and electric motor run in parallel mode for greater power delivery due to increased load requirements.

    One of the best examples of a series hybrid is a diesel locomotive.

    I was just pointing out that higher speed engines are already considered doable for the consumer market

    High revving engines have been around in motorcycles for a long time. The problem isn’t with the output itself, but how you manage to put it down.

    It would be possible to replace a 3.0-liter, 150 HP motor with a 1.0-liter, 150 HP motor in a 3000 lb sedan. These are peak numbers of course, but assuming similar efficiencies, the 1.0-liter motor will need to spin at three times the rate of the 3.0-liter motor. Gearing will have to take care of this aspect, and spinning at 10K rpm versus 3000 rpm for same power output can be perceived or felt very differently in the same car. Not in terms of power, but in terms of NVH. And, high rpm isn’t the best way to increase fuel economy.

    As for weight, yes, if the 3.0-liter engine weighed 310 lb. as does Honda’s V6, and the 1.0-liter engine weighed 126 lb. as does Honda’s I-3 (in Insight), than you do gain 184 lb. in weight and the vehicle can be lighter. But, that’s probably going to, may be, compensate for added losses of higher revving design (in the engine, and the transmission itself).
  • toyolla2toyolla2 Posts: 158
    robertsmx, In your first paragraph you say that when

    ... discussing efficiency, you have to realize losses not just horsepower.
    ...But to relate power and fuel efficiency, we really need to look at BSFC.

    If we were discussing a stationary power plant I would agree entirely with those statements and the Specific Fuel Consumption (in lbs/Hp-hr)is king. But carrying excess weight on a mobile platform will require more horsepower and you will have more losses no matter how good your SFC is.

    As an extreme example even though we know jet engines are dreadfully inefficient we don't see WestJet or any other no frills airlines running around in Super Constellations no matter how more efficient their engines might be. So I am going to stick to my guns on this one that while SFC is important - in automobiles (and airplanes) Mass is too.

    Your last sentence of your post seems to infer a softening of your position

    ...vehicle can be lighter...that’s probably going to, may be, compensate for added losses of (a) higher revving design.

    I've always contended that such high revving will only occupy a small fraction of time over the full driving cycle anyways. The steeper gradients or the stoplight Grand Prix, that kind of stuff. I would anticipate that most of the time the ICE would be below 4000rpm @ 50mph so engine wear would not be an issue. As a reality check to what a typical car needs most of the time let me refer you to this piece that I just dug out, an old 1983 advertising copy from Ford. It says " Aerodynamically designed, LTD needs only 6.7Hp to push it through the air at 50mph".

    Oh and by the way, ...if saving 184lbs does compensate for the less efficient high revving...

    If we could be a little more optimistic here, supposing it does more than compensate... in which case, maybe, you just gained an increase in the torque/mass ratio of the vehicle.

    Then if you are not saying engine efficiency is paramount - no matter how much it weighs - where do you draw the line. I speculate Toyota went with the most advanced 1.5L engine block that was available at the time, they were taking enough risks.

    We know they certainly don't view high RPM as being a problem; they now have MG1 turning @10Krpm. In fact if they decided now on a liquid cooled motorcycle engine there is wiggle room on the PSD to have its ratio changed to suit.

    You make a point of the rpm being inversely proportional to the swept volume in the cylinders i.e. a 1.0L needing to run three times faster than a 3.0L. 2100rpm v 700rpm.
    The waverunner engine produces 16.5Hp per 1000rpm.
    Remember the LTD needing 6.7Hp @50mph, so while cruising in that car @1000rpm this engine would still have 10Hp in reserve via the throttle.
    A two cylinder version of the waverunner in this car (8.2Hp/1000rpm) would be quite highly loaded with only 1.5Hp in reserve. Increasing engine speed to 2000 rpm would restore a 10Hp reserve.

    If we go back to the real world, 2000rpm is just abit more than twice the minimum speed of the 3.0L VVTi 1MZ-FE engine, mine idles around 750 I can tell you.
    It has a capability of 36Hp/1000rpm assuming constant torque, giving 27Hp at idle.

