Mazda’s Capacitor Based Automotive Regenerative Braking System

Discussion in 'In the News' started by xcel, Nov 25, 2011.

  1. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    [​IMG]It is called 'i-ELOOP'.

    [fimg=left][/fimg]Wayne Gerdes - CleanMPG - Nov. 24, 2011

    Mazda's 'i-ELOOP' regenerative braking system

    Mazda released details on a groundbreaking regenerative braking system that uses a super capacitor in leiu of a battery for quick storage. The system, which Mazda calls 'i-ELOOP', will begin to appear in Mazda's vehicles in 2012. Mazda claims that in real-world driving conditions with frequent acceleration and braking, 'i-ELOOP' improves fuel economy by approximately 10 percent. We know better but there will always be an advantage with regenerative braking rather than throwing it away any time you have to step on the brake.

    Mazda's regenerative braking system is unique because it uses a capacitor that temporarily stores large volumes of electricity. Compared to batteries, capacitors can be charged and discharged rapidly and are resistant to deterioration through prolonged use. 'i-ELOOP' efficiently converts the vehicle's kinetic energy into electricity as it decelerates, and uses the electricity to power the climate control, audio system and numerous other electrical components.

    Regenerative braking systems are growing in popularity as a fuel saving technology. They use an electric motor or alternator to generate electricity as the vehicle decelerates, thereby recovering a portion of the vehicle's kinetic energy. Regenerative braking systems in hybrid vehicles generally use a large electric motor and dedicated battery.

    Mazda developed its regenerative braking system to handle a large influx of current and slowly give it back. And they somehow did it without the use of a dedicated electric motor but instead of a reversing alternator which sounds to me like a dedicated motor generator by a different name?

    'i-ELOOP' features a new 12-25V variable voltage alternator, a low-resistance electric double layer capacitor and a DC/DC converter. 'i-ELOOP' starts to recover kinetic energy the moment the driver lifts off the accelerator pedal and the vehicle begins to decelerate. The variable voltage alternator generates electricity at up to 25V for maximum efficiency before sending it to the Electric Double Layer Capacitor (EDLC) for storage. The capacitor, which has been specially developed for use in a vehicle, can be fully charged in seconds. The DC/DC converter steps down the electricity from 25V to 12V before it is distributed directly to the vehicle's electrical components. The system also charges the vehicle battery as necessary. 'i-ELOOP' operates whenever the vehicle decelerates, reducing the need for the engine to burn extra fuel to generate electricity. As a result, in "stop-and-go" driving conditions, fuel economy improves by approximately 10 percent.

    There is no way to improve fuel economy by 10% through a 12-25V system but on the Japan Test cycles known to the world as magic pixie dust, maybe 10% is about right?

    The name 'i-ELOOP' is an adaptation of "Intelligent Energy Loop" and represents Mazda's intention to efficiently cycle energy in an intelligent way.

    'i-ELOOP' also works in conjunction with Mazda's unique 'i-stop' idling stop technology to extend the period that the engine can be shut off.

    Mazda is working to maximize the efficiency of internal combustion engine vehicles with its groundbreaking SKYACTIV TECHNOLOGY. By combining this with i-stop, i-ELOOP and other electric devices that enhance fuel economy by eliminating unnecessary fuel consumption, Mazda is striving to deliver vehicles with excellent environmental performance.

    SuperCap systems used for hybridization in R&D projects from the past found the Super Cap to be prohibitively expensive with the resultant payback smaller than what was hoped. Who knows, maybe Mazda has discovered the holy grail but when I hear of 12-25V systems returning a 10% increase in fuel efficiency, I will be just as skeptical as I am with SKYACTIV which so far has produced 7 more HP and the same highway fuel economy from the much hyped 2.0L in the new Mazda3 as the standard every day 2011/2012 Elantra with its MPFI 1.8L.

    We will have to wait and see…
  2. RedylC94

    RedylC94 Well-Known Member

    Your skepticism is justified. I doubt even powering the alternator with magic would improve fuel economy by 10% in normal circumstances in a non-hybrid car. It would be possible if we assume unusually heavy electrical demands, and a lot of time idling or moving very slowly.
    Last edited: Nov 25, 2011
  3. herm

    herm Well-Known Member

    Perhaps for the average non-hypermiler.. its a fancy smart alternator.. maybe they got a good deal on a super-capacitor. An advantage to that system is very high efficiency.

