Mazda's daft fuel saving idea.

**Mazda have announced that next years' cars will be fitted with a capacitor, which is charged by the alternator and, in turn, will operate the car's electrical system for a period (the alternator will be turned off). Assuming a 10 Farad capacitor, I figure that equates to around 3,000 Watt/seconds of power. Plenty to run a car stereo for a few minutes, but, to put it into motive terms, about enough to run the car for about 20 Metres.

Unless the capacitor is very much larger than I assume it is.

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Trevor Wilson www.rageaudio.com.au
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Trevor Wilson
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There are storage systems that have proven to work, such as the KERS system in formula one cars:

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This regenerates the breaking energy back into real forward motion energy.

I am just wondering if Mazda have used the term capacitor, a little loosely in this case.

Don...

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Don McKenzie 

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Don McKenzie

Found it:

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Regenerative breaking system to a capacitor:

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some capacitor. I wonder what the specs are?

Don...

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Don McKenzie

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**Even being extremely generous and assuming Mazda are using a 100 Farad cap, the final result would hardly be worthwhile.
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Trevor Wilson www.rageaudio.com.au
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Trevor Wilson

Perhaps it's a Flux Capacitor.

With the world ending tomorrow, it won't be worth while. :-)

Don...

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Don McKenzie

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Perhaps it won't store sufficient energy to "drive off from the lights", but if it could simply store enough to smooth out the on/off cycling of the accelerator pedal in traffic it may be worth while.

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Dennis

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the final result would hardly be worthwhile.

Mazda aren't using the capacitor to drive the car forward, as in an electric vehicle, they are recovering some otherwise wasted energy from braking and using it to power the auxiliary electrical loads and recharge the main battery. The energy saved would have to have been provided by the alternator, which Mazda can then apparently unload, further reducing losses. They claim benefits in stop-start driving, which makes sense as most real-world driving in cities is like that. I would like to see some comparative test results before declaring it worthwhile or not though.

Reply to
yaputya

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the final result would hardly be worthwhile.

vehicle,

real-world

results

**All we need to know is the size of the cap used, in order to determine it's usefulness. I have heard an unconfirmed report that the cap is rated at 1,200 Farad. If the cap is as large as one source claims, then, suddenly, the system appears viable.
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Trevor Wilson www.rageaudio.com.au
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Trevor Wilson

Apparently Maxwells have them:

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linked story here:

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Don...

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Don McKenzie

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cap, the final result would hardly be worthwhile.

vehicle,

energy

real-world

results

usefulness. I have heard an unconfirmed report that

then, suddenly, the system appears viable.

After thinking about this a bit more, I guess we could do some basic calculations (ball park) to see whether this stop-start capacitor-storage concept is valid. (It must be valid or there wouldn't be so much money going into it, eh? It ain't like Joh Bjelke Petersen's water-powered car, surely!!!)

Feel free to correct me if you see a flaw...remember these are ball park calcs. A reasonable requirement of a stop-start system would be to store the energy in making a single stop in traffic conditions. Let's say a 1000kg car being stopped from about 50km/h or 14m/s. The cars kinetic energy is half m v-squared which works out at about 200,000 Joules. (m is mass, v is velocity) (The rate of deceleration determines the maximum charging current rating of the capacitor required to capture all of it.

A capacitor's energy storage is half C V-squared (C is capacitance in Farads, V is voltage). According to the Mazda website their capacitor has a rating of 25V. So in order to store 200,000 Joules at 25V the capacitor needs to be at least 640 Farad. Using the data from

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it seems a 1,200F parallel array of 10 K2-BCAP cells would have rating of 27V and an ESR of around 5milliohm. Using ball park calculations this would mean an initial charging current from 25V of 70A and time constant of 6 seconds, which seems reasonable for braking from 50km/h in normal city driving. The K2-BCAP caps can easily handle this current and if fully charged to 25V would store 375,000 Joules. I leave detailed calculations as an exercise for the student......

Reply to
yaputya

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cap, the final result would hardly be worthwhile.

vehicle,

to

energy

real-world

results

usefulness. I have heard an unconfirmed report that

then, suddenly, the system appears viable.

calculations

ain't

calcs.

in

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V is voltage).

Farad.

and

which

There is a mistake in the above, a simple SERIES array of 10 1200F K2-BCAP cells required to achieve the 25V voltage rating would only have a tenth of the capacity of each cell, i.e. 120F instead of 1,200F. However there are other modules which come closer to what is required for a viable system.

Reply to
yaputya

. . .

You keep taking a guess at the capacitance. What about the voltage rating? That is just as important - or more important since the energy stored is proportional to the square of the voltage.

Andy Wood snipped-for-privacy@trap.ozemail.com.au

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Andy Wood

**I already know the Voltage rating and operating Voltage of the system. Sorry I neglected to add that earlier. It is 25 Volts. I have been informed that the capacitor is rated at 1,200 Farad. If true, then the system should accomplish what it is supposed to do. At around 375,000 Joules of energy storage, there should be sufficient recovered braking energy to make a worthwhile improvement to the system.

My mistake was assuming that energy storages in the order of 1,000 Farad (@ 25 Volts) were economically viable, in a small enough package. Apparently they are.

I still have my concerns about stop-start technology, but time will tell if it is viable in the market-place.

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Trevor Wilson www.rageaudio.com.au
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Trevor Wilson

What is their method for doing that?

Reply to
terryc

From

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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 examined automobile accelerating and decelerating mechanisms, and developed a highly efficient regenerative braking system that rapidly recovers a large amount of electricity every time the vehicle decelerates. Unlike hybrids, Mazda's system also avoids the need for a dedicated electric motor and battery. 'i-ELOOP' features a new 12-25V variable voltage alternator, a low-resistance electric double layer capacitor and a DC/DC converter.

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yaputya

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