    My conclusion is that most of the time this 0.5L engine need run only just over twice as fast as a conventional V6. Not 6 times faster as you would have proposed might be expected. Not forgetting that it is the sole ability of the PSD via MG1 to change its ratio so rapidly that makes this system usable.
    They have to make the Prius lighter and less expensive, I believe this is one of the ways open to accomplish that.
    Other than that let us agree to disagree.

    robertsmx, your postings certainly raise some points, too many to address in one go.
    By the way NVH = ? please

    The recycling of power is important but I see no system having advantage over any other where electronic regeneration back to the main pack is concerned.

    One more thing.
    The efficiency of the prime mover is not the be-all of the system as you infer. The transmission is also key - and it pivots on which of the SHEV or Prius PSD methods can do this function in the most efficient way.
    The SHEV is basically a system biased towards using larger power electronics.
    The PSD is a system biased towards mechanics.

    I did a post on separation of losses, some weeks back, because SHEVs get dismissed with what I call "lazy explanations".

    But if you want a supreme example of what can happen when a group of mechanical engineers try their hand at electrical engineering.....

    Next time it will be "Shark week for Honda"

    I will be discussing the IMA with figures gleaned from Honda's own website, in answer to previous posts.
    T2
  • vietviet Posts: 847
    Hi Robertsmx,

    I have enjoyed very much your well-written messages on automobile engineering. I do learn something from you. You must have lot of automobile engineering experience.
  • toyolla2toyolla2 Posts: 158
    Since this board has more to do with physics and electrical/engineering I hope no one who owns a hybrid will get upset with statements written here in good faith. It may be a truism that the effect of advertising is not merely to attract new buyers but to affirm to new owners that they made the right choice.
    To those I say, knowledge and experience are something you gain just after you needed them.
    To ruffle feathers is not my intent any more than writing here is part of a popularity contest.

    The Honda IMA is a motor affixed to the engine crankshaft. A 3-phase controller and a 144v NiMnH battery complete the system.

    Figures in bold are from Honda's website for the Honda Civic Hybrid.

    It's been written, ad nauseum, that the IMA's sole purpose is to reclaim kinetic energy normally lost by mechanical braking, the IMA becomes a generator and supplies current to the 144v battery, it therefore becomes a load on the shaft and slows the vehicle down. The slight brake pedal travel is detected as gentle braking so the system works on the IMA first , later more aggressive use of the brake pedal will engage the mechanical system.
    On acceleration the IMA becomes a motor and draws current from the 144v battery. This happens as long as the ICE revs are kept low. Aggressive acceleration keeps the revs high and the IMA may not be able "to motor". Honda's figures tell this story, they don't hide this fact, but no-one to my knowledge has ever interpreted this data in a forum anywhere. To most people this stuff is as unintelligible as a Mutual Fund prospectus anyway.

    The IMA is rated at 10kw and Honda further says their motor produces 36 lbs-ft @1000RPM but this is only represents 5.1 KW when you do the math. Assuming the torque remains constant, by extrapolation we can probably expect the full 10kw @ 2000rpm.

    So torque 36 lbs-ft @1000rpm
    increases to 36+87 lbs-ft @ 2000 rpm
    with the engine now pulling at full torque.

    We can expect that the IMA torque component, assuming constant 10kw Power, will decay inversely to speed. Right ? Sorry, Wrong. Torque roll-off is much more severe than that.

    See the figures from the Honda website, I noticed from their figures that at 3000rpm the IMA provided only 18lbs-ft of torque?
    But by the inverse law for constant horsepower shouldn't 36 lbs-ft @ 2000rpm
    become 24lbs-ft @3000rpm. What's with this?
    My calculator shows 18lbs-ft @3000rpm to be only 7.67kw. Where did the 10KW and 24lbs-ft, you would have expected, go to? And where will the torque be approaching 6000rpm? Try 3-4 lbs-ft.

    Well the problem is with the inverter being limited to 144v battery voltage. The first thing you have to be aware of is that the frequency of the applied voltage must always match the speed of the motor. This applied voltage produces a rotating magnetic field around the stator of the machine and must be in synchronism with the powerful magnets attached to the rotor. This is fairly easy to achieve with a crankshaft encoder feeding positional data to the electronic controller.

    But here are the problems. The stator winding producing this magnetic field has inductance. Inductance opposes changes in current. To make the motor rotate faster, higher frequencies have to be applied. The inductance produces even more opposition to this faster changing current. The net effect is that the controller finds increasing difficulty getting current into the motor. Torque drops.

