Mazda's daft fuel saving idea.

[Trevor Wilson]

**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.

 

[Don McKenzie]

**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.

There are storage systems that have proven to work, such as the KERS
system in formula one cars:
http://www.formula1.com/inside_f1/understanding_the_sport/8763.html

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...


--
Don McKenzie

$30 for an Olinuxino Linux PC:
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The World's Cheapest Computer:
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Add VGA Monitor/TV, and PS2 Keyboard, or use USB Terminal
Arduino Shield, Programmed in Basic, or C.

 

[Don McKenzie]

There are storage systems that have proven to work, such as the KERS
system in formula one cars:
http://www.formula1.com/inside_f1/understanding_the_sport/8763.html

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...

Found it:
http://www.mazda.com/publicity/release/2011/201111/111125a.html

Regenerative breaking system to a capacitor:
http://www.caradvice.com.au/wp-content/uploads/2012/09/Mazda-i-ELOOP1-625x338.jpg

some capacitor. I wonder what the specs are?

Don...


--
Don McKenzie

$30 for an Olinuxino Linux PC:
http://www.dontronics-shop.com/olinuxino.html

The World's Cheapest Computer:
DuinoMite the PIC32 $25 Basic Computer-MicroController
http://www.dontronics-shop.com/the-maximite-computer.html
Add VGA Monitor/TV, and PS2 Keyboard, or use USB Terminal
Arduino Shield, Programmed in Basic, or C.

 

[Trevor Wilson]

Found it:
http://www.mazda.com/publicity/release/2011/201111/111125a.html

Regenerative breaking system to a capacitor:
http://www.caradvice.com.au/wp-content/uploads/2012/09/Mazda-i-ELOOP1-625x338.jpg


some capacitor. I wonder what the specs are?

Don...

**Even being extremely generous and assuming Mazda are using a 100 Farad
cap, the final result would hardly be worthwhile.

 

[Don McKenzie]

On 12/20/2012 10:44 AM, Don McKenzie wrote:

**Even being extremely generous and assuming Mazda are using a 100 Farad
cap, the final result would hardly be worthwhile.

Perhaps it's a Flux Capacitor.

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

Don...


--
Don McKenzie

$30 for an Olinuxino Linux PC:
http://www.dontronics-shop.com/olinuxino.html

The World's Cheapest Computer:
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http://www.dontronics-shop.com/the-maximite-computer.html
Add VGA Monitor/TV, and PS2 Keyboard, or use USB Terminal
Arduino Shield, Programmed in Basic, or C.

 

[yaputya]

**Even being extremely generous and assuming Mazda are using a 100 Farad cap, 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.

 

[Trevor Wilson]

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.

**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.

 

[Don McKenzie]

**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.

Apparently Maxwells have them:
http://www.tecategroup.com/ultracapacitors-supercapacitors/maxwell.php

linked story here:
http://seekingalpha.com/article/608361-stop-start-realities-and-ev-fantasies

Don...



--
Don McKenzie

$30 for an Olinuxino Linux PC:
http://www.dontronics-shop.com/olinuxino.html

The World's Cheapest Computer:
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http://www.dontronics-shop.com/the-maximite-computer.html
Add VGA Monitor/TV, and PS2 Keyboard, or use USB Terminal
Arduino Shield, Programmed in Basic, or C.

 

[yaputya]

**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.

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
http://www.tecategroup.com/ultracapacitors-supercapacitors/maxwell.php
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......

 

[yaputya]

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
http://www.tecategroup.com/ultracapacitors-supercapacitors/maxwell.php
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......

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.

 

[Trevor Wilson]

. . .

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
[email protected]

**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.

 

[terryc]

they are recovering some otherwise wasted energy from braking

What is their method for doing that?

 

[yaputya]

What is their method for doing that?

From http://www.mazda.com/publicity/release/2011/201111/111125a.html

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.