# 2015 Fiat 500e



## 2015Fiat500E (Mar 5, 2017)

Hello All,
I'm looking to add range extender to my Fiat 500e. Could someone point me in the right direction as to where I could get the right equipment to add to the rear of the vehicle? Fiat 500e comes with no spare tire and there is an ample space to install range extender. KPSG used Fiat as their test bed but they are not ready to go to market. Ideally I would like to setup charging batteries until full and than a switch to powering the motor and accessories. If there would be no degradation in batteries the second option would be to charge batteries as electric motor draw it load from the batteries. The car comes with 24kwh battery pack with heating and cooling. I would have to overcome factory firmware that prevents the vehicle movement while charging.
Any help would be greatly appreciated.


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## dcb (Dec 5, 2009)

you should add one of these to the rear:









or maybe something like this:









or go buy a gas car.


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## 2015Fiat500E (Mar 5, 2017)

Look, if I was looking to get a degraded and silly posts I would not join this forum. The reality is that a number of sub 100 mile range cars present challenges every day to many people so I'm sure that this is not off the wall concern. After spending significant amount of time searching none of current range extender developments are ready for the market (that I'm aware of). I was hoping that someone here could potentially be willing to help me with perhaps finding solution instead of making jokes about it. Just look at the current market where sub 100 miles ev only range used cars are dropping like a rock on resale market. Almost all manufacturers come to the same conclusion and I don't believe they are all wrong. Used EV market will continue to grow and extending their range will give hope to petrol only users to build confidence in 70% EV and perhaps 30% petrol commutes. That in itself would represent significant lift to resale and new customer acquisitions. Isn't that what we are all after? 
Can some on this forum engage with my particular situation and perhaps offer some help and direction.
Thanks


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## DrJeff (Apr 24, 2015)

I also have a Fiat 500e (2014) LOVE IT!

(The motor cycle photo may not have been that far off)

As regards Range Extenders, the best option I can think of is the REX module from the BMW i3. Of course I have not tested this idea and it may be a dud, but it is somewhere to start.

I don't know enough about the I3 (especially the interface from the engine to the electric system - I would assume the engine is directly connected to a generator on the main shaft?)

Jeff

PS. The motor cycle photo may not have been that far off, the BMW i3 uses a motor cycle engine for range extension.


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## 2015Fiat500E (Mar 5, 2017)

Thanks for reply DrJeff, technology I was researching is based on free piston engine that is designed for it's efficiency and simplicity. There are only few moving parts and virtually no maintenance. Some of the labs (Israel) and others have been able to successfully test it. Since you have a Fiat 500E their model is perfectly suited for the application as it produces 30kw of power and as you know if you are using level 2, the most it will take is 5.5 - 6 kWh. The battery (24kwh) is small enough that it could work great not only in serial application but also if generator was used to power motor and accessories. Watching my power meter I have rarely experienced power demand over 30kw. The challenge would be power plant that can easily fit in the rear of the vehicle (500E does not come with spare only because battery pack is taking 2in of diameter needed to fit one) utilizing space underneath and where tire repair and 110V chargers are stored. The second would be to modify firmware to allow charging while moving, ability to provide power to the motor bypassing battery as well as enabling DC-DC charging (checking with several sources Bosh did build it with that functionality but apparently that feature is factory disabled) The word is that electronically Bosh built both BMW i3 and Fiat 500E with same techology. What I could use the most here is helping to find a source that would be willing to sell free piston engine/generator with rating of 25-30kw setup for common gas fuel (they claim that there is a great flexibility of alternate fuels that can be used and the adjustment of compression is electronic) and finding someone that have downloaded all of the codes to understand ECU's instructions and how to modify them to accommodate range extender. KPSG have done a nice job with Fiat 500E in retro fitting their two cylinder engine but it is designed with old ICE technology (their engine seams very quiet and well balanced but they said it will be at least two years before they enter the market) There are few jet turbine based as well but it's footprint would be a challenge to space available in Fiat 500E. The coolest thing about free piston is that combustion chambers are lateral so it's hight is nominal.
I hope I can get some of you engaged in this conversation and perhaps with multi effort we can find some prototypes that are available now, so some of us that are willing to use their vehicles as a test bed would be able to move it from the labs into the real life testing experience.
Thanks again


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## 2015Fiat500E (Mar 5, 2017)