    And there is another effect that is even more insidious. The magnets on the rotor produce a strong static magnetic field. When the rotor starts rotating this field similarly rotates with the rotor. The field passes through the stator winding and generates what's known as a back-emf.
    You want back-emf because that value multiplied by the current is a measure of motor power at that instant.
    This voltage increases with rotational speed until it reaches the battery voltage at which point it will be impossible to inject current into the motor. Torque will drop to zero.

    I predict this starts happening after the motor passes through 3000rpm at which point unless it it is disconnected the motor will behave as a generator and start charging the battery whether it needs to be charged or not.

    Of course the designers bank on you not being able to tell when this torque drop is happening. Neither do designers hang out in the advertising offices. So misleading sales information that adds the IMA power to the engine power sounds reasonable but is pure hype. Sales will need a greater MSRP for a hybrid, why not let the customers think they are getting a slightly more powerful system in the horsepower department.
    A case can be made that engine production spreads of +/- 5Hp at the top end are quite acceptable. This variation swamps the IMA power anyway so who cares.

    That doesn't change the fact that at the low end the extra 36lbs-ft helps extend the useful torque band down to 1000rpm so you may be able to hold 2nd gear from 10 to 50mph and achieve respectable acceleration.

    Of course for long road trips the IMA does nothing for mpg compared to what a tall gear in a non hybrid Civic could be doing.

    As I stated in a previous post for the HCH I think they should have set the IMA base speed for 1000rpm and picked up 72ft-lbs instead of the 36ft-lbs. I notice in the HAH they are using an 850 rpm 15Hp IMA. The Accord is not significantly heavier than the Civic so the reclaim energy is going to be roughly the same.
    The system components will therefore be similar too.
    I rest my case.

    Despite all this I can't help but say that winding electrical machines for low base speeds to improve the torque bandwidth of the gasoline engine is a misapplication of electrotechnology in automobiles. GM's EV1 had no problem regenerating to a stop with the same motor that would take it to 60 mph in a little over 8 seconds.
  • "Of course the designers bank on you not being able to tell when this torque drop is happening. So misleading sales information that adds the IMA power to the engine power sounds reasonable but is pure hype."

    .
    FALSE.

    They didn't hide anything. The Insight brochures include this graph, which *clearly* shows the actual engine+motor horsepower & the fall-off in motor torque at 2000 rpm:
    http://www.insightcentral.net/encyclopedia/enperformance.html

    (Please Note: The Prius' electric motor does the same torque falloff at 2400 rpm.)
  • xcelxcel Posts: 1,025
    Hi Toyolla2:

    Although I use IMA’s capabilities very sparingly, one item that you have not brought to light is that IMA acts as a quasi-balance shaft for the 3-cylinder ICE’s in all Insight’s.

    In terms of FE, IMA starts from a straight or forced Auto-stop is a force multiplier that a non-IMA equipped Honda lacks. There will always be traffic conditions not conducive to high FE that a non-IMA equipped Civic/Accord will not be able to take advantage of. The Honda hybrid’s on the other hand can achieve spectacular results even under the worst traffic conditions because of IMA. That is if the traffic conditions are handled properly with the IMA equipped Honda.

    Good Luck

    Wayne R. Gerdes
  • toyolla2toyolla2 Posts: 158
    First I must mention that a post I was making here two weeks ago suddenly disappeared wiping out four to five hours of diligent work on the IMA system and wiping out an equal amount of enthusiasm. Too bad the edit box can't have a save feature. I am just going to have to discipline myself to make smaller posts.

    In the meantime tigercat21's post appeared linking to one of the best writeups of power electronics applied to automobile technology that I have read in a long time. Congratulations tigercat21for digging it out.

    I would like to add --
    A conventional engine costs about $70 per horsepower...
    For a parallel hybrid yes...but
    for a SHEV this cost could be lower since peak horsepower could be delivered at very high RPM, such an unconventional engine may bring the costs down to $30/Hp

    Power under the hybrid hood has to be converted and transformed again and again...
    Electric power-massaging equipment already is...


