# BMW Z4 conversion by Kostov - AC or DC?



## Plamenator (Mar 6, 2009)

Hello guys,

I am starting this thread to document the conversion of my Z4 into electric. The car weights about 1300kg and has a 192hp ICE.
I realised from the beginning it is not a very good conversion choice as being a cabrio it weights a lot and has a meagre 215kg payload.
Yet it is such a nice car that I immediately fell in love. So I guess I am ready to sacrifice range for looks 
Here are some pics from last Wednesday when we started:


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## Plamenator (Mar 6, 2009)

I am considering 2 possible alternatives:

1) K11" 250V together with Soliton1 and 90 cells of 90Ah each from ThunderSky:
http://kostov-motors.com/tractionmo...c)/seriesdcmotorsforelectricvehicles/k11250v/
http://kostov-motors.com/tractionmo...ollersandmotoraccessories/soliton1byevnetics/
http://kostov-motors.com/tractionmo...c-dc)/lithiumbatteriesbmsandchargers/lyp90ah/

2) The other option is to go AC. I suspect it will not be as fast as DC (at least initially) but it will allow me to test our new AC motors together with the Curtis 1238R controller:
http://kostov-motors.com/tractionmo...-phaseacmotorsforelectricvehicles/18ac9100hz/
http://www.curtisinstruments.com/index.cfm?fuseaction=Datasheets.downloaddatasheet&prodid=529
The Z4 will probably use a dual AC motor with 2x1238R controllers.
Each of the two AC motors will be bigger than the ones in the above link but we are still at prototype stage so nothing on our site yet.
I am not quite sure how 2 controllers will work together in AC.
I plan to have them connected in parallel to the battery (36 cells of 160Ah each) and running from a common throttle, rpm sensor and thermistor.
Curtis has a factory in Sofia so I hope to get some qualified help from them. All suggestions welcome


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## DavidDymaxion (Dec 1, 2008)

Looks like an awesome project, thanks for posting updates!


Plamenator said:


> I am considering 2 possible alternatives:
> 
> 1) K11" 250V together with Soliton1 and 90 cells of 90Ah each from ThunderSky:
> http://kostov-motors.com/tractionmotors/kostovevmotors(ac-dc)/seriesdcmotorsforelectricvehicles/k11250v/
> ...


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## Tatsushige (Mar 24, 2011)

I had the Z4 for a year, very nice car. 

I would go AC myself.


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## glaurung (Nov 11, 2009)

Hi Plamen, nice to see your conversion moving on.
In my opinion you should do DC first to get behind wheel and enjoy your ev. In AC you are more on doing research and develoment than just getting Beamer converted. 
When you have one ev working it would be easier to engineer more complex technical solution. And maybe upgrade later if needed.
Good luck with your conversion
Regards, Harri


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## Plamenator (Mar 6, 2009)

R&D is big part of my motivation to make it AC - after all I will make my own AC motors.
Here is the scheme I am considering.
Have not thought too much on so wondering if I am missing something big.


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## Salty9 (Jul 13, 2009)

Any hints about your motor?


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## Plamenator (Mar 6, 2009)

Each motor will be 96VDC 3-phase IEC160/60kg (11" - 240mm diameter of the stator) optimised for 100-130Hz and 0-8000rpm.
I expect to get like 50-70kW peak from each.
Only passive cooling for the prototype with water cooling planned for the future. It will look just like the one on the picture at the start of this thread, but bigger.
I intend to drive in second gear only the vast majority of time.
Not sure if second gear will survive at 8000rpm in the long run, what do you think?


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## cruisin (Jun 3, 2009)

Plamenator said:


> Each motor will be 96VDC 3-phase IEC160/60kg (11" - 240mm diameter of the stator) optimised for 100-130Hz and 0-8000rpm.
> I expect to get like 50-70kW peak from each.
> Only passive cooling for the prototype with water cooling planned for the future. It will look just like the one on the picture at the start of this thread, but bigger.
> I intend to drive in second gear only the vast majority of time.
> Not sure if second gear will survive at 8000rpm in the long run, what do you think?


I dont know what your final ratio would be in 2nd at say 60mph. I use 3rd only with the AC-50 and electric reverse so no gear shift necessary. The AC-50 is turning about 4600rpm at 60mph. I would think that any transmission running 2nd only at rpm speeds of 6000 is going to take a dump sooner than later. I guess time will tell.


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## Qer (May 7, 2008)

http://www.youtube.com/watch?v=DcdyYlDEd_o

No further comment.


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## glaurung (Nov 11, 2009)

I´ll have to comment that my XJS will have dual 11". Very nice XK
Harri


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## Yabert (Feb 7, 2010)

Personally, I think this sort of "promotional" car must have impressive performance!... So, go with DC 300v 1000A!

If you make a car with ordinary performance, most people will think that Kostov motors offers ordinary performance. 

Instead, if you manufacture a high performance car, people will say: What motor it is there inside? The Answer will be Kostov and after this will those people will choose Kostov motor (any kind: DC, AC, 9" or 11"). A bit like many people choose the soliton Jr because they was impress by the performance of the soliton 1.

The high performance things naturally impress the human!
Instead, high range (200-300 miles) or high efficiency only impress a fraction of people.


And if you think going for high performance, 90 thundersky battery isn't the answer! You need better powerful cells.


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## Plamenator (Mar 6, 2009)

I really do not want to make this into another DC or AC thread.
I know that a brushed series excitation motor is almost impossible to beat under 250V by a similarly sized AC one. After all series DC motors are my first love... They have proven the perfect toy for enthusiasts.
Yet brushed DC has its limitations - high rpm are a problem, no regen, impossible to isolate properly from the elements, unsuitable for water cooling and unsuitable for high voltage.
So despite their stellar performance, no serious auto producer has adopted them so far.
Yabert is right that my AC design will be mediocre and inferior to a 300V DC set.
But such promotional DC cars have been done over and over yet they have failed to promote brushed DC technology.
If I decide to use AC, it will be with the purpose of seeing just how "bad" AC can be with the currently accessible low voltage AC controllers.
So I would really appreciate your comments on how to make my AC setup the best possible. Have in mind that Curtis is prototyping a new 144V controller - 2 of those with a dual motor can give any DC the run of its life. And it does not need to cost ridiculuously more than a DC combo while offering water cooling and regen.


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## Qer (May 7, 2008)

Then it seems you've already made up your mind and that the threads subject is misleading.


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## efan (Aug 27, 2009)

Plamenator said:


> I really do not want to make this into another DC or AC thread.
> I know that a brushed series excitation motor is almost impossible to beat under 250V by a similarly sized AC one. After all series DC motors are my first love... They have proven the perfect toy for enthusiasts.
> Yet brushed DC has its limitations - high rpm are a problem, no regen, impossible to isolate properly from the elements, unsuitable for water cooling and unsuitable for high voltage.
> So despite their stellar performance, no serious auto producer has adopted them so far.
> ...


I agree that DC has been done over and over, and you should therefore go for an AC setup. With that said, you should try and get your hands on that 144v Curtis controller.
One question that I have is, what kind of torque curve do you expect from the AC motor that you are planning to produce at 144v (500a ? controller)?


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## Plamenator (Mar 6, 2009)

Qer said:


> Then it seems you've already made up your mind and that the threads subject is misleading.


I am heavilly leaning on AC indeed but not yet 100% decided.
I guess I am too interested in my new toys.
(Soliton3 sounds like a good name BTW )

The new Curtis controller is expected to be 144V/550-650A but it could be a few months or a year away from market. I am desigining the car so that it can be upgraded to 144VDC later on.

Torque curve is more or less standard.
I have attached a rough sketch of the torque of 18AC9":
http://kostov-motors.com/tractionmo...-phaseacmotorsforelectricvehicles/18ac9100hz/
In fact we managed to go to 180Nm at one point but motor smoked in 5-6sec.
The new motor will be significantly bigger but shape of curve will be similar. I hope we can safely get the 180Nm on this one.


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## steven4601 (Nov 11, 2010)

Hi ,

What about cooling the motor with water/oil? Cool the stator windings so they can be used way further than 5A/mm2 for short bursts. A step further is assembling the motor so that very thin oil can be run through the motor from back to front cooling also the rotor. The only design snatch is to put enough kevlar on the rotor and yet make it smooth enough so the oil cannot find cavities on the surface to build up unwanted pressure/friction.


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## Plamenator (Mar 6, 2009)

I would stay away from oil cooling of the rotor but stator water cooling is definitely in the plans once we develop the AC range.

Unfortunately we do not have much experience with water cooling.
I was hoping that someone would be selling ready made jackets like in the picture. However I cannot find such jackets that would be both aluminum and big enough (internal d=200-240mm; the one in the picture is by Leopard and meant for very small hobby RC motors and not at all sure it has a double wall).


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## steven4601 (Nov 11, 2010)

Cooling jackets as you call them are basically press fits / interference fits one tube over the other. The inner tube is may have a maze pattern in it for maximum surface area. Other solution is to use two tubes and two bolt-on flanges. Those flanges could also house the bearings, rotor sensor etc.

What about 'axial flux' motors like YASA tries to license as a design? Axial flux motors where already in 1970's computers floppy drives..... No law suits ever can be started over that kind of technology.


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## Salty9 (Jul 13, 2009)

Have you considered lost foam aluminum casting? I've lost the thread but some Canadian had a detailed procedure for diy aluminum casting.


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## Plamenator (Mar 6, 2009)

I did not know they are press fits but now that you told me I can think of several constructions that will do - thanks 
Next problem is that I cannot use steel as it will be bad for motor electrically. So it has to be either aluminum or cast iron.
Cast iron will add lots of weight while I am not sure if tubes from both aluminum or cast iron are available with the needed sizes.

Actually if I can use aluminum I can just heat up to 400C the outer tube so it expands and slide it on top of the inner tube. Do you think this will make for a water-proof joint?


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## Plamenator (Mar 6, 2009)

Salty9 said:


> Have you considered lost foam aluminum casting? I've lost the thread but some Canadian had a detailed procedure for diy aluminum casting.


I do not understand what you mean by lost foam aluminum casting.
How is water cooling going to be implemented with that?


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## JRP3 (Mar 7, 2008)

You could always try something like this for water cooling:


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## Salty9 (Jul 13, 2009)

You make the water cooling jacket using cast aluminum as in this video.

http://www.videosurf.com/video/marksworx-casting-session-1-lost-foam-casting-110582527


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## Yabert (Feb 7, 2010)

Plamenator said:


> I am not sure if tubes from both aluminum or cast iron are available with the needed sizes.


Do you only try to find europeen material?
Maybe US tube can match your needs. It have also pipe tube.


Also, do you have never think build a motor for direct drive application? Something with 600-1000 rpm as nominal. One motor for each wheel can be awesome.
What can be the problem? Efficiency, overheating?... or do you think it's useless?


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## JRP3 (Mar 7, 2008)

Yabert said:


> Also, do you have never think build a motor for direct drive application? Something with 600-1000 rpm as nominal. One motor for each wheel can be awesome.
> What can be the problem? Efficiency, overheating?


Probably both, and you don't get the torque multiplication from gear reduction.


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## Plamenator (Mar 6, 2009)

JRP3 said:


> You could always try something like this for water cooling:


 
I have tried this on a DC motor 
It does not work.
But it probably works much better for AC - still looks too DIY...


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## Plamenator (Mar 6, 2009)

Yabert said:


> Do you only try to find europeen material?
> Maybe US tube can match your needs. It have also pipe tube.
> 
> 
> ...


 
Yes, I have only looked at European materials.
I do not think I can find a US company which even if they had such a thick wall pipe, would send me 3-4 feet to try. Maybe you can proove me wrong?

Direct drive would call for 6-8 poles which would kill power at the expense of torque - at least if you are stuck at 96-144V. Maybe this calls for more than 3 phases but then controller becomes even more of a problem. And imagine the cost and installation complexity of those motors.


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## Plamenator (Mar 6, 2009)

Salty9 said:


> You make the water cooling jacket using cast aluminum as in this video.
> 
> http://www.videosurf.com/video/marksworx-casting-session-1-lost-foam-casting-110582527


 
I know sand/clay casting 
We often use it for prototyping but the model is usually from metal or wood (you take it out of the clay prior pouring the aluminum so it can be reused).
It can indeed be used to make a prototype if I cannot find a proper aluminum tube. If successfull, then a mould for casting under pressure can be made.
But again, I need to get the motor right beforehand or there is no point in water cooling


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## Yabert (Feb 7, 2010)

Plamenator said:


> I do not think I can find a US company which even if they had such a thick wall pipe, would send me 3-4 feet to try. Maybe you can proove me wrong?