Thanks for reply DrJeff, technology I was researching is based on free piston engine that is designed for it's efficiency and simplicity. There are only few moving parts and virtually no maintenance. Some of the labs (Israel) and others have been able to successfully test it. Since you have a Fiat 500E their model is perfectly suited for the application as it produces 30kw of power and as you know if you are using level 2, the most it will take is 5.5 - 6 kWh. The battery (24kwh) is small enough that it could work great not only in serial application but also if generator was used to power motor and accessories. Watching my power meter I have rarely experienced power demand over 30kw. The challenge would be power plant that can easily fit in the rear of the vehicle (500E does not come with spare only because battery pack is taking 2in of diameter needed to fit one) utilizing space underneath and where tire repair and 110V chargers are stored. The second would be to modify firmware to allow charging while moving, ability to provide power to the motor bypassing battery as well as enabling DC-DC charging (checking with several sources Bosh did build it with that functionality but apparently that feature is factory disabled) The word is that electronically Bosh built both BMW i3 and Fiat 500E with same techology. What I could use the most here is helping to find a source that would be willing to sell free piston engine/generator with rating of 25-30kw setup for common gas fuel (they claim that there is a great flexibility of alternate fuels that can be used and the adjustment of compression is electronic) and finding someone that have downloaded all of the codes to understand ECU's instructions and how to modify them to accommodate range extender. KPSG have done a nice job with Fiat 500E in retro fitting their two cylinder engine but it is designed with old ICE technology (their engine seams very quiet and well balanced but they said it will be at least two years before they enter the market) There are few jet turbine based as well but it's footprint would be a challenge to space available in Fiat 500E. The coolest thing about free piston is that combustion chambers are lateral so it's hight is nominal.
I hope I can get some of you engaged in this conversation and perhaps with multi effort we can find some prototypes that are available now, so some of us that are willing to use their vehicles as a test bed would be able to move it from the labs into the real life testing experience.
Thanks again


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## Duncan (Dec 8, 2008)

Hi
How much range do you need?
And how often?

If I was doing this I would be looking at a small trailer - probably with another battery pack

The idea would be that the trailer pack would normally earn it's living at home working with my solar panels - but it would be available to tow behind to increase the range

An IC range extender will give you a surprisingly poor economy and high emissions


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## DrJeff (Apr 24, 2015)

My Fiat 500e is my daily driver (commute car 90-100 mile range), so not a candidate to experiment with.

The free piston discussion is interesting, but I am interested in pragmatic solutions - i.e. solutions that don't have me doing R&D and ones where you can actually get your hands on motors, equipment, software. Unless you're a research lab, getting to work on those types of motor and tech is very unlikely.

I've already got a large project (TesLorean) and it is dependent on 'developing technology' (some by me and some by others). It takes a very long time and lots of effort (plus $$$) to be able to get to the point of a rolling & safe automobile.

A key phrase for projects that are at the boundaries of technology development...
"In theory, practice and theory are the same, but in practice they are not."

I also studied range extenders and came to the conclusion that they filled an evolutionary hole in battery development. That hole is quickly closing, and will likely be closed by the time any commercial add-on range extender gets fully commercially developed (if ever).

Jeff


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## rmay635703 (Oct 23, 2008)

http://myimiev.com/forum/viewtopic....r&sid=4383db04d4735f9f2fed8591f0e25caf#p16453

About the only cheap working range e tender is listed above.

All other schemes tend to be expensive, void own warranty and usually not all that effective.


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## rmay635703 (Oct 23, 2008)

2015Fiat500E said:


> Look, if I was looking to get a degraded and silly posts I would not join this forum.
> Thanks


You talk about a free piston engine that is silly and not available and then denigrate two real world examples of what you want.

Whether you like it or not streamlining your car coupled with hypermiling can double your cars range with virtually no out of pocket cost, the car shown is the aero civic which you can find a build thread on ecomodder.

It's very real and I doubt you have the patience to streamline as well as he did.
Streamlining your car costs time but very little money.

Next a motorcycle extender is real, if you want a cheap extender that's it, again like it or not it's how others have done it.

The link I provided above is to jrays extender, it can be made the best looking but is the same range extender EV heads have used since the 1970's.

I guess you need to ask yourself, do you want something that will
1. Get done
2. Work

Or do you want to push forward technology and fail to get anything done?


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## Karter2 (Nov 17, 2011)

2015Fiat500E said:


> Look, if I was looking to get a degraded and silly posts I would not join this forum.
> Thanks


 For someone critical of the sensibility of that reply, you certainly throw in a enqually implausible proposal...a generator system that is not actually available !!
This question get thrown up every few months ( which you would know if you did some research) and the most sensible , workable, available , practical solution is always.....install a bigger / secondary battery.
Or sell the Fiat and buy a PHEV. !
Also whilst you are at it, invest a few dollas into a humour transfusion.


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## dain254 (Oct 8, 2015)

http://www.harborfreight.com/900-pe...63cc-2-cycle-gas-generator-epacarb-63024.html

This would be in my opinion the obvious solution... string a few of these together in a manor that would generate enough juice to give you the amount of range extension desired. They could be easily attached to a small frame that would slip into the hitch receiver. Make sure to use extra 2 stroke oil so that they are well lubricated internally to optimize output! RANGE EXTENSION FOR 500 BUCKS!


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## dcb (Dec 5, 2009)

fwiw, I picked up a 4000/3500 watt 4 stroke 120/240 generator from menards clearance for < $200. I'm not recommending it* except in an emergency* as it is horribly loud and inefficient as compared to driving a wheel directly, but please don't buy 5 2 stroke generators for 3x the money and 500x the smoke and twice the weight, and no way to get them all in phase for your charger (let alone supplying it with 240v). 

Either way it is a plan for turning a decent EV into a crappy hybrid that gets humvee type mpg.



dcb said:


> go buy a gas car.


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## dain254 (Oct 8, 2015)

Having the smoke was the only reason I suggested a 2 stroke! Then a person could still roll coal on a Prius, but with an annoying loud and smokey collusion of 2 stroke engines!!

There are a few branches of my place of employment that actually have charging stations for EV's. That in my mind is the only truly practical way to extend the range of an already existing sub 100mile range EV for a persons daily commute is to charge during the day.


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## dcb (Dec 5, 2009)

I did think add extra 2 stroke oil was a nice touch


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## DrJeff (Apr 24, 2015)

Someone must have done the calculations for dragging an additional battery module behind the car. When the car's primary module runs out, you could switch (an exciting moment) to the reserve trailer pack (ignoring for a moment how unsafe a 400v flexible connection would be between the trailer and the car).

But there must be some cutoff here as you're pulling an additional say 600lbs (400lbs of battery and 200lbs of trailer), but you only get the benefit of additional miles. Some of the capacity of the first battery will be 'wasted' on just dragging around the second battery, which will in turn have some of its capacity wasted pulling around the primary battery.

This suggests a capacity (i.e. weight) and range tradeoff (for a given battery energy density).

Jeff


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## dain254 (Oct 8, 2015)

I was able to conjure a quick model AND rendering of what your Fiat 500e could look like with range extending features - note the improvements to aerodynamics, visibility, as well as overall vehicle aesthetics! The module at the rear which may appear to the untrained eye to be a rocket propulsion unit is actually an aerodynamic housing in which several 2 cycle generators are mounted. The amount of fire an smoke shown in the rendering is nearly half of actual!


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## dcb (Dec 5, 2009)

DrJeff said:


> Someone must have done the calculations for dragging an additional battery module behind the car.


fwiw, I think it depends on many factors. fwiw I had a trailer loaded with camping crap behind my saturn sw2 5 speed, and eeked out 45mpg for the whole trip. If I know I have an extra 600lbs of mass I might tweak my driving style to suit. On the flats in city it shouldn't make a lot of difference if you use minimal braking/regen anyway. The ecomodder guys have discussed aerodynamic trailers too, so might actually help?


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## GoElectric (Nov 15, 2015)

EV Drive has a REX, not sure if they sell it, but I would try them.

They have pics on their website - very small, rotary engine, I believe.

Jim


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## brian_ (Feb 7, 2017)

GoElectric said:


> EV Drive has a REX, not sure if they sell it, but I would try them.
> 
> They have pics on their website - very small, rotary engine, I believe.
> 
> Jim


Thanks for the tip; I'm interested in what's available. This one: EVD Car-e46 / 150-REX-100

The specs:


> *2. EVDrive REX (range extender) Module*
> 
> Continuous Power output 25kW @ 350VDC
> Uses highly efficient EVDrive proprietary PMAC brushless generator technology
> ...





> ...
> Small and light package is contained entirely in rear of vehicle within the spare tire well
> Volume of module is similar in size to typical inflated spare tire wheel, allowing placement into spare wheel well.
> ...


Interesting... and implausible. According to EVDrive, the engine-generator module fits in the spare tire well - not in a space the size and shape of the spare tire well, but actually in the spare tire well. Does anyone wonder how that cools, where it gets its combustion air, and what happens to the exhaust?  I think they really mean that you cut out the well - or at least chop big holes in it - to install the module.

There's a photo, and it shows that the system is larger than the "typical inflated spare tire wheel"; the portion of the system in the module in the spare tire well area doesn't appear to include fuel, radiator, or exhaust system. Effective exhaust systems for rotary engines are notoriously large. So much for "entirely in rear of vehicle within the spare tire well".



> ...
> Liquid cooled rotary engine can run on gasoline, propane, ethanol, or CNG. (rotary mfg. claims EPA emissions certifications – California CARB TBD)
> Current fuel tank gives about 300 mile range – if OEM fuel tank were used, we could expect up to 750 miles range.


Wankel-type rotary engines are notoriously inefficient. After a few decades, Mazda has finally given up trying to make them acceptable for cars. Does anyone believe that an overweight BMW 3-series can be driven for 300 miles by an inefficient small engine on the fuel that fits in the spare corners of a spare tire well that also contains and engine, generator, radiator, and exhaust system? That's what, 6 US gallons of fuel plus all the hardware in a 15-gallon space... Seriously, there's that photo, and it shows that module in the spare well doesn't include the fuel tank. Range means nothing when you haven't specified the fuel tank size and don't include the fuel tank in your package volume.

I assume that nothing about this system has been honestly presented by this company. I don't doubt that they do good work... they just play pretty loose with information and claims.

A 40-horsepower rotary is likely a single-rotor with about 400 cc chamber volume - so about 1.2L displacement. Is that very small? It's compact, at least, which is one of two rotary advantages (the other is rotational balance).

This EVDrive demonstration system is in a BMW 3-series sedan. It's a rear-wheel-drive car designed to carry an engine in the front. It seems strange to me to stack hefty batteries in the front and put a light and small engine-generator setup in the back.


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## GoElectric (Nov 15, 2015)

Hi. I have phoned them and am pretty impressed by this company. Have a look at their website, they custom-make battery packs and their PM motors are Bad Ass. And if that doesn`t impress you enough, they are the ones who built the 150kW REX for that super-semi which was just unveiled. 

Yes, of-course it has an air intake, an exhaust and a fuel tank, but I don`t doubt the output of the motor, or that it is more than your average rotary engine. Your scoffing is a bit over-done.

This whole thread seems to be a magnet for inane comments (humor appreciated) but - really - this guy is on the right website (right?) and deserves to be taken seriously. 

