# Most practical vehicle is a Mild Hybrid - I know we can build it! (But should we?)



## dnarby (Mar 7, 2011)

Hi All,

After having followed DIY and commercial hybrid and EV progress for over a decade, I finally came to the conclusion (as have others) that the most practical solution given the current level of ICE and battery technology is a vehicle with:

1. An electric motor and battery pack sufficient to get it up to highway speed quickly, with a range of around 25 miles

and

2. An ICE with around 30HP, matched in gearing to most efficiently keep the keep the car at highway speed (with enough extra HP left over to run all accessories and re-charge the batteries).


Why this configuration? It's the most cost effective from a $/mile standpoint. Electric motors are great for acceleration but currently have power storage issues. ICE's are great for steady RPM power applications and have great energy storage, but are horribly inefficient when used to accelerate. Solution: Use each for it's best purpose.

My understanding is the average passenger car only needs 20hp to overcome wind resistance at highway speed. 30hp leaves enough to run all accessories and recharge the battery pack (under all but I expect would be considered 'race conditions').

A 25 mile EV only range is enough for the majority of around-town driving (to the store and back).

This configuration would keep the vehicle's weight close to the original curb weight, so handling would be the same and suspension components won't need augmenting.

As technology becomes available (better batteries, motors, etc.) they can be swapped in, and the vehicle will be easily customizable for greater performance vs. efficiency, EV range, etc.

I personally think this is likely to be worth doing when gas hits $8.00 a gallon, but I'm an optimist.

I also think that the automakers will eventually start building these (they have to have come to the same conclusion years ago), but again, I'm an optimist.

All input is welcome.

TIA,

Dave


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## Salty9 (Jul 13, 2009)

I agree. Have you planned a vehicle? I am planning on a reverse hybrid trike using a small motorcycle engine and rear wheel with the front wheels driven electrically. I will be using the sub frame from a small disposable econbox for the front frame.


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## Bowser330 (Jun 15, 2008)

I agree as well..

What 30hp motor will you use?

Is a motorcycle engine fuel efficient enough? How much do they weigh?


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## Salty9 (Jul 13, 2009)

A small diesel engine fueled with biodiesel would be the greenest hybrid but I think they are not common. I know less about diesels than electric motors.


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## dnarby (Mar 7, 2011)

I have not planned a vehicle yet, although I have a 91 Volvo wagon which would be a good candidate (lot of room in the engine compartment & the back so weight distribution will be easy, and it's rear-wheel drive).

Really, it doesn't matter what vehicle you want to use, after you've determined what you need it for (super thrifty commuter, safe family 'errand vehicle', ICE sports car killer, etc.) the main issues AFAIKT are motor candidates, controllers & transmissions.

A good candidate for the ICE is a big single cylinder motorcycle engine (e.g. Suzuki Savage, 650cc, 30hp) for efficiency. The ideal engine would be a single cylinder turbo-diesel, but that might be difficult to source.

You would probably have to design it so the ICE can be removed allowing the car to initially register as a pure electric (thanks to our gov't 'knowing what's best' for us...).

To get the power to the road a manual transmission would probably be easiest, but v-belt drives (e.g. lawn tractors or belt driven factory machinery) are fairly efficient TTBOMK, and might allow for a DIY CTV (chain or direct gear drive would be optimal, but there's always trade offs).

If you were going for pure MPG, I would actually skip the electric motor and drop a motorcycle engine in an areodynamic three wheeler. If you want efficiency, use a 250cc single cyl enduro motor, pure performance use a 'superbike' motor (e.g. Hayabusa), a trade off would be a big twin (e.g. Kawasaki Vulcan) motor. The advantage of an electric would probably be offset by the weight increase (smaller vehicle means bigger % of the total weight is your electric drive train).

The main issue I can see is how to control the electrics to only kick in when needed. I was thinking a combination of throttle position sensing and/or possibly a knock sensor - knock sensor kicks in, electric turns on to help the ICE, or if you depress the pedal past 1/2 (or whatever you desire).

After that, the generator control would be important. You don't necessarily want the generator putting a lot of drag on the ICE during acceleration (you only want it charging when the ICE is at peak efficiency RPMs).

Lots of things to work out here.

Naturally, after we figure it out the automakers will copy it, but someone needs to kick them in the ass to get them to do the right thing...


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## dnarby (Mar 7, 2011)

I have not planned a vehicle yet, although I have a 91 Volvo wagon which would be a good candidate (lot of room in the engine compartment & the back so weight distribution will be easy, and it's rear-wheel drive).