    This is an idea I put forward in earlier posts as electrodynamic conversion
    While those writers infer an upper limit of 500vDC, most industrial inverters are run on 660vDC because diode input bridges on 3-phase 460vac will produce this voltage across their main bus. But as I have pointed out before, there are 575vac inverters available off-shelf and, assuming they are not front ended with a 3-phase SCR half-bridge soft start, their IGBTs are probably working with an 800vDC bus. However for automotive use I believe designers will be looking at 1000vDC to be the limit. This limit would be set by the production of acceptably priced IGBTs when thinking in terms of power levels approaching 100kw. I remember some time back that there was a price premium on 1400/1600v 150amp replacement SCRs that I was ordering over the original 1200v devices, IGBTs will probably have similar price curves.
    One of the things that will have to disappear is this mindset with voltage - it causes problems. My experience has been that voltage should only be increased as power levels increase. For instance 10VA transformers on 220vac and 1/4Hp 3-phase 460v induction motors have a higher failure rate because the wire gauges used are fragile at these voltage/power levels. Similarly at the other end of the spectrum 240v 300 amp motors will need extra care and maintenance with wiring terminations than 500v 150amp machines. At those higher current loadings contactors whose connectors become loose have a tendency to burn up.(we found)

    About six years ago a 42volt consortium was set up because the limit of 3kw at 12volt was being felt in some vehicle designs as constraining future design improvements. Active suspension and replacement of hydraulic braking come to mind. Anyway a Prof at MIT in electronic engineering was spearheading an attempt to get vehicles equipped with 42v battery systems. The problem was that they thought in terms of moving all the existing systems into this next generation voltage. If active suspension was added in at the same time, this new technology would be moving in two dimensions at once. I would imagine some executives would not be thrilled at what effect this would have on long term reliability were that to happen.

    Of course a broadside move to 42volts was never necessary, and consequently never happened. The writers in tigercat21,s link mention Electric power-massaging equipment and that's what was necessary for the 42v crowd to do.

    An alternator wound for a stator voltage of 42 volts at idle rpm and a step down regulator to supply the 12v battery was all that was needed. If electronic valve actuation joins the mix then 42v will be required even when the alternator is stopped. In which case an upconverter from the 12v to 42volt bus would be needed. It could be enabled by turning the ignition key until such time as the alternator is able to supply the 42v load directly which would be as soon as the engine starts. Thus most of the components that require just 12volts could be left as is.
    I read the industry was also asking them for a combination starter -generator but I doubt that idea would be worth the expense and reduced reliability of a 42v battery that would then be needed IMO.
    Retaining the 12v battery and then trying to use a six-pack of high current starter motor transistors working off the 12 volt battery rail could be expensive particularly when they would have to survive 42v when the engine starts and the motor becomes a generator. But then there are 40amp surface mount devices that transform 3.3v to 0,8v for Pentium processors and they don't cost an arm or a leg so what do I know !

    The battery is there primarily for energy storage not to supply specific voltages that come in handy, that function is now for power conditioning circuits.
    Automotive suppliers seem to forget this important fact. Er.. where are the booster cables ?

    When it comes to stealth driving and regen I agree more storage should come with higher voltage. This is an area where not agreeing on an industry standard voltage was a big mistake by the car companies, it would certainly allay fears surrounding battery pack replacement costs if this component could have become a more common commodity item.
  • stevewastevewa Posts: 203
    If higher voltage is such a good idea, why did HSD go with a lower voltage battery than THS? Higher volts == more cells for a given battery technology, meaning more cells to monitor for reverse-charging. From a battery complexity and lifespan perspective, fewer, larger capacity cells are better.
  • PFFlyer@EdmundsPFFlyer@Edmunds Pennsylvania Furnace, PAPosts: 5,808
    I'd only add this caveat on higher or lower voltage being better or more efficient... given current technology. Who can say what breakthrough or discovery is waiting around the corner? I may not know what it is at this point, but I'm certain it's out thre waiting to be found. I recall a Windows Magazine cover froma few years back telling us that the 66 Mhz Pentium chip was it. We've hit the limit and can't possibly go any faster on chips. Same with the 28.8 modem, yada, yada...

    Like the song said, the future's so bright you gotta wear shades!

    PFFlyer@Edmunds

    Moderator - Hatchbacks & Hybrid Vehicles

  • stevewastevewa Posts: 203
    That's why I said for any given battery technology. Obviously if they go from something like NiMH (1.25 v/cell) to LiPoly (3.6 v/cell) you can get more voltage from the same cell count. The complexity problem is the cell count, not the battery voltage or technology.

