# Rehashed idea for series or parallel hybrid



## tinkeringgreg (Mar 27, 2008)

Sounds possible My buddy at work and I are planning to do something very similar to your version #2 with a small diesel engine running a generator


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## Mastiff (Jan 11, 2008)

> 2) Get a small engine hooked up to a generator head, produce electricity.... use that to power the electric motor at highway speeds saving battery power for stop and go city driving.


This is called a Series Hybrid.


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## MrCrabs (Mar 7, 2008)

Yes I know whats its called... which is why the title of the thread is "rehashed idea for series or parallel hybrid"

I was putting these ideas out there to see if anyone had thought of/planned out something similar and would share their ideas/opinions, or if anyone has designed some type of hybrid and calculated vehicle performance.

Many beginners will ask why they simply can't carry a generator to help power the car, and the answers are.
It adds weight which reduces battery only range
Generators aren't very clean or efficient compared to modern car engines.

I'm trying to figure out if it is feasible to make a homebuilt series hybrid that would actually help extend range, and pollute less than a regular car

This weekend I'll have to sit down, and try and come up with a weight limit for a vehicle, and see if a motor, generator, engine, controller and batteries could fit in that weight limit, and if the performance would be acceptable.


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## SirisC (Feb 8, 2008)

Why can't an efficient car engine be connected to an electric generator and run at it's most efficient load/rpm? (Thinking a VW TDI motor)


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## CPLTECH (Sep 14, 2007)

MrCrabs said:


> Many beginners will ask why they simply can't carry a generator to help power the car, and the answers are.
> It adds weight which reduces battery only range
> Generators aren't very clean or efficient compared to modern car engines.
> quote]
> ...


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## MrCrabs (Mar 7, 2008)

CPLTECH said:


> One area of vital concern so often overlooked is: How do you handle the heat developed?
> 
> The ever common air-cooled Advanced 9" DC motor is a mere 28HP continuous. For me at 120V, 185A (more or less) is the rated HP. Going up slight grades or trying to go freeway speeds can & will exceed those numbers, many times. That's OK for a few minutes - the insulation on the motor windings have been improved for EV use. How does the ambient temp in summer affect motor cooling? Better put a temp gauge on it! I've only seen water-cooled motors in the AC variety for EVs that Ford & GM built in 1997-98 small trucks.


Are you talking about the heat developed in the electric drive motor? So do you have to avoid any roads with speed limits of 50 mph or higher?
Do you have a blower forcing air into/over the motor?


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## ww321q (Mar 28, 2008)

MrCrabs You have the same idea as I have . Being My electric motor is a little on the small size I thought that using a small ICE motor for assistance would be good . In the 70s Dave Arthur and Mother Earth News built some hybrid cars with a small generator . MEN claimed 83.6 mpg on a 78mile run using a small diesel generator . I was thinking of using a double clutch . One to the trany or driveshaft and the other clutch to a generator . ...J.W.


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## MrCrabs (Mar 7, 2008)

I saw those articles on Mother Earth News, and thats what planted this whole EV idea into my head... then I found this site (thru google i think)
Now I spend lots of my free time reading, researching and planning how to make my own EV


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## CPLTECH (Sep 14, 2007)

RE:_Going up slight grades or trying to go freeway speeds can & will exceed those numbers, many times._ 

I should clarify... That sentence was poorly worded. When I said "many times" I should have stated "many times I exceed 185A. Sorry for any confusion.

On one 4mile interstate stretch of a slight grade of my commute, I keep it between 47-52MPH (depending on whether a head or tail wind) and 200-250A. I did do 250-300A once and was greeted with an motor odor. So from my experience, adding a generator to go faster would just cause the EV motor an early death. Can I do 65+ on less than 185A? Yes, until the tires touch a grade. On the other hand, increasing battery pack from 120V to 144-156V would provide more HP with less overall heat and would give more speed. So, like any type of vehicle made, I, too, know the limitations I have to live with & therefore drive accordingly. Don't try to reinvent the wheel philosophy. I try to express on this forum my experiences (as seen from an electronic/electric prospective) so that others will have a good experience. For that reason I question those who want to use 72V or generators. If you want to race as a hobby & can afford the motor/battery replacements, go for it. In some situations, you are better off financially with an economy ICE. I just realize that with my setup, it's a second vehicle good for at least 40 local miles at moderate speeds and expect nothing more.


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## ww321q (Mar 28, 2008)

CPLTECH I agree with what you say for the most part . If you are overloading your motor the generator is a bad way to go . But if your battery pack is to small the generator would help . The main reason I would would install the 10hp diesel I have is to take some of that load off the to small motor (coupled to trans). It would also double your range . At the lest a second set of batteries for my 120v sys. would add 600lbs of load to a to small motor . The 10hp diesel adds 120lbs and removes load when needed . thanks ..J.W.


