Mazda i-ELOOP capacitor-based regenerative braking system - The Technical Forum Archive (2025)

primer

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Mazda reveals i-ELOOP capacitor-based regenerative braking system

Excerpts:

Mazda's regenerative braking system is unique because it uses a capacitor, which is an electrical component 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' 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.

IMO this is the ideal hybrid system. I wish more manufacturers use this tech, Mazda are unfortunately not big enough to matter.

Grumbles

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Magoo

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IMO this is the ideal hybrid system. I wish more manufacturers use this tech, Mazda are unfortunately not big enough to matter.

It is pretty neat, with the limitation that it can only operate accessories, charge the traditional battery, and so on.

I remember forecasting here and elsewhere some years ago that one day all cars would have systems and characteristics previously identified as "hybrid," a prediction that was regarded as a bit nutty at the time.

Fat Boy

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I remember forecasting here and elsewhere some years ago that one day all cars would have systems and characteristics previously identified as "hybrid," a prediction that was regarded as a bit nutty at the time.

You only joined in Oct. 2010. How many years ago could it have been?

jcbc3

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You only joined in Oct. 2010. How many years ago could it have been?

http://forums.autosp...l=magoo mcguire

Magoo

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You only joined in Oct. 2010. How many years ago could it have been?

It was UNDER a previous SCREEN NAME.

Tony Matthews

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desmo

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Catalina Park

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Greg Locock

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cheapracer

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primer

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Well most bike guys know capacitors have been replacing batteries since the 60's at least and Norton had a large capacitor along with a small battery standard.

cheapracer

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I wasn't having a go at Mazda's system just pointing out that capacitors as a temp storage in a vehicle's electrical system are not a new thing in itself..

http://www.google.co...1957l1.7.4l12l0

Edited by cheapracer, 29 November 2011 - 13:36.

mariner

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I seem to recall that BMW did a " hybrid" X5 with rear motors and a very big capacitors.

It had some serious 0 to 60 times , not so sure on the energy benefits though!

Greg Locock

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Almost all battery types appeciate being treated as gently as possible, whereas caps are very good at high currents. So since the year dot mobile phone batterys have had caps alongside their batteries, so that the peak currents can be delivered by the cap not the battery.

Oddly, lead acids will take and deliver almost any current you can think of (it does damage them if sustained)... but they have a very poor Peukert number, which is to say they have much greater capacity if you restrict the current.

Modern battery chemistruies have a coulombic efficincy (amp hours out/amp hours in) of almost 100% whereas traditional lead acid is around 70%. SO with lead acids it is greatly advantageous not to be shunting energy in and out of them.

gruntguru

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primer

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The 10% mileage improvement sounds optimistic. What they are saying is more than 10% of energy (city cycle) goes into electrical accessories.

Good observation. The Mazda prototype must have a serious sound system to make those numbers possible, heheh.

rory57

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The weight/size/cost of a capacitor is pretty much dependent (for any given capacitor structure) on it's Capacitance multiplied by it's Voltage maximum.
However the energy stored within a capacitor is given by 1/2 it's Capacitance x the stored voltage squared.
Thus to store a useful amount of energy from deceleration any such system should use a much higher voltage than the 25v featured by this Mazda system.
The 5 Farad / 25V Super-capacitor from NEC stores a maximum of 1562 Joules of energy in an 895cc volume (they don't quote a weight).
For comparison that is the same quantity of energy as is possessed by 1000Kg moving at 1.8 metres/second.
Similarly 895cc of petrol holds about 31 000 000 Joules of energy.
If you are really serious about using the kinetic energy of the moving vehicle, coast! In urban or rural driving it is practical to be in neutral for a surprisingly large part of many journeys.
I would like to see a serious comparison of the real-world fuel consumption benefits of a transmission freewheel with these complex regenerative systems.

www.cantecsystems.com/ccrdocs/brief-history-of-supercapacitors.pdf

www.nec-tokin.com/english/product/supercapacitor/application02.html

desmo

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Tony Matthews

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I think you can get a fair tell on any driver's IQ by watching their brakelights; the more they flash on, the lower the IQ- and doubly so on the highway.

That's about right. I don't coast because you are not in full control of the vehicle and - it's illegal in the UK.

gruntguru

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The only loss of control is a slight delay in re-application of power if required. A manual trans in neutral is not much different to "throttle off" down to lowish speeds in top gear. In both cases you need to select a low gear to get useful acceleration.

The lack of engine braking in neutral is no different to power-off in an auto where the trans will select the highest gear and the torque converter will unlock -> no engine braking.

Tony Matthews

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The only loss of control is a slight delay in re-application of power if required. A manual trans in neutral is not much different to "throttle off" down to lowish speeds in top gear. In both cases you need to select a low gear to get useful acceleration.

The lack of engine braking in neutral is no different to power-off in an auto where the trans will select the highest gear and the torque converter will unlock -> no engine braking.

I didn't say you have no control, just not full control, which 'a slight delay in re-application of power' constitutes, and even that pre-supposes the instant engagement of the relevant gear every time it's needed. I was only refering to manual transmission, as even now there aren't that many auto boxes on British roads. The fact that coasting is (or certainly was) illegal must mean something, although the illegality of any action doesn't mean I will automatically refrain from doing it!

