# Why can't our ICE cousins use regen?



## sj281708 (Apr 29, 2014)

Almost 60 percent of the car's energy is lost to non-driving activities...so why can't a gas driven car use regenerative braking? I know, I know, the ICE doesn't use an electric drivetrain, and it would not be able to redirect the lost energy back to the wheels, but can't it take the place of an alternator?

I've heard that regen can be achieved in gas vehicles by adding a clutch to the alternator; which engages when the vehicle is coasting or braking causing the alternator to help slow the engine as it charges the 12v battery under the hood. Presently, cars charge using the engines rotation via a belt to the alternator, right? Can't regen power (at least to a degree) the radio, headlights, power windows etc.?

Just wanting to know what you guys thought.  Thanks, guys.


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## Karter2 (Nov 17, 2011)

sj281708 said:


> Almost 60 percent of the car's energy is lost to non-driving activities...so why can't a gas driven car use regenerative braking? I know, I know, the ICE doesn't use an electric drivetrain, and it would not be able to redirect the lost energy back to the wheels, but can't it take the place of an alternator?
> 
> Just wanting to know what you guys thought.  Thanks, guys.


 Check out the new Mazda 6 specs !
http://www.mazda.com/technology/env/i-eloop/

But it isnt simple or easy !


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## sj281708 (Apr 29, 2014)

Karter2 said:


> Check out the new Mazda 6 specs !
> http://www.mazda.com/technology/env/i-eloop/
> 
> But it isnt simple or easy !


Can this be done in a DIY retrofitted way? I.e without changing the alternator?  Thanks!


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## Caps18 (Jun 8, 2008)

Isn't this what the Prius and other hybrids do?


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## sj281708 (Apr 29, 2014)

Caps18 said:


> Isn't this what the Prius and other hybrids do?


Yes, but I'm wondering if non-hybrids/non-EVs can do it, as in cars with no ECM or electric drivetrain, just good old gas engine spinning wheels...


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## Karter2 (Nov 17, 2011)

To get any significant amount of retardation from regen you need some serious, high power, "retarders" .
Either a very beefy alternator as the Mazda, or some other electro mechanical converter.
In order to cope with many kW of braking energy, you either have to generate very high current , or high voltage.....
..... Most likely both if you are in the 50-100kW zone.
Not many "normal" alternators will do that, nor batterys adsorb that much charge quickly ....which is why the Mazda has very different Alternator and energy storage (Ultra-caps) to soak up the energy spikes and then slowly recharge the battery/power the alternator via a complex voltage converter system.
Like i said..it isnt simple or easy. !


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## Duncan (Dec 8, 2008)

_Almost 60 percent of the car's energy is lost to non-driving activities...so why can't a gas driven car use regenerative braking?_

About 70% is lost as heat 
but you can't get that back

about 10% (depending on how and where you drive) can be reclaimed by re-generative braking 

So the "reward" is not that big 
Which is why hybrids took so long to be developed/used 

the lowest hanging fruit is the idle eliminator
if you drive a lot in traffic these cars simply shut the engine off when you idle and use an oversized starter to get going when you press the go pedal


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## sergiu tofanel (Jan 13, 2014)

This is not just for F1 cars any more. It's a very compact system and usable with today's car technology. My understanding is that KERS can also be purely mechanical, with no electrical components whatsoever:

http://www.youtube.com/watch?v=3UA7t8c5I6s


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## dcb (Dec 5, 2009)

No, there is electrical bits, motor generators/etc, even more now that F1 dropped KERS and went to ERS
http://www.sportskeeda.com/f1/kinetic-energy-recovery-system-formula1/?ref=sportspage-recent-8

Plus they have a budget that consumers don't (and shouldn't)


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## Karter2 (Nov 17, 2011)

sergiu tofanel said:


> My understanding is that KERS can also be purely mechanical, with no electrical components whatsoever:
> 
> http://www.youtube.com/watch?v=3UA7t8c5I6s


 Your Youtube link was not very useful, but i asume you were thinking of the "Flybus" system using a high speed flywheel to adsorb and return kinetic energy.

Yes its works ..but it isnt simple , easy, or cheap !
..and best suited to heavy vehicles that do a lot of stop/start journeys..garbage trucks, buses, delivery vans etc


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## arklan (Dec 10, 2012)

leave the alternator mechanically connected
have a brake light switch in the accellerator pedal that connects and disconnects the alternator.

when u r driving the alternator will just free wheel, when u take ur foot off the accelerator pedal the alternator comes on.


