# VW Polo G40 goes "E40"



## brian_ (Feb 7, 2017)

Welcome! 

A Polo a nice size to convert, since it is relatively small and light. That will make it difficult to fit in a substantial battery pack (such as the Kia Soul pack that you have chosen), but you'll need that large battery to meet your performance goals.

I look forward to the build thread when you get started on your project. It will be interesting to see how you fit a Tesla drive unit in that car.


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## Jack-Lee (Mar 29, 2019)

Hello,


30kWh is not too big battery. A normal Tesla has more than three times as much on board. 250km range should also be achieved 
And since I threw out all the interior, I have enough space for batteries 
PS. anyone know how i got a speed-signal out of the Tesla-Engine?


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## brian_ (Feb 7, 2017)

Jack-Lee said:


> 30kWh is not too big battery. A normal Tesla has more than three times as much on board.


While 30 kWh is a suitable capacity for this vehicle, it is a big battery for the size of the car. Yes, a Tesla Model S has a much larger battery, but it is also a *much* larger car...
*VW Polo Mk IIF*:

Wheelbase = 2,335 mm (91.9 in)
Length = 3,655 mm (143.9 in) to 4,030 mm (158.7 in)
Width = 1,570 mm (61.8 in) to 1,590 mm (62.6 in)
curb weight = 736–804 kg (1,623–1,773 lb)
*Tesla Model S:*

Wheelbase = 2,960 mm (117 in)
Length = 4,980 mm (195.9 in)
Width = 1,964 mm (77.3 in)
curb weight = 2,108 kg (4,647 lb) (85 kWh 2WD model)

The Model S battery fills the whole length between the axles and width between the rockers of that big car.

The *Kia Soul EV* has a different floor than the regular Soul, to fit the battery under the seats... and the Soul is larger than a Polo:

Wheelbase = 2,550 mm (100.4 in)
Length = 4,105 mm (161.6 in) to 4,120 mm (162.2 in)
Width = 1,786 mm (70.3 in)



Jack-Lee said:


> And since I threw out all the interior, I have enough space for batteries


I assume that you are going to use the rear seat space, and perhaps cut out the floor in that area to combine the fuel tank space with the seat space to provide room for the battery... that's what would make sense to me.


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## brian_ (Feb 7, 2017)

Jack-Lee said:


> Target: under 6seconds from 0 to 100km / h, over 250km range
> ...
> 350V 30kWh of a Kia Soul... According to the data sheet, however, one cell can deliver 450W. That would be 90kW for the battery pack. I hope I can tickle out more.


The Soul EV battery can definitely handle 90 kW: that's the Soul EV's stock motor power. It can probably handle more, briefly, at the expense of shorter life.

6 seconds 0-100 km/h is half the time of a stock Polo, and substantially faster than a 90 kW Soul EV. Although the converted Polo will be lighter than a Soul EV, the difference might not be enough to make that acceleration time on 90 kW; it might be good to plan on needing more power than that.

The Soul EV goes 150 km (93 miles) on that 30 kWh; that's 200 Wh/km (320 Wh/mile). Again, the Polo will be lighter, and it has less frontal area so it will likely have less drag, but an extra 100 km (120 Wh/km or 193 Wh/mile) seems to me like a big range improvement to expect. Would you be satisfied with a 200 km range?


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## Jack-Lee (Mar 29, 2019)

Depending on which battery it will be, I will accommodate them differently. Your idea is one of them 

The "YAEC" Excel helps with these decisions. Have you just discovered here in the forum. Without wheel slip, a setup with a maximum of 90kW would come in 4.9sec to 100km / h. The car weighs less than 750kg with driver and electrical conversion. Thus, less than half the power must be applied for the same acceleration. The effective frontal area of ​​0.53m² (cw0.30 after some improvements, A = 1.78m²) is also quite good.

I have also recalculated how much torque I get on the road at all. At the weight and then lower center of gravity are the max. 800nm. Thus, under 100Nm from the engine (since 1: 9,34 gearing) to have permanently spinning tires. The intended setup means: spinning wheels up to 90km / h.

A Hyper9 really seems the more usefull choice, especially since I then have no problems with the mechanical speedometer.
But I have to remember that makes the gearbox in the long term.

PS. Could i get squeeze more out of the Hyper9?


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## Duncan (Dec 8, 2008)

Hi Jack

I'm not doing much better than 4.9 seconds to 100kph - I did 7.9 to 150 kph

My car is 800 kg - rear wheel drive with 55% on the rear wheels and a Limited Slip Diff and sticky tyres - but I have about 400 Kw

I just don't see 90 kW giving you anywhere near 4.9 seconds to 100 kph


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## Jack-Lee (Mar 29, 2019)

Hi,


And i know that 5sek is unrealistic, but only because wheelspin. 