Maybe!

What kind of tube do you need?
Maybe rework a 8'' schedule 40 Aluminum Pipe 6061 T6 or a 8'' tube can acheive your need.
If not, can you roll and weld a sheet metal plate?


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## steven4601 (Nov 11, 2010)

Plamenator said:


> I did not know they are press fits but now that you told me I can think of several constructions that will do - thanks
> Next problem is that I cannot use steel as it will be bad for motor electrically. So it has to be either aluminum or cast iron.
> Cast iron will add lots of weight while I am not sure if tubes from both aluminum or cast iron are available with the needed sizes.
> 
> Actually if I can use aluminum I can just heat up to 400C the outer tube so it expands and slide it on top of the inner tube. Do you think this will make for a water-proof joint?


Interference fit (heating it up to make it fit) is great for easy assembly. The ends can be waterprooved by welding the seam or pouring a liquid gasket / resin over it.
You'll also need a good bond with the stator, this can be done by a mild interference fit and or resin.


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## Plamenator (Mar 6, 2009)

Fitting the inner tube to the stator is not a problem - as you say, use a mild interference fit (love technical terms) - we do it all the time for the standard AC motors we produce.
Then another mild interference fit for the outer tube and we are ready to go.
Bending the aluminum sheet to make a tube also seems plausible for the prototype (that is how we make the cases of the DC motors just that aluminum is more difficult to weld but can be done - I hope the weld will not crack during the heating/fitting).
I will definitely explore this! Thanks guys.


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## Plamenator (Mar 6, 2009)

Petrol engine is finally removed.
The parts taken out so far are:
-engine: 195кг
-radiator with coolant: 25kg
-exhaust pipes: 25kg
So 245kg in total.

One peculiar thing is that there seems to be no pump for the driving wheel...or at least I can see none.


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## JRP3 (Mar 7, 2008)

That looks a lot like the manual steering rack in my Fiero, which does fine without power steering.


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## toddshotrods (Feb 10, 2009)

Why does the cooling jacket have to be one, interference-fit, piece? It seems more logical (to me anyway) to use two halves that bolt together on the motor case, and are plumbed together externally. If they were made with a process like lost-foam casting, you could have very sophisticated coolant passages. Do CAD modeling and analyses to figure out the shapes and patterns for maximum effectiveness, have it 3D printed, and cast. Use a thermal compound whan assembling for maximum heat transfer. You would also be able to remove the entire cooling system, and remove the motors, without breaking the coolant seal...


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## steven4601 (Nov 11, 2010)

Heat transfer and thermal compound without some clamping force does not work that well. A weak interference fit will be enough, as when the stator heats up it starts to interfere more with the cooling jacket improving the bond when needed. 

Interference fits are for ease of assembly think. Lost foam fabrication is great too, but you'll need an oven for liquid aluminium. A simple burner is easier to come by. I also used an interference fit for my motor shaft adapter. here: http://z3.fiberhosted.nl/index.php?n=Conversion.AdapterDrawings

Physics is fun


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## toddshotrods (Feb 10, 2009)

steven4601 said:


> Heat transfer and thermal compound without some clamping force does not work that well...


That's why I suggested two halves that bolt together. I guess I should have specified that I was thinking they're basically clamping around the motor, but assumed it would be assumed... 

You can design the cooling cases to tolerate whatever degree of clamping force is needed. A slight interference fit is no problem. Just design the cooling cases accordingly, so that they cannot be easily slapped together on the motor, but are pulled onto it with the clamping bolts. You would probably need a few taps with a rubber mallet, dead-blow hammer, etc, to get them off. Same concept, just modular.

I tend to approach engineering from a technician's perspective. There are a lot of automotive "great ideas" that some engineer dreamed up, that are a nightmare to service. Ideally, you want to be able to break things down into components and systems for assembly, disassembly, and servicing. We had a customer leave Autozone a week or so ago, frustrated, because he had to disassemble practically the entire front end of his engine (accessories, belts, cover, timing belt, etc), re-time the engine, and reassemble everything, to replace a $5 part that is a 15-30 minute job, with minimal disassembly, on most vehicles.

If I had a system similar to what Plamenator is considering, I would really appreciate being able to easily split the cooling system off and have the motor on the bench in a matter of minutes, instead of fiddling with fluids and lines, and then having the additional concern of not damaging the cooling system in the process.

On the original subject - it's the same either way. DIY-style DC has been done to death, and medium performance factory-style AC has been as well. Tit-for-tat... You have to figure out what you want the overall package to "say" and choose what best accomodates that goal. Blistering supercar performance? DC or a massive budget to develop a complete AC system from scratch. Luxury-sport refinement and sophistication? AC. I'm looking at this from the perspective of it being a marketing tool for Kostov, not a typical DIY project.

Just my two pence...


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## Ams_AK (Jan 24, 2011)

Plamen!

Hands down, go for the best DC build that can be made! I know you are rightfully excited by your upcoming AC line, and if your heart is set then I am talking to the wind here..but consider:

-You could be making a killer car where EVERY EV part can be ordered right from your site, right NOW
-The build blog would add a how-to section for the same parts and give credibility to Kostov as a premium supplier (for some, Bulgarian products need a little PR boost )
-I know you consider DC 'hobby market', but EV conversions as a hobby has only just started, especially in Europe, your 'back yard' so to speak
-The Soliton1 now has integration with EV speedo, Android open source digital dashboard that is really cool.
-I would be able to do a side-by-side build as I just got the Exact DC drivetrain you proposed (<-I am bias and I know it ) 

With a bit more volume on orders and production you could get this killer DC kit down to about 10-11K Euros, and show how well it can perform! Also you will be smoking tires and parading around Sofia next month while the sun is out and the girls can see you .. then if you really get bored you will do an even better AC build for next spring..

Anyways, good luck on your build, I'm sure it will be top-notch whatever you decide!

AK
New Electric


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## JRoque (Mar 9, 2010)

Hi. I vote for AC. I believe the Curtis controllers have design features to run them together as you suggest. In fact, the HPEV guys converted a Jetta with two of their AC motors and Curtis controllers. 

As for motor weight, I have an 18kW industrial motor that weighs 72Kg - 25HP and 160 lbs in real money  They achieve the relatively low weight by using castings on each end with a thin rolled steel body in between. Then tie those two ends with an exoskeleton of sorts using 4 long screws - not what I would've done but it seems to work for industrial applications. Even the motor base is stamped/formed steel.

JR


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## Plamenator (Mar 6, 2009)

toddshotrods said:


> That's why I suggested two halves that bolt together. I guess I should have specified that I was thinking they're basically clamping around the motor, but assumed it would be assumed...
> 
> You can design the cooling cases to tolerate whatever degree of clamping force is needed. A slight interference fit is no problem. Just design the cooling cases accordingly, so that they cannot be easily slapped together on the motor, but are pulled onto it with the clamping bolts. You would probably need a few taps with a rubber mallet, dead-blow hammer, etc, to get them off. Same concept, just modular.
> 
> ...


Thanks for the suggestions Todd.
Interference fit seems easier to make a prototype out of.
It can further be used as a structural part of the motor to attach the flanges to it.

Having 2 parts has its merits but also brings some technical problems - for example how to go around the long bolts that keep the flanges together.
Our technical director really liked your idea so we spent lots of time debating it


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## Plamenator (Mar 6, 2009)

Ams_AK said:


> Plamen!
> -You could be making a killer car where EVERY EV part can be ordered right from your site, right NOW
> -The build blog would add a how-to section for the same parts and give credibility to Kostov as a premium supplier (for some, Bulgarian products need a little PR boost )
> -I know you consider DC 'hobby market', but EV conversions as a hobby has only just started, especially in Europe, your 'back yard' so to speak
> ...


Seems like I will have real problems with my wife if I go DC 

EV speedo looks nice - I was thinking of something similar using a Galaxy and a CAN to USB adaptor but lack the skills to do it.
Curtis has this:
http://curtisinstruments.com/index.cfm?fuseaction=Products.Engage7
But is very expensive and cannot compare to a Galaxy.
Do you think the EV Speedo will work with a Galaxy?


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## Plamenator (Mar 6, 2009)

JRoque said:


> Hi. I vote for AC. I believe the Curtis controllers have design features to run them together as you suggest. In fact, the HPEV guys converted a Jetta with two of their AC motors and Curtis controllers.
> 
> As for motor weight, I have an 18kW industrial motor that weighs 72Kg - 25HP and 160 lbs in real money  They achieve the relatively low weight by using castings on each end with a thin rolled steel body in between. Then tie those two ends with an exoskeleton of sorts using 4 long screws - not what I would've done but it seems to work for industrial applications. Even the motor base is stamped/formed steel.
> 
> JR


Actually you can have up to 16 Curtis controllers running like 1 master and 15 slaves that do exactly like the master....and virtual differential too. Quad AC..hmmm? 
You can probably get much more than 25Hp from 72kg as your industrial motor is optimised for 50/60Hz rather than a more EV like 100-150Hz (you know Power=Torque x RPM...sort of). You will probably get very poor efficiency if you run your motor above 80-100Hz.


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## JRoque (Mar 9, 2010)

Hi. I think you meant that I will not get much more than 25HP. You're right that the max "safe" speed of that motor is 5400 RPM. I was merely pointing out how they made it lighter.

You're still in the early staging of prototyping so when you can:

- How much more you expect the 3 phase to cost over your DC
- Will you include a shaft position sensor?
- Double end shaft?
- I assume class-H insulation, what diameter wire?
- Estimate max current per phase

Thanks for sharing the development of this project with us; looking forward to see it work.

JR


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## toddshotrods (Feb 10, 2009)

Plamenator said:


> Thanks for the suggestions Todd.
> Interference fit seems easier to make a prototype out of.
> It can further be used as a structural part of the motor to attach the flanges to it.
> 
> ...


Thanks, tell your technical director he/she has good taste - j/k! 

What long bolts? A properly designed cooling case would have short bolts in bosses (designed into the cases). Properly designed, the torque from clamping them together would pull pretty evenly around the cooling cases, improving the contact surface with the motor frame. I don't have time right now to get in CAD and show you what I mean. I can see it in my head, but it's hard to describe.


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## Plamenator (Mar 6, 2009)

JRoque said:


> Hi. I think you meant that I will not get much more than 25HP. You're right that the max "safe" speed of that motor is 5400 RPM. I was merely pointing out how they made it lighter.
> 
> You're still in the early staging of prototyping so when you can:
> 
> ...


What I wanted to say is it will get more than 25HP if designed for 100-150Hz.

AC will only be sold as a kit with a controller - there is too much to program to leave it to the client not to speak about the needed equipment to do the programming properly.
We still do not have a developed range of motors let alone speak of future prices. Also 1238R costs around 2500$ - so combo will always be at least 4000$ 

It will be a class H, double shaft motor with an rpm sensor bearing.
Both ends of the motor are identical so it is difficult to speak of front/rear end.
Below is a picture of the smaller motor in 9" we already have.
Shaft/flange coupling is the same like that of Kostov/WarP DC motors.
Max "safe" current for the 9" is 300A while the 11" will probably go to the controller's max 650A.
Of course this is still work in progress - it is possible that nothing comes out of it.


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## JRoque (Mar 9, 2010)

Hi.


Plamenator said:


> AC will only be sold as a kit with a controller - there is too much to program to leave it to the client not to speak about the needed equipment to do the programming properly.


I guess that's not such a bad thing since there are so few AC controllers out there anyway. But a modern AC drive should also auto-tune to the connected motor. My cheap VFD does. But yes, a >144V controller would be nice.



Plamenator said:


> We still do not have a developed range of motors let alone speak of future prices. Also 1238R costs around 2500$ - so combo will always be at least 4000$


I wouldn't  at ~$4000, it's competitive and especially if you're talking about an 11" motor. Also having both ends be the same lends itself to pairing which I'm sure was your intent.



Plamenator said:


> it is possible that nothing comes out of it.




JR


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## Bowser330 (Jun 15, 2008)

Plamenator said:


> What I wanted to say is it will get more than 25HP if designed for 100-150Hz.
> 
> AC will only be sold as a kit with a controller - there is too much to program to leave it to the client not to speak about the needed equipment to do the programming properly.
> We still do not have a developed range of motors let alone speak of future prices. Also 1238R costs around 2500$ - so combo will always be at least 4000$
> ...


Using Curtis is great and all but what about the voltage limitation?

Its the same current struggle with the AC50 kits, we think it could take more voltage but it has yet to be seen... Everyone knows you need amps & volts to make power but a more usable powerband with more area under the curve is obtained from higher peak rpm = higher voltage....

Plamenator, what is the maximum voltage these motors can accept? I am assuming its not as easy as 300V * 300A = 90kw


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## Plamenator (Mar 6, 2009)

Well, AC is not exactly like DC.
It can easilly take 400V provided you calculate the stator coils for 400V.
1238R can work with up to 130V. We aim to put 36 cells for 115V nominal or 130V at 3.6V charge.
Therefore we are designing our motors to match 1238R's capabilities and the motors will not tolerate more than 150VDC I guess...but frankly this is up to testing.
If you can show me a good higher voltage AC controller, it is not a problem to make a motor for it.

JRogue: indeed Curtis does autotune, but then you need to know the procedure which Curtis does not share freely, you need a 500$ programmer and you have tons of settings that a client may/will get wrong and possibly melt the motor.


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## JRP3 (Mar 7, 2008)

Plamenator said:


> If you can show me a good higher voltage AC controller, it is not a problem to make a motor for it.


Jack Rickard is using a controller from Rinehart Motion with his higher voltage MES motor. Rather pricey, and he is still working the bugs out with them, but maybe he'll get it sorted out.


> JRogue: indeed Curtis does autotune, but then you need to know the procedure which Curtis does not share freely, you need a 500$ programmer and you have tons of settings that a client may/will get wrong and possibly melt the motor.


There is a way around using their programmer.
http://www.buggiesgonewild.com/electric-golf-carts/15316-programming-curtis-controller-19.html


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## Bowser330 (Jun 15, 2008)

Plamenator said:


> Well, AC is not exactly like DC.
> It can easilly take 400V provided you calculate the stator coils for 400V.
> 1238R can work with up to 130V. We aim to put 36 cells for 115V nominal or 130V at 3.6V charge.
> Therefore we are designing our motors to match 1238R's capabilities and the motors will not tolerate more than 150VDC I guess...but frankly this is up to testing.
> ...


Your K9-220V (1750$) + Soliton jr (2000$) = 80kw & 175nm = 107hp & 130ftlbs @ 4250rpm = 3,750$
http://kostov-motors.com/files/productattachments/6ff70418861d3230f01fc0340802fb1f_S220E01.pdf

115V nom (90V sagged) * 650A = 58kw = 4000$


http://www.tritium.com.au/products/TRI74/
$6,000.AUD = $4,433.EUR = $6,424.USD 
Not cheap, but says 165kVa (132kw)
If you can make a higher voltage 130kw AC motor for 2,000$USD = 8,500$USD = 130kw AC = damn good deal vs. other systems currently for sale.


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## Plamenator (Mar 6, 2009)

I suppose 130kW is peak.
I think we can go to 100kW peak with current components but bigger components can also be bought to make a bigger motor.

I will need Tritium's assistance for that and I am not sure they will be interested.


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## Bowser330 (Jun 15, 2008)

Is the Curtis AC inverter that hard to replicate? Instead of people working from scratch to build AC inverters, why not just make improvements or upgrades to existing inverters? I know its not as simple as how I am stating it, but if someone were so inclined, is it not possible?


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## JRoque (Mar 9, 2010)

Hi. It should be possible. Eric Tischer modified his industrial VFD with external drivers, current sensors, etc. Of course, Kostov can't do that or release a product counting on people modifying a Curtis.

If anything Curtis is being too slow (Curtis Lowe (slow), Skynyrd ) updating their controllers. True, they don't see us as a huge market but it shouldn't be that hard to swap some FETs, caps and maybe the current sensors. Go to your microcode and up the limit to ~170V and be done with it. Ok here come the flames on how it takes a long time to make this kind of change, etc.

JR


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## JRP3 (Mar 7, 2008)

My very limited understanding of the Curtis situation is that it is a MOSFET based design and is therefore limited by existing available MOSFETS. To do it with IGBT's would be a complete redesign. Supposedly higher powered MOSFETS are coming, hence their higher current version, and hopefully soon to come higher voltage version.
The problem with the Tritium and Rinehart inverters is they are lower current and higher voltage units, which means a crap load of cells.


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## JRoque (Mar 9, 2010)

Hi. Don't know what Curtis uses today but paralleling a few of these can let them do ~170V @ 600A: http://ixdev.ixys.com/DataSheet/DS99557F(IXFK-FX140N30P).pdf

JR


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## Plamenator (Mar 6, 2009)

Got a bit of a setback from Curtis today.
Apparently there are 2 models of 1238R - 75XX for 550A peak and 76XX for 650A peak.

1238R-75XX/550A is in regular production and is part of HPEV's AC50 kit.
1238R-76XX/650A is 500$ dearer and lead time is 13 weeks 

So I guess I will start with a single 1238R-75XX I already have and upgrade to twin 76XX in 13 weeks.


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## Tesseract (Sep 27, 2008)

Plamenator said:


> I suppose 130kW is peak.
> I think we can go to 100kW peak with current components but bigger components can also be bought to make a bigger motor.
> 
> I will need Tritium's assistance for that and I am not sure they will be interested.


This certainly raised an eyebrow... why wouldn't Tritium be interested?


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## Plamenator (Mar 6, 2009)

I guess it depends a lot on the circumstances.
I should probably write them a mail and find out 

Speaking of that, what are the chances of EVnetics making an inverter soon? You probably know that there are IGBT modules complete with water cooling, DSP and even control algorythms. Seems a small step...


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## JRP3 (Mar 7, 2008)

Plamenator said:


> Seems a small step...


Oh no, now you've done it. Tess just loves threads telling him how easy it is to build a 3 phase inverter


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## Tesseract (Sep 27, 2008)

Plamenator said:


> Speaking of that, what are the chances of EVnetics making an inverter soon? You probably know that there are IGBT modules complete with water cooling, DSP and even control algorythms. Seems a small step...


Are you talking about Semikron's SKAI modules? I got a quote on the 100kW system about a year ago... was $4k, IIRC.


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## tomofreno (Mar 3, 2009)

HPEVS said they "traded off" less torque at lower rpm for higher running torque (at higher rpm). So the "knee" of the torque speed curve is at about 3000 rpm for the AC50 with 96V pack versus around 2000 rpm for the AC31 with 96V pack, permitting higher power output from the AC50. As people have said, the AC50 is limited in power due to the max voltage of the 1238 controller. I think the knee of the curve for the AC50 is at about 3900 rpm with a 115V nominal pack (I have 36 180Ah CALB cells). It does fairly well at lower speeds, but can't sustain high enough torque at higher speeds. That is above about 45 mph in my car where it hits the knee in second gear. Shifting to third just trades off mechanical advantage for higher motor torque, resulting in less wheel torque due to the power limitation. That is mainly what prevents fast acceleration to 60 mph. The higher voltage motors/controllers can have both higher peak torque and higher base speed. Maybe a 180V/650A controller would permit a motor designed for say 120 ft-lb peak torque and a "knee" at around 4700 rpm giving shaft power of about 80kW, 107 HP, and not require "a crap load of cells" (about 52 for 52*3.4V = 177V rest voltage after full charge, 166V nominal, maybe 150V at 650A).


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## cruisin (Jun 3, 2009)

tomofreno said:


> HPEVS said they "traded off" less torque at lower rpm for higher running torque (at higher rpm). So the "knee" of the torque speed curve is at about 3000 rpm for the AC50 with 96V pack versus around 2000 rpm for the AC31 with 96V pack, permitting higher power output from the AC50. As people have said, the AC50 is limited in power due to the max voltage of the 1238 controller. I think the knee of the curve for the AC50 is at about 3900 rpm with a 115V nominal pack (I have 36 180Ah CALB cells). It does fairly well at lower speeds, but can't sustain high enough torque at higher speeds. That is above about 45 mph in my car where it hits the knee in second gear. Shifting to third just trades off mechanical advantage for higher motor torque, resulting in less wheel torque due to the power limitation. That is mainly what prevents fast acceleration to 60 mph. The higher voltage motors/controllers can have both higher peak torque and higher base speed. Maybe a 180V/650A controller would permit a motor designed for say 120 ft-lb peak torque and a "knee" at around 4700 rpm giving shaft power of about 80kW, 107 HP, and not require "a crap load of cells" (about 52 for 52*3.4V = 177V rest voltage after full charge, 166V nominal, maybe 150V at 650A).


i agree with you, but I have found in a VW, AC50 w/650a controller, using 3rd gear only there is a lack of amp from the controller until the RPM's pick up unlike the DC. However, with 4000rpm at 65mph, this is the ultimate. 2nd gear is too low, but would provide a lot more torque coming off the line. If you are not racing, the configuration above really works the best. IMPORTANT, the 1238 needs to be fine tuned to get the most out of it. Its not at its BEST from the factory.


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## Plamenator (Mar 6, 2009)

Tesseract said:


> Are you talking about Semikron's SKAI modules? I got a quote on the 100kW system about a year ago... was $4k, IIRC.


 
Exactly  
It is what Brusa uses for their inverters as well and sells the final product for EUR 19200 to enthusiasts...

I heard SKAI HV IGBT is EUR 2500 which comes to about 3600$.
Anyway, do you think one can easilly make an inverter out of the SKAI module (setting aside the cost)?


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## Plamenator (Mar 6, 2009)

Now, I am not pretending to be an expert in AC so the below is just an opinion that has to be taken with a healthy dose of doubt.

I suppose you are calling a knee point the region where constant torque starts falling and power becomes constant. At this knee point the controller is pumping maximum AC voltage possible (67VAC for a 96VDC battery)
This is usually the point for which the motor is calculated to work with the best efficiency. I.E. AC50 and 18AC9" are probably both optimised for 100Hz hence knee point is around 3000rpm.
The Curtis controller has a parameter called nominal battery voltage.
If this is set to 96VDC, controller is supplying the motor with maximum 67VAC and it does not matter if your nominal voltage is actually 115 or even 130VDC. At the same time the max value for this parameter in 1238R is 96VDC. Hence it seems like knee point will always be at 3000rpm regardless of your pack voltage.
Knee point also depends on amps drawn - the higher the amps the earlier the knee point occurs at (this is an empirical observation).
This is well illustrated by Brusa:
http://www.brusa.biz/index.php?id=135&L=1
You can see that knee point for max power happens earlier than knee point for nominal power.

A 180V/650A controller will not give you by itself a 4700rpm knee point.
You can get that knee point if motor is optimised for 150-160Hz.
A 180V/650A controller will however give you peak power.
The motor that will go in my Z4 will be like 200A nomial so only 650/200=3.25 times overload.
A 144V AC motor of the same power will only need 96/144*200=133A.
So overload will be 650/133=4.9 times - much closer to a DC 

Cruisin: check your field weakening value - it can actually limit your amps so motor efficiency is kept high. Cannot remember the specifics but it is well explained in the Curtis manual.


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## JRoque (Mar 9, 2010)

Hi. I was also quoted close to $6K for a prototype Semikron module, insane. 

These guys are working on an.. ahem "open-source", 3-ph controller project: http://www.tumanako.net. 

Anyway, I hear they have working prototypes and can sell you the main board plus the power module so you can put it in a box, cool it, etc. Some of the guys working on the code and whatnot are also members on this forum. They also have a mailing list and usually answer questions pretty quickly.

JR


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## tomofreno (Mar 3, 2009)

> i agree with you, but I have found in a VW, AC50 w/650a controller, using 3rd gear only there is a lack of amp from the controller until the RPM's pick up unlike the DC.


 I think that is because you are monitoring battery current. If you monitor the Current_RMS parameter you will see that if you floor it you get max current almost immediately. Monitoring the Modulation_Depth parameter will show that it goes to 100% almost immediately indicating it is using full available voltage.


> However, with 4000rpm at 65mph, this is the ultimate. 2nd gear is too low, but would provide a lot more torque coming off the line.


 I use a transmission, so my lowest 0 to 60 mph time, about 16 seconds, is achieved starting in first gear, shifting to second at a bit over 25 mph, then shifting to third at a bit under 50 mph, even though I probably loose about 1 second or more shifting twice since my tranmission does not shift too quickly. My 0-60 mph time starting in second gear is more like 20 seconds, but I do much of my driving in second, even when starting from a stop if I don't need to accelerate quickly.


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## cruisin (Jun 3, 2009)

tomofreno said:


> I think that is because you are monitoring battery current. If you monitor the Current_RMS parameter you will see that if you floor it you get max current almost immediately. Monitoring the Modulation_Depth parameter will show that it goes to 100% almost immediately indicating it is using full available voltage.
> I use a transmission, so my lowest 0 to 60 mph time, about 16 seconds, is achieved starting in first gear, shifting to second at a bit over 25 mph, then shifting to third at a bit under 50 mph, even though I probably loose about 1 second or more shifting twice since my tranmission does not shift too quickly. My 0-60 mph time starting in second gear is more like 20 seconds, but I do much of my driving in second, even when starting from a stop if I don't need to accelerate quickly.


I always used 2nd up to about 45mph when I was running the Impulse 9 with a 1000a controller, but with the AC50 I start off a little slower but then get up to about 65mph faster and dont have to shift. The tranny is going to last a whole lot longer by not doing the 1st and shifting routine. Also, by only using 3rd I have very little tranny noise compared to using 1st and 2nd.


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## tomofreno (Mar 3, 2009)

> I suppose you are calling a knee point the region where constant torque starts falling and power becomes constant.


 Yes.


> The Curtis controller has a parameter called nominal battery voltage.
> If this is set to 96VDC, controller is supplying the motor with maximum 67VAC and it does not matter if your nominal voltage is actually 115 or even 130VDC. At the same time the max value for this parameter in 1238R is 96VDC. Hence it seems like knee point will always be at 3000rpm regardless of your pack voltage.


I am not an AC motor expert either, but I expect that frequency is increased with voltage to maintain constant airgap flux for max torque until the controller hits its max output voltage, limited by the battery pack voltage. Frequency is then increased from there (the “knee”) for higher motor rpm, and torque falls off due to lower airgap flux. I guess you are saying the controller doesn’t use the full pack voltage available, only the value you enter for nominal voltage? If this is the case, I would expect max vehicle speed to be independent of pack voltage. 

According to this post: http://www.diyelectriccar.com/forums/showpost.php?p=249273&postcount=291
EVTV clocked the AC-50 with it's matching 650A controller on a dyno putting out about 74 HP and 109 ft/lbs of torque to the wheels. Motor shaft power would be a bit greater than 74 HP due to drive train losses. If you assume 10% for drive train losses then the knee of the curve should be somewhere around 3900 rpm for peak motor shaft power of about 81 HP, 60kW: 60,000*60/(2*pi*147.8) = 3879 (torque in N-m). 


> Knee point also depends on amps drawn - the higher the amps the earlier the knee point occurs at (this is an empirical observation).


I would expect some decrease just due to more pack voltage sag at higher currents. Are you saying there are other effects? Edit: Ah, I see now...not as much motor input voltage is required at lower motor currents, so the motor rpm where the controller is using the full pack voltage will be at higher rpm compared to when running higher motor current. But of course you are running at lower than peak torque then. I am used to visualizing the torque-speed curve with peak torque up to the "knee".


> Cruisin: check your field weakening value - it can actually limit your amps so motor efficiency is kept high. Cannot remember the specifics but it is well explained in the Curtis manual.


 According to the manual field weakening only seems to affect motor power at higher motor rpm:

*Field Weakening *0–100 % Determines the amount of high speed power the controller will allow,
_Field_Weakening 0_–_1024 _while still maintaining maximum effficiency at the allowed power. Reducing
this parameter effectively reduces controller current at high speeds, which
can reduce energy consumption and motor heating, but at the expense of
reduced available torque from the motor.
It seems to be a way to run the motor at high speed under lower torque (load) conditions at higher efficiency.


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## tomofreno (Mar 3, 2009)

> This is usually the point for which the motor is calculated to work with the best efficiency. I.E. AC50 and 18AC9" are probably both optimised for 100Hz hence knee point is around 3000rpm.


 I monitored the controller _Frequency_ parameter and had it up at about 280 Hz driving at roughly 35 mph and 7k rpm in first gear. Max motor rpm is 8k so I would guess f goes up to at least 300 Hz. I don't like running the transmission at that rpm so it was a very quick test. Edit: the AC50 is a 4 pole motor so rpm should be equal 30*f. A frequency of 280 Hz would give 8400 rpm so I must have read something(s) wrong. I read frequency first, so I may have let my foot up a bit when I looked at the speedometer then read rpm.


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## tomofreno (Mar 3, 2009)

Btw, you can see the controller output power is about equal input power minus losses, by monitoring the _Current_RMS_ and _Modulation_Depth_ parameters. At about 32% modulation depth (I'm trying to watch multiple things here!) the motor rms current was about 165A and battery current was 54A, about 32% of motor current. At about 75% modulation depth motor rms current was 244A and battery current was 181A, about 74% of motor rms current. Edit: I realize this is expected, just thought it was neat to see the numbers.


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## Tesseract (Sep 27, 2008)

Plamenator said:


> I heard SKAI HV IGBT is EUR 2500 which comes to about 3600$.
> Anyway, do you think one can easilly make an inverter out of the SKAI module (setting aside the cost)?


I finally found the price quote I got from Semikron concerning their SKAI2 inverter system. This quote is over a year old so take it with a grain of salt, but at that time pricing in single quantities for the system (ie - IGBT module + gate driver + inverter DSP) was $8355, dropping down to a mere $4000 in quantities of 100. 

Now I've haven't actually messed around with the SKAI2 system so I don't know how easy it would be to make an AC motor controller for EVs out of one, but given that it is more or less a complete inverter minus the enclosure and some minor support hardware, it certainly *looks* like it would be easy.


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## JRoque (Mar 9, 2010)

Aha! We got a foot in the door guys, pile up on Jeff! 

Hey, how's this: http://www.pwrx.com/Result.aspx?q=PM600CLA060. It's barely at a Junior level but that module + driver board + Qer's mind + maybe a divorce or two at Evnetics can get you closer to a 3 phase system. 

JR


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## JRP3 (Mar 7, 2008)

JRoque said:


> Aha! We got a foot in the door guys, pile up on Jeff!












How's that inverter coming along down there?


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## Qer (May 7, 2008)

JRoque said:


> Qer's mind + maybe a divorce


Yep, that'd be me. Or at least I'd end up living in the dog house.

I checked my PM pile and the first messages between me an T started to swap back and forth in September -08 and the cooperation started with the now almost hilarious phrase "I actually would be interested in swapping a little bit of hardware design for a little bit of software design". Back in -08 I've started to look into building my own controller (pretty much like P&S I guess) uttering the bold statement "How hard can it be?". I started to freshen up my knowledge about power electronics (which never was good to begin with and definitely not even close to a black belt in kW) and realised that the answer to that bold question was "Very!". So when T dropped into the forum with the opposite opinion that "Software, how hard can it be?" we kinda realised that a little cooperation would be a good thing. Both being a bit of perfectionists we kinda lost that "little bit" along the way and the "Just another DC-controller" quickly turned into the feature monster you know today... 

During -09 I spent more or less all of my time working on the Soliton most of my spare time after my day time job. Late April -09 we had the first prototype running hard amps through a block of carbon and it seems that Dimitri started to drive around with one in May, but that was still "just" a 500 Amps very primitive Soliton, but it gave us some really good data so after summer -09 we started to torture motors with 1kA, blowing up a few in the process and at the end of -09 the first Solitons were sold.

-10 was spent improving the product (especially on the software side, if you haven't upgraded to AT LEAST 1.2 you really should) and starting on the Jr. We also did a few small side orders but the main bulk of my spare time (besides my day time work, which I still have) still got poured into making Soliton even greater. So in essence I've had very little spare time for over 2 years now, and sales haven't still taken off to a level where I could say thank you and good night to the boss and live on the EV-business alone, no matter what sacrifices I'd be prepared to do, because in the end it turned out that people saw that price tag of 3 grand and went for a shoe box controller (some went for several, creating fireworks and big amusement along the road, literally), even many of those that claimed they'd get an S1 as soon as they came out (they never did).

So, as I said we also started on the Junior since those 3 grand was too stiff for many. This has resulted in (at least) three things:



Despite that even 600 Amps can wreck a WarP 9" in less than a minute people complain that it's too weak and go for some other inferior design that claims higher numers but seldom gets even close (but they sure are cheaper).
Some people think that $2k is still too much and go for cheaper stuff or make (and break) a few P&S along the road.
Jr has cannibalised a LOT on S1, so the net gain on a smaller, cheaper controller is probably debatable at best.

Meanwhile the garden has turned into wilderness and the house is in desperate need of being fixed due to two years of neglect and you happily chirp about trying to get me in at least a third year of next to no spare time (with next to no revenue) to create an inverter that will most likely:



Not get a competitive pricing, thus not sell to DIYers anyway.
Cannibalise further on S1-sales.
Not pay for it's own development cost (just like it's siblings).

Unless someone/something makes it possible for me to do this without having to sacrifice most of my spare time to write the software at a salary level that would make an employee at Wal-Mart point and laugh I have only one thing to say...

...but text media doesn't really carry the full impact from explicit languages in a way that would satisfy me, so I'll refrain from it.


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## JRP3 (Mar 7, 2008)

Translation: Don't expect a 3 phase inverter from the boys, unless you plan to fund the development, (and at that point you may as well just drop the coin on an ACP system.) Can't blame them, Qer paints a bleak picture.


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## drgrieve (Apr 14, 2011)

How much is the EV market growing year by year? There should be more $ being spent in the coming years. 

Hopefully I'll be one of them ....


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## Qer (May 7, 2008)

Well, Think Car just went bankrupt again. It's the fourth time...

Yeah, eventually EV's will take off, but who knows when plus, of course, that doesn't necessarily mean that DIY will take off.


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## Plamenator (Mar 6, 2009)

Unfortunately Qer is more or less right.
Motors are much simpler than controllers and yet I am only able to make a profit on them because they represent less than 1% of our total turnover.
I.E. there is something else to pay for the overheads.

Still without risk and faith there is no profit.
If you are not prepared to invest (time in Qer's case) pursuing something uncertain and in the hope of a battery breakthrough/gas price hike (200$/barrel sounds nice), you will never profit if it happens.


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## Qer (May 7, 2008)

Plamenator said:


> Still without risk and faith there is no profit.
> If you are not prepared to invest (time in Qer's case) pursuing something uncertain and in the hope of a battery breakthrough/gas price hike (200$/barrel sounds nice), you will never profit if it happens.


True, but if you're gonna play on the horses it's usually better to pick the strong and healthy looking ones than go for the high odds creatures that will win the race the day hell freezes over.

The experiences from the Soliton brothers has taught me that it's quite possible to sell a high quality high performance motor controller to the DIY crowd and make profit on it IF you're prepared to wait years for development cost and time to pay off. Those DC-controllers does generate some revenue now and it's definitely worth continuing to improve the software to make them even more useful and versatile, but the sanest thing I can do is to consider that year developing version 1.0 a very useful and good experience that looks good in my CV, 'cause it sure don't pay off in money. It probably never will.

I don't need another year of development experience in my CV. One year looks good (it has already come in handy when I've applied for new jobs), a second year will probably look like I'm unable to draw sane conclusions from past experiences. This doesn't mean we will keep selling Solitons and be satisfied with that, only that going for another complicated product like an inverter is at the moment about as tempting as getting my head nailed to a board. We do consider new products and now when the Soliton software actually starts to feel really mature with the upcoming 1.4-release I start to feel tempted to go for a new challenge again even though things are a bit sketchy still (we're flinging ideas at eachother, shooting them down almost as fast as they're flung).

You can pile up as much as you like, unless it's a pile of dollars this decision stands.


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## JRoque (Mar 9, 2010)

Pile +1

Here's a suggestion (easy for me to say): diversify. 

You have a solid ~150kW controller (Junior) that would make a killer charger with a few more parts. Markets include EV and photovoltaic. Check out pricing for a 150kW charger and you'll see how there's opportunities in there. Hey, one of the PV market leaders named their company "Sunny Boy". You can't tell me that doesn't make you jump in and smack them down.

JR


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## Plamenator (Mar 6, 2009)

I got to working on the throttle.
Apparently it is an electronic one employing 2 Hall sensors.
One of the sensors is 0.5-4.5V and the other 0.25-2.25V so both are used as a fail safe device.
I will try to make it work with Soliton1 (still have no Curtis 1238R in stock, but if it works on Soliton1, should work on Curtis too...hopefully).
Problem is it has 6 wires - 3 for each sensor (5V, GND and signal) and I cannot identify the ones for the 0.5-4.5V sensor.
(turning on ignition and measuring the inputs from the ECU does not work - probably some protection is enacted as there is no ICE)
Suggestions welcome


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## jackbauer (Jan 12, 2008)

Plamen , that looks very like the e46 hall pedal i use in my car. I have a pinout.