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## steelneck (Apr 19, 2013)

In the early nineteens there where some experiments here in Sweden with buses that used a large compressor for braking and stored the energy as compressed air in large air tanks. Then had some kind of turbine to claim back that energy when accelerating. It worked and those buses was in traffic for a while, but i do not think it was efficient and i have never seen experiments like that since then. I remember they had a very special sound coming to stop and starting.

Also, the heavier a vehicle is, the more there is to be gained by generative braking compared to a small car.


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## dcb (Dec 5, 2009)

Well, to avoid confusion like amps=power, really what limits the gain in regen is the weight * change in velocity. So a lighter weight F1 car going 200mph to 40mph, repeatedly, stands to recapture a fair bit of braking energy like a slow moving heavy bus.


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## sergiu tofanel (Jan 13, 2014)

KERS systems are beyond the scope of the home mechanic. One can store large amounts of kinetic energy by either turning heavy flywheels or turning light flywheels very very fast. The latter option makes KERS units suitable for road cars. However, fast lightweight flywheels are required to operate in pairs (to cancel out angular momentum torque) and in vacuum (60000+ RPM creates a lot of drag) in order to be effective. Volvo is testing such a prototype in the S60. We will see these systems on future ICE cars.


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## sergiu tofanel (Jan 13, 2014)

steelneck said:


> In the early nineteens there where some experiments here in Sweden with buses that used a large compressor for braking and stored the energy as compressed air in large air tanks. Then had some kind of turbine to claim back that energy when accelerating. It worked and those buses was in traffic for a while, but i do not think it was efficient and i have never seen experiments like that since then. I remember they had a very special sound coming to stop and starting.
> 
> Also, the heavier a vehicle is, the more there is to be gained by generative braking compared to a small car.


There are similar hydraulic systems on the market today. 

http://fuel-efficient-vehicles.org/energy-news/?p=1022


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## sj281708 (Apr 29, 2014)

arklan said:


> leave the alternator mechanically connected
> have a brake light switch in the accellerator pedal that connects and disconnects the alternator.
> 
> when u r driving the alternator will just free wheel, when u take ur foot off the accelerator pedal the alternator comes on.


Got it. So would the battery still be charged to an acceptable level? Would I need additional capacitors?


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## Karter2 (Nov 17, 2011)

arklan said:


> leave the alternator mechanically connected
> have a brake light switch in the accellerator pedal that connects and disconnects the alternator.
> 
> when u r driving the alternator will just free wheel, when u take ur foot off the accelerator pedal the alternator comes on.


 The typical alternator is 14v ~ 20A, so 300W approx.
Do you think that will offer significant braking effect ??
Not very effective on an auto...
and i would not want that system if i did much night driving !


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## arklan (Dec 10, 2012)

the smallest car i have ever owned is a suzuki mighty boy, it has stock 543cc engine 19kw at 6000rpm
this has the 20amp alternator u describe

a daewoo matiz with an 800cc engine has a 40amp alternator

a ford falcon (dont know what ford calls it in america) has 60 and 80 amp alternators

this aside, the purpose of *regenerative* braking is to regen some power from the inertia of your car spinning the motor when you arent give it any go pedal

if it was called motor brake assist then i would understand your point of view


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## arklan (Dec 10, 2012)

sj281708 said:


> Got it. So would the battery still be charged to an acceptable level? Would I need additional capacitors?


what do u call an acceptable level?
the bigger the alternator u use the more power u get when its engaged/not using the accelerator pedal

but the motor has to spin the weight of the rotor in the alternator so that power is wasted when its not regening

i dont think it would give anywhere near as much as regen braking in an ac car but if u want ac braking like in an ac car u have to use an ac motor


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## Karter2 (Nov 17, 2011)

The amount of energy recovered from even well designed, fully developed regenerative braking systems is small.
However many users do site the benefits of much reduced wear and maintenance of the vehicles brakes as a major advantage.
So maybe an effective regenerative* braking* system has more to it than just energy recovery.

And, unless you are into cooking battery's, the alternator is only going to output as much current as the battery needs until its fully charged


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## sj281708 (Apr 29, 2014)

arklan said:


> what do u call an acceptable level?
> the bigger the alternator u use the more power u get when its engaged/not using the accelerator pedal
> 
> but the motor has to spin the weight of the rotor in the alternator so that power is wasted when its not regening
> ...


I am a noob when it comes to that kind of stuff: How does the alternator motor spin and help slow down the car in an ICE when regen is activated/brake pedal is pressed? Is there no way of getting small surges of power in an ICE vehicle from converting potential energy in braking to chemical energy in batteries? An acceptable level means whatever current ICE based 12v battery needs to stay at/demand from vehicle's electric system.


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## sj281708 (Apr 29, 2014)

Karter2 said:


> And, unless you are into cooking battery's, the alternator is only going to output as much current as the battery needs until its fully charged


So would a secondary, auxiliary battery connected through a split charing relay or isolator (much like leisure batteries in RVs) be a worthwhile candidate to be used here to grab some of these mega outputs? Would it help to have a capacitor in place to absorb these surges?


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## arklan (Dec 10, 2012)

my 'plan' i guess u could call it is purely about getting energy back when ur not pressing the pedal, it wont help u slow down any noticeable amount.
a guy was using this setup in place of a dc dc converter and didnt get enough out of it to keep his auxilery battery topped off so youd still need a dc dc converter or have the alternator connected all the time.

alternators have regulators in them to stop them over charging batteries


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## dougingraham (Jul 26, 2011)

sj281708 said:


> How does the alternator motor spin and help slow down the car in an ICE when regen is activated/brake pedal is pressed?


A 100 amp alternator at 14.4 volts output is a 1440 watt generator which would provide about 2 horsepower of braking energy. Four wheel disc brakes on a car can provide braking energy levels up to the 1000 horsepower range in a panic stop. So although a 2 horsepower level of recharge is not much you might see a tiny range increase in a well done system. Your best bet would be to find a device that could boost the 14.4 volts at 100 amp output to your traction pack voltage and put the energy back into the traction pack. This would be a device of similar complexity and cost to manufacture to that of the DC-DC converter. Upside is a small increase in range if used properly. Downside would be a reduction in range due to the addition of an estimated 30 lbs of stuff to the car and a small increase in rolling resistance because of the mechanical resistance of the alternator to the spinning of the motor. Upside occurs only when you activate the system. The downside is always present. Which has a greater effect on the vehicle depends on how the vehicle is used.



sj281708 said:


> Is there no way of getting small surges of power in an ICE vehicle from converting potential energy in braking to chemical energy in batteries? An acceptable level means whatever current ICE based 12v battery needs to stay at/demand from vehicle's electric system.


Probably not into the 12 volt vehicle system battery. Once topped up there would be no place to put the energy. If a lot of your driving is at highway speed then this system would be a net loss. Your car systems don't use all that much power normally. The big recharge load is replacing the energy used when starting the ICE so you can drive a block and then start the car again.

If you really want regen the only practical way to go about it is with an AC motor/controller where you get all of this essentially for free and it does not add anything additional to the mass of the vehicle. Look at it this way, if you manage to add only 30 lbs to the mass of the vehicle with the alternator/control electronics then your wh/mi will become worse by about 1% in a 3000 lb (1364 kg) car. It would be surprising it you gained back that 1% even if you do a really good job of integrating it into the car systems. And 1% is going to be lost in the noise. Essentially impossible to measure if it has hurt you or helped you.

Best Wishes!


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## dougingraham (Jul 26, 2011)

sj281708 said:


> So would a secondary, auxiliary battery connected through a split charing relay or isolator (much like leisure batteries in RVs) be a worthwhile candidate to be used here to grab some of these mega outputs? Would it help to have a capacitor in place to absorb these surges?


The output of an alternator is tiny at best compared to your traction pack charger. With a 100 amp alternator is would be about like a Level 1 charging station that only runs for a few seconds at a time. There would be no mega surges from an alternator. From the motor regen you can see charging power levels similar in scope to the discharge currents when under hard acceleration. Which means that with our normal LiFe batteries the batteries can easily absorb these energy levels without any additional help. The addition of caps doesn't help when you have a large enough battery packs to absorb the regen energy.

There are cases when caps could be used like is found in some of the start/stop systems used by ICE vehicles. But with todays capacitor technology they don't help us in our plug in EV's. The additional cost would be far better served by just adding some additional batteries.


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## sj281708 (Apr 29, 2014)

dougingraham said:


> The output of an alternator is tiny at best compared to your traction pack charger. With a 100 amp alternator is would be about like a Level 1 charging station that only runs for a few seconds at a time. There would be no mega surges from an alternator. From the motor regen you can see charging power levels similar in scope to the discharge currents when under hard acceleration. Which means that with our normal LiFe batteries the batteries can easily absorb these energy levels without any additional help. The addition of caps doesn't help when you have a large enough battery packs to absorb the regen energy.
> 
> There are cases when caps could be used like is found in some of the start/stop systems used by ICE vehicles. But with todays capacitor technology they don't help us in our plug in EV's. The additional cost would be far better served by just adding some additional batteries.


Just to make sure...we are still talking about ICE's right? How are we/can we use AC motor for regen in an existing ICE?