A timed run with my 89hp and heavy Polo "Genesis" (840kg) reach 4,3m/s² max. and 8.9sec.


https://network.perfexpert-app.com/results/ki8KBic2GV


25% lighter and 50% more Power (with continous torque) should be enough to get the 6s. from my 1.4l Turbo. This was driven with slicks. With normal tires 7-8sec are realistic.


Does anyone have tips regarding the converters and loaders?


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## MattsAwesomeStuff (Aug 10, 2017)

> I was self-employed for almost 10 years and built recumbents.


Oh, then you will certainly appreciate my first EV project...

https://www.youtube.com/watch?v=sc0HNuTwcBg










Isn't it beautiful? The craftsmanship, unequaled.


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## Duncan (Dec 8, 2008)

Just realised the 90kW is from the battery

Don't worry!! you can draw a LOT more than that for a short period - and you will only need it for seconds

I am drawing 400 kW from 12 kWh of Chevy Volt batteries 

You will be able to feed your Tesla motor with full power! - 

You WILL spin the tyres


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## Jack-Lee (Mar 29, 2019)

Ok, thats good news. Whats with the heating of the battery? The teslapacks are watercooled, most of the others Not.
and should i take the hyper9, more efficent and easy to build in, or tesla, pure Power.


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## Duncan (Dec 8, 2008)

Jack-Lee said:


> Ok, thats good news. Whats with the heating of the battery? The teslapacks are watercooled, most of the others Not.
> and should i take the hyper9, more efficent and easy to build in, or tesla, pure Power.


Tesla!
The hyper9 is expensive and wimpy!


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## Jack-Lee (Mar 29, 2019)

And whats with a emrax 268? Anyone used one? With a small differential from passat or different bmw this setup wight less then half of the tesla with much better efficenty. Price is only a little more.


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## Jack-Lee (Mar 29, 2019)

PS. A hyper9 with Controller cost 4000€, a small tesla 8000. Why you say hyper9 is expensive?


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## Duncan (Dec 8, 2008)

Jack-Lee said:


> PS. A hyper9 with Controller cost 4000€, a small tesla 8000. Why you say hyper9 is expensive?


Because it's a LOT less power than a $200 forklift motor


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## brian_ (Feb 7, 2017)

Jack-Lee said:


> The teslapacks are watercooled, most of the others Not.


In fact, many EV and plug-in hybrid packs are liquid cooled

Tesla (Model S/X and Model 3): coolant tubes snake between rows of cylindrical cells
Chevrolet Volt: coolant passes through plates between pouch cells
Chevrolet Bolt, Chrysler Pacifica, various German models: aluminum fins from one edge of each pouch pressed against "cold plate" base with coolant circulating in it

The Leaf battery is (or was, for a while) very commonly used in EV conversion projects, and is a relatively rare example of a modern EV pack without active cooling.


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## brian_ (Feb 7, 2017)

Jack-Lee said:


> ... should i take the hyper9, more efficent and easy to build in, or tesla, pure Power.


I'm not sure that the HyPer9 is any more efficient than a Tesla motor. Why are you expecting that... because the Tesla would be used well away from its ideal operating point of load and speed?


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## Jack-Lee (Mar 29, 2019)

The battery of the Kia Soul is also "only" air-cooled.
How much do the batteries heat up at all? I have no experience there.

The Hyper9 has a better efficiency in use has two reasons (Tesla Model 3 use a reluctance motor):
-Synchronius reluctance permanent magnet motor (almost no losses in the rotor! What also means that you could cool the engine pretty well)
-5Gang manual transmission -> always in the right power range
better especially in low speed and power range

To the Forklift engine:
-more than double the weight for the same performance
Controller costs a lot

A question to the forum:
What speaks against z.b. a Hyper9 (not HV) with other controller at e.g. to operate at 180V?
And does anyone have experience with the Emrax engines?
@Duncan : You ever tested the Hyper9?

Greeting,
Patrick


PS. anyone send me a PM, but i cant open it?!


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## Duncan (Dec 8, 2008)

Hyper9 $4,150 - PEAK power 88 Kw

My $200 Forklift motor with a $1000 controller - peak power 400 Kw 

DC series motors are simple crude and easy to work with

There are three options these days

DC (forklift) - cheap cheerful and powerful

Re-purposed OEM (Tesla/Leaf) - much more sophisticated - cost a bit more

Then there are the "Motors for EV's" like the Hyper9

MORE expensive than OEM motors and less powerful 

Saying that you are talking about a Tesla motor for $8000 - my innate Scottishness would not permit me to buy that

In your shoes I would be looking for a crash damaged Leaf for about $4000

You get the lot! batteries/charger DC-DC motor Inverter - everything


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## Jack-Lee (Mar 29, 2019)

We dont have much e-cars here in Germany (eg. 5000 Nissan Leaf. In the USA are over 110000 of them) Find a "crashed one for 4000€" is nearly impossible...
And a 200kg Forkliftmotor ist way too heavy.