Look at the wiring plug.With the pedal facing downwards and the connector pins on your left.The bottom right terminal (brown wire) is 0V. Bottom left (white wire) is signal and middle left terminal (yellow wire) is +5v.

Note that this throttle has a detent (at least mine does) so press it to full gives +4.2v then press harder and it clicks to full which outputs 4.5v


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## Plamenator (Mar 6, 2009)

Thanks - seems exactly what I needed.
Do you think I can damage something if I get it wrong?
For example connect 5V to GND or signal?


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## jackbauer (Jan 12, 2008)

I don't think you can cause damage. I once had 5v and ground reversed. it just didnt do anyting. Hookup a milliameter. It should draw a steady 5mA at 5v.


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## Plamenator (Mar 6, 2009)

It works...at least with Soliton1.
Thanks Jack.

This is hugely convenient.
Appears the ECU needs pedal input in order to control properly the power steering though no idea why for the moment.


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## efan (Aug 27, 2009)

any progress on the BMW conversion or updates on the motor development?


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## Plamenator (Mar 6, 2009)

Quite a lot of progress actually.
About 2 weeks ago the prototype (a single motor for the moment) 10" AC motor came out.
We managed to get like 44-45kW peak out of it with the 550A version of the Curtis 1238R controller (remember I am in for a 13 week lead time for the 650A one).
The motor weights 64kg and is the middle one in the picture (in between 18AC9 and the new version of K13" DirectDrive).
It is optimised for 100Hz. 
One of the big questions so far are should we not design it for 130-150Hz?
This will allow higher peak power but lower torque.

Anyway, appears a dual 10" AC motor like the prototype will weight 128kg with a peak of about 110kW (with the 650A 1238R) which is not good. Problem is that the controller is handicapped at 96VDC/67VAC which really kills the peak potential. For example we designed (on paper only as we have no suitable controller) a 380VDC version of that same 10"/96VDC AC motor. We could get 26kW nominal with 80A at 110Hz. A controller like Tritium (Australian) with its 300A peak power would allow 100kW peak out of that motor which is a whole different story.
A further problem are the batteries - I planned to install 35 160Ah cells but those are 280mm high. Putting them above the motor means I will not be able to close the hood of the engine compartment.

When I get to my office tomorrow I will post some more pictures and my solution to the above.


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## efan (Aug 27, 2009)

all sounds very interesting! and clearly a higher voltage motor controller would be better, is this controller going to work with the motor?

http://kellycontroller.com/khb1480124-144v800aopto-bldc-controllerwith-regen-p-822.html


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## piotrsko (Dec 9, 2007)

DUUUUUUde: cut a hole in the hood for God's sake.


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## JRP3 (Mar 7, 2008)

Plamenator said:


> Problem is that the controller is handicapped at 96VDC/67VAC which really kills the peak potential.


Remember it actually goes to 130V, most of us are using 36 cells 115V nominal, 122 when fully charged at rest. You might be able to sneak in 37 depending on what regen does to the pack.


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## Plamenator (Mar 6, 2009)

DC input of 1238R indeed goes to 130VDC.
Unfortunately whatevel the input voltage, AC output is limited to 67-70VAC. This was one of the first things I tested 
So the only purpose of going to 115V nominal is to prolong range and to ensure that DC is >96V even with sag. It also lets you use smaller cells which seems more convenient.


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## Plamenator (Mar 6, 2009)

efan said:


> all sounds very interesting! and clearly a higher voltage motor controller would be better, is this controller going to work with the motor?
> 
> http://kellycontroller.com/khb1480124-144v800aopto-bldc-controllerwith-regen-p-822.html


No idea frankly.
I am a bit unclear as to what is the difference between BLDC and AC with permanent magnets. Both seem to have AC style stator laminations and PM in the armature and 3 phases.
Yet most ACIM controllers I know only seem to work with ACIM and ACPM but none mentions BLDC. Likewise, BLDC controllers do not mention ACIM/ACPM.
Examples of such ACIM controllers are:
http://www.sevcon.com/media/2092/gen4_size_8_data_sheet.pdf
http://www.tritium.com.au/products/TRI74/TRI74.015v3_Datasheet.pdf

Maybe someone more competent can answer this for you.
BUT, if the Kelly can work with ACIM, you can use our new 10" AC motor with 144VDC/100VAC and it will produce more peak power - it will be like we made it for 100VAC but optimised for 150Hz.

In all cases I am suspicious to a 7kg controller claiming 800A.


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## pm_dawn (Sep 14, 2009)

what about the gpAC from the Sevcon?.

They also have a GenV version that looks much like the Gen4 controller.
They use that for the Yasa motor.

Regards
Per


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## DawidvC (Feb 14, 2010)

Plamenator said:


> No idea frankly.
> I am a bit unclear as to what is the difference between BLDC and AC with permanent magnets. Both seem to have AC style stator laminations and PM in the armature and 3 phases.
> Yet most ACIM controllers I know only seem to work with ACIM and ACPM but none mentions BLDC. Likewise, BLDC controllers do not mention ACIM/ACPM.


The real difference between ACSM (AC with permanant magnets) and BLDC motors are supposed to be in the structure of the windings - the BLDC is supposed to be optimised for a more squarish waveform, while the ACSM has windings supposedly optimised for sinewaves. I use ssupposedly, because there are some bldc motors from well-known manufacturers like Siemens which are known to be more efficient in sinewave commutation than their ACSM that is very similar. 

I am running out of language here - but it seems to be a semantic game by some manufacturers. BTW, most decent modern drives, especially the ones that claim some form of vector control, can actually control ACIM, ACSM and BLDC motors, primarily because the whole FOC-system is based on the original control scheme for BLDC motors.

I hope this helps a bit.

Regards
Dawid


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## Baldbruce (Aug 1, 2011)

Why not use both AC and DC motors since you plan to use two anyway? Gearing the DC motor for maximum torque at lower speeds and the AC motor geared for more torque at higher rpms might give the best of both worlds. Am I crazy? Thoughts on strength and weakness of this concept? Perfect AWD system with an AC on the front end and DC driving the rear?


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## JRP3 (Mar 7, 2008)

I've had the same thought, so either we're both crazy or it's a decent idea


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## Jan (Oct 5, 2009)

How do you prevent, in that hybrid setup, the DC motor from over revving? If you want the most torque at low speeds, you have to gear de DC motor down, in stead of up. And considering the significant lower max RPM of a DC motor that seems to me a serious problem.


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## JRP3 (Mar 7, 2008)

Depends on the motors you are using. A Warp11HV can take pretty high RPM's as I recall, and you don't have to use the full RPM's of an AC motor since power drops off near the top anyway, so I think gearing could be pretty close.


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## Jan (Oct 5, 2009)

OK, I understand. The AC peaks at top speed than. But it is not exactly that you get the most torque from the DC motor at low speed. It's more a trade off. But still interesting. 

Another thing: Isn't it that AC motors are usely getting more efficient beyond their max power point? You would loose that advantage. If true.


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## JRP3 (Mar 7, 2008)

Jacks graphs of the AC50 show a pretty flat efficiency curve dropping off a bit near the top.
http://4.bp.blogspot.com/-ldkF9pB0oSY/TarvvmO19sI/AAAAAAAACJ4/yIByagsM-Nk/s1600/spyder7501-3rd.jpg


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## Plamenator (Mar 6, 2009)

Well, if you put the DC and AC on a common shaft, you will have huge problems in syncronizing rpm.
A reasonable setup would be to have the AC motor first than some kind of planetary/electromagnetic clutch and than the DC motor.
When you accelerate and need low rpm peak power use the DC (which will also rotate the AC shaft but it can do that easilly), than as rpm rise above 4000 switch on to the AC while disconnecting the DC. All that at 2nd gear (assuming it can take it) with an AC motor optimised for 150-200Hz.
Maybe someone more competent than me can devise setup with a specialised clutch that can allow both the AC and DC to combine forces under 5000rpm...
In all cases it will be much more complicated than I can handle.


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## Jan (Oct 5, 2009)

Plamenator said:


> Well, if you put the DC and AC on a common shaft, you will have huge problems in syncronizing rpm.


I understood that the idea is to put the DC on the rear, and the AC on the front wheels. DC for the greater power at lower speed to accelerate prety stout with rearwheel drive. And AC on the front wheels for getting the most out of regen braking. And for power at higher speeds.

Both motors should be powered by the same pack. So they should be in the same voltage range. There is not much choice, but still, there is.

The idea is appealing, but makes everything even more complex and expensive.


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## Plamenator (Mar 6, 2009)

JRP3 said:


> Jacks graphs of the AC50 show a pretty flat efficiency curve dropping off a bit near the top.
> http://4.bp.blogspot.com/-ldkF9pB0oSY/TarvvmO19sI/AAAAAAAACJ4/yIByagsM-Nk/s1600/spyder7501-3rd.jpg


Note that efficiency here is combined for motor+controller.
Curtis 1238R is quite inefficient at low rpm - starts with 75% and than increases with frequency:
http://hpevs.com/images/stories/AC-50 HP Torque.xls
This counteracts the falling efficiency of the motor at higher frequency and makes for the flat curve.


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## Plamenator (Mar 6, 2009)

Jan said:


> I understood that the idea is to put the DC on the rear, and the AC on the front wheels. DC for the greater power at lower speed to accelerate prety stout with rearwheel drive. And AC on the front wheels for getting the most out of regen braking. And for power at higher speeds.
> 
> Both motors should be powered by the same pack. So they should be in the same voltage range. There is not much choice, but still, there is.
> 
> The idea is appealing, but makes everything even more complex and expensive.


You can also keep the ICE in front and put a motor at the rear with a small pack to give you 20-30km range


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## JRP3 (Mar 7, 2008)

Plamenator said:


> Well, if you put the DC and AC on a common shaft, you will have huge problems in syncronizing rpm.


Is that a given? I thought with an AC motor in torque mode it would self adjust the amount of torque supplied needed to match the speed of the DC motor. Or something like that


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## Plamenator (Mar 6, 2009)

I think torque mode means that 0-100% of throttle results in 0-100% of max torque rather than 0-100% of max rpm. Torque mode is appropriate for EV traction applications but it does not self adjust the torque.
For example if max torque is 100Nm pressing the pedal to 40% will give you constant 40Nm so car will accelerate until friction and wind resistance equalise with torque and speed settles (stays constant).


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## Plamenator (Mar 6, 2009)

BTW, below is a test result from 10AC9" which we initially designed for 48VDC/75Hz but ran at 96VDC for the test. The motor description is here:
http://kostov-motors.com/tractionmo...3-phaseacmotorsforelectricvehicles/10ac975hz/

Controller now has much more voltage to play with.
Hence the results are surprisingly good. The 2 sets are for nominal and peak power and within each set the 2 lines are with Field Weakening set to 100% and to 0%.
Makes a good argument for designing EV AC motors for higher frequncy. Any opinions?


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## Plamenator (Mar 6, 2009)

Going back to my conversion, I have decided to opt for DC.
Reason is that 96V are really low and cannot match a 250V DC system even if going dual AC. At the same time Z4 has only 235kg payload and cannot afford the extra weight of dual AC along with the associated bigger batteries. 
Still I am going for 80 cells of 90Ah each which will allow me to switch to AC if I ever find a suitable higher voltage AC controller. Next 10" AC prototype is also in the plans that will be optimised for 150Hz - maybe this will allow a dual AC system to match a DC setup even at 96V.

So the changed setup is:
K11" 250V
Soliton1
80x90Ah to give 256V nominal and 23kWh.

There will be 2x40 cell packs - one in the front and one in the trunk. Those can eventually be re-wired in parallel to accommodate the dual AC...eventually


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## tomofreno (Mar 3, 2009)

> The Curtis controller has a parameter called nominal battery voltage.
> If this is set to 96VDC, controller is supplying the motor with maximum 67VAC and it does not matter if your nominal voltage is actually 115 or even 130VDC. At the same time the max value for this parameter in 1238R is 96VDC. Hence it seems like knee point will always be at 3000rpm regardless of your pack voltage.





> DC input of 1238R indeed goes to 130VDC. Unfortunately whatevel the input voltage, AC output is limited to 67-70VAC. This was one of the first things I tested
> So the only purpose of going to 115V nominal is to prolong range and to ensure that DC is >96V even with sag.


These torque-speed curves for the HPEVS AC50/Curtis 1238-7501 from Curtis with a 96V pack sagged to 86V, and Jack Rickard with a 115V pack sagged to 104V clearly show the controller does make use of the higher pack voltage Plam. 
Both are data from dynos. Peak power occurs at about 3200 rpm with the 96V pack and moves out to about 4200 rpm with the 115V pack, and peak power is about 51 HP with the 96V pack and about 63 HP with the 115V pack.
View attachment AC50.7501, 96V torque spd.pdf

View attachment AC50.7501.115V torque spd.pdf


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## Plamenator (Mar 6, 2009)

We are now closed for summer break till 11SEP so I cannot re-test.
But I specifically tried to make the 1238 output more than 67-70VAC and could not even with a 115VDC input. Perhaps I should put more attention to that as higher AC voltage will really make a difference.
Note that at 86VDC sagged, AC is 59VAC so with Jack's battery you have a good 7VAC more. This alone increases inflection point rpm from 3200 to 3200*67/59=3633rpm. Than there are many settings that can increase rpm a bit too - field weakining/base speed to name the first that come to mind.
Also the higher peak power can simply be the result of the increased rpm.


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## efan (Aug 27, 2009)

Hey Plamenator, 
keep us updated on the progress of your conversion, what performance do you expect from the DC set up (0 to 60, top speed?)... and in the mean time you might also want to look at this: http://www.diyelectriccar.com/forums/showthread.php/uniteks-bamocar-62230.html


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## Plamenator (Mar 6, 2009)

I expect to match the performance of the original ICE engine so 7-8sec for 0-60 miles:
http://catalog.auto.ru/catalog/cars/card/1445.html

This is like 900-1000A at 200-230V (with sag) at 75% motor efficiency.
There is also the added benefit of having all torque from 0 rpm but cannot quantify that.

My biggest problem is the ammount of interconnected electronics in Z4.
Apparently neither the ABS (break apparatus with ABS is rumoured to be smaller than without ABS so if ABS does not work, brakes will be inadequate) nor the EPS (electronic power steering) will work without the central ECU. And the ECU does not want to start without the ICE and all the sensors in it. So we will have to design emulators to trick the ECU of thinking ICE is still there.
So we have hooked the ICE to the ECU (ICE is placed next to car and wired to the ECU) and we will start designing the emulators one by one.
Especially tough is the fact that the ECU reads 3 Hall sensors for speed from the ICE, all of which have to be emulated so they give the electric motor's rpm correctly while if electric rpm are <800, 800rpm should be fed to the ECU...hmmmm.

I hope my explanation is clear but to be honest this goes above our competences so it will be quite a challenge. I am lucky to have a friend that is really into electronics but he has not broken into a BMW ECU either 

Suggestions as always are welcome...


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## steven4601 (Nov 11, 2010)

The Ice doesn't need to start as long it has an RPM signal the ECU will very likely accept its condition as running. DSC will complain about the lack of air entering the engine and lack of the throttle possition sensor. Something may need to be manufactured to satisfy DSC/traction control part of the ABS system or it has to be ignored. Have you tested the PS with only 12V connected? Dead as a flat mouse or is it overly powered like in city mode?


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## Plamenator (Mar 6, 2009)

Throttle position will be reported correctly to the ECU as we will use the original throttle (it is electronic with Hall sensors). So throttle goes to ECU and we will intercept the signal from ECU to fuel valve and feed it to the Soliton1...or at least that's the plan assuming signal is not modified while passing through the ECU. Maybe we can also parallel the signal prior entering the ECU so one set goes to Soliton and one set of signals to ECU. Which do you think is better?

Problem is we do not know how to set up the 3 original rpm sensors so they feed the correct signal to the ECU. We do not even know the exact wiring for those so it has to be researched.

Probably a stupid question, but what is PS?
DSC indeed complained about lack of air. However there is a DSC off button which I will try tomorrow (just thought of it ).


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## steven4601 (Nov 11, 2010)

There's a decade between my z3 and your z4. I chose to remove the ECU. It made life simpler and less restrictive. I suspect ABS will work without the ECU present. Just the DSC part will not.

Power steering (PS). Its directly driven by an electric motor without transmission oil?

About RPM, there's often only one sensor used as the actual RPM sensor input. Others are for cam/fuel related inputs. Probing by injecting 1khz through a function generator might help finding the one. It is possible hear some relays tick in their on position if the idle RPM has been detected the 'engine'/function generator is running to power things such as the heated oxygen sensor and or other power sapping devices . 

Is the instrument cluster wired with an tacho rpm input ? or is it solely CAN based? If it needs CAN input you may be better of with the ECU though.


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## Plamenator (Mar 6, 2009)

DSC has a button to turn it off. However from what I have read, ABS in Z4 is not autonomous and will not work without the main ECU having all its sensor inputs.
Or do you think ABS will work if I turn DSC off?

EPS is driven by an electric motor without oil but with a dedicated controller, in turn managed by the ECU. It has a complex control algorythm dependent heavilly on car speed.

We intended to try with a function generator indeed.
I have not yet got to the instrument cluster - plan to use an Android tablet with EV Speedo.

Z3 is indeed easier to make electric. I was hooked on Z4 looks though


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## steven4601 (Nov 11, 2010)

As far from a safety point of view. ABS should work with or without DSC enabled if it works at all. 

Z4 is nice too. Maybe it will be my next conversion, first things first. I still have to finish the Z3. Hopefully I will go according to plan, before the end of this year.  I had a big EV grin yesterday from installing the motor and re-connecting the drive-shafts. Feels good to have everything mechanically sorted.


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## Plamenator (Mar 6, 2009)

I must admit I am really poor at documenting stuff...
Anyway, after much effort, the beta version of Z4 is operational

At the end we managed to fool the ECU into running even without ICE.
There is a dedicated PCB with processor which simulates the signals from all sensors that were in the ICE so ECU does not know ICE is gone. ABS and EPS work just fine.

I had lots of problems with the Manzanita and the BMS. As the battery pack is divided in 2, the long singal BMS wire between the packs gets really contaminated by the PFC30 charger so BMS goes nuts and keeps turning the charger on and off. Manzanita seems not to be properly grounded as well - when it is bolted to the chasis I get electrocuted (seems like static electricity but is quite shocking) just by touching the car. Result is I can only do a "blind" charge which is a problem given the cells are new (working to add some immunity to that wire).

I also still do not have a DC-DC converter so car runs 15km only and then lead 12V battery gets exhausted

There is also a problem with EVSpeedo. I have the paid version of EVSpeedo (1.54 I think it was) with a Motorola Xoom Honeycomb 3.2 but I still have a huge 40-50sec delay of UDP broadcast from Soliton1.


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## JRP3 (Mar 7, 2008)

You might try connecting the BMS to an external switch to shut down the charger instead of relying on the regbus.


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## Plamenator (Mar 6, 2009)

That is what I am doing - there is a solid state relay controlled by the BMS. The noise in the signal wires leads to BMS error and BMS shuts down the charger, restarts itself and starts again but only manages to charge for 15-20sec before getting an error again.

Regbus is not used at all.
Problem is in the huge ammount of noise the PFC generates.


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## JRP3 (Mar 7, 2008)

I don't use a BMS so I never noticed. What BMS are you using? Have others using a Manzanita with a BMS encountered similar issues?


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## mizlplix (May 1, 2011)

The roundy-round racers that use second or third gear to extremes usually lose the transmission in 3-4 races. But when they install a transmission pump and cooler circuit, they can make a whole season easily. 

Anyway, it is worth a thought.

Miz


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## DavidDymaxion (Dec 1, 2008)

Plamenator: Most impressive, I bow in your general direction! Fooling the ECU is great stuff. Thanks for the pics, too, that's a great looking conversion.


Plamenator said:


> I must admit I am really poor at documenting stuff...
> Anyway, after much effort, the beta version of Z4 is operational
> 
> At the end we managed to fool the ECU into running even without ICE.
> ...


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## Plamenator (Mar 6, 2009)

Here is a short basic log of a 5min drive limited to 450A and 4500rpm. Series 1 is amps, series 2 is voltage.

What worries me is the voltage drop towards the end from 245 to 195V at 450A only.
Do you guys think this is normal? Can it be invoked by the Soliton1 going to amp limit?
Have in mind battery (75x90Ah Winston cells) has never been cycled as I am still waiting for the "proper" Chinese charger to arrive


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## dimitri (May 16, 2008)

Plamenator said:


> Here is a short basic log of a 5min drive limited to 450A and 4500rpm. Series 1 is amps, series 2 is voltage.
> 
> What worries me is the voltage drop towards the end from 245 to 195V at 450A only.
> Do you guys think this is normal? Can it be invoked by the Soliton1 going to amp limit?
> Have in mind battery (75x90Ah Winston cells) has never been cycled as I am still waiting for the "proper" Chinese charger to arrive


Only 450A? That's 5C for these poor cells, yes, they will drop to 2.6V at 5C and will get hot too. You better set lower battery current limits in Soliton.

BTW, I sent you a PM few weeks back, did you see it?


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## Bowser330 (Jun 15, 2008)

Plamenator said:


> Here is a short basic log of a 5min drive limited to 450A and 4500rpm. Series 1 is amps, series 2 is voltage.
> 
> What worries me is the voltage drop towards the end from 245 to 195V at 450A only.
> Do you guys think this is normal? Can it be invoked by the Soliton1 going to amp limit?
> Have in mind battery (75x90Ah Winston cells) has never been cycled as I am still waiting for the "proper" Chinese charger to arrive


I think your worries are valid...That is a large voltage drop for 5C, I would expect that drop at 10C....

75 x 3.2V = 240V
75 x 2.6V = 195V
0.6V drop is 19% voltage drop at only 5C (90AHx5=450A)


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## Plamenator (Mar 6, 2009)

I was hoping sag will diminish after a few discharge cycles to 10-12%.
Further, this is at starting when I motor probably only sees 20-50V.
So it is 450A but at 50V say out of a 250V pack.
Anyone with real life experience with those cells?

Dimitri, just replied to your PM, sorry.


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## dimitri (May 16, 2008)

Plamenator said:


> I was hoping sag will diminish after a few discharge cycles to 10-12%.
> Further, this is at starting when I motor probably only sees 20-50V.
> So it is 450A but at 50V say out of a 250V pack.
> Anyone with real life experience with those cells?
> ...


What makes you think sag will diminish? There is no such thing as "training period" for LiFe cells.

I assumed 450A was battery current, not motor. How are you measuring cell voltages? Pack level? Can you trust the measurement? Are you assuming that all cells equally contribute to sag? Verify measurements of battery current and cell level voltages by trusted tools, check all cell terminals for tight/clean connections and see if they get too warm after heavy loads.

5C is a lot for these cells, in my opinion these should not be subjected to over 2.5C on regular basis, although some people here would argue otherwise. I speak from personal long term experience.


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## Tesseract (Sep 27, 2008)

Plamenator said:


> Here is a short basic log of a 5min drive limited to 450A and 4500rpm. Series 1 is amps, series 2 is voltage.


Is this battery or motor current? One would assume battery current, but comments you make later on confuse the issue...



Plamenator said:


> Can it be invoked by the Soliton1 going to amp limit?


Why in the world would you blame a drop in battery voltage on the controller?


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## Plamenator (Mar 6, 2009)

I think it is motor current but you make me doubt that now.
Unfortunately I can double check on Monday as I have only the pic here while original log file is in my office PC.

However, if I get 450A battery current at low rpm start up, does this not imply motor current was well over 1000A?


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## Tesseract (Sep 27, 2008)

Plamenator said:


> I think it is motor current but you make me doubt that now.


Logger reports *motor current* and *duty cycle*. You have to calculate battery current by multiplying those two values. Unless you actually did that to the logger data, then, no, you are reporting motor current, but you are talking as if it were battery current...



Plamenator said:


> However, if I get 450A battery current at low rpm start up, does this not imply motor current was well over 1000A?


The only thing you can infer about motor current from battery current is that it can't be less... And given that the Soliton1 limits motor current to 1000A, that is as high as it (and therefore battery current) can go.


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## Bowser330 (Jun 15, 2008)

Tesseract said:


> Logger reports *motor current* and *duty cycle*. You have to calculate battery current by multiplying those two values. Unless you actually did that to the logger data, then, no, you are reporting motor current, but you are talking as if it were battery current...
> 
> 
> 
> The only thing you can infer about motor current from battery current is that it can't be less... And given that the Soliton1 limits motor current to 1000A, that is as high as it (and therefore battery current) can go.


Where does that voltage line come from? is that also a line the logger reports?


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## Plamenator (Mar 6, 2009)

Voltage comes directly from the Soliton log file.
This becomes ever stranger.
As I did not multiply current by duty cycle, apparently I am reporting motor current. But if motor current is 450A at low rpm (low motor voltage) then battery current should be less than 450A (probably a lot less). Yet there is a big voltage drop. Or am I missing something big here? Might be that I got wrong the Excel import...


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## Tesseract (Sep 27, 2008)

Bowser330 said:


> Where does that voltage line come from? is that also a line the logger reports?


Yep. All explained on p24 of the manual...


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## Bowser330 (Jun 15, 2008)

Plamenator said:


> Voltage comes directly from the Soliton log file.
> This becomes ever stranger.
> As I did not multiply current by duty cycle, apparently I am reporting motor current. But if motor current is 450A at low rpm (low motor voltage) then battery current should be less than 450A (probably a lot less). Yet there is a big voltage drop. Or am I missing something big here? Might be that I got wrong the Excel import...


You keep saying "low rpm" however the graph you attached shows that at 450A the rpm was 2168...or am i reading that wrong?


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## Plamenator (Mar 6, 2009)

That 2168rpm is only towards the end of the 450A period.
Even than 2168rpm is a lot less than the nominal 5400rpm so motor voltage is certainly much less than "nominal motor voltage" (192V as motor is configured in parallel field mode).


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## Jozzer (Mar 29, 2009)

That graph looks about right to me, the battery voltage sages more as RPM increase bringing battery current up with it, data seems correct.
It's a little more sag than I'd expect, but not much. Anything over 3C is punishing these cells IMO.
That said, it's worth checking all your connections after a run and making sure none of them are getting hot. Also any cells warmer than others indicating you have one or two with higher IR than usual. Check both cell connections and cabling/fuses/contactors/controller terminals.

Steve


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## DavidDymaxion (Dec 1, 2008)

Let's assume battery Amps for a moment.

R = V / I

R = ( 245V - 195V ) / 450A / 75 batteries

R = 1.5 milliOhms per battery

If I go to this web site: 

http://en.winston-battery.com/index.php/products/power-battery/item/wb-lyp90aha?category_id=176

Per the graph I calculate:

R = ( 3.2V - 2.9V ) / ( ( 5 - 0.5 ) * 90 A ) = 0.7 milliOhms

So you are getting twice the internal resistance. Are your batteries old? The newer ones are supposed to be better. It's also possible that spec sheet is optimistic.

If that was motor Amps and your battery current is lower, things are even worse.



Plamenator said:


> Here is a short basic log of a 5min drive limited to 450A and 4500rpm. Series 1 is amps, series 2 is voltage.
> 
> What worries me is the voltage drop towards the end from 245 to 195V at 450A only.
> Do you guys think this is normal? Can it be invoked by the Soliton1 going to amp limit?
> Have in mind battery (75x90Ah Winston cells) has never been cycled as I am still waiting for the "proper" Chinese charger to arrive


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## drgrieve (Apr 14, 2011)

Nice to see some real world data! 

I'll add my 2 cents worth.

I'd suspect that this was at 100% duty rating and thus was 450 battery amps. 

For reference Jacks Calb 180 cells sagged over 20% to 2.6v at 5.5C.

I suspect thundersky have a higher sag than calb so this is in the ballpark.

The charts linked to are the same for every cell type so I think that chart not worth much, also we are seeing here pack sag, which is different to the sag in an individual cell.

Also I wouldn't think you'd do any damage to the cells for brief bursts at 5C. Sagging to 2.6 volts is not that much. Any proof that a little sag does anything? That's why low voltage warnings are fairly useless you have to set them so low if you want any fun.

Would be better to test the sag out on cold cells (20-30 celsius), the 5 minute warm up may have improved the results somewhat - any idea of the temperature of the cells?


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## Plamenator (Mar 6, 2009)

It was a 5min drive so cells started with ambient temp of around 12-15C.
No idea what temp was like at the end.
As I had so much problems with the noisy Manzanita, BMS is still not working properly so no input from it for the moment.

My reasoning was that while 90Ah cells have small capacity, when I accelerate motor voltage would be like 0-100V. So 3C at 250V of 270A translates into 250/100*270=675A at 100V which is more or less acceptable and would produce decent torque.

Apparently I need to check my data and do new tests.


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## Plamenator (Mar 6, 2009)

Following Tesseract's advice, I re-did the chart from Soliton's logger file.
This time I have included motor amps, battery amps (MotorC x PWM/100) and pack voltage.
Apparently my rpm sensor is not properly calibrated or a bit too far from the rotating bolts on the motor shaft so rpm data is rubish and I have discarded it.
Big voltage drop occurs at 400A battery current when Soliton1 has applied 91% PWM - i.e. motor amps=1.1 x battery amps.
X-axis is time.


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## Jozzer (Mar 29, 2009)

Did you check for any poor connections yet? Or, check 1 cell voltage whilst under load to see if they really are sagging that bad? (Put meter on terminals direct, NOT on the busbar/connector to check that cell sag rather than poor connection somewhere is the problem.)

If you want some stiffer battery's drop me a line I've got 10% sag at 1000A..


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## dimitri (May 16, 2008)

Plamenator said:


> Big voltage drop occurs at 400A battery current when Soliton1 has applied 91% PWM - i.e. motor amps=1.1 x battery amps.
> X-axis is time.


Perfectly normal sag at 4.4C for these cells. Don't subject them to such sag for more than few seconds at a time, as it causes heat accumulation inside the cell and will shorten their life. Set battery current limit in Soliton config.


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## Plamenator (Mar 6, 2009)

I finally got a "proper" charger and DC-DC converter (200-320VDC in, 12VDC/70A out). Charger is up to 337VDC/14A with CAN that is compatible with my BMS. Both from http://www.tccharger.com/english/.
I hope this will work!

Strangely, the new 14A charger is 10 pounds heavier than the Manzanita PFC30 with its 30A. Hope the difference is safety features


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## efan (Aug 27, 2009)

Hey Plamenator,
How is the BMW? do you drive it? on daily basis? how about performance are you happy with it? 

Regarding Kostov's 10AC9 motor...you have some limited information on your web page, but can you give some more details, what does it weight? and the performance curves show power but not torque...what is peak torque etc? 

Since the 650a Curtis controller is with long lead time and somewhat expensive, have you considered using a Sevcon G8055 (http://www.sevcon.com/media/2104/gen4_data_sheet.pdf) its max DC voltage is 118vdc so you can probably run 32-33 cells, and it seems to be priced more reasonably at around $1200 (http://www.electricmotorsport.com/store/ems_ev_parts_controllers_sevcon_gen4_72-80_550.php)

what are your thoughts on Sevcon paired with 10AC9?


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## Plamenator (Mar 6, 2009)

It is winter now so not really good for a cabrio.
Nice and shiny at the moment but still -5C  so I do not drive it a lot.

Performance is miserable due to the battery problem.
The Winston 90Ah cells only give me around 450A peak so peak motor power is around 80kW compared with the original ICE at 150kW.

I am researching new batteries like:
http://www.alibaba.com/product-free/112342518/HEADWAY_38120P.html
http://www.alibaba.com/product-gs/503436327/Headway_LiFePO4_38120HP_lithium_ion_power.html

Any feedback on the red ones will be highly appreciated.
Problem with those is the low density of 75Wh/kg.
A123 20Ah prismatic goes to 130Ah/kg but cannot really find a reliable source of them. I heard Mavizen is selling A123:
http://www.mavizen.com/A123.html
But not sure they will sell me for a personal conversion. Ideas?

10Ac9 goes to about 150Nm peak.
I already have stock of Curtis and will soon be uploading kit price on the website.
I much prefer Curtis because we have already invested a lot of effort into getting to know their programming and they have a plant in Sofia just 10km away from me. So I can easilly get support in Bulgarian


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## steven4601 (Nov 11, 2010)

From the graphs you made, I think the Calb cells are performing excellent! 1.3mOhm per cell average is quite darn good.

80kw is quite nice tbh! If you want more, adding a few cells can make a huge difference in driver experience. I did my first tests at 200 Volt of the designed 430V . It was quite slow, until all modules where hooked up, at 430V it was actually quite nice. The thing with power is you want it as soon as possible at its max and keep it also at its max if possible. I don't want to start a torque vs power war , but if you have limited power, you want it to reach peak power early in the acceleration / gear. IF you select 5th gear, you are ~ 150km/h away from peak power. If you select 2st gear you are about 30 to 50km/h away from peak power.


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## JRP3 (Mar 7, 2008)

You could try these guys for A123:
http://www.alibaba.com/product-gs/514989142/lifepo4_battery_cells_A123_20AH_cells.html

Or these guys:
http://www.osnpower.com/productID/product_detail-12630699.html


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## tomofreno (Mar 3, 2009)

steven4601 said:


> From the graphs you made, I think the Calb cells are performing excellent! 1.3mOhm per cell average is quite darn good.
> 
> 80kw is quite nice tbh! If you want more, adding a few cells can make a huge difference in driver experience. I did my first tests at 200 Volt of the designed 430V . It was quite slow, until all modules where hooked up, at 430V it was actually quite nice. The thing with power is you want it as soon as possible at its max and keep it also at its max if possible. I don't want to start a torque vs power war , but if you have limited power, you want it to reach peak power early in the acceleration / gear. IF you select 5th gear, you are ~ 150km/h away from peak power. If you select 2st gear you are about 30 to 50km/h away from peak power.


What you want is peak torque for as long as you can get it, since it is wheel torque that supplies the tractive effort to accelerate the vehicle. The motor power will change with angular velocity of the motor. Since that is increasing for an accelerating vehicle, the power will necessarily increase as long as you can maintain peak torque. It will decrease when torque starts falling off faster than the increase in angular velocity. You don't want that to occur earlier. You want to extend peak torque out to as high of rpm as you can, which is what higher voltage does. You can of course shift to a higher gear to decrease motor angular velocity and maintain peak torque, but you loose mechanical advantage, which lessens wheel torque and acceleration unless the the gain in torque was greater than the loss in mechanical advantage.


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## Plamenator (Mar 6, 2009)

The cells are actually Winston, not CALB.
I read the spec sheet saying 20C as "burst" (burst is probably like 0.1sec...).
I assumed the Chinese are exaggerating so thought 10C is a reasonable figure. Hence the actual 4.5-5C surprised me.
The original ICE had 150kW so at 80kW car is not very fun to drive 
Still easilly tops 100km/h but sport spirit is not there.

Anyway, the 500 amps limit peak torque as well, especially as motor exceeds 4000rpm in second gear or during 3rd/4th gear overtaking.
Tomofreno - thanks for the great and simple explanation.
I knew it vaguely prior I read your post but it made it very intuitive to understand relation between torque and power during acceleration.


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## steven4601 (Nov 11, 2010)

Im not really up to date with Series DC,Is the power decay above 'nominal'* speed severe. 

* the point where battery and motor current become equal when utilizing a motor current control method


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## JRP3 (Mar 7, 2008)

Plamenator said:


> The cells are actually Winston, not CALB.
> I read the spec sheet saying 20C as "burst" (burst is probably like 0.1sec...).
> I assumed the Chinese are exaggerating so thought 10C is a reasonable figure. Hence the actual 4.5-5C surprised me.


Are you sure it's the cells that are limiting you? I get 5.5C out of my CALB cells which is limited by my controller max, I have no doubt they could put out a higher C rate above 5.5C for short periods.


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## DIYguy (Sep 18, 2008)

Put it in a garage, heat it up nice and toasty warm to 75F for a several hours. Take it out and stomp on it. You will see a huge difference. I am quite surprised by the difference in performance with cold temps. (you mentioned -5C. . . performance, voltage sag and current out will drop like a rock). I don't think most ppl realize how much difference it is, unless they have them and drive them in cold temps.


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## tomofreno (Mar 3, 2009)

steven4601 said:


> Im not really up to date with Series DC,Is the power decay above 'nominal'* speed severe.
> 
> * the point where battery and motor current become equal when utilizing a motor current control method


For the motors I am familiar with, both torque and power decrease above this point, both AC and DC. Both Azure Dynamics and HPEVS AC motor charts show decreasing power above this point. So I think all motor/controllers exhibit a curve where you have constant peak torque (determined by the maximum current the controller can deliver) and increasing power out to this point, then decreasing torque and power, though the rate of fall off varies. Shifting gears just shifts this point relative to vehicle speed, and changes the peak wheel torque for maximum controller current. Something like this (there are three graphs):
View attachment AC50, ADC 8 inch, ADC 9 inch, wheel torque.pdf

Increased pack voltage moves the point out to higher motor rpm and vehicle speed in a given gear.
Hopefully major will correct me if I have overlooked something.


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## efan (Aug 27, 2009)

this z4 conversion looks really nice, and i would love to hear and see more of it, so:
it's probably getting warmer in Bulgaria, have you noticed any improvement in performance with the TS cells? have you maybe decided to go with a different battery pack?


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## Plamenator (Mar 6, 2009)

I am considering switching to A123 prismatic cells:
http://kostov-motors.com/tractionmo...icvehicles/a12320ahpouch-lithium-ionbattery-/

I plan to install 240 pouches - 3 in parallel and 80 in series for a total of 15kWh. I currently have 23kWh but cannot get more than 450A out of the Winstons. I hope the A123 will be able to give me 900A (15C if 3 in parallel) - any opinions on that?

An added plus will be that the 15kWh A123 pack will fit in the engine bay only (no batteries in trunk) and will shave 120kg off the car. I guess I am sacrificing range for performance 

I have already ordered 10 cells for testing - those are supposed to be real A cells with A123 warranty behind them (though A123 does look a bit shaky).


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## somanywelps (Jan 25, 2012)

Plamenator said:


> I am considering switching to A123 prismatic cells:
> http://kostov-motors.com/tractionmotors/kostovevmotors(ac-dc)/seriesdcmotorsforelectricvehicles/a12320ahpouch-lithium-ionbattery-/
> 
> I plan to install 240 pouches - 3 in parallel and 80 in series for a total of 15kWh. I currently have 23kWh but cannot get more than 450A out of the Winstons. I hope the A123 will be able to give me 900A (15C if 3 in parallel) - any opinions on that?
> ...


Who did you order from?


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## Plamenator (Mar 6, 2009)

Mavizen in the UK, who apparently are an official A123 distributor.
Price is 68$ a piece for 500-1000 pouches.


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## DIYguy (Sep 18, 2008)

Plamenator said:


> I am considering switching to A123 prismatic cells:
> http://kostov-motors.com/tractionmo...icvehicles/a12320ahpouch-lithium-ionbattery-/
> 
> I plan to install 240 pouches - 3 in parallel and 80 in series for a total of 15kWh. I currently have 23kWh but cannot get more than 450A out of the Winstons. I hope the A123 will be able to give me 900A (15C if 3 in parallel) - any opinions on that?
> ...


How about building a small pack of A123 pouch cells, 1 series by 75 or whatever ur current pack number is and connect in parallel with ur current pack. No problem to charge with same charger at the same time. Discharge will double your current capability and protect the batteries you have. Your range will increase, ur performance will increase, and your wallet will take a much smaller hit. . . not to mention the reduction in work to change everything. As long as you have room of course. 

I'm doing something similar, with A123 cylindricals. 

Buying direct from Mavizen is crazy! lol
Cheers.
Gary
PS, BTW, yes opinion on the discharge of 3 parallel is 1200 amps minimum. Probably more for a short while, if they are warm.


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## steven4601 (Nov 11, 2010)

ever returning question.
how are you going to build a pack wit those floppy cells?


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## JRP3 (Mar 7, 2008)

Those Mavizen prices are terrible.


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## Plamenator (Mar 6, 2009)

Yes, Mavizen prices are quite high.
Yet does anyone know a cheaper alternative for class A prismatic A123 cells?


I have not decided how to make a pack out of the pouches so suggestions welcome. I will explore the opportunities when the 10 cells for testing arrive.
I am thinking about using a 3-5cm thick insulation plate (plastic/micanit?) so that the pouches hang from it. I will then drill canals/holes in the top side of the plate so that the terminal connections are within the plate. Hope you understand my explanation


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## JRP3 (Mar 7, 2008)

I think Jack Rickard has been getting his from http://victpower.company.weiku.com/ 
for around $20 per cell.
http://victpower.company.weiku.com/


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## DIYguy (Sep 18, 2008)

Plamenator said:


> I have not decided how to make a pack out of the pouches so suggestions welcome. I will explore the opportunities when the 10 cells for testing arrive.
> I am thinking about using a 3-5cm thick insulation plate (plastic/micanit?) so that the pouches hang from it. I will then drill canals/holes in the top side of the plate so that the terminal connections are within the plate. Hope you understand my explanation


My comment was not about the construction methods of a pack, it was about the system design WRT current pack, parallel addition, and directed at the root issue of low current while considering cost, work, and capability.....


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## jackbauer (Jan 12, 2008)

I have been quoted just over USD1900 for this 42s3p pack:
http://victpower.en.alibaba.com/pro...ry_A123_Prismatic_module_42s3p_126v_60ah.html

Plan to sell a kidney on ebay to fund two!


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## tomofreno (Mar 3, 2009)

jackbauer said:


> I have been quoted just over USD1900 for this 42s3p pack:
> http://victpower.en.alibaba.com/pro...ry_A123_Prismatic_module_42s3p_126v_60ah.html
> 
> Plan to sell a kidney on ebay to fund two!


 $1900 USD?! That is much less cost per Wh than I paid for my CALB cells.


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## somanywelps (Jan 25, 2012)

jackbauer said:


> I have been quoted just over USD1900 for this 42s3p pack:
> http://victpower.en.alibaba.com/pro...ry_A123_Prismatic_module_42s3p_126v_60ah.html
> 
> Plan to sell a kidney on ebay to fund two!


Was that shipped?


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## Batterypoweredtoad (Feb 5, 2008)

Remember that the A123 modules were dying in the Fiskers. Those Victpower A123 modules are very very tempting, but there is no sort of warranty and I have yet to see an accurate description of the problem with the A123 modules. If the problem was known maybe a repair would be possible and make the risk of getting a dead module worthwhile. I still may buy a bunch because I have poor impulse control.


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## jackbauer (Jan 12, 2008)

Shipping to Ireland via ups was an extra USD1000 for 2 modules.


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## DIYguy (Sep 18, 2008)

Just thought I would jump in here. I have a very good supplier (has become a friend) in Hong Kong. He works for a company that sells all types of batteries. He has been very trustworthy and worked hard to help me get rare batteries and special orders. He gave me inside info on untrustworthy trader on Taobao also. I even sent him 50$ US as a token of my appreciation for his personal help and hard work. He would not accept it. . and promised to always do his best. Just some background to put it in perspective.

Anyways, I asked him about these packs. He tells me that A123 paid money to have them scrapped and that this company that took them sold them to Chinese market. His company bought some packs and tested them. He said that several had dead (zero volt cells) some cells were found at about 1 volt and some seemed fine. He said that because of this, they decided it was not worth the effort and worried about warranty issues even if sorted. So, maybe they weed them out, but it does explain the price point . . . which is "too good to be true".


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## JRP3 (Mar 7, 2008)

I'm guessing they don't weed them out and you are taking a gamble, and it's probably worth buying some extra pouch cells to replace any potential bad ones. Replacement may not be easy with the laser welded bus bars.


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## Batterypoweredtoad (Feb 5, 2008)

If you look at the cells it looks like the bussbars wrap over the top of the tab and the center 1/3 of the top of the tab/bussbar are welded together. It looks as if some work with a dremel would make the cell removable (after cutting the straps). Reattaching a new cell to the bussbar would be interesting.


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## Plamenator (Mar 6, 2009)

I have a strange problem with my 78 Winston cells of 90Ah each.
At 3-12A they charge OK up until 3.35-3.40V when some of the cells suddenly jump to 4.00V in a matter of minutes.

I tried to individually discharge those cells and it takes just a few minutes to go from 4V to 3.28 where they start discharging really slow - takes hours to get from 3.28 to 3.20.

Then I try charging at 12A again and some other cell does the same trick.
Any ideas?


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## DIYguy (Sep 18, 2008)

Plamenator said:


> I have a strange problem with my 78 Winston cells of 90Ah each.
> At 3-12A they charge OK up until 3.35-3.40V when some of the cells suddenly jump to 4.00V in a matter of minutes.
> 
> I tried to individually discharge those cells and it takes just a few minutes to go from 4V to 3.28 where they start discharging really slow - takes hours to get from 3.28 to 3.20.
> ...


This is the behavior of cells which are fully charged. You need to decide on a balance/charge strategy (top or bottom) if u are not using a balancing bms. If you are, then implement it I guess.

As for the voltage at which the upper charge knee is evident, perhaps these cells are slightly different chemistry than the old TS or maybe your volt meter is off a bit. ?? Either way, this is full behavior.


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## Plamenator (Mar 6, 2009)

Thanks for the quick reply.
I use a balancing BMS - http://www.elektromotus.lt/en/products/bms with a 4kW Elcon charger that are interconnected via CAN.
I think it uses top balancing with a small shunt on each cell to parallel some of the current.
Voltage is correct - I measured it both with the BMS and with a multimeter.

I always assumed a cell should charge quicker when it exceeds 3.35-3.40V but not that much quicker! Further not all cells jump to 4.00V, only a few but as soon as they get to 4V (while the rest stay at ~3.40), the BMS stops the charging process.


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## DIYguy (Sep 18, 2008)

Plamenator said:


> Thanks for the quick reply.
> I use a balancing BMS - http://www.elektromotus.lt/en/products/bms with a 4kW Elcon charger that are interconnected via CAN.
> I think it uses top balancing with a small shunt on each cell to parallel some of the current.
> Voltage is correct - I measured it both with the BMS and with a multimeter.
> ...


I'm not familiar with your BMS, but my best guess is that it is trying to top balance but will need a few charge/disharge cycles to get the job done. 
Verify proper function of the bms (check for balance current) and do some cycles. Perhaps the cells are far enough apart at the top that your system won't do it in one shot. 

Also, just my opinion but, if u r relying on BMS to shut down charger, install a completely separate voltage and/or AH counter as redundant backup to shut down charging in case of failure. 

Good luck.


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## JRP3 (Mar 7, 2008)

Those voltages don't sound right, especially for TS cells which have more room above 3.4V than CALB cells, and my CALBs don't shoot up that fast at those currents from 3.4V. You may have some funky cells there, keep an eye on them.


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## DIYguy (Sep 18, 2008)

JRP3 said:


> Those voltages don't sound right, especially for TS cells which have more room above 3.4V than CALB cells, and my CALBs don't shoot up that fast at those currents from 3.4V. You may have some funky cells there, keep an eye on them.


Ya, for sure. That's why I was wondering about the DVM. 
Suggestion, if u have a spare cell, if not, remove one from the BMS and charge it from below the knee to see behavior. There may b some influence there from the BMS. Also, double check all the settings in the BMS relative to chemistry, shunting, charge control etc.


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## Erikvonhalle (Sep 22, 2012)

My dream is to have a BMW electric. If anything happens to my z3 I might convert it also. I am so pleased you are pioneering the way for me. Please post more.
Evh
Oak Ridge, TN


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## mrmike328 (Feb 25, 2011)

Any updates??


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## Erikvonhalle (Sep 22, 2012)

*Re: BMW Z3 conversion by Erik - Drive train or Wheel?*

No updates from the original z4 poster. I have a BMW z3 model year 2000.
I am doing some research on the Michelin Wheel. I think that wheel mounted electric motors would give me front wheel drive and lots more room in the engine compartment for batteries. 

I don't know what I am doing. Without the drive train and transmission..... What needs to be removed? What do I have to do to keep the power steering unit working when there is no internal combustion engine?

I am just exploring possibilities. It is much more likely to use a brushless dc motor, an adapter plate, and the current drivetrain.

Erik Von Halle
Oak Ridge, TN


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## circuit (Jan 16, 2012)

Plamenator said:


> Thanks for the quick reply.
> I use a balancing BMS - http://www.elektromotus.lt/en/products/bms with a 4kW Elcon charger that are interconnected via CAN.
> I think it uses top balancing with a small shunt on each cell to parallel some of the current.
> Voltage is correct - I measured it both with the BMS and with a multimeter.
> ...


Hi Plamenator,

Interesting project you have here! How is it going?
Have you solved the problem with Emus BMS?
What you were describing earlier, i.e. that cell voltage goes up to 4.0V and only then charger disconnects, looks like a misconfiguration of the BMS. It sounds like it is detecting an error condition (OVC) and shuts down. This should not happen in normal operation. I'm sure there is some misconfigured parameter.
If you are not sure what parameter means what, please don't hesitate to contact us and we will do our best to solve it.

Also you have mentioned problems with BMS communication line between two packs - I'm sure we will be able to help with that.


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## marcolasvegas (May 20, 2017)

Has anyone ever converted one of these cars with a 2 speed automatic or a torque box? is anyone on this thread familiar with torque trends? Im strongly considering converting a z4 myself! Thanks!


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