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## sj281708 (Apr 29, 2014)

dougingraham said:


> Probably not into the 12 volt vehicle system battery. Once topped up there would be no place to put the energy. If a lot of your driving is at highway speed then this system would be a net loss. Your car systems don't use all that much power normally. The big recharge load is replacing the energy used when starting the ICE so you can drive a block and then start the car again.


So do cars waste a lot of output from the alternator when the battery is topped up? I was under the impression that it free wheels when the voltage regulator senses no load? An extension to that question: What kind of drop in mpg would I see if instead of 1 12v battery, the alternator would have to keep 2 12v batteries topped up at all times?


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## dougingraham (Jul 26, 2011)

sj281708 said:


> Just to make sure...we are still talking about ICE's right? How are we/can we use AC motor for regen in an existing ICE?


I think I went off topic a bit. I think the only way to make this practical in conjunction with an ICE is in Hybrids.


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## Karter2 (Nov 17, 2011)

sj281708 said:


> So would a secondary, auxiliary battery connected through a split charing relay or isolator (much like leisure batteries in RVs) be a worthwhile candidate to be used here to grab some of these mega outputs? Would it help to have a capacitor in place to absorb these surges?


Mazda didnt engineer the i-Eloop system on the "New 6" just to show off.
All the components are included for a reason.
Have a look at the on line description of their system to get an idea of what would be required to make any sort of workable system.
so ,... bigger (special) alternator, Ultra Capacitors, voltage converters, better /bigger batteries, logic control system, etc etc
And also bear in mind that there is an element of "sales propaganda" in some of what car companies will do to appear to be going "green". !


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## sj281708 (Apr 29, 2014)

dougingraham said:


> I think I went off topic a bit. I think the only way to make this practical in conjunction with an ICE is in Hybrids.


So there has to be an element of eletric powertrain in the car, not just extra batteries?


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## sj281708 (Apr 29, 2014)

Karter2 said:


> Mazda didnt engineer the i-Eloop system on the "New 6" just to show off.
> All the components are included for a reason.
> Have a look at the on line description of their system to get an idea of what would be required to make any sort of workable system.
> so ,... bigger (special) alternator, Ultra Capacitors, voltage converters, better /bigger batteries, logic control system, etc etc
> And also bear in mind that there is an element of "sales propaganda" in some of what car companies will do to appear to be going "green". !


I agree, but is there no real way of grabbing the excess wasted energy from ICE in a set of batteries? How does a DC to DC converter work where the alternator can output small amounts but still top off batteries?


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## dougingraham (Jul 26, 2011)

sj281708 said:


> So do cars waste a lot of output from the alternator when the battery is topped up? I was under the impression that it free wheels when the voltage regulator senses no load?


There is always going to be some load from the belt, cooling fan, and bearings. I also doubt that it ever shuts off completely because a running car is a load on the battery and the alternator system supplies the power when the vehicle is running.



sj281708 said:


> An extension to that question: What kind of drop in mpg would I see if instead of 1 12v battery, the alternator would have to keep 2 12v batteries topped up at all times?


Slight drop mostly from carrying the additional weight of the second battery. A 40 lb battery in a 4000 lb car would have an average reduction of perhaps 1%. This would be in stop and go situations. On the highway you would see very little loss, it would be due to an increase in rolling resistance. There would also be a tiny amount due to the self discharge characteristics of the additional Lead Acid battery.


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## dougingraham (Jul 26, 2011)

sj281708 said:


> So there has to be an element of eletric powertrain in the car, not just extra batteries?


An alternator is not a large enough generator to get any significant regen advantage from. A hybrid has a large enough system to make it all work out.


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## sj281708 (Apr 29, 2014)

dougingraham said:


> An alternator is not a large enough generator to get any significant regen advantage from. A hybrid has a large enough system to make it all work out.


theoretically however, a larger alternator would be able to do the trick? Or no matter what the alternator is like, any type of good regen is out of the question?


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## dougingraham (Jul 26, 2011)

sj281708 said:


> theoretically however, a larger alternator would be able to do the trick? Or no matter what the alternator is like, any type of good regen is out of the question?


What comes to mind would be substituting the generating of electricity for the back pressure of the ICE when you take your foot off the throttle. Substituting the regen for the motor braking. That is a similar amount of energy recovery. You can't do this without reworking all the mechanicals in the car. Because you need to uncouple the ICE from the drive train and connect the alternator to the drive shaft instead. But this means you cannot operate the alternator when the car is stopped. If you figure out all of that you still need a place to put the recovered energy. You would have to do something like use an oversized battery and only charge it to an average of 80% full so you have some place to put repeated stops. Lead batteries like being fully charged and their life is shortened if not kept fully charged. This is all so complicated and the amount of gain is going to be so minimal that I would say it is out of the question. If it was worth doing the OEM's would be doing it as this is just a small fraction of what they do in Hybrid cars.