I too like the idea of a push-trailer, but think he wants extended range on a daily basis. Why he can`t plug in at work, I don`t know, but lay-off guys. I wonder if the OP hasn`t been chased away by now.


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## dcb (Dec 5, 2009)

GoElectric said:


> Have a look at their website


I took a look too and I saw a lot of red flags myself, things that didn't quite add up or that were misleading.



GoElectric said:


> but - really - this guy is on the right website (right?)


meh, hybrids aren't electrics, and he wasn't open to valid suggestions and went on about a free-piston (typically 2 stroke) series thingamabob. And not many here have the time/patience/skills to do a proper job on a hybrid, and series hybrid is a big red flag in itself.

also this makes it clearly not electric, since he wants to recharge fully from the gasser:


2015Fiat500E said:


> Ideally I would like to setup charging batteries until full and than a switch to powering the motor and accessories.



And this assertion makes me think he bought the wrong vehicle. Most DIY do NOT want higher resale on EVs fwiw (well, except for their own), but we don't want higher initial sales prices either, this was supposed to be so simple technology compared to ICE's. And tesla is doing everything possible to ensure it is anything but, even adding robot drivers (how's the resale on your OTR job?) and lobbying.



2015Fiat500E said:


> to build confidence in 70% EV and perhaps 30% petrol commutes. That in itself would represent significant lift to resale and new customer acquisitions. Isn't that what we are all after?


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## GoElectric (Nov 15, 2015)

That was pretty level-headed; I was worried I might have initiated a thermal runaway. Glad you are not a hot-head, just opinionated (smile). Others can make their own judgments about hybrid/series hybrids etc.... 

I'll admit to being pretty smitten by the EV Drive REX (as presented) and fancy the idea, but don't know a lot about them.


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## brian_ (Feb 7, 2017)

GoElectric said:


> I too like the idea of a push-trailer, but think he wants extended range on a daily basis.


I agree that a trailer with an engine (push or generator) is to adapt the vehicle for occasional long trips, not regular use.


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## brian_ (Feb 7, 2017)

GoElectric said:


> Have a look at their website, they custom-make battery packs and their PM motors are Bad Ass.


The original poster was asking about a engine-generator set, the EVDrive unit was an excellent reference, and my comments were about that installation. I'm not questioning EVDrive's battery or electric motor expertise, but their description of this engine-generator installation has little credibility.



GoElectric said:


> And if that doesn`t impress you enough, they are the ones who built the 150kW REX for that super-semi which was just unveiled.


That doesn't impress me at all. Without hard data, it's just promotional fluff. It is obviously not just possible but relatively common practice to assemble an engine-generator set (they're commercially available in a wide range of sizes with various types of engine); the hard part is making it perform. That turbine engine-generator set was an interim piece anyway - the "Nikola" project is now on the hydrogen fuel cell bandwagon, and any REX previously supplied by EVDrive is not shown on the Nikola Motors website.

Nikola Motors gives the impression of an investment scam to me, but that's a discussion for another thread. I don't know if EVDrive is a willing participant, a simple component supplier, or a victim of the scam. While much slicker than EVDrive, they have some of the same description issues, such as calling their 6x6 drivetrain a 6x4; I'm not sure that the website author understands automotive terms.



GoElectric said:


> Yes, of-course it has an air intake, an exhaust and a fuel tank, but I don`t doubt the output of the motor, or that it is more than your average rotary engine. Your scoffing is a bit over-done.


So why does EVDrive claim these all fit in the spare tire well, when they obviously don't? Less hype and more reality would make exactly the same installation much more credible, and attract less scoffing.

I don't question EVDrive's rotary (most likely drone) engine output. A build blog entry labels with it with "40 hp", and that would match the 25 kW generator. When an engine is described as "very small" that may suggest that it is light or consumes little fuel, neither of which will be true of this one. The engine looks vaguely like one I've seen (but not quite), which puts out 32 hp from a 300 cc per chamber single-rotor; a 400 cc per chamber single-rotor engine at 40 hp at roughly the illustrated dimensions seems plausible.

There is a tendency for small companies hyping their product to claim that their components perform better than comparable components from everyone else. EVDrive doesn't even make the engine, and whatever company does is small and inexperienced in rotary engines compared to Mazda, so it seems wildly unreasonable to assume that their product is more effective... and EVDrive isn't even making such a claim anyway. The 40 hp rotary will likely be comparable to the Rotron RT-300, but a bit bigger to suit the higher output. I have no issues with that, but it won't be particularly efficient.



GoElectric said:


> This whole thread seems to be a magnet for inane comments (humor appreciated) but - really - this guy is on the right website (right?) and deserves to be taken seriously.


While my comments about EVDrive's offering are critical, I didn't criticize the original poster's REX-in-rear scheme or question his sincerity. A hard look at packaging realities can only help.

EVDrive's rotary-engined generator set is a good example of available components used for this type of application (although a smaller set would be suitable for the 500), and a critical look at it shows the challenges of this sort of installation.


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## Karter2 (Nov 17, 2011)

> I don't question EVDrive's rotary (most likely drone) engine output. A build blog entry labels with it with "40 hp", and that would match the 25 kW generator. When an engine is described as "very small" that may suggest that it is light or consumes little fuel, neither of which will be true of this one. The engine looks vaguely like one I've seen (but not quite), which puts out 32 hp from a 300 cc per chamber single-rotor; a 400 cc per chamber single-rotor engine at 40 hp at roughly the illustrated dimensions seems plausible.


FYI.. Last time i checked, there were several companies producing "small" rotarys (Wankle design), of various capacity and outputs.
Everything from tiny 2hp versions for model planes up to large high output units for lightweight military power generation sets
Freedom power in the US was one such, but the real inovative lightweight designs were coming out of Europe , Rotron, AEI (UK), (Wankle)Germany, (Axro) Switzerland, (Parrilla) Italy,.. all have products around the 100-300cc , 10-80 hp range and have been producing them for many years.
Very compact , lightweight, power units, but they have a major issue with emmissions .
I suspect the "free piston" engine the OP refered to was likely the "Liquid Piston" X series,..still under development. http://liquidpiston.com/technology/x-engines-diesel/ 
Sorry if this has drifted OT.


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## dcb (Dec 5, 2009)

"2) Due to the unusual shape of it's combustion chamber (higher surface to volume ratio), the rotary is about 10% worse on BSFC (fuel burn) than a piston engine. " from the perspective of aircraft usage.
http://n4vy.rotaryroster.net/WhyMazda.html


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## 2015Fiat500E (Mar 5, 2017)

Great information from all of you that have contributed to this thread. Evaluation of free-piston had few things that really stand out:
1) No engine cooling needed (less space)
2) Only one moving part (common shafts that drives piston movement and generator coil
3) Gas spring for piston return
4) Electronic type of fuel adjustment (compression)
5) Horizontal layout for very small rectangle box shape 
6) Piston firing on every evolution if setup with opposite chambers or 2 cycle if common chamber setup for two pistons in center.
7) With high single or two cycle design generator becomes very efficient, 400cc displacement produces north of 30kw of electric power
8) Exhaust becomes much cleaner than standard ICE
9) No vibration

I know there are other options that could be explored and provide immediate gratification moving the project forward however above mentioned benefits are very compelling. There has been number of companies involved in R&D of free-piston including Israel's Sterling that is in talks to PSA group. 
Let's explore more information about companies researching or perhaps ones that are ready for small production of genset's on the market.
Thanks again for all of your input!


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## dcb (Dec 5, 2009)

To put it nicely, that is a load of crap.


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## DrJeff (Apr 24, 2015)

2015Fiat500E said:


> Let's explore more information about companies researching or perhaps ones that are ready for small production of genset's on the market....


 If this is your passion, go for it, I for one would be interested to hear what you find out.

You seem convinced the free piston thing is a great idea. Perhaps its just me, but great engine ideas seem to pop up all the time, but great engines don't. I'm too much of a pragmatist (or maybe too old) to spend much time on it.

Then there's the issue of solving yesterday's problems - range extension and efficient engines. Battery energy density and fast charging are the interesting future problems.

Jeff


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## dain254 (Oct 8, 2015)

Since you didn't bite on the flurry of generators which is essentially a free piston since it is so cheap... why not give harbor freight's solar department a look??

http://www.harborfreight.com/45-watt-solar-panel-kit-10-pc-kit-68751.html

It would only take 66 of these to completely recharge your 24kwh battery in a single 8hr workday! I bet they would even give you a price break if you bought that many... build a simple lightweight trailer to attach them all to and act as an aerodynamics improving device as well! RANGE DOUBLED!


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## GoElectric (Nov 15, 2015)

I'm outta here.


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## brian_ (Feb 7, 2017)

Karter2 said:


> FYI.. Last time i checked, there were several companies producing "small" rotarys (Wankle design), of various capacity and outputs.
> Everything from tiny 2hp versions for model planes up to large high output units for lightweight military power generation sets
> Freedom power in the US was one such, but the real inovative lightweight designs were coming out of Europe , Rotron, AEI (UK), (Wankle)Germany, (Axro) Switzerland, (Parrilla) Italy,.. all have products around the 100-300cc , 10-80 hp range and have been producing them for many years.
> Very compact , lightweight, power units, but they have a major issue with emmissions .


Yes, most Wankel-type rotaries are from Europe (as were Felix Wankel, the guy who made Wankel's engine viable - Paschke - and their employer). I wasn't trying to suggest that there were not established companies doing this, only that Mazda has been the big player in this technology for over 40 years. Even General Motors tried to improve on Mazda's design sufficiently to make a production-worthy automotive engine to the much less demanding standards of the 1970's and failed.

While I haven't noticed emissions as a part of this discussion so far, I agree that this is a serious challenge for rotaries. Choosing a rotary typically means sacrificing efficiency and emissions in favour of compact size and smooth operation, and possibly mechanical simplicity. That's why they have been popular in applications such as unmanned aircraft, experimental aircraft, and racing karts.

Those displacements are per chamber, so 100 to 300 cc means engine displacements from 300 to 900 cc (for a single rotor). 80 hp would take very high operating speed even with a 900 cc displacement, or two rotors for much more displacement. For an example of a continuous-duty engine rating, Mistral's engines (which are likely based on the Mazda 13B) put out 100 hp per rotor, with a 655 cc chamber displacement and 6353 rpm engine speed... twice the size and power of the likely size we've been discussing for the engine used by EVDrive, but roughly in proportion.

For an example, AIE sells a 225 cc per chamber single-rotor putting out 40 hp... at 8000 rpm and 310 to 350 g of fuel per kWh (which is not good by automotive standards).
The Aixro XF-40 has a 294 cc chamber volume and is rated for 35 hp at 6500 rpm and 370 g/kWh.

Sachs (originally Fichtel & Sachs) made Wankel-type rotaries for a long time (which were used in motorcycles, snowmobiles, and lawnmowers, among other applications), but the company was later bought by ZF and as a ZF division it no longer produces engines of any kind.

Parilla is one of the brands of IAME, which is apparently the big name in karting engines under various brands including Komet. The Parilla name only shows up in the "museum" section of the IAME website now, so it seems they don't use it anymore. I don't see any rotary engines in the product listing, so it look like they've given up on them... but I have seen photos online of old karts with rotary engines.

There is even at least one company selling model aircraft engines of the Wankel rotary design. Of course, like all engines of that size they're dirty, noisy, and inefficient - that's not the fault of the rotary design.

Compact engine size can be more important than efficiency for some of these battery-dominant series hybrids. In that case, a rotary might be a reasonable choice.


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## brian_ (Feb 7, 2017)

The small rotary engines I mentioned earlier listed specific fuel consumption from 310 to 370 g/kWh.

For comparison, the fuel consumption of Toyota's smaller Prius engine is well known from a 2004 publication, and is under 230 g/kWh over a broad range of speed as long as the engine is near full load; other modern gasoline automotive engines can be almost as good. 50% more fuel consumption than that is not impressively efficient. Large diesels are the efficiency kings, but even large turboshafts and recent automotive-sized diesels can get down to as low as 205 g/kWh, although that's probably not a reasonable expectation in the small package size needed for a car's engine-generator set. Certainly an efficient very small turbine is not currently available.

If you know how much energy it takes to move the car (kWh per distance travelled) - with the extra weight of the engine and generator - you can calculate your fuel economy when using the engine. The use of a series hybrid design (of which an example is adding a "range extender" engine and generator to a battery-electric vehicle) can allow the engine to run at its most efficient output; while this requires the use of the battery (and not just "powering the electric motor" with the engine) and losses due to battery inefficiency as a result, it can to some extent make up for the relatively poor efficiency of small engines and massive battery-electric drivetrains.

Fiat USA (which is really FCA for the U.S.) says on their 500e web page that the 500e uses "30 Kilowatt Hours (kWh) Per 100 Miles". That's 300 watt-hours or 0.3 kWh per mile. With a engine using 330 g/kWh, that's 100 grams of gasoline per mile, or if the density of gas is 750 g/L that's 133 mL/mile, or 0.035 gallons per mile, or 29 miles per US gallon... ideally. This doesn't seem like a winning idea for frequent use.


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## brian_ (Feb 7, 2017)

2015Fiat500E said:


> Great information from all of you that have contributed to this thread. Evaluation of free-piston had few things that really stand out:
> 1) No engine cooling needed (less space)
> 2) Only one moving part (common shafts that drives piston movement and generator coil
> 3) Gas spring for piston return
> ...


I agree with dcb that these are not generally valid; some are nothing but wishes without physical basis.



2015Fiat500E said:


> I know there are other options that could be explored and provide immediate gratification moving the project forward however above mentioned benefits are very compelling. There has been number of companies involved in R&D of free-piston including Israel's Sterling that is in talks to PSA group.
> Let's explore more information about companies researching or perhaps ones that are ready for small production of genset's on the market.


There seem to be two very different topics in this thread, corresponding to two very different goals for the proposed 500e to series hybrid conversion project.


Adding an actual engine-generator set to a real 500e to make a plug-in series hybrid (or call it a battery-electric car with range extender if you refuse to admit what it is ). This is real possibility which could be implemented immediately if functional and available components were used.
Use of a free-piston engine in a series hybrid system. This cannot be done effectively today because there is no such engine even close to being available. Pursing development of a practical free-piston engine would logically include a serious technical understanding of engine design.

By the time a practical free-piston engine for this purpose is available, this particular 500e will probably have been worn out and sent to a scrapyard long ago.

Why not split the discussion into two corresponding threads? The conversion of the 500E could focus on available components and how to select and use them. The free-piston engine discussion... well, that probably belongs somewhere other than a Do-It-Yourself electric vehicle forum.


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## brian_ (Feb 7, 2017)

Karter2 said:


> I suspect the "free piston" engine the OP refered to was likely the "Liquid Piston" X series,..still under development. http://liquidpiston.com/technology/x-engines-diesel/


I hope not - that's not a free-piston engine at all, so if that's what he's referring to, he has no idea what a free-piston engine is.

For fans of Wankel-type rotary engines, I'll note that as I recall reading (in the 1980's) about Felix Wankel's work which led to the DKM design, he systematically considered combinations of rotors and housing of various numbers of lobes. Many could function as engines (due to changing chamber volume between the inner and outer rotors), but most are not practical engine designs due to the challenges of induction and exhaust, and sealing. The strangely-named Liquid Piston design is one of those combinations, with a two-lobed rotor and three-lobed housing.

I assume that the OP _does_ know what a free-piston engine is. It makes sense that the only engine design which doesn't have a rotating shaft output would be considered as a power source for a series hybrid, which doesn't use a rotating shaft to transfer power from the engine to the driven wheels.



2015Fiat500E said:


> ... KPSG used Fiat as their test bed but they are not ready to go to market.


My guess is that this is just a typo, and was intended to be "KSPG"; the engine in the KSPG's 500e test vehicle for their range extender is not a free-piston, but rather a conventional vertical-shaft V-twin (like my lawn tractor's Briggs&Stratton). Since that vehicle was assembled, the company has become Rheinmetall Automotive AG.

The comments about possible free-piston engines only come up in later posts, as potential technology being researched by the OP. He's not the only one: people have been working on free-piston generators - in the form of free-piston linear generators - since 1934, I recall discussions in magazines in the 1970's, and companies as mainstream as Toyota (see R&T article) have seriously tried... without practical success so far.


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## brian_ (Feb 7, 2017)

DrJeff said:


> As regards Range Extenders, the best option I can think of is the REX module from the BMW i3.
> ...
> I don't know enough about the I3 (especially the interface from the engine to the electric system - I would assume the engine is directly connected to a generator on the main shaft?)


I haven't been able to find a clear photo or drawing of the configuration. The i3 uses a inclined parallel-twin motorcycle engine with the crankshaft transverse and the cylinders inclined rearward. I can't see whether the generator is directly mounted to one end of the crankshaft or driven less directly. It is common in this sort of setup to use a belt (or gears, or perhaps a chain) to link the engine and generator, either for packaging or to allow a faster-turning - and thus lighter and smaller - generator.

The i3 unit is far too tall to fit in a spare-tire-sized space. It occupies all of the available space on the right-hand side of the rear of the i3 under the (very high) cargo floor, beside the car's drive motor.


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## Karter2 (Nov 17, 2011)

Brian,....you may be aware, but.
Mazda have recently filed patents relating to the rotary based genset "Range Extender" system they used in their experimental "2" based Hybrid EV they produced a few years ago.
That was a 22 kW unit based on a 330 cc single rotor, tucked away in the rear with the battery etc.
http://www.caradvice.com.au/261593/mazda-2-ev-rotary-range-extender-review-quick-drive/

And .... One more rotary based genset...
http://freedom-motors.com/freedom_industrial.html
But doesnt look to have much going for it ...5kW @ 600+ lbs !


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## brian_ (Feb 7, 2017)

Karter2 said:


> Brian,....you may be aware, but.
> Mazda have recently filed patents relating to the rotary based genset "Range Extender" system they used in their experimental "2" based Hybrid EV they produced a few years ago.
> That was a 22 kW unit based on a 330 cc single rotor, tucked away in the rear with the battery etc.
> http://www.caradvice.com.au/261593/mazda-2-ev-rotary-range-extender-review-quick-drive/


Yes, I had heard of that one. It is entirely relevant, as it is exactly the sort of configuration that is desired here.

Mazda has been promoting use of a rotary engine in this type of application essentially since they gave up on normal automotive use. They continue to develop engines - the latest for conventional use is called SkyActiv-R - but that doesn't mean they'll ever make it to production. Their company history web page for the rotary engine claims that the "range extender" application is ideal because it allows constant operation at ideal speed and load, admitting that over a normal operating range performance (particularly efficiency) is not adequate. Of course, the same applies to reciprocating piston engines; the rotary advantages are compact packaging and smooth operation, as usual.

There are some interesting numbers in the article:


> The single rotor has a capacity of 330cc with a power output of 22kW at 4500rpm and a potential 28kW at an engine speed of 6000rpm.
> 
> The Mazda 2 EV can run on electric power alone until lithium-ion battery power – with the T-shaped battery pack sitting under the floor – starts to become depleted and the rotary engine kicks in, where it’s designed to run at a constant 2000rpm.


So while it's efficient at 2000 rpm and only something less than 10 kW, it could push out 22 kW if needed (but at the expense of efficiency), and brief surges to 28 kW are possible. That's from an engine with one-litre displacement (three chambers at 330 cc each). Since it isn't the same chamber displacement as any production Mazda rotary or the SkyActiv-R, they have likely put some serious development work into this one - rotaries don't have easy modifications corresponding to reciprocating piston bore and stroke changes.



Karter2 said:


> And .... One more rotary based genset...
> http://freedom-motors.com/freedom_industrial.html
> But doesnt look to have much going for it ...5kW @ 600+ lbs !


Interesting 
And it's not that bad: it looks like the 5kW @ 665 pounds is for the old and heavy conventional competition. That page shows a range of power from 2 - 5 kW, and weight from 20 - 40 pounds, which seems unrealistic for a complete genset. Rotapower doesn't actually sell gensets, but one of the images includes a comparison chart which suggests that they think their proposed set would put out 12.5 kW from an 80-pound, 3.25 cubic foot package. Of course that's still too large and not powerful enough to be practical for a car...