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## michaeljayclark (Apr 3, 2008)

just for example, this generator
http://www.electricgeneratorsdirect.com/catalog/product_info.php?products_id=345

weighs 450 pounds. but that is with the gas tank, battery, tires, and frame. Maybe shave off 50 pounds if you just mount the generator to the frame of the EV.

says can run 10 hours from 16 gallons at half load. 15,000 watts at 12 volts gives 1250 amps. 7,500 watts at 12 volts gives 625 amps.

how fast could 625 amps charge a set of batteries? Using all 1250 amps would make the generator run like crazy making it use more than 1/2 gallon per hour. 1/2 gallon per hour would be the most to get a benefit. The EV prob would at best average 35 miles per hour in city traffic. burning 1/2 gallon per hour would almost equal 70 miles per gallon per hour....

Have one set of batteries run the motor for an hour. have the motor switch to the 2nd set of batteries and then have the generator recharge the first set of batteries for an hour. Then when the motor exhausts the battery bank it is on switch back to the battery bank getting charged. Switch the generator back to the discharged battery bank, etc...

I guess the answer depends on how fast the generator could recharge batteries and stay below half load. could it keep the batteries charged to keep the motor in the EV running at an average speed of 35 miles per hour through a city?


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## michaeljayclark (Apr 3, 2008)

ac propulsion wrote a 10 page doc on a gas powered trailered generator for an ev for long distances. the forum limit doesnt allow me to upload and share it. just send me an email and Ill be happy to forward it like its hot....

[email protected]


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## MrCrabs (Mar 7, 2008)

Found this guy who puts a Honda generator in the back of his pickup when needed.

http://www.evalbum.com/122.html

http://www.vehiculevert.org/index.php?lien=generatrice

Doubles his range from 40 miles to 80 miles


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## weelliott (May 12, 2008)

I had a similar idea. I don't know if I'm overlooking a reason that it is not possible, or if others are overlooking the fact that it is possible, but I'd think it would be much easier to incorporate teh ICE generator into the system as a way of sending juice to the electric motor versus sending juice to the batteries. 

Sending juice to the batteries, then using it later seems much less efficient than just using it as it come from the generator. Ideally, I'd picture using the electricity form the ICE genset when I needed high current, like on the highway. The surplus juice would go to the batteries, and any deficit would be fulfilled by the batteries, but the amount of current flowing into and out of the batteries would be low, which means more efficient motoring, and it's better for the life of the batteries. 

As for ICE engines for the generator, diesels are attractive for their efficiency and longevity. However, cold start performance and really poor weight to power ratios deter me. A tiny high revving four stroke gasoline engine seems a better choice to me.

I've been looking at the honda line of four stroke motorcycle engines. I can't find any stats on the emissions, but honda in general tries to make clean burning engines. An attractive part of a motorcycle engine is they are powerful for their size, they are relatively small, and with the integrated transmission, they can be geared to run near their peak efficient speed while still being able to turn a genset at it's required speed.

There are 150 cc and 250 cc sizes that make 21 and 28 HP respectively in the bikes. I'd assume that once they are pulled out of the bike and gelded with an acceptable exhaust that would make them bearable as they buzz along at nearly 10 grand, 18 and 24 would be closer to reality.

Once transmission efficiencies and mechanical to electrical conversion takes place, I'd guess the total input to the electrical system at about 13 and 18HP, or 9 and 14 Killowatts. 

As for weight, they are fairly light. I can't find exact weights, but have read in places weights from 50 pounds to 80 pounds. I'd imagine that a total engine/genhead setup could be built that weighs around 150-175. That's like three batteries. It would provide a lot more energy storage than three batteries though. 

So the good side is that you'd get more range, less overall vehicle weight, warmth for batteries or people in the winter, and more range. Did I mention range?

On the downside, the controller would be more complicated. You'd have to get cooling air to the motor. It is large enough to only fit in a few places in a car. You'd need to quiet it down somehow. You'd also still be using gas. 

It would be a much more efficient use of a gasoline engine though. Not only are you actually using a large portion of the energy generated by the motor, but you are using it at it's most efficient engine speed and throttle setting(WOT).

Thoughts?


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## joseph3354 (Apr 2, 2008)

connecting the generator to the battery pack has a capacitor like effect.most likely the generator can not produce the 150 to 300 amps necessary to drive your vehicle.here is a link to what can happen to a generator that does not have the correct output.

http://www.thebackshed.com/Windmill/FORUM1/forum_posts.asp?TID=902&PN=1&TPN=1


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## MrCrabs (Mar 7, 2008)

I've pretty much given up on the idea to doing a homemade hybrid, at least for my first conversion. I think a simple pure EV conversion is the best for a beginner. 

This Rav4-EV Range extender is pretty interesting, however its a very complicated setup.
http://www.evnut.com/rav_longranger.htm
They built a trailer which holds a Kawaski motorcycle engine, and a modified AC Propulsion systems AC motor, to act like a generator, which can output a constant 20kW. That would be beyond my budget for a DIY project. Plus the trailer steers itself when backing up to help the driver out.


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## michaeljayclark (Apr 3, 2008)

Thats the same paper that I have. AC Propulsions idea about a trailered generator. they believe that water cooling just like an ICE engine would require a trailer. I believe there are ways to extend the back of the car to accommodate a generator.

I saw a 10,000 watt generator for $1000 that runs for 24 hours on 16 gallons at half load.

If you charge at 30 amps that is half load. The charger should charge the batteries pretty quickly at 240 volts 30 amps and the generator still be at half load.

I do not see a way that you could have the generator keep up with the amp draw of the electric motor. The onboard generator would be to extend range but not make range unlimited without stopping.

I have no illusions that a generator could do that and burn fuel efficiently. A generator going crazy to try to keep up with a heavy load would burn fuel like crazy and then just burn up. They are only air cooled and running at full bore would catch them on fire. I have heard of truckers using small generators to run AC while stopped and they used cheap undersized generators.

Thats why I say that the generator can only be at half load to matter, other than that it would waste gas just like the ICE you are replacing.
There is a 17.5 Kw generator for 3000 dollars but it burns 16 gallons in 10 hours at hal load, not as efficient.

I like the motorcycle engine idea. generators designed to be turned by tractors can be as high at 100 Kw but the higher you go the more horsepower you would need to turn them.

I bet a 20 Kw PTO generator can be turned by a good sized motorcycle engine. Only question is how much gas does it burn per hour?

I think the idea of onboard generator for an EV is frowned upon because EVs are supposed to be pure electric. But then the onboard generator can be a diesel that burns waste vege oil, or a gas engine that is easily made to burn propane or even compressed hydrogen with a simple adapter.


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## Thalass (Dec 28, 2007)

I would like to remodify my EV at some point after it's finished. It's an off-road type car originally, so if I can eventually give it a range similar to ICE powered versions it'll be worth lifting it and beefing it up for proper off-road trips with the other Subarus around town.

But until I can find a generator with a decent output and decent mass it won't happen. I'm fairly sure that if you design a generator specifically for series hybrid EVs you could get close to the ideal, maybe.


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## EL Escort (May 8, 2008)

I had come up with a similar idea, And concluded that if I was going to do that I'd might as well leave the ~1900 cc 4 cyl in the front. Install a modified "DeLco" PMA with some sort of regulator charger circut going to the EV batteries that power a rear wheel drive, direct drive set-up in the back of the car. Operate gas or electric only. Maybe not even change modes when rolling. Left foot throttle for the electric side of it.
Then add gas miles and electric miles together and have an adjusted MPG figure.


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## mattW (Sep 14, 2007)

I'm thinking if I get a running bike for my conversion I could use a second PM motor to make a series hybrid side car attachment for long trips with the original engine powering the generating motor which would power the bike electrically. But it's not really something I want to get into until the bike is done and I know the power requirements and whether I would ever need it at all.


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## weelliott (May 12, 2008)

I've looked into the motorcycle engine and generator a little more. It does seem possible to have a 250 or 500 cc engine put out enough power to keep the car cruising at highway speeds, but probably not accelerating. However, that is somethign that can be overcome with controller programming. 

Currently the big wrench in the works is that I can't find a decent size generator(20KW or so) that doesn't weigh a ton. They are in the 300-500 pound range. 

Does anyone know of a smaller one? I've used electric motors that were in the 5-7 HP range, and they were light enough to pick up. That's about 3.5 to 5 KW. I wonder if I could put a few of these together. I also wonder if collectively they would be less than 300 pounds.

The Aptera hybrid mentions the use of a lightweight generator. Anyone know any manufacturers of these?


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## tinkeringgreg (Mar 27, 2008)

one issue that needs to be addressed on an ICE other than a Diesel is rpm limiting. Diesels have a built in governor that gas engines don't. If the load was reduced from a gas engine at WOT the engine will over rev and your car wont be a hybrid any more just an EV. Some type of speed regulation needs to be in place to control the ICE. With that said thank you for the motorcycle engine idea we may pursue that when we get around to building the hybrid right now I am busy making parts for my EV which gets built first.


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## weelliott (May 12, 2008)

Pretty much every engine made since the mid eighties has had a rev limiter on it. If not, many more engine fatalities would have occured. Sometimes it is in the form of a mechanism in the distributor that stops sending spark once a certain speed is reached(think centrifugal here and it is pretty simple.) Nowadays the ECU provides cutout on fuel injected engines. 

Many gasoline engines are running electronic fuel injection. With some tinkering of the ECU, or even using a megasquirt unit, you can easily keep the RPM constant at a programmed speed. 

A friend of mine from college worked for Ford for a few years as a calibrator. His job was to develop the algorythms in the electronic controls that control the engine that would allow the engine to idle at a constant speed regardless of many things. This sounds easy when you only consider relatively stable things like ambient temperature, or atmospheric pressure, but it gets more complicated when you account for sudden loads on the alternator or the air conditioning compressor engaging.

It is definitely a task that can be tackled, and even with the little that I remember from my controls class in college, I think I could develop a system that could stay at a predetermined engine speed, or in the least never go above a certain speed.


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