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 Post subject: So why do we have Hybrid Electric Vehicles.
PostPosted: Fri Jan 04, 2019 11:57 pm 
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Joined: Thu Feb 26, 2015 5:58 pm
Posts: 738
Location: Near Port Macquarie Australia
As I think it is a interesting topic I wish to discuss Hybrid Electric Vehicles. You never know we all may learn something. I know I love learning. :D

Now lets start with a definition of HEVs.

Wikipedia states:

"A hybrid electric vehicle (HEV) is a type of hybrid vehicle that combines a conventional internal combustion engine (ICE) system with an electric propulsion system (hybrid vehicle drivetrain). The presence of the electric powertrain is intended to achieve either better fuel economy than a conventional vehicle or better performance."

Ok I think most of us would have known that. Now HEVs have been around for a while and I will not go into all the history here but I will start off with the Toyota Prius, a car which I have owned, which is considered to be first mass produced HEV according to Wikipedia.

Now why did Toyota produce the Prius which no matter what we think of them Toyota has sold millions. Edit approx 6 million up to 2016 from what I can see including all variants.

Well Toyota themselves stated:

"The initial research team's notion of a compact car with a wide interior and excellent fuel efficiency reemerged as a core development concept."

So it would appear to me the reason that Toyota used the hybrid vehicle drivetrain was fuel efficiency and NOT performance. Remember that first definition I posted above.

Now what did Toyota do to achieve, or not, the excellent fuel efficiency as stated as a core development concept.

Well from me that will have to wait till tomorrow as I have to go now.

To be continued............


Last edited by Trex on Sat Jan 05, 2019 5:08 pm, edited 1 time in total.

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 Post subject: Re: So why do we have Hybrid Electric Vehicles.
PostPosted: Sat Jan 05, 2019 1:19 am 
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Joined: Wed Sep 09, 2015 5:05 pm
Posts: 384
Location: Australia
In my case, I wanted an electric car, that I could also use in the country areas where there is no option to recharge.

95% of my usage is electric only. That other five percent would require a second car.

(Remember, country travel so no public transport options)

YMMV

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 Post subject: Re: So why do we have Hybrid Electric Vehicles.
PostPosted: Sat Jan 05, 2019 4:06 am 
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Joined: Mon Sep 07, 2015 2:34 pm
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Location: Devon UK
When asked about the drive system on my PHEV I always liken it to a 'diesel-electric locomotive'...with an added battery...and charging capability. This seems to satisfy most technically minded people. ;)

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 Post subject: Re: So why do we have Hybrid Electric Vehicles.
PostPosted: Sat Jan 05, 2019 5:37 am 
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Joined: Mon Dec 03, 2018 8:47 am
Posts: 42
Location: Southern end of North Yorkshire, UK
Tipper wrote:
When asked about the drive system on my PHEV I always liken it to a 'diesel-electric locomotive'...with an added battery...and charging capability. This seems to satisfy most technically minded people. ;)


Me too. And the reason locomotives use diesel electric is because it means you can run the ICE at its optimum speed and load to get good economy and emissions compliance whilst using the flexibility of electric motors to give huge torque at low speeds where it’s needed and because the car has a battery it’s even more flexible because it can charge and discharge that to give more ways of working.

I don’t see it as a pure EV car with an on board generator for when the battery runs out. I see it as a car that uses petrol and battery as required, depending on the situation. And the economy even with a depleted drive battery is still easily three-four times better than my 15 year old Subaru Outback 3.0 would do on my short commute.

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1991 Mitsubishi Pajero 2.5 LWB (WVO)
2008 Volkswagen Caravelle (diesel)
(recently departed - 2004 Subaru Outback 3.0Rn (LPG))


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 Post subject: Re: So why do we have Hybrid Electric Vehicles.
PostPosted: Sat Jan 05, 2019 6:50 am 
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Joined: Mon Sep 26, 2016 11:18 pm
Posts: 981
Location: Poland
My why is relative common:

- This car allow to make my daily commute in EV mode, which means spending 4 time less then using fuel.

But ... the reason why I bought this PHEV, it was because 2nd hand was relative cheap, and it was a nice update from my previous diesel SUV

The plus is an excellent economy for daily commute
The cons, is that consumption at speed 130km/h or more is very high .. which is normally my speed on long trip (which often I do with my old BMW 335i for have more speed and better fuel economy)

PS: A pure EV make sense for a 2nd car ... not only the infrustructure in most of europe is not ready for EV, but I'm also not ready to spend 45min or more waiting for charging the car.

PS: If I would have to design a PHEV .. I would follow the i3 REX example ... a bigger battery (25/30kwh) with a smaller ICE (40kw ICE I think is enough), but with a bigger fuel tank compared to the micro tank on the BMW i3


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 Post subject: Re: So why do we have Hybrid Electric Vehicles.
PostPosted: Sat Jan 05, 2019 11:54 am 
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Joined: Fri Jul 18, 2014 4:46 am
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richr wrote:
Tipper wrote:
When asked about the drive system on my PHEV I always liken it to a 'diesel-electric locomotive'...with an added battery...and charging capability. This seems to satisfy most technically minded people. ;)


Me too. And the reason locomotives use diesel electric is because it means you can run the ICE at its optimum speed and load to get good economy and emissions compliance ...


I'm not sure that is true - diesel electric locomotives have been around for many years - far longer than fuel economy or emissions control has been considered important. My understanding of diesel electric locomotives is that they are primarily built to simplify the transmission. In the absence of the electric component, the locomotive unit would require a multi-speed gearbox and a clutch mechanism that is capable of transmitting very high power levels reliably. My primary interest in owning a hybrid is similar - I have had very poor experiences of gearboxes and clutches over the years and always seek to avoid both. Prior to the Prius and PHEV, we have chosen traditional automatic transmissions with torque convertors and planetary gearboxes. These are becoming increasingly difficult to find these days - the majority of so-called automatics I've seen recently are really servo operated manual transmissions.


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 Post subject: Re: So why do we have Hybrid Electric Vehicles.
PostPosted: Sat Jan 05, 2019 12:27 pm 
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Joined: Wed Oct 29, 2014 8:23 pm
Posts: 299
Location: Dee Why
Your title says HEV, not PHEV, however, all replies so far talk about the virtues of the PHEV.
The HEV as in the Toyota was developed primarily as a fuel saving technology, especially in stop-start urban environments. The best analogy for the way it works is perhaps to compare the battery setup with a a flywheel. The engine can run at its most efficient power band and the electric motor can help with acceleration as well as recover energy when braking. It works very well in that scenario. On the highway, there is not that much advantage as can be shown in the fuel consumption where it is similar to a modern fuel efficient conventional petrol car. A diesel can still be better! Another approach is in some performance cars where the electric propulsion is also used to provide a big increase in torque to supplement an ICE, a bit like the PHEV in parallel mode.


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 Post subject: Re: So why do we have Hybrid Electric Vehicles.
PostPosted: Sat Jan 05, 2019 5:00 pm 
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Joined: Thu Feb 26, 2015 5:58 pm
Posts: 738
Location: Near Port Macquarie Australia
Now what did Toyota do to achieve, or not, the excellent fuel efficiency as stated as a core development concept.

Well first they had to have a goal of how much more efficient than a conventional car they wanted. Toyota stated for their new Prius:

"Fuel efficiency 1.5 times the conventional car wasn't good enough―we needed to double it,"

So we need to get that into perspective here. Toyota with the Prius wanted to go from approx 7.2 lts/100kms (Edit this was in 1994) they could achieve with say a comparably sized car like the Toyota Corolla to approx 3.6 lts/100kms with the Prius.

Well did they? Toyota state:

"The proudest accomplishment of the team was the achievement of 28 kilometers per liter under the Japanese 10-15 test cycle."

Well I do not know about anybody else but I am impressed. 28 kilometers per liter is approx 3.6 lts/100kms . 8-)

So how did they achieve it? Well Wikipedia state:

"ICE torque output is minimal at lower RPMs and conventional vehicles increase engine size to meet market requirements for acceptable initial acceleration. The larger engine has more power than needed for cruising. Electric motors produce full torque at standstill and are well-suited to complement ICE torque deficiency at low RPMs. In a power-split hybrid, a smaller, less flexible, and more efficient engine can be used. The smaller engine, using a more efficient cycle and often operating in the favorable region of the brake specific fuel consumption map, significantly contributes to the higher overall efficiency of the vehicle."

I think we can see what they are saying here. My simplified interpretation. Use a smaller engine, an Atkinson cycle engine in Toyota's case, to cover average loads when cruising and back it up with electric motors and a battery. Then we have regen and stop/start technology to also help efficiency and emissions.

But why go to all this trouble? Some might say we have losses going into and out of the drive battery. That cannot be efficient. A larger battery to degrade......... I could go on but still why go to all the trouble? Just what is the problem with the the ICE (Internal Combustion Engine) that we need to address.

The sad truth. It is inefficient. Wikipedia state:

"In the past 3–4 years, GDI (Gasoline Direct Injection) increased the efficiency of the engines equipped with this fueling system up to 35%."

Now this claim:

"Most internal combustion engines are incredibly inefficient at turning fuel burned into usable energy.

The efficiency by which they do so is measured in terms of "thermal efficiency", and most gasoline combustion engines average around 20 percent thermal efficiency. Diesels are typically higher--approaching 40 percent in some cases.

Toyota has now developed a new gasoline engine which it claims has a maximum thermal efficiency of 38 percent--greater than any other mass-produced combustion engine."

Lets just say the ICE is approx 40% efficient just remember that is maximum thermal efficiency. Sitting at the traffic light idling a big V8 it will not be 40% efficient. Only when it is in the favourable region of the brake specific fuel consumption map will we be seeing this. In this region the throttle plate that controls the air that comes into the pistons to be burnt with fuel is fully open and so reduced pumping losses.

Lets get our heads around this. At least 60% losses. :shock: and according to Toyota most gasoline combustion engines average around 20 percent thermal efficiency. 80% losses. :o The 15-20% losses we talk about around here in the conversions of electricity are starting to sound low to me.

To be continued.............


Last edited by Trex on Sun Jan 06, 2019 12:07 am, edited 3 times in total.

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 Post subject: Re: So why do we have Hybrid Electric Vehicles.
PostPosted: Sat Jan 05, 2019 6:31 pm 
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Joined: Thu Feb 26, 2015 5:58 pm
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Location: Near Port Macquarie Australia
So on I go.

Now in my last post we talked about the inefficient ICE. At least 60% losses.

Now my previous question in my last post was:

"But why go to all this trouble? Some might say we have losses going into and out of the drive battery. That cannot be efficient. A larger battery to degrade......... I could go on but still why go to all the trouble? Just what is the problem with the the ICE (Internal Combustion Engine) that we need to address."

In spite of the what some would say of increased complexity, losses in conversions etc I think that Toyota have proven that using a hybrid vehicle drivetrain they improved the efficiency compared to a conventionally powered car.

How? Now this is how I have stated it here before as simply as I can. If you have to start that petrol motor run it in its most efficient "zone" and at all other times try and turn the bloody inefficient petrol motor off. I still think that true to this day. Some may consider that over simplified. But that is my simplified interpretation.

Now lets talk about the PHEV. Now it is a HEV ie Hybrid Electric Vehicle with a P for Plug in. It has a lot of the same feature of the Prius I have already discussed. Small petrol engine, although not Atkinson cycle yet like in the Prius, a drive battery and electric motors/generator etc. Now I do not want to do a direct comparison here between Toyota's
HSD and Mitsubishi's drive-train. We can discuss that later if we want. Plus I do not want to get into the complexities of series and parallel hybrid, Power-split or series-parallel hybrid.......at this stage of my discussion. I just want to say I think we have "similar system" in the PHEV to the Prius.

I also think the PHEV has the same "philosophy" as the Prius ie If you have to start that petrol motor run it in its most efficient "zone" and at all other times try and turn the bloody inefficient petrol motor off.

Edit Ok I know the petrol motor runs in the PHEV at times NOT in most efficient "zone" like heating and I would consider series mode and if we drive it above certain speeds etc but I think most here would give me some leeway on the statement above.

Now I will finish this here and I could have brought in some "pretty" pictures and graphs but I or we can later if we require.

I can also show the articles where I got this information if you require. Just feeling a bit buggered at the moment. Been a wee bit warm here lately. :roll:


Last edited by Trex on Sat Jan 05, 2019 9:02 pm, edited 2 times in total.

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 Post subject: Re: So why do we have Hybrid Electric Vehicles.
PostPosted: Sat Jan 05, 2019 7:03 pm 
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Joined: Thu Feb 26, 2015 5:58 pm
Posts: 738
Location: Near Port Macquarie Australia
Now AndyInOz,Tipper,richr,elm70,maby and HHL. I know I just rudely pressed on without even acknowledging you but I did not want to be distracted on my mission of getting down my research into the thread.

"My mission". That sounds like something out of The Blues Brothers movie. Yep, I was on a mission from God. :D


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