So the small tesla Engine is the best option i had at this time, right? (but its about 5000€ more expensive then the Hyper9...)


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## Duncan (Dec 8, 2008)

Why do you think a forklift motor is 200 kg?

My 11 inch Hitachi is 102 Kg - and it's a big bugger

If I had the option at the time I would have gone for a 9 inch motor at about 60 kg

With front wheel drive you won't be able to just throw away the gearbox and drive direct to the diff so a 9 inch motor would be ideal for you

Germany has a LOT more Leafs than we do! (NZ)


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## Jack-Lee (Mar 29, 2019)

Whe have other Prices here for Motors. I cant find any "Forkliftmotor für 200€ with 200kW". No chance. The most Motors have less then 10kW .. And a 5kW Motor weights above 25kg. 

And Siemsens-Motors are much more expensive as you say...
https://www.ebay.de/itm/Siemens-Motor-Generator-1FV5139-6WS28-Z-Mercedes-A-6665480103-Cito-Evo-Bus-LKW/162488739721?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D1%26asc%3D20170920101110%26meid%3Ddd3bf042c08846d38a7f0eeef0c3cd66%26pid%3D100010%26rk%3D1%26rkt%3D2%26sd%3D152523016870%26itm%3D162488739721&_trksid=p2047675.c100010.m2109
And this monster weights 120kg for 110kW.


PS. it seems the small tesla engine could run backward at full power (pump in gearbox) ?


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## Duncan (Dec 8, 2008)

You don't understand - you will be over volting and over currenting your forklift motor

My Hitach is 102 kg and is rated at 10 kw

I am feeding it 1200 amps and 340 volts

It won't take that for long - but it does not have to!

I did blow up my first motor last year - after five years driving - but I think it failed from a place where I had gouged one of the coils

My replacement ($150) worked fine and at our last Drag meet I was faster than all the supercharged V8's
I was second fastest car - one of the turbocharged 4WD machines just pipped me


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## Jack-Lee (Mar 29, 2019)

When you overpower a 10kW brushed DC Motor to 400kW! or so... why i shouldnt overpowered a hyper9 or something (Use a normal Hyper9 instead of the HV on 180V? When the tourqe holds until 8000rpm, we have over 180kW) -> ? This Motor cost 1900€, not much for a new one i think.
Which Component limits the maximum output power?


The War9 Motors used for Dragracing, and there ratet with 1/2 of the Power of the Hyper9...


PS: my Gearbox rated with 150Nm. 240Nm is MUCH more and i dont know how long they could hold this.


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## Duncan (Dec 8, 2008)

_why i shouldnt overpowered a hyper9 or something (Use a normal Hyper9 instead of the HV on 180V? When the tourqe holds until 8000rpm,
_

Because the controller will limit you to 88 kw! and you can't get a controller that will work with that motor that will give you lots of power 

The motor is not the limiting factor - it's the controller

With a DC series motor any controller will work with any motor

With an AC motor its the motor and it's dedicated controller

If you knew exactly what you were doing you could probably do something about that - but I sure as hell don't 

And I suspect that you don't either!


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## Jack-Lee (Mar 29, 2019)

There are many controllers that come with various AC motors. The Curtis work only with asynchronous motors, but e.g. The X1 controller can drive almost any motor (asynchronous, BLDC, reluctance). I do not want to use DC motors with brushes.
If only the controller is the "problem", I can just use a more powerful one if the performance is not enough. (The X144 Controller should allow parallel use from more controllers on one Motor...)


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## Boxster-warp (Jun 22, 2014)

Hello
Come also from Germany and have a new warp11 which was never installed. Unfortunately I can not continue with my boxster conversion. Had possibly synonymous still a Used controller. 
The Controller Are the netgain Classic 1400 ampere 360 Volt.

Together a monster combination.

I am considering whether I should go ahead or prefer to buy a finished converted car with significantly less power. Unfortunately, time is the biggest problem.
Greetings Boxster-Warp


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## Jack-Lee (Mar 29, 2019)

Everyone use a I3 Motor in his EV Buildup?
I should use them with another Controller... I get the Batterie for 4500€, and the Motor for 1000


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## brian_ (Feb 7, 2017)

*Battery cooling*



Jack-Lee said:


> The battery of the Kia Soul is also "only" air-cooled.
> How much do the batteries heat up at all? I have no experience there.


The Soul EV has forced air cooling for the battery pack (using air from the car's interior, which is cooled if the air conditioning is running); the Leaf doesn't even have that.

The next generation Soul EV (like other Kia EV models) has a much larger battery, which is liquid cooled... but anything available used now and for a while would be the original air-cooled battery.

Batteries do get hot. This seems to be an issue only in heavy use and/or hot weather.


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## brian_ (Feb 7, 2017)

*Motor efficiency*



Jack-Lee said:


> The Hyper9 has a better efficiency in use has two reasons (Tesla Model 3 use a reluctance motor):
> -Synchronius reluctance permanent magnet motor (almost no losses in the rotor! What also means that you could cool the engine pretty well)
> -5Gang manual transmission -> always in the right power range
> better especially in low speed and power range


An induction motor has losses to electrical resistance in the rotor winding, but all motors have other losses (both electrical and magnetic), so it's hard to predict between two motors with nothing in common which will be more efficient.

Keeping motor speed in the most desirable range does help efficiency, but every major EV manufacturer has concluded that it makes so little different that a multi-speed transmission is not worthwhile. I think a multi-speed transmission is useful in a conversion only if the motor doesn't have full (or sufficient) power available over a wide enough speed range.


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## brian_ (Feb 7, 2017)

*BMW i3 motor*



Jack-Lee said:


> Everyone use a I3 Motor in his EV Buildup?


I assume that this was intended to be "anyone"...

The i3 is very uncommon (at least in North America) compared to other models, so its motor is not commonly used in conversions. Since the difficulty of using production EV motors is all in working with the control system (or matching an aftermarket inverter to the motor) and mechanical mounting and coupling of the motor (if not using the stock transaxle), it's a lot easier to work with a motor that other people have used, since they have worked out these issues (to some extent).

There has been some work done on the i3 motor (mostly the controller) and reported in this forum, although that didn't include actually using it in a conversion:
DIY BMW i3 Controller

It's probably a good motor, like other modern permanent magnet AC motors in EVs.


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## Jack-Lee (Mar 29, 2019)

The BMW I3 is one of the most sold EV in Germany, so i could get a good Price for Battery/Motor (With a little bit of Luck).


I would use a Rinehart-Controller with this Motor and throw out the original Controller.


But... This Engine has not more Torque then the Hyper9 and at 120km / h the speed limit is reached (12000U/min).


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## Duncan (Dec 8, 2008)

I was quite impressed with the BMW I3 - we had one at our last drags - If I was asked to choose between a Hyper9 and the I3 it would be the I3 in a heartbeat!

In unmodified form it is at least as powerful
BUT the BMW is designed for 300,000 km with almost no failures - it is in an entirely different league to the Hyper9

If I was doing it I would try and get a complete car that has had a mild accident


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## Jack-Lee (Mar 29, 2019)

The car is over 1000km away (and the crash is not "mild")... So the whole car is not an option. But i should try to build in the I3 Motor


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## brian_ (Feb 7, 2017)

*i3 motor versus HyPer9*



Jack-Lee said:


> But... This Engine has not more Torque then the Hyper9 and at 120km / h the speed limit is reached (12000U/min).


The i3 motor is rated for 184 lb-ft (250 Nm) of torque up to its base speed, while the HyPer9 is rated for 163 lb-ft (221 Nm) in the regular version, and 163 lb-ft (235 Nm) in the high-voltage version, so I don't see a torque problem with the i3 motor. Combined with the 170 hp (127 kW) power rating, the i3's base speed appears to be 4850 rpm... about 40% of the peak speed, which seems reasonable. The base speed of the HyPer9 appears to be about 3800 rpm.

Torque does not matter by itself, anyway. Torque multiplied by speed is power, and the i3 motor can produce more power throughout its speed range than the HyPer9. The only place you can directly compare motors by torque is where the speed is the same, such as at the wheels, or at the input to the final drive if you are stuck with a specific final drive ratio.

Since the i3 motor can run to 12,000 rpm (or 12 000 U/min in Euro style ) and even the high-voltage HyPer9 (with the associated controller and motor voltage of 96 VRMS) can only produce power to 6,000 rpm (well, higher, but it drops off rapidly above 6,000), the i3 can be used with a much higher gear reduction ratio... roughly double the gear reduction, so double the torque multiplication. If you put the i3 motor and the HyPer9 on the same Polo transmission and used 3rd or 4th gear for the HyPer9, you could use 1st or 2nd gear for the i3 motor and have double the torque to the wheels (meaning double the drive force, if only you had the traction).

Of course more gear reduction means a lower road speed, for the same motor speed. You have the same problem with any motor; the only solution to get the a motor speed near ideal across a broad range of speeds is a multi-speed transmission. Production EVs don't use multi-speed transmissions... they just use a large enough motor.

If using the i3's stock transaxle (which does make a lot of sense), the only issue is that it is geared for the i3's relatively tall tires. They only turn 470 to 475 rev/km, while the Polo's tires probably turn 570 rev/km or more, so the i3 9.70:1 gearing will limit the Polo's speed to much lower than the i3. The Polo can probably fit somewhat taller tires; will that make enough difference? How high does the top speed need to be? If this gearing just won't work, then I suppose the i3 transaxle is out.

Based on the set of Polo specs that I found, the i3's overall reduction ratio of 9.70:1 is a little taller than first gear in the Polo, and you would want something more like second gear (2.09:1 second gear multiplied by 3.33:1 final drive = 6.96:1 overall... like a Nissan Leaf). Driving around all of the time in something equivalent to second gear sounds crazy, but it makes sense with a motor which is safe and efficient up to 12,000 rpm, in contrast to a engine for which the gearing is chosen to keep the engine speed down to 3,350 rpm at 120 km/h.


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## Jack-Lee (Mar 29, 2019)

The Front driven polo cant Transfer the Power of the Motor to the street. Only 800nm on the wheel are possible. The i3 engine has a Reduktion near 10:1. So 2500nm in the wheels, much much more then i could handle with. Gearing about 5:1 are more usefull.


PS. Everyone use this ACP 150 Gen2 Set? It looks interesting and the price is very good.


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## Jack-Lee (Mar 29, 2019)

Hi, i received the Engine and the Battery yesterday  Could i use the BMW I3 BMS/Charger-Unit ? Any "hacks" out there?


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## Jack-Lee (Mar 29, 2019)

The VW Museum has a "VW Polo Sprint". This one has a rear engine (1.9l 156hp) and even uses the standard rear axle (which has been slightly modified).
That's why I'm planning the conversion with rear-wheel drive, if the TÜV with makes.
Four batteries arrive in the engine compartment, four under the rear seat. The engine fits between the rear axle and is flat enough not to protrude into the interior.


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## brian_ (Feb 7, 2017)

I see from the 19 April post that the components chosen are a Tesla small rear drive unit and a complete set of battery modules from a BMW i3 (~33 kWh).



Jack-Lee said:


> The VW Museum has a "VW Polo Sprint". This one has a rear engine (1.9l 156hp) and even uses the standard rear axle (which has been slightly modified).
> That's why I'm planning the conversion with rear-wheel drive, if the TÜV with makes.


The Polo Sprint project was similar to the many cars built by putting the powertrain from the front of a front-wheel-drive production car into the back of the same car. Some made it to production (the Renault R5 Turbo and Peugeot 206 T16), generally as race cars which were made streetable so they could be called production cars for racing classification. For rear suspension, those cars typically use either another front suspension, or something custom. The body is radically modified to fit the engine, but this might not be required for the electric motor and transaxle.

The Sprint is different in that it used a rear- (rather than mid-) engine placement (using a T3 engine and transaxle), so it had no trunk but retained the rear seat. That transaxle also means that it works with many rear suspension designs, unlike a typical transverse engine setup intended for the front of a vehicle.

I'm not sure if you're suggesting that the TÜV would consider this project to be an acceptable design because VW made a Polo this way, but the Sprint was never a production vehicle.


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## brian_ (Feb 7, 2017)

*Battery module placement*



Jack-Lee said:


> Four batteries arrive in the engine compartment, four under the rear seat.


The four modules in the front fit nicely, but keep in mind that:

they need a protective housing, and
the top layer of modules can't be supported by the bottom layer of modules, so you need a structural frame.
It will be interesting to see how four more modules fit in the fuel tank space under the rear seat. Two layers of modules (at about 150 mm thick each) would be much too tall to fit without removing the rear seat, cutting the floor out, and building a box up into the interior. Is there space for a 600 mm x 800 mm or 400 mm x 1200 mm group of four modules in one layer?


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## brian_ (Feb 7, 2017)

*Drive unit and rear suspension*



Jack-Lee said:


> The engine fits between the rear axle and is flat enough not to protrude into the interior.


The complete drive unit might fit under the Polo floor, but keep in mind that there are other components. In his Tesla-powered "elVito" van, Steel found that he needed to add a big box to hold this stuff.

This is a nice arrangement, particularly in a hatchback body which would retain a very functional cargo area (unlike the ones with engines), and similar rear-drive conversions have been discussed several times in this forum, for various models. I'm not aware of any actually being built, for two reasons:

most proposals are hybrids, which are too complex to be workable for a DIY project (but this is a pure battery EV, which is much more practical), and
most base vehicles don't have a suitable rear suspension to accommodate being driven, and the physical dimensions of the drive unit.
The Polo MkII rear suspension appears to be the usual front-drive VW design of trailing arms linked by a beam (one style of "twist beam" suspension). It would work with almost any drive unit that places the motor behind or on the axle line, but would need to be a version from an AWD vehicle, or modified substantially to accommodate driven hubs and to place the springs and shock absorbers out of the way of the axle shafts. Since a Polo using this suspension design (which is no longer used in the current model) has never been offered in AWD, the only practical approach would probably be to use the rear suspension from a Golf Mk2 or Mk3 Syncro, if it can be made to fit with the Polo's structure and if the greater width (the Golf is about 100 mm wider than the Polo) can be handled, perhaps with fender flares. The Golf Syncro does not use that same suspension as the Polo and the front-wheel-drive Golf: instead, it has semi-trailing arms on a subframe, which might mount to the same body points as the twist-beam, plus another rearward central point. Regardless of the approach, this will not be a straightforward bolt-in exercise.

This is a Golf Mk2 Syncro rear suspension with final drive, from a workshop manual website:








None of the parts are the same as a Polo (or 2WD Golf) suspension, but it fits in about the same space (although Golf Syncros apparently had a raised floor to accommodate it...)


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## Jack-Lee (Mar 29, 2019)

http://www.polodriver.com/polo-1981-1994/1983-polo-sprint-155bhp-125mph-0-60mph-in-8-seconds/


There used slightly modified original Rear-Axle.
An other Option is the rear-Axle of a BMW E30 with modified frame


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## brian_ (Feb 7, 2017)

Jack-Lee said:


> http://www.polodriver.com/polo-1981-1994/1983-polo-sprint-155bhp-125mph-0-60mph-in-8-seconds/
> 
> There used slightly modified original Rear-Axle.


The link is to an article in German from Planet-Polo (Studie Polo Sprint), but the displayed text is a link to the same article from PoloDriver.com that I linked.

The Planet-Polo article's description of the rear suspension is this (via Google Translate):


> As a drive axle, the torsion beam axle used in the standard Polo was formed, which found space under the engine-transmission block. At its rear ends, Passat front axle pivot bearings were welded upright, through which the drive could be guided. The torsion beam axle had to be set lower.
> In the service of research, the Wolfsburg have designed the spring-damper system harder and adapted the camber and toe angles of the new situation; so that high end speeds and sharp cornering are manageable.


That's cutting out the original bearing carriers and welding in Passat front hub parts, plus other suspension changes not related to the conversion to a drive axle. The spring and shock mounting may have been changed as well.

The PoloDriver.com article says that "The power was transmitted through the standard Polo trailing beam rear axle...". This is simply not true because it is not physically possible.

You would need to look at the parts in detail to see what it would take to do the required modifications, but they will not be "slight"; certainly the modifications described by Planet-Polo are substantial.



Jack-Lee said:


> An other Option is the rear-Axle of a BMW E30 with modified frame


Yes, there are lots of similar semi-trailing arm rear suspensions, especially from BMW (who used this design on most models for a decade or two). A VW suspension would be desirable, because it is more likely to be compatible with the same wheels as the front, and because the suspension from a closely related model might fit some of the structural mounting points.

I assume that VW didn't use Golf Syncro parts only because the Sprint was built in 1983 and the Syncro was not in production until 1986.


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## Jack-Lee (Mar 29, 2019)

After a few long phone calls, I had to admit that the conversion to rear-wheel drive is too expensive. The tests for the TÜV with strain gauges and 2000km race track driving are simply expensive.

When implementing the front-wheel drive, the following question arises: Can the Tesla engine also run backwards? The engine itself does not cause any problems, but what about the controller and especially the gearbox?


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## brian_ (Feb 7, 2017)

Jack-Lee said:


> After a few long phone calls, I had to admit that the conversion to rear-wheel drive is too expensive. The tests for the TÜV with strain gauges and 2000km race track driving are simply expensive.


I'm sorry to hear that. You're not alone - lots of places have restrictions which make radical conversions (or in some cases even simple conversions) impractical or expensive, whether due to safety regulations or insurance issues.


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## brian_ (Feb 7, 2017)

Jack-Lee said:


> When implementing the front-wheel drive, the following question arises: Can the Tesla engine also run backwards? The engine itself does not cause any problems, but what about the controller and especially the gearbox?


I agree that the direction of rotation is a non-issue for the motor itself.

Phase order determines the direction of rotation. The inverter will run in either phase order, presumably at the same power and frequency. The controller programming, on the other hand, probably has restrictions on reverse speed and power. I assume that the solution is to swap two of the cables between the inverter and the motor to change the phase order and presumably change the wiring or configuration of the shaft speed sensor as well.

The gears certainly can run in reverse, although they are helical so drive force causes axial forces on gears, which means that the bearings are subject to axial thrust. The bearings can obviously handle this thrust in both directions (because they take one direction for normal driving and the other direction for regenerative braking and reverse), but I don't know how well it would work to be in reverse all of the time.

The bigger issue for the gearbox is oil flow for lubrication and cooling: the gear oil is moved by a pump which is driven from the ring gear, so while in reverse the oil is pumped the wrong way and it will not scavenge properly (and would go through the components including the heat exchanger in the wrong order). This is okay for the brief time that a car drives in reverse, but not for normal operation. The gear driving this pump could be replaced by a two-gear set with idler, or by a small electric motor, or the whole pump could be replaced by an external oil pump. It would even be possible to turn the drive unit over (upside-down), keeping the same rotation direction (of the motor and the gears and the pump) for forward but moving the motor to the front; however, the oil would collect in the wrong part of the gear casing so the pump would need a new pickup location, and there could be other problems in oil flow.

The oil pump, attached hoses, and black polymer drive gear are clearly visible in the excellent teardown photos which Chris provided in _*Tesla Small Drive Unit* - post #23_.


The reason for running backwards would be to allow the motor to be placed ahead of the axle line, instead of behind it. Nearly every production EV drive unit other than the Tesla Model S and X has the motor on the axle line or ahead of it, usually copying the engine location in the car on which the EV is based. Even the drive unit in the RAV4 EV - which was supplied by Tesla - has the motor ahead of the axle. While I understand the desire to use the Tesla motor (because it is available and because lots of people have modified or replaced the controller so it is practical to use), just about any other drive unit would be a better fit in the front of a transverse engine front-wheel-drive vehicle like this.


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## Jack-Lee (Mar 29, 2019)

The problem with the helical gears and the oil pump was known to me, so the question of whether someone has already operated this engine "backwards" permanently.

Photos of the interior of the transmission of the small front and rear engine show that the oil pumps look different. The gears seem the same, as do the bearings. Thus I have to change "only" input and output of the connections of the pump. The pump itself should be a simple gear variant and work in both directions.
I will dismantle the engine during the day to get more information.


PS. the Model 3 use a electrical Pump. I could use this too


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## brian_ (Feb 7, 2017)

Jack-Lee said:


> The problem with the helical gears and the oil pump was known to me, so the question of whether someone has already operated this engine "backwards" permanently.


Not as far as I know, but it certainly could have been done.



Jack-Lee said:


> Photos of the interior of the transmission of the small front and rear engine show that the oil pumps look different.


Front and rear units are different for two reasons:

they are mirror images: the front unit has the motor on the right side, while the rear unit has it on the left side, reversing the arrangement of components; and,
the front motor is mounted higher than the final drive to clear the front of the battery pack, while the rear motor is mounted level with the final drive to keep it low to fit under the floor.



Jack-Lee said:


> The gears seem the same, as do the bearings. Thus I have to change "only" input and output of the connections of the pump. The pump itself should be a simple gear variant and work in both directions.
> I will dismantle the engine during the day to get more information.


If the connections are both hose, and there is enough free hose length to cross them over, this could work.

To be sure that the oil flows properly, you should have a good look at how it will come off of the gears in the new rotation direction, and so how it flows down to the pickup,



Jack-Lee said:


> PS. the Model 3 use a electrical Pump. I could use this too


This certainly seems practical, as long as you are careful with the way fluid connections are made through the case, and you in some way ensure that if the pump fails the controller knows to shut down or at least severely limit power. Even if the Model 3 didn't use an electric pump it's an obvious solution, which is why I listed it, but if anyone knows how the Model 3 pump is controlled it would be informative.

An electric pump could allow fluid flow in proportion to power, instead of just in proportion to speed, which would help low-speed cooling. Anyone running one of the Tesla Model S/X small drive units and having cooling issues should be interested in this solution, even if they are running in the normal direction.


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## Tomppa (Jun 30, 2012)

Hi Jack-Lee

I did a similar conversion few years back. My Polo has 49 TS 90ah cells, 14,1kwh, on the back seat. The car weights 890kg and the most I've driven with a single charge is 86km. Could do the 100km which was calculated using the same calculator, YAEC. So I find 30kwh and 200km plausible 

The Polo's engine bay is quite small. With stock gearbox the max. motor diameter is 9". I guess you use different approach? I will follow this build closely with joy

-Tomi


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## brian_ (Feb 7, 2017)

Tomppa said:


> The Polo's engine bay is quite small. With stock gearbox the max. motor diameter is 9". I guess you use different approach?


Some of the images from that thread very clearly illustrate how interference between the CV joint for the car's right-hand axle shaft and the motor casing limits the motor diameter when using the stock transaxle. Fortunately for Jack Lee, this isn't an issue when using a complete EV drive unit such has the one he has from a Tesla; however, it is a reminder that the case of the Tesla unit will extend further forward (if it can be run that way) than the engine crankcase, so clearance needs to be checked.


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## Jack-Lee (Mar 29, 2019)

Hi,
i switch the car... From Polo to Smart. 


EDIT: I also draw a 3D Modell from the smart.


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## brian_ (Feb 7, 2017)

Jack-Lee said:


> i switch the car... From Polo to Smart.


That's a very different situation!

Are you planning to fit Smart ED components into the Roadster, or are you going to use the Tesla drive unit and i3 battery modules that you have? Tesla drive unit it might be usable without reversing it (although that would require a complete suspension change), but I'm sure that it won't fit behind the axle in the Smart without modifying the car's structure. I don't know where all (or even a few) of those modules would go in a Roadster, although at least a Roadster has a front trunk that the ForTwo doesn't have.


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## Boxster-warp (Jun 22, 2014)

Hello
Cool. 
I Drive a Smart Roadster Coupé since 2006.
Greetings Boxster-warp


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## Boxster-warp (Jun 22, 2014)

Hello
Tesla Moduls Are too big for the Front Trunk.
Greetings Boxster warp.


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## brian_ (Feb 7, 2017)

Boxster-warp said:


> Tesla Moduls Are too big for the Front Trunk.


That's what I would have guessed, but while Jack-Lee was intending to use a Tesla drive unit (at least for the Polo), he has BMW i3 battery modules (as shown in posts #37 and #38). They're nearly square, not nearly as long as the Tesla Model S/X modules, and thicker than Tesla modules.


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## Boxster-warp (Jun 22, 2014)

Hello
4 years ago I wanted to rebuild a roadster myself on electric. 
Problem is the low payload, little space for batteries and the ESP. Otherwise, the car is already very good. With a little money you can do something. Emrax engines fit very well there. 
Greetings boxster-warp


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## Jack-Lee (Mar 29, 2019)

I probably get 4Module in the rear and two more in the front without the load compartment to reduce. The car is empty with 870kg and allowed to load up to 1020kg.
The Roadster Coupe is also available with 810kg empty weight. Savings potential is available.
The ESP is deactivated.


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## brian_ (Feb 7, 2017)

Jack-Lee said:


> I probably get 4 Module in the rear and two more in the front without the load compartment to reduce.


What does "without the load compartment to reduce" mean? If it means that you think you can fit these six modules in without using the trunk spaces... I can't see how that could possible in the front. Even in the rear, the engine space doesn't seem likely to be big enough, the fuel tank space is awkwardly shaped, and combining those spaces seems like a structural issue. Do you have a link for good image of the space available in the rear?

Also, would high-speed performance be adequate with the voltage resulting from using only 6 of the 8 i3 modules?


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## Jack-Lee (Mar 29, 2019)

I could place two packs under the plastictrunk.
But i couldnt draw the detailed innards yet, so i need more messurements.


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## brian_ (Feb 7, 2017)

So the plan is for the motor to be ahead of the axle, just like the stock engine. This requires the Tesla transaxle to run in reverse (as already discussed), but is good for a few reasons:

fit with the suspension
fit with the structure
mass distribution
It looks like suspension clearance is to be confirmed, but it's promising. 

This means that the only spaces for battery modules in the back are:

the fuel tank space (modules standing on edge?)
the engine space, above the drive unit (above the original engine block and transaxle)
the rear trunk (which is very high for this much mass, and in the interior)
Are the grey boxes over the drive unit the rear battery modules? If so, are they under the engine cover (in the engine space), or above it (in the trunk space)?



Jack-Lee said:


> I could place two packs under the plastic trunk.


I'm surprised that there is that much unused space there. If there is, they could have made the trunk deeper in that area... but perhaps they wanted to keep the trunk floor flat.


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## Jack-Lee (Mar 29, 2019)

The grey Blocks are the battery Packs. They fit in the engine space above the axle and below the trunk.
in the Front the cooler get out, more space for the battery.


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## Jack-Lee (Mar 29, 2019)

Hi,
anybody nows which and how much Oil should I put in the Roadster-Gearbox?


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## Boxster-warp (Jun 22, 2014)

Hello
Motul Multi atf or liqui Moly 1200 atf.
1,4 Liter.
Good idea, the Car and the oil Are 16 years old.
Greetings Boxster-warp


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## Jack-Lee (Mar 29, 2019)

I mean the Tesla Gearbox 
But the Oil from the Smart get changed too.


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## brian_ (Feb 7, 2017)

That was confusing, because of course while the car being converted is (now) a Smart Roadster, there was a Tesla Roadster.

A quick web search yielded a discussion which included this:


> Telsa now recommends a 1 year/ 12500 mile transmission oil change. Flush and refill with Dexcon VI. 1.4 quarts per motor. Walmart @ $4.27/qