# Hybrid EV realizable?



## IamIan (Mar 29, 2009)

KirillSp said:


> Hello all,
> 
> Inspired by the bi-moto project
> http://www.diyelectriccar.com/forums/showthread.php?t=28287&highlight=shaft
> ...


Yes it is doable.

It is the the same kind of concept explored explored by the DIY community for HEVs many years before the auto companies started making HEVs.

Keep in mind the limits of using a 5kw system ... not allot of power there.

If you were going with a power level this low you might want to consider dropping it in as a replacement for the alternator and starter ... that would help save you some weight.


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## TX_Dj (Jul 25, 2008)

And well, if the ICE is in place as-is, there would be no way for the EV motor to hold the speed AND the ICE to charge batteries.

You would have to have an EV drive system capable of regen braking. Even then, if the batt is flat while driving and you want to charge, you will put a harder load on the ICE than what it takes to simply drive the car forward, thereby limiting or eliminating the gains realized by having the hybrid drivetrain.

You would be better off using the EV drivetrain for short-distance, lower-speed driving and cut the ICE to neutral and shut it down, and then have the EV drivetrain do a lot of braking force to recharge itself... even then, you possibly set your self up for disaster, and here's why: When you brake, the majority braking force happens in the front axle. Approximately 70/30 split, sometimes more or less each direction, just depends on how it's setup and how it's braking. If you have your EV components on the back axle, then only 30% of the braking forces can be recaptured as potential regen power (even less once all the inefficiencies are taken from the motion/charging), any more than that and you risk locking the back wheels, which can be a recipe for a slide.

It's not impossible to do, by any means, but without a lot of in-depth analysis and engineering, you may have a hard time getting everything just right.

A better hybrid design, in my opinion, is one where the ICE never touches the drivetrain, but just drives a generator. This is how locomotives work, and is also how the Volt was designed. This is called "series hybrid". Conversely, the Prius/Insight and most other common Hybrid systems are what's called "parallel hybrid" where both the ICE and EV motors drive the wheels, and thus the ICE can use the EV motor to recharge in motion (without losses imposed by dragging wheels around to turn the EV motor as a generator).

The series hybrid design will be the next big evolution for hybrid drivetrains, and Chevy will bring one of the first to market, first for the big car makers at least.


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## KirillSp (May 17, 2010)

IamIan, I think that 4-5kW should be enough for city driving at least.
See http://www.evconsultinginc.com/articles/hybridizing_dc_system.html , it's a very interesting article!

'If you were going with a power level this low you might want to consider dropping it in as a replacement for the alternator and starter ... that would help save you some weight.' <-- Could you explain that further, please?

TX_Dj, the ICE is charging the starter battery through the alternator permanently, right? So what about forwarding the energy into the small battery pack by connecting the starter battery with the small battery pack?

If the battery pack is empty or the motor cant mess with higher speeds, then the ICE would move the car (maybe with the e-motor together to save fuel?) by itself, the motor would be turned by the driving car then and act as a generator, what about that? As I think, the ICE wouldnt touch the e-motor in that concept, what do you think?

So I think, it would be also possible for the ICE to act as a generator and one e-motor on the bottom (see bi-moto project) would move the car.
Would that be easy to make?

Thank you!


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## TigerNut (Dec 18, 2009)

You might only need 4 to 5 HP to sustain a 30 to 40 mph speed, but it will take you an eternity to accelerate or do hills if that's all the power you have available.


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## IamIan (Mar 29, 2009)

KirillSp said:


> IamIan, I think that 4-5kW should be enough for city driving at least.


I don't think so ... just my 2 bits ... at least , unless you are in a extremely light vehicle... crawling speed in stop and go traffic maybe ... or only on flat level type of ground ... but it just isn't allot of power for hills, acceleration, inertia, etc.

The IMA motor in my Gen-1 Insight is 10kW ... and when I drive it into a EV mode , the limits of 10kW are apparent ... and that is for a small 2 seat light weight aluminum framed vehicle , with a good aerodynamic design.

Yes for those who will point out , OEM there isn't a EV mode in the Gen-1 ... but, I'm not 100% OEM.



KirillSp said:


> 'If you were going with a power level this low you might want to consider dropping it in as a replacement for the alternator and starter ... that would help save you some weight.' <-- Could you explain that further, please?


The short term cranking power of many starter motors can dish out this kind of power ( ~5 kw ) ... 12V * 400 Amps ( cranking power ) = 4.8kW.

If you keep the starter and alternator and just add on the ~5kW you add on more weight than using the ~5kW to replace those other two electric motors.