    Higher voltage is easier to work with because you can get the same power with less current, thus use lighter conductors.
  • PFFlyer@EdmundsPFFlyer@Edmunds Pennsylvania Furnace, PAPosts: 5,808
    Now that news story the other day about Toshiba coming up with a battery that recharges 60 times faster than current batteries is an interesting development. They're talking about the type of battieres used in laptop computers, but if you could achieve the same with batteries that would have enough power and duration to use in a hybrid, that might be something to see.

    PF Flyer
    Host
    News & Views, Wagons, & Hybrid Vehicles

    PFFlyer@Edmunds

    Moderator - Hatchbacks & Hybrid Vehicles

  • Yes, it means that Electric Cars would have unlimited range: Just recharge for 2 minutes while drinking your 7-11 coffee & then continue your cross-country drive.

    troy
  • toyolla2toyolla2 Posts: 158
    If higher voltage is such a good idea, why did HSD go with a lower voltage battery than THS?

    Hi Steve, you are perfectly right, IIRC :
    The Prius THS 2001-2003 had 38 cell packs for 274v
    and the Prius HSD 2004 has 28 cell packs for 201v
    As you point out - fewer but larger capacity cells are better.
    It provides for less possibility that an infant mortality could occur
    within one cell that could cause reverse charging and overheating
    and possible explosion.
    However I hate being annoying... But , IIRC, doesn't the HSD have an
    upconverter to raise the battery voltage to 500v so that MG1 can run at
    10k rpm max from the previously 6000 rpm max ?

    This was the paradigm shift in Toyota's thinking. They had needed to upgrade the THS. They had wanted more power at lower roadspeeds.To do this they obviously would need to run the ICE faster. This requires MG1 to run even faster and to support this would require a higher battery voltage perhaps 500v.
    They decided as you would have Steve, that this would impact the battery size, cost and reliability. So they looked around. Rewinding MG1 to run at 10k rpm on 274v was an option. But this gives a new problem for MG1's inverter which has to transfer the power from an MG1 which now must generate about 30% more current at its new max rpm. They were able to trade away both these problems by leaving MG1 as is and adopting the use of an upconverter.

    I don't think I have compromised my earlier statement that battery considerations should be for the storage function leaving power conditioners (an upconverter in this case) to handle special applications. tigercat21's link was also in the same vein.

    The 2004 Prius battery pack -from The Great Battery Debate forum
    The new Prismatic cells had an energy density only 15% more than the older cylindrical cells, though there were 28 cell packs rather than 38 previously. So the stealth range was reduced for the '04 Prius. The power density of these new cells increased from 800W/kg to 1300W/kg. This should allow 180 amps motor/regen current draw for a power of 36.4kw for as long as two minutes this is quite a performance change from the earlier cells.
    The 7.2v cell packs are rated 6.5amp/hr and weigh in at 1.04kg per pack.
    28 X 7.2 = 201v

    And if they were going to use an upconverter it would upconvert as easily from 201v as from 274v up to 500v.

    So in response to your post, although the HSD went with a lower voltage battery it did in fact use a higher operating voltage.

    Going back to that article in Electronic Engineering Times, and I quote :
    "The question on 42v is economics"
    No!! the question on 42v is electrocution.

    I wonder if it occurred to the 42volt guys that if you got booster cables wrong you could end up with 84v relative to the frame of the other car - you could risk being electrocuted while giving someone a jumpstart !
    I'm not sure I would like to make the National Enquirer posthumously.
    Then again if according to Dennis Miller the prospect of hydrogen fueled cars gives him a feeling of meeting two hundred potential Hindenburgs in a supermarket parking lot, cars with this 42v system might be off putting to most people. Though people are comfortable with car names like NEON, they would prefer not to find themselves glowing like one.
  • 84 volts doesn't sound deadly to me. It would be like touching an electric fence. Ouch. But not death.

    troy
  • PFFlyer@EdmundsPFFlyer@Edmunds Pennsylvania Furnace, PAPosts: 5,808
    I don't know for sure whether you'd get fried or just zapped, but having been zapped by a regular car battery before, I bet that a battery pack that can supply enough power to move a vehicle would give you a VERY healthy jolt to say the least!

    PFFlyer@Edmunds

    Moderator - Hatchbacks & Hybrid Vehicles

This discussion has been closed.