Really, it doesn't matter what vehicle you want to use, after you've determined what you need it for (super thrifty commuter, safe family 'errand vehicle', ICE sports car killer, etc.) the main issues AFAIKT are motor candidates, controllers & transmissions.

A good candidate for the ICE is a big single cylinder motorcycle engine (e.g. Suzuki Savage, 650cc, 30hp) for efficiency. The ideal engine would be a single cylinder turbo-diesel, but that might be difficult to source. Motorcycle engines can vary quite a bit in weight, but generally the less pistons, the lighter the motor (I think the savage motor is 150lbs including the transmission?).

You would probably have to design it so the ICE can be removed allowing the car to initially register as a pure electric (thanks to our gov't 'knowing what's best' for us...).

To get the power to the road a manual transmission would probably be easiest, but v-belt drives (e.g. lawn tractors or belt driven factory machinery) are fairly efficient TTBOMK, and might allow for a DIY CTV (chain or direct gear drive would be optimal, but there's always trade offs).

If you were going for pure MPG, I would actually skip the electric motor and drop a motorcycle engine in an areodynamic three wheeler. If you want efficiency, use a 250cc single cyl enduro motor, pure performance use a 'superbike' motor (e.g. Hayabusa), a trade off would be a big twin (e.g. Kawasaki Vulcan) motor. The advantage of an electric would probably be offset by the weight increase (smaller vehicle means bigger % of the total weight is your electric drive train).

The main issue I can see is how to control the electrics to only kick in when needed. I was thinking a combination of throttle position sensing and/or possibly a knock sensor - knock sensor kicks in, electric turns on to help the ICE, or if you depress the pedal past 1/2 (or whatever you desire).

After that, the generator control would be important. You don't necessarily want the generator putting a lot of drag on the ICE during acceleration (you only want it charging when the ICE is at peak efficiency RPMs).

Lots of things to work out here.

Naturally, after we figure it out the automakers will copy it, but someone needs to kick them in the ass to get them to do the right thing...


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## dtbaker (Jan 5, 2008)

I predict you'll find hybrid technology too complex and expensive. full-electric with 50 to 100 mile range from large format lithium is already adequate and cost effective for the majority of 'in-town' commute, so why not commit to that, and use a bio-diesel for long haul if and when you need it?


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## dnarby (Mar 7, 2011)

Here's why not:

1. I typically drive more than 50 miles, and frequently quite a bit more than that
2. Charging at work is not an option
3. Charging virtually ANYWHERE other than home is not an option
4. I'd rather not have to buy another vehicle just to travel outside the EV range
5. Biodiesel is a lot more trouble than I'm willing to go to. I'm looking to save money.
6. LiOn is really expensive compared to deep-cycle lead acids, and for this theoretical vehicle we don't need very many batteries. Batteries can be upgraded later when they come down in price.


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## dtbaker (Jan 5, 2008)

dnarby said:


> Here's why not:
> 
> 1. I typically drive more than 50 miles, and frequently quite a bit more than that
> ---
> ...


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## dnarby (Mar 7, 2011)

You are being argumentative.

With respect, I would rather discuss how best to achieve my goal than conform to what you think I should be doing.


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## nimblemotors (Oct 1, 2010)

I've said for years that a plug-in hybrid is the next step after hybrid,
before we can get to all-electric for a signficiant percentage of cars on the road (or new ones sold). Remember that while millions of hybrids sold, they are still a tiny percentage of cars on the road or even new sold.

But you really must distinguish between what car makers will make,
and what YOU can make or build for yourself or 10-1000 others.
A hybrid is more complex mechanically for a DIY. Not sure it is really worth the trouble or effort, this really is a hobby for 99% of us right? A pure EV is much easier to build, if not the most "practical" because of range. But I am building a hybrid currently, as my hobby is doing what is hard, not easy. 
Used small motors are cheap, it is batteries that are expensive for DIY.

As for controls, my simple plan is to power the electric motor and gas motor in parallel, basically make the ICE work less hard and thus get much better MPG.



dnarby said:


> Hi All,
> 
> After having followed DIY and commercial hybrid and EV progress for over a decade, I finally came to the conclusion (as have others) that the most practical solution given the current level of ICE and battery technology is a vehicle with:
> 
> ...


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## Bowser330 (Jun 15, 2008)

You have some sound ideas .... my recommendation is to take what you want form the advice or comments members give you and dont take what you dont want, its that simple. 

I plan to run my generator/small engine through my battery charger, which is governed by a basic BMS with LowV and HighV switches..maybe you could do it that way...


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## Salty9 (Jul 13, 2009)

Anyone ready to start a build thread yet?