So if you want to add a motor that is only going to have ~5kW of power, this motor will be easily able to replace the starter motor for the ICE ... so you reduce the weight of the vehicle by removing the starter and letting this ~5kW motor do that function... and if you have a motor controller that allows for regen ... than you can use this same motor as an alternator as well, thus also removing the weight of the alternator.

This is effectively the same kind of design as Honda's IMA system ... except I assume you will have a larger battery capacity and a grid charger as well... so you can use the ~5kW motor to 'help' power the vehicle which will thus replace / offset some of the gasoline used with electricity from the grid charged battery instead.

If you wanted to you could put this ~5kW motor on a clutch separate from the ICE ... that way it doesn't have to turn when you don't want it to... kind of like how some AC compressors have a clutch that connects and disconnects them as wanted.

Putting it in this position to replace a starter and alternator also allows it to gain the gearing benefits of your transmission.

- - - - - - - - 

By all means go ahead ... best of luck ... and tell us all about it , during of course and after as well.


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## KirillSp (May 17, 2010)

Thanks for the detailed reply!

If the 5kW motor is not enough for city driving, then its a good idea to put it on the place of the starter and alternator.
So the idea of forwarding the energy from the e-motor acting as a generator is right (if you have some more batteries on board)? Or would I have to charge the battery pack everytime by myself through the charger?

What exactly would be the benefit of the battery pack? Would the e-motor turn by itself (it would be connected through a belt with the ICE of course) and make the ICE get lower amounts of fuel for doing its work? What if the battery packs energy gets low? Would the e-motor act as a generator then?

The other concept (maybe after the first one is already realized) would have one stronger motor (like 10kW) under the cars floor (like bi-moto) and turn the rear wheels by itself with energy from the bettery pack which would be charged for myself. The ICE engine would not be switched off but remain in neutral running. When the battery packs energy is low, I would drive the car with the ICE (all controlled manually by me), the e-motor would put the energy back from the turning wheels then. Would that be counterproductive as the ICE would need more energy to turn the e-motor then as well?


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## IamIan (Mar 29, 2009)

KirillSp said:


> Thanks for the detailed reply!


you're welcome 



KirillSp said:


> If the 5kW motor is not enough for city driving, then its a good idea to put it on the place of the starter and alternator.
> So the idea of forwarding the energy from the e-motor acting as a generator is right (if you have some more batteries on board)? Or would I have to charge the battery pack everytime by myself through the charger?
> 
> What exactly would be the benefit of the battery pack? Would the e-motor turn by itself (it would be connected through a belt with the ICE of course) and make the ICE get lower amounts of fuel for doing its work? What if the battery packs energy gets low? Would the e-motor act as a generator then?


The benefits are a few but there are multiples.

A single ~5kW motor to do the job of both the starter and the alternator might end up being lighter and using less space than the two motors it is repacing.

The ~5kW motor as said can provide some power ~5kW of motor power to help move the vehicle , which slightly reduces the demands of the ICE to power the moving of the vehicle, thus while operating in Assist ... you will get better MPG.

To get the best benefit the ~5kW motors battery should be charged by the grid were possible ... this is a charge depleting hybrid ... it is less efficient when it has to operate as a charge sustaining hybrid.

Although less efficient as a charge sustaining hybrid there reaches a point where under some conditions it is still a net benefit for the load leveling benefits of the charge sustaining hybrid design... this can get complicated to pin down when it is a benefit and when it isn't... but as long as you are operating as a charge depleting hybrid and recharging the battery when you get home it is almost always a MPG benefit... of course there are exceptions to everything.



KirillSp said:


> The other concept (maybe after the first one is already realized) would have one stronger motor (like 10kW) under the cars floor (like bi-moto) and turn the rear wheels by itself with energy from the bettery pack which would be charged for myself. The ICE engine would not be switched off but remain in neutral running. When the battery packs energy is low, I would drive the car with the ICE (all controlled manually by me), the e-motor would put the energy back from the turning wheels then. Would that be counterproductive as the ICE would need more energy to turn the e-motor then as well?


yup ... another example of that kind of thing is the 5th wheel Mike did shown here... which raises or lowers when he wants to use it at low speeds and when he doesn't want it touching the road at high speeds. 

About half way down the page here:


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## KirillSp (May 17, 2010)

Thanks for explaining the benefits further, it is much more clean to me now!

So wouldnt it be also counterproductive (cost more energy to charge the 5kW generator) to charge the generator as charging the smaller (1-2kW) alternator before, if I dont charge the batteries right?