A typical current genset for use in a recreational vehicle (with dual air conditioners) is the 5.5 kW Onan RV QG 5500 EFI, which has a 653 cc V-twin (similar to the BMW i3 REX), occupies about six cubic feet, and weighs 288 pounds complete...still too heavy, too bulky, and not enough power. I have an older (carbureted rather than EFI) model of this unit, and it's not quiet. At least it can putt along for days at a time (which is the point of the design), with an engine that needs to run at only half of its maximum power to produce full rated electrical output. Rotapower probably chose their relatively high power density because they didn't allow for such low-stress operation. A practical configuration for a series hybrid (or "range extended") car is somewhere between the industrial and full-power-blast extremes.


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## Karter2 (Nov 17, 2011)

> ....it could push out 22 kW if needed (but at the expense of efficiency), and brief surges to 28 kW are possible. That's from an engine with one-litre displacement (three chambers at 330 cc each). ......


....ahh, the old displacement question again !...
A 330cc chamber single rotor wankel is " equivalent" capacity to a 660 cc piston engine !


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## brian_ (Feb 7, 2017)

Karter2 said:


> ....ahh, the old displacement question again !...
> A 330cc chamber single rotor wankel is " equivalent" capacity to a 660 cc piston engine !


Equivalent for racing regulations (where still allowed), yes, but not in physical reality. In a full cycle of the engine - which takes three turns of the main shaft - all three chambers of each rotor go through a combustion cycle. In a 4-stroke reciprocating piston engine, this takes two crankshaft revolutions. In a 2-stroke reciprocating piston engine, this takes one crankshaft revolution. Crankshaft/mainshaft turns are irrelevant to the physical process of the Otto cycle, although someone selecting an engine does need to understand how fast the shaft will turn to manage connecting it to a generator.

Identifying a Wankel-type rotary engine by the displacement of a single chamber is fine, but doesn't say much about the potential capability of the engine unless the number of chambers per rotor and the number of rotors are considered as well. Long ago all Ferrari engines were V-12s, and Ferrari models were identified by the displacement of a single cylinder plus some letters for the style of car - the famous 250GTO was the "Gran Turismo Omologato" style model with with 250 cc per cylinder (and thus 3-litre displacement). No one tried to race the car in the class for 250 cc engines! 

A realistic understanding of engine output - for engine design, competition classification, or taxation - requires a physically meaningful evaluation of displacement; however, this understanding doesn't really matter for the purpose of selecting an engine... such as in this discussion. For just selection, as long as the weight, bulk, power, and fuel consumption are suitable there could be hundreds of gasoline-drinking hamsters pedalling on cranks inside... and we could count the hamsters.


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## Karter2 (Nov 17, 2011)

As the wankel is a 4 strole cycle.
...one rotation of the crank on a 330 cc chamber wankel, burns 330 cc of fuel mixture.
One rotation of a conventional 660cc, 4 stroke piston engine, also burns 330 cc of mixture ( assuming it is at least a 2 cylinder construction.
Equivalent working volumetric displacement.....race or road ..its the same


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## nucleus (May 18, 2012)

Karter2 said:


> As the wankel is a 4 strole cycle.
> ...one rotation of the crank on a 330 cc chamber wankel, burns 330 cc of fuel mixture.
> One rotation of a conventional 660cc, 4 stroke piston engine, also burns 330 cc of mixture ( assuming it is at least a 2 cylinder construction.
> Equivalent working volumetric displacement.....race or road ..its the same


Don't forget 3 faces per rotor.


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## Karter2 (Nov 17, 2011)

nucleus said:


> ....Don't forget 3 faces per rotor.....


 Not forgotten,. All included in the 330/660 cc comparason.
Your graphic, ... ( though not simple to read. Why so many cycles ?)...verifies that conclusion.


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## brian_ (Feb 7, 2017)

Karter2 said:


> As the wankel is a 4 strole cycle.


Defining the action of this engine in "strokes" doesn't really make sense to me (because the piston isn't stroking in and out of a cylinder), and any internal combustion engine has those same four stages of operation (induction, compression, power, and exhaust), but I do get the point that - unlike a 2-stroke reciprocating engine - induction and exhaust are done separately. Each of the four "corners" of the outer housing defines the area used for one stage of operation.



Karter2 said:


> ...one rotation of the crank on a 330 cc chamber wankel, burns 330 cc of fuel mixture.
> One rotation of a conventional 660cc, 4 stroke piston engine, also burns 330 cc of mixture ( assuming it is at least a 2 cylinder construction.
> Equivalent working volumetric displacement.....race or road ..its the same


Yeah, that's the rationalization traditionally used to explain the 2:3 handicap applied in favour of rotary engines. Although I don't think it makes physical sense (as I mentioned previously), it does work out okay: the output of a rotary is so low (due to the combustion chamber shape) that the handicap is about right. A piston engine with six cylinders of 416 cc each (for a total of 2.5 L) has similar performance (1993 Mazda 626: 164 hp) to the last non-turbo Mazda rotary (1992 RX-7 with 160 hp) with six chambers of 655 cc each (for a total of 3.9 L, race classified at 2.6 L).

To select a engine to stuff in the back of a car, figure about 20 cc of piston engine displacement, or 10 cc of rotary single-chamber volume, per kilowatt of output. A 4-stroke piston engine needs to be a two- or three-cylinder to be smooth enough, but no more to be light and compact enough; a rotary needs to be a single-rotor (three chambers).


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## rmay635703 (Oct 23, 2008)

https://pushevs.com/2018/01/10/fiat-500e-improved-scuderia-e/


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