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## dnarby (Mar 7, 2011)

nimblemotors said:


> I've said for years that a plug-in hybrid is the next step after hybrid,
> before we can get to all-electric for a significant percentage of cars on the road (or new ones sold). Remember that while millions of hybrids sold, they are still a tiny percentage of cars on the road or even new sold.
> 
> But you really must distinguish between what car makers will make,
> ...


You make a great deal of sense, and perhaps the path of least resistance/cost effectiveness is to just buy a hybrid and hack it. I'm just not a fan of trying to fix things that have intentionally been made overly complex (all cars eventually break, and fixing them is a major cost of driving).

To your plan, that sounds like a logical starting off point. Once you have it running, you can play around with throttle configurations.


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## fj1200 (Dec 23, 2008)

dnarby said:


> Hi All,
> 
> After having followed DIY and commercial hybrid and EV progress for over a decade, I finally came to the conclusion (as have others) that the most practical solution given the current level of ICE and battery technology is a vehicle with:
> 
> ...


I'm with ya Dave but my question is why not use the electric motor as the drive mechanism and have the ICE handle charging duties alone? It seems to me that would simplify the issues. The motor could be tailored to the type of driving that you need while the ICE could be chosen solely on charging efficiency.

Just a thought.


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## dnarby (Mar 7, 2011)

fj1200 said:


> I'm with ya Dave but my question is why not use the electric motor as the drive mechanism and have the ICE handle charging duties alone? It seems to me that would simplify the issues. The motor could be tailored to the type of driving that you need while the ICE could be chosen solely on charging efficiency.
> 
> Just a thought.


That's how the Chevy Volt works, but the problem is efficiency. When you burn fuel to turn to electricity to store in a battery and discharge in a motor you lose energy to heat at every step of conversion. 

It's much more efficient to use the fuel push the car down the road directly. In fact, a 15hp motor keeping a full size vehicle at highway speed would be really efficient - The problem is accelerating, climbing hills, towing, etc. This was the whole reason for my starting this thread.


After sleeping on it a couple of days, it struck me that perhaps the first step (for me) would be to mount an electric motor to supplement the ICE motor in my wagon. It even has an auxiliary pulley already installed on the crank pulley assembly.

If I fabricate a bracket (and find a place to mount it!), I can easily install an electric motor to assist the ICE. The batteries to run this motor could be charged via grid or solar. When the batteries discharge, I could turn the electric motor idle.

If that helps improve cost per mile driven, then I could increase the final drive ratio for the vehicle, add more batteries, increase the electric motor size, etc. to improve on it.

One consideration I can think of is heat - Under the engine compartment is a pretty hostile environment, so I would need an electric motor that is rated to handle high temperatures and temperature extremes, or I would have to fabricate an enclosure with ventilation to prevent the motor from baking to death under the hood. Do any motors come to mind that would fit that bill?


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## Salty9 (Jul 13, 2009)

Some AC motors are water cooled. I saw a cutaway drawing of a transmission in a Chevy truck that had two electric motor-generators integrated with it. They were evidently cooled with the tranny fluid.

Edit: Additional info

http://en.wikipedia.org/wiki/Global_Hybrid_Cooperation


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## dnarby (Mar 7, 2011)

Thanks Salty,

That's good to know, as even coming from a cooler transmission oil is going to be pretty damn hot.

A quick Google search turns up some motors that are rated for continuous service at 155 deg F, which is pretty hot. This is fortunate, as another search turns up that center hood temperatures of a typical vehicle can approach 200 degrees!

Looks like I will have to probably get a temperature-ruggedized motor AND build a heat shield around this thing and vent it as well to get it to work.


Interestingly, the concept of an electric "booster motor" is the principle that most current hybrids work of of.


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## Salty9 (Jul 13, 2009)

Most auto trannies run hot because the cooler is part of the radiator and they pick up heat from the ICE coolant. I put after market tranny coolers on every truck with automatics that I've owned.


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## aeroscott (Jan 5, 2008)

I did a wire welding hybrid(MiG) , worked great . 24 volts of truck starter battery , 10 hp Briggs and stratton engine turning a 24volt aircraft generator . no need for a starter motor just hot the battery to the generator . no controller of any kind . if engine under charges batteries generator motors the engine .speed the engine up to get the amps wanted . as for the welding amps are controlled by wire feed speed , more wire more amps , makes for a nice steady smooth arc . I have the same setup for my solar array (48 volts) a PM motor out of a floor sweeper. doesn't get the 48v so I charge 24v 2 times by splitting the battery pack . need higher voltage motor for that . A hybrid only needs a amp meter , contactor and throttle control . For max efficiency PM generators .


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