Like you said before: 'If you wanted to you could put this ~5kW motor on a clutch separate from the ICE ... that way it doesn't have to turn when you don't want it to... kind of like how some AC compressors have a clutch that connects and disconnects them as wanted.'
Just put 10kW or another number inside your sentence.
If I want to realize the 2nd concept, it seems to be the only way to separate the stronger motor under the cars floor from the ICE when the battery pack gets low on energy. How could that be realized? Thanks again!


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## IamIan (Mar 29, 2009)

KirillSp said:


> Thanks for explaining the benefits further, it is much more clean to me now!
> 
> So wouldnt it be also counterproductive (cost more energy to charge the 5kW generator) to charge the generator as charging the smaller (1-2kW) alternator before, if I dont charge the batteries right?


not all components are created equally ... what is the operating efficiency curves for the 1 to 2 kw automotive alternator? ... is it more or less efficient than the ~5kW? ... what is the operating efficiency of the automotive 12V starter? ... is it more or less efficient than the ~5kW?

Electric motors also often times scale well ... for example ... a single 5 kW electric motor can be smaller and lighter than two 2.5kW electric motors... not a guaranteed thing ... one more detail that can help the single motor setup... how much does the current starter and alternator weigh together? ... that might be a good starting point to look at if you are thinking of a lower powered Hybrid like a ~5kW system.

Also keep in mind ... even just ~5kW of regenerative braking is more than zero kw of regenerative braking ... conventional brakes throw away 100% of the mechanical energy you have as vehicle momentum when you slow down ... any amount of regenerative braking ... even as little as 1% efficiency is better than Zero / Nothing.

The amount of energy the alternator or motor in regen takes is variable depending on the type of motor and the controller... just because you have ~5kw doesn't mean you always have to use all 100% of it... if the ~5kw motor & controller function in regen as efficiently as the automotive alternator does ... if say both regen ~1kw at about ~90% efficiency ... ~1kw engine load is ~1kw engine load... is won't matter if it comes from a ~1kw rated alternator or a ~5kw rated motor in regen... remember the 5kw can also do 2kw or 3 kw... or 0.2 kw.

- - - - - - - - - - - - 

Also if the batteries are charged from the grid ... while in a charge depleting hybrid system mode ... every bit of grid energy is that much less gasoline the vehicle has to use.

Even if you just looked at the alternator load ... that is one less load you have to put on the engine ... one less thing you have to use gasoline to power, etc... All the electrical power in a normal car comes from gasoline.



100Wh gasoline energy
ICE takes the 100Wh of chemical energy and gives out about ~30Wh of mechanical energy.
Alternator if at 90% takes the ~30 Wh in and only gives out ~27 Wh of electrical energy.
Normal car Battery Lead Acid varies , but can be as low as about ~60% cycle efficiency... so that car battery takes the ~27 Wh of electrical energy in , but might only give back about ~16wh of electrical energy out.


Of course all of those thing vary depending on conditions and such ... but if Your charge depleting hybrid mode is getting its electrical power from the grid ... that is ~30Wh worth of mechanical energy you don't have to take away ... let it move the vehicle.

if designed well you can start out as a charge depleting hybrid ... and than if battery SoC drops too low ... just switch over to charge sustaining mode, and drive like a more conventional HEV.



KirillSp said:


> Like you said before: 'If you wanted to you could put this ~5kW motor on a clutch separate from the ICE ... that way it doesn't have to turn when you don't want it to... kind of like how some AC compressors have a clutch that connects and disconnects them as wanted.'
> Just put 10kW or another number inside your sentence.
> 
> If I want to realize the 2nd concept, it seems to be the only way to separate the stronger motor under the cars floor from the ICE when the battery pack gets low on energy. How could that be realized? Thanks again!


There are a number of ways to disconnect a motor when you don't want it attached.

In the example you referenced ... I was referring to the car's belt system ... that can already handle the starter motor loads ... the alternator loads ... the AC system loads ... power steering loads ... etc...

For example... before I disconnected it the AC system in my car was one of the loads on the serpentine belt ... but the AC was not always needed ... so Honda had a electrically controlled clutch on it ... that way when the AC load was not needed the clutch would disconnect the compressor from the pulley that was turned by the serpentine belt ... and the pulley remained in place but just spun freely ... thus not putting the AC compressor load on the serpentine belt or the engine... than is AC was needed the AC clutch would connect the AC compressor to it's pulley and the engine would now see the AC system load on the engine.

So you have an system that connects and disconnects as desired ... don't need to run the system as an alternator or in Regen because you have plenty of battery SoC... don't connect it, no load on engine... if you want that electric assist to boost your MPG a bit... connect it and off you go.

This method will be limited to lower power amounts that are comparable to the amount of load an accessory might pull... ~5kW range is doable for this ... depending on the vehicle and how much fabrication you want to do... will determine how much higher you can go.

Above ~10kW I would generally not connect this method ... but that is just a personal preference / opinion.

Also for my 2 bits... the more powerful the electric motor ... the less power you need from the ICE ... this is another factor that helps the MPG of commercial HEVs ... because electric motors keep their torque at low RPMs much much better than ICE do... as the electric motor is sized more and more to take the peak loads ... the ICE only has to handle the average load ... and can be smaller , lighter, etc.

For example ... at low RPMs down at about ~1,000 the little 10kW IMA motor on the Insight is putting out ~58% of the drive system's net torque ... all by itself... even though it does less than ~20% of the peak kw of power of the combined system ... Electric motors kick ICE's ass at low end torque... that's why the diesel electric train hybrids have been in operation for over 40 years.

At a certain point the electric motor & batteries are powerful enough to take 100% of the peak loads on their own ... at this point the ICE is only there to extend the range beyond what the batteries provide... by this point, unless you travel more than 50 miles in a day it isn't even worth the weight of still having a ICE at all.


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## pinetree (Jun 10, 2010)

I'm the guy with the ultra-light British sportscar, a '59 Berkeley, about which I have posted a few Q's on this forum lately. I started wondering, since my motor/tranny only weigh about 140 pounds, should I leave it there and add e-power to the rear wheels. I even asked about in-hub motorcycle wheels, as my car weighs only 660 pounds, so the mc wheels could take the load easily. (Probably won't do it that way, though.) But a small pack, to allow slow and stop and go in city traffic without idling the ICE would be a nice feature. I'm going to consider it further, and hope you will too. I think the big Q is how small a battery pack will get you going at a light, in traffic, without annoying the other drivers. With my little car, the requirements are small enough that Lithium is affordable. Heavier cars do not have that luxury. What is your 'donor', and could you use a Geo Metro or similarly small ride to economize on conversion costs? Keep us informed!


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## IamIan (Mar 29, 2009)

pinetree said:


> as my car weighs only 660 pounds,
> 
> I think the big Q is how small a battery pack will get you going at a light, in traffic, without annoying the other drivers.


There are allot of 'calculators' and such out there to help with this.
Getting accurate can easily get complicated.

There are two competing forces.

#1> size for the cranking power to get the acceleration you want.
#2> size for range you want of your average drive cycle.

They are not the same thing.

What has the best power density W / kg ... which determines your acceleration ... are never the same and what gives you the best energy density wh / kg... which gives you your range.

so we have to make a compromise somewhere between the two extremes.

For example there are capacitors that can put out over 20kw / kg ... a 60 kw drive for acceleration of your 660 pound car would only need to weigh ~3 kg ... but the energy density is very low... usually like ~5wh/kg or less ... so you could have massive acceleration from tiny light weight device ... but it would only last for ~1 second before you used up the energy storage.

While on the other hand / other end of the extreme... BetaVoltaic nuclear cells only put out ~24W/kg ... about 1/1,000 the capacitor's power density ... but it's energy density is crazy high ... in ~12 years it will put out about ~1.8 MWh of energy and still be pumping out ~12W/kg ... it won't be done for a very very long time ... but the power density starts bad and gets worse... so on this extreme the power density is so low it would barely move even that light weight vehicle at all ... but it would keep on barely moving it for decades.


Exactly where in the middle you end up ... depends on what your priorities are and what your budget is.


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## ace_xp2 (Jul 1, 2010)

Would a Mars double Stack (when released) be adequate to move at only 60kph? That would also allow the use of a regen controller wouldn't it?


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## Tronthor (Aug 2, 2010)

IamIan,

Excellent points about charge density and charge capacity. This reminded me of something, my father once mentioned to me that someone had come up with a very high capacity capacitor which was capable of both very fast charge and very fast discharge - which seems to be the best of both worlds. I will have to ask him about it again. Regardless, what about a hybrid system - of energy storage.

You have capacitor like storage (comprised of ... capacitors!) and low(er) rate storage which has high capacity (comprised of battery like things like ... batteries!) Thus giving you the ability to size your cruising power storage in the best of that world, while giving you a place to dump high rate charging currents - rapid regen braking, lightening strikes, fallen power lines and the like - and a place to draw off high rate loads - acceleration from standing stop, and passing the guy in the gremlin who's stuck in 2nd gear! Beep-beep, Beep-beep, my ev goes beep, beep, beep....

It's an idea I had when dad mentioned the things years ago, but never followed up on - or made note of. I've been thinking about this stuff for a long time...

Are you aware of anyone having done anything like this?


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