    They should have gone a step further and gotten rid of the starter also.
  4. herm

    herm Well-Known Member

    Has anyone done a proper study to find out what the real savings for regen braking are?.. you could do it with a fleet of Priuses, disable regen on half of them and see what you get with the average driver. Lots of heavy cars these days and lots of kinetic energy.
  5. phoebeisis

    phoebeisis Well-Known Member

    Just how much power does this capacitor hold-50 watt hrs or so?

    The Prius system allows Toyota to gear it really tall-since the electric motor can kick in to prevent lugging.So it improves FE is a less obvious way.
    Bet our 2006 averages just 1400 rpms at 60 mph-in 2006 the average 4 cyl probably turned 2400 rpms at 60 mph. The Prius would be lugging some of the time if not for the electric boost.
    Current small 4's-non hybrid-still don't rate as high EPA hy-Maybe it is because they don't dare gear as tall as the Prius
    Last edited: Nov 25, 2011
  6. Rokeby

    Rokeby Gen II Prianista

    Regen is meaningful in that it recovers kinetic energy that would otherwise be turned
    into waste heat. But it is a lossy system, due the energy conversions between wheel
    and battery.

    kinetic -> (wheels) -> mechanical -> (gen/alt) -> electrical -> (batt) -> chemical

    I've read that in the Prius the energy recovery efficiency is ~40%. A smart Prius driver
    minimizes the losses by using regen as little as possible by "driving without brakes',"
    traffic and topography permitting. If you're really trying to drive efficiently, regen is a
    measure of your mistakes in being caught going too fast in changing real world

    So, different drivers will see different amounts of regen and determing "real savings"
    would require removing the human factor somehow.

    Stopped in my Prius w/ScanGuage, I do notice a slow reduction in charge in the HV
    battery as it feeds the 12V bus via the DC-to-DC converter. So, Madza's regen system
    coupled with the i-Stop would provide an alternate energy source for the "housekeeping"
    electrical loads when stopped. I wonder though if the small gains are worth the necessary
    extra cost and complexity.

    I expect to see the old "What's the payback period?" question come up soon. :D

    All that said, Mazda is to be complemented in doing something to recover otherwise lost
    energy. I'd guess that driving in the "Zoom-zoom" style would generate a lot of regen,
    but very little energy recovered relative to the amount of fuel that propelled the zooming
    in the first place.

    Last edited: Nov 25, 2011
  7. lightfoot

    lightfoot Reformed speeder

    Great point. The Prius normally uses the electric motor to get going from a dead stop (assuming the ICE is warmed up). I hadn't thought about the savings from higher gearing, but starting on electric also avoids gas-wasting high throttle/low rpm usage of the ICE.

    I'm not a big fan of regen. As rokeby says, braking of any kind, regen or not, is often a sign of inefficient driving: you've wasted energy to get more momentum than you need.

    Another problem with regen is that most often it's a high current/short time event. For example, braking to a stop sign or red light: 10-20 seconds of regen?? Batteries recapture charge better from longer, lower current events. The SOC in either of my cars rarely budges after a typical stop like this. Maybe a capacitor captures energy from these events better than a battery does.

    What DOES show on the SOC is regen during long descents and gradual decels on long freeway offramps, but these opportunities are less frequent.

    I sometimes think that the main advantage of regen is that it reduces wear on the friction brakes so less money spent on brake jobs!!

    Mazda's iStop autostop technology seems really great. Apparently they haven't used it more because of the demands on the battery during autostop, and this cap storage is a missing piece of the puzzle.
    Last edited: Nov 25, 2011
  8. Conrad

    Conrad Member

    Ok, guys. Step down from your hypermile horse for a moment: brakes are there for a reason. You will need to use them, and likely more in the future as traffic density increases. There's not a way for our road system support 380 million hypermilers unless we leave the driving to computers, otherwise you'll have to always maintain 10x extra spacing for the one person out there that doesn't...

    As for the technology, one of the more inefficient pieces of regen braking is the charge loss to the battery. Charging to a capacitor is far more efficient, although not as efficient as directly spinning a mechanical flywheel. In any event, Mazda will be able to get more that the 40% recovery number of the Prius's.

    Where Mazda's mild hybrid will still lose out is the lack of a good EV only mode, but this will be as effective as Honda's IMA. At the end of the day, that's all it's about, is using less energy to support the inefficiencies of having a human driver that doesn't want to be efficient.
  9. ItsNotAboutTheMoney

    ItsNotAboutTheMoney Super Moderator Staff Member

    I think lightfoot has the key in mentioning i-stop. i-stop works with piston positioning instead of using an auxiliary battery. So, in addition to the gains by use of a smart alternator, and, I presume, higher efficiency in the charge and discharge process, many of the gains with i-eloop may simply be making up for deficiencies in i-stop.

    The cost of the capacitors is obviously a key issue. However, just as the Prius' HSD saves by displacing multiple conventional parts, i-stop plus i-eloop displaces the auxiliary start/stop battery, and should reduce the draw from the main 12V battery and extends its life. Then, an extremely durable capacitor would have value at end of vehicle life. However, if large capacitor is heavy if could negatively affecting fuel economy. To become a dominant system the capacitor has to be durable and cheap enough to beat the displaced battery-based systems. But for Mazda's purpose, it just has to be cheap and durable enough to be able to make a profit on it: it does have a coolness factor on its side. I hope it at least indicates some price drops in large capacitors.
  10. lightfoot

    lightfoot Reformed speeder

    Umm, this IS the hypermiling site, so why shouldn't we be on that horse??

    Other thoughts:
    - I think all hypermilers DO use brakes, we just try to drive so that we are not forced to use them, which also happens to be a big part of safe defensive driving.
    - Population of the USA is about 310 million, not all are drivers. About 190 million licensed drivers in 2000.
    - I'm baffled why hypermiling would put a strain on the road system. Surely lower speeds would allow increased traffic density??
    - Between 30,000 and 40,000 people die in traffic accidents on US highways every year, even larger numbers of serious injuries, so what we're doing now isn't working very well. Maybe it's time to change things??

    Using technology to support unsafe driving by people that don't want to change to safer driving behaviors hasn't worked, so why believe that technology will work any better to make them more efficient? The number of people that manage to get a Prius down to 40mpg is a good hint. Humans are remarkably good at circumventing technology.

    It would make more sense to put effort into improved driver training and testing*, retesting for relicensing, traffic enforcement, etc. Changing driving behavior can improve both safety and fuel efficiency at the same time. And lower speeds could enable engineers to design cars so that they are just as crash-worthy at the lower speeds as current cars are at high speeds, only much lighter/smaller, which would improve fuel economy.

    So I'm stayin' on that horse, thanks!

    * - Given the current political climate, it's unlikely that government would do this, but maybe insurance companies would. In the motorcycle arena, insurance companies more or less force you to take motorcycle safety training before they will insure you, and those courses are supported by the manufacturers and are very good.

    I'll leave it there, this is way way OT, apologies!!
    Last edited: Nov 25, 2011
  11. phoebeisis

    phoebeisis Well-Known Member

    Sure regen-mech>elec> battery chemical> electrical>mech -with lots of little changes in between is inefficient- I'm surprised it is anything like 40%

    But for some reason the PRIUS (2006 1.5) gets 50 mpg at 63mph by just setting the cc.
    The current crop of 4 cyl-non hybrids-probably can't do that(maybe the Cruze can with the MT- but not with the AT).I wonder what RPMs the bigger 1.8 turns-on average- at hy speeds?
    The Prius system is at its worst in hy driving, but it is still better than the rest at its worst. It is probably more clever- allowing taller gearing-than you give it credit for)
  12. Chuck

    Chuck just the messenger

    If I didn't know any better, I'd say you were an upset gearhead still clueless on what hypermiling is all about.

    How can a country of about 313 million have 380 hypermilers on the road?

    Who is saying never to use brakes?

    After you calm down why don't you read more on hypermiling with an open mind?
  13. ItsNotAboutTheMoney

    ItsNotAboutTheMoney Super Moderator Staff Member

    This (i-eloop + i-stop) isn't even a mild hybrid system since there's no electric motor. It's a combination of a more efficient auxiliary power supply system and an engine control system that enables the engine to be turned off. It's actually an alternative to hybridization.

    Mazda's system will help with no-gas driving (in the city or steep highway downgrades) but it's certainly not IMA and won't be as efficient: IMA allows for engine downsizing and cycle modification.

    But it will definitely be good to see the system in use because it will shift some money from conventional car batteries to ultra-capacitors.
  14. wick1ert

    wick1ert Well-Known Member

    Interesting timing re the retesting for relicensing. I just renewed my license this week to a federally compliant one (why not, didn't cost me anything extra), and the only requirement for doing it was reading a line of letters on a eye chart. Well, that and paying the fee to renew. The license is good for 5 years in DE, and I'm sure there have been changes to the laws in that 5 years. What those changes are/were, I couldn't tell you.

    I'm guessing they'll be covered in the defensive driving course I'll be due to renew in a year or two.
  15. Conrad

    Conrad Member

    You're right that there's no electric motor, so it's not really a hybrid. However, I still believe it will be competitive. The electric/battery power in a non-plugin hybrid is all generated at one point from the gas engine+alternator.

    Not taking to account engine technology (direct injection and atkinson cycle which Mazda's Skyactive engine does btw), while the IMA gets the advantage of "allowing" a smaller displacement, it suffers from significantly extra weight for the electric motor and battery. At equal power/weight ratio, I'm not sure that a 1.5L engine, vs a likely same 1.5L engine with IMA gets significantly better running FE. (Eg. compare the Honda Fit to the CR-Z)

    Mazda recaptures regenerative brake energy more efficiently and powers electrics, which is more efficient than converting it back to mechnical energy (elec motor), and then having to run an inefficient alternator more to recharge. As you point out, there will probably be times where an IMA system can engine cut-off more while the car is in motion, but I think this more or less balances itself out in city operation. It will lose out in crawl traffic operation though, and no difference in highway.
  16. Conrad

    Conrad Member

    Didn't mean to offend, just responding to this comment: "As rokeby says, braking of any kind, regen or not, is often a sign of inefficient driving: you've wasted energy to get more momentum than you need."

    Using that logic, we should remove seat belts and airbags has we try not to get into accidents... No, the point is that while an inefficient driver would only get 40mpg in a prius, he would get far less in an SUV. If we're all about saving fuel/energy, why would we not want to support a technology that makes the vechicle/system more efficient?

    I have generally high regards for Wayne Gerdes and the cleanmpg community. In many ways, Wayne is like a Lewis Hamilton, but instead of trying to take a route as fast as possible, he does so as efficiently as possible. It that regards, Wayne is an artist of his trade, and I deeply appreciate the beauty of that for what it is.

    That said, the best part about what Wayne is he always puts hypermiling with a positive message, showing by example. Hypermiling is not extreme, having only 500cc engines in cars, or not having human drivers or cars altogether are more extreme.

    We're human, we choose to be inefficient and in lots of ways other than just driving. How about living in houses too big, or taking longer than "navy" showers, excessive garbage, multiple tvs, computers and electronics? In becoming more efficient, it's both consumer education and technology, and I support both.
  17. phoebeisis

    phoebeisis Well-Known Member

    And WG manages to make folks with vehicles that are out and out guzzlers(1/2 tons of various types,and mid sized SUVs) feel comfortable.
    This is important because as you guys imply-changing habits can improve FE and save Huge amounts of fuel.
    AND SAVE $$$
    With the poor economy most folks are stuck with whatever they have-
  18. ItsNotAboutTheMoney

    ItsNotAboutTheMoney Super Moderator Staff Member

    As far as I can tell, ultracapacitors are actually quite heavy. It's their efficiency and charge/discharge characteristics that provide the benefits. If you have any more information on it, I'd appreciate it.

    IMA's ability to allow the engine to be downsized, cannot be ignored. The smaller engine helps reduce weight and decreases fuel consumption. You really shouldn't compare the Fit to CR-Z. The CR-Z has an oversized 1.5L engine for performance reasons. A better comparison is the Insight-II, which has a 1.3L engine. Similarly, the Civic Hybrid has a 1.5L engine while the conventional Civic has a 1.8L engine. Note that the downsizing is possible despite the extra weight of the IMA system.

    Besides, IMA's bad city rap is really just in comparison to power-split hybrids. The city ratings are CR-Z 35 mpg , Insight 41 mpg, Civic 44 mpg. (Note that Honda hybrid real-world performance compares well to EPA ratings.) Conventionally-sized, conventional gasoline ICEVs don't come close.

    Mazda's system will certainly help city mileage but it cannot beat hybridization for efficiency, simply because it cannot make a difference to inefficiency in the largest use of energy: the system helps with stop, but not with the start.

    At least, it can't make a difference for now. Perhaps this investment will lead to cheaper, lighter capacitors that can be used in hybrid and electric cars.
  19. Rokeby

    Rokeby Gen II Prianista

    Well, in an effort to keep things from appearing to be confrontational, when in fact I don't
    believe they are, I am prepared to believe that you and we -- others at CleanMPG -- have
    a different understanding of the term "driving without brakes." For us it is not a safety
    related issue, we have brakes, but when driving we try to look ahead and arrange things
    so that using our brakes is minimized.

    Similarly, you could say that all good -- read, safe -- drivers drive as if they don't have
    seat belts and air bags. They have the equipment, but they drive so that their deployment
    isn't about to happen moment to moment.

    "Driving without brakes" is a basic strategy that virtually anyone who is interested in
    driving efficiently discovers on their own, or otherwise employs early in their FE quest.
    It is not a some radical, wild-eyed, here-comes-the-apocalyptse, devil-may-care stunt.

    There are quite a few threads here that discuss it. "The search tool is your friend."

    Even Wiki presents it in a low-key, not a hazard to safety/society-as-we-know-it way:

    ...Generally, fuel economy is maximized when acceleration and braking are minimized.
    So a fuel-efficient strategy is to anticipate what is happening ahead, and drive in such a
    way so as to minimize acceleration and braking, and maximize coasting time.

    The need to brake in a given situation is in some cases based on unpredictable events
    which require the driver to slow or stop the vehicle at a fixed distance ahead. Traveling at
    higher speeds results in less time available to let up on the accelerator and coast. Also the
    kinetic energy is higher, so more energy is lost in braking. At medium speeds, the driver
    has more freedom and can elect to accelerate, coast or decelerate depending on whichever
    is expected to maximize overall fuel economy. Traveling at posted speeds allows for best
    civil planning and should allow drivers to best take advantage of traffic signal timing.

    While approaching a red signal, drivers may choose to "time a traffic light" by easing off
    the throttle, or braking early if necessary, far before the signal. For example, a driver who
    is approaching a red light should adjust vehicle speed in advance, such that the vehicle
    arrives at the intersection when the light is green. It is also important to account for the
    time it takes for the stopped traffic at the light to start moving again. In theory, the ideal
    situation is the driver slowing immediately to the calculated speed that allows the car to be
    barely behind the car in front as that vehicle is accelerating from the light. If the driver
    does this the instant the red light is recognized, this will result in the vehicle having
    maximum speed, and kinetic energy, as it reaches the intersection. This means that energy
    lost to braking is as little as possible.

    Fuel_economy-maximizing_behaviors; Acceleration_and_deceleration

    Be careful out there, it is the CleanMPG preferred way of driving. :woot:
  20. Conrad

    Conrad Member

    It's about power/weight vs fe. We could stick a 250cc engine in a car and get way better fuel economy, problem is that only hypermilers would drive it. The Insight only has 98hp, and in fact the CR-Z has a lower power/weight ratio that the 1.5L Fit... come on. Don't you think that if you stick Ford's 1.0L 3-cylinder which should get around 100hp in an Insight body that you'll get pretty much the same FE if not better and likely better overall performance due to the reduced weight and smaller engine displacement?

    To compare: the 1.3L Fit in Japan vs the 1.3L Fit Hybrid gets 20.6km/L vs 26.0km/L on the JC08 cycle, about 25% difference. That 25% difference is likely due to three things: engine idle at stop, regenerative braking, and engine stop "at speed". How much of this do you think Mazda can claim back with their engine stop and regenerative brake system?

    Electric assist is poor in the sense that you're using the gas engine to turn the alternator to charge a lead-acid battery inefficiently only to dump it back to an electric motor back to mechanical. The Prius in large part gets better fuel economy numbers because US fuel economy tests are allowed with a fully charged battery, and that the Prius's battery is large enough that it doesn't have to recharge itself as much as Honda's smaller IMA batteries during the test. Wayne's steady state FE numbers are way better on the Insight II because of the smaller displacement engine. Look at the FE for a Volt when it's running the gas engine to run the electric motor... and look at the real world FE numbers of the Insight II vs Prius...

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