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## Karter2 (Nov 17, 2011)

I say again.... Mazda didnt develop their i-eloop system just for fun.
I doubt even it gives a significant improvement in efficiency, but probably enough to justify its costs.
If there were an easy , cheap, quick , way of getting anything like similar results, they would not have wasted their time and resources.
Also, even if Mazda overlooked a simple solution, dont you think one of the hundreds of auto makers .....craving for efficiency improvements to shout about......might just have found this "holy grail" of low cost energy recovery ?


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## arklan (Dec 10, 2012)

get a 2 piston air compressor and run that off the exhaust.

so instead of the exhaust powering a turbo for extra power u power a compressor and that would spin the alternator for u, faster at higher rpms same as the car already does.

problems i see is all the shit coming out of the exhaust, maybe have a water cushion to absorb it all?


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## rmay635703 (Oct 23, 2008)

http://www.greencarreports.com/news...-tech-peugeot-to-offer-in-2016-on-subcompacts

Your ice does have a built in air compressor.


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## sj281708 (Apr 29, 2014)

dougingraham said:


> What comes to mind would be substituting the generating of electricity for the back pressure of the ICE when you take your foot off the throttle. Substituting the regen for the motor braking. That is a similar amount of energy recovery. You can't do this without reworking all the mechanicals in the car. Because you need to uncouple the ICE from the drive train and connect the alternator to the drive shaft instead. But this means you cannot operate the alternator when the car is stopped. If you figure out all of that you still need a place to put the recovered energy. You would have to do something like use an oversized battery and only charge it to an average of 80% full so you have some place to put repeated stops. Lead batteries like being fully charged and their life is shortened if not kept fully charged. This is all so complicated and the amount of gain is going to be so minimal that I would say it is out of the question. If it was worth doing the OEM's would be doing it as this is just a small fraction of what they do in Hybrid cars.


Could I perhaps also replace the alternator with a small electric motor (which doubles as an alternator) directly connected to the drive shaft like you said? Then it can pull out or push in a lot more energy. The supercapacitors might be a win over Li ion or NiMH batteries for a system with a little less energy storage because they should not wear out the way the batteries do.

I thought that the reason OEMs did not do this, is because there is no place for this energy to go to, since if the 12v battery is charged, any more energy burst will damage it. But what if I had another battery to charge?

Thanks


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## Karter2 (Nov 17, 2011)

Ever heard of GM's BAS system ?...
From Wiki..


> General Motors introduced a mild hybrid system called *belt alternator starter* (or *BAS*) in the 2007 Saturn Vue Green Line. The BAS system is also used in the Chevrolet Malibu Hybrid and Saturn Aura Green Line. It operates similarly to other mild hybrids with a start-stop system, in that it shuts down the engine as the vehicle comes to a stop and instantly restarts it when the brake pedal is released.[1]
> The BAS system is capable of providing modest levels of power assist during launch/acceleration and similarly modest levels of "blended" regenerative braking during deceleration. Although unable to operate in pure all-electric EV mode, the BAS system provides improvements to both city and highway fuel efficiency over similar non-hybrid versions. In more powerful eAssist versions, a BAS system can add power to prevent excessive gear changes under variable load. According to the EPA the 2009 Saturn Vue BAS hybrid garners an improvement of 32% city (19>25mpg) and 24% highway (26>32mpg) making the combined economy improvement 27% (22>28mpg) over the base 4cyl FWD version.[2] The system is reasonably simple and inexpensive, making BAS equipped vehicles some of the least expensive hybrids available.[3][4][5]
> A 36 volt electrical system (operating at 42-45 Volts) is used to operate a permanent magnet motor/generator unit mounted to the engine in a similar fashion to a conventional alternator. Then through a high-tension drive belt, the BAS system is capable of starting or assisting the 2.4L Ecotec engine. A conventional 12V starter motor is retained and used whenever the engine is cold as during initial start-up. The air conditioning compressor continues to be operated through a belt-driven pulley, but for fuel economy improvement it can be disabled in auto-stop mode if the "ECO" A/C mode has been selected by the operator.
> Vehicles with the BAS system use a conventional 4T45-E automatic transmission which has been modified to include a more efficient final-drive ratio and includes an electrically driven pump to provide pressure in auto-stop mode.
> ...


 Note however
115v Lithium battery system
15kW generator/motor ( thats 10 X a "normal" alternator capacity )
and most of the fuel savings come from shutting off the motor at stop lights.


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