Edited to add this from the on-line edition of The Highway Code.

122

Coasting. This term describes a vehicle travelling in neutral or with the clutch pressed down. It can reduce driver control because
•engine braking is eliminated
•vehicle speed downhill will increase quickly
•increased use of the footbrake can reduce its effectiveness
•steering response will be affected, particularly on bends and corners
•it may be more difficult to select the appropriate gear when needed

Edited by Tony Matthews, 05 December 2011 - 01:06.

gruntguru

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Very interesting. That looks suspiciously ancient in both its wording and the technology of the vehicles it refers to. Brakes? Coasting is certainly no more taxing on brakes than auto trans.

bigleagueslider

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I do a lot of coasting in urban driving. And I mean a lot. It doesn't take a lot of downhill slope to maintain speed at 50 or under km/h. If I see anything likely to force me to reduce speed ahead- into neutral. I also like coasting to a stop on uphills so that if I've judged it right I only apply the brakes to keep the car from rolling backward. I think you can get a fair tell on any driver's IQ by watching their brakelights; the more they flash on, the lower the IQ- and doubly so on the highway.

F1 drivers both (left foot) brake and apply full throttle at the same time when cornering. The car's electronic throttle control makes this possible. Keeping the throttle floored while braking allows the best throttle response exiting a corner.

Of course F1 cars don't have brake lights to measure the driver's IQ from.

Catalina Park

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Very interesting. That looks suspiciously ancient in both its wording and the technology of the vehicles it refers to. Brakes? Coasting is certainly no more taxing on brakes than auto trans.

It almost looks like it was written for 1950s truck drivers.

Tony Matthews

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Keeping the throttle floored while braking allows the best throttle response exiting a corner.

Except that that is not the reason for doing it...

DrProzac

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Costing? I prefer proper engine braking.

The 10% mileage improvement sounds optimistic. What they are saying is more than 10% of energy (city cycle) goes into electrical accessories.

Maybe it's also about allowing a stop-and-go system (iStop in Mazda?) to stop the engine more often.

Tom17

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I wonder how the fuel savings compare between coasting in neutral (where the engine is still using fuel) and slowing down with engine braking on a modern car where it shuts off the injectors on over-run (they do this now, right? Or am I mistaken?).

You won't spend as long slowing down with the latter method, but you do spend that slowing down time without using any fuel...

Tom17

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I broke this thread so it's been forgotten about. I am kinda curious though if anyone here has any insight on my previous post.

Tom...

rory57

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I broke this thread so it's been forgotten about. I am kinda curious though if anyone here has any insight on my previous post.

Tom...

I don't think idling engines use much fuel.
Engine braking with closed throttle is quite strong compared with deceleration when coasting so most times we feather the throttle so the fuel cut-off is not activated.
(Have modern engines dropped over-run cut-off because they have to keep the fire burning even on the overrun, in order to keep the catalyst hot?)
When coasting the kinetic energy of the car's mass is spent on rolling and aerodynamic friction, when in gear it is also spent on engine friction and pumping work against the closed throttle.
I would like to try a combination of transmission freewheel and automatic engine stop/start. I feel it would compete well against electric hybrid as described above by Mazda and at much less cost.

Greg Locock

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my fiesta uses about 0.7-0.9 litres an hour when idling, which is, I was about to say,not much. But overall it averages 6.5 litres/100km, at an average speed of 48 kph, so when it is actually being used it is only using 3.2 litres per hour. That's interesting, hadn't really thought of it that way before.

Dunno about overrun cutoff, I'll look at the instantaneous mpg when I'm going downhill today.

Lee Nicolle

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Coasting is dumb,, and dangerous. And have an accident the law may charge you and your insurance may not pay you. And the amount of fuel saved is very minimal anyway.If really any.

And coasting up to the lights is stupid, that is what causes traffic disruption, and road rage. Accelarate briskly [not heavily] from the lights and brake moderatly to them. That way a lot more traffic goes through the lights causing far more fuel to be saved by everyone. The clowns coasting and driving like geriatric grandmas are the ones that jam up traffic no end.

Oh and auto trans do give engine braking, not quite as much as a manual but still quite a lot. And when you select a lower gear it is basically the same as a manual. I do it when towing all the time because if you do not you end up with no brakes!

Greg Locock

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downhill, no throttle, fifth gear at 60 kph the instantaneous fuel consumption was 1.8 l/100km. I couldn't tell if this was as low as it would display, or a genuine figure. If it is genuine then it is about the same as the idle fuel consumption, so there is no advantage in coasting. OK, that is a very broad brush argument.

Tony Matthews

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Coasting is dumb,, and dangerous. And have an accident the law may charge you and your insurance may not pay you. And the amount of fuel saved is very minimal anyway.If really any.

And coasting up to the lights is stupid, that is what causes traffic disruption, and road rage. Accelarate briskly [not heavily] from the lights and brake moderatly to them. That way a lot more traffic goes through the lights causing far more fuel to be saved by everyone. The clowns coasting and driving like geriatric grandmas are the ones that jam up traffic no end.

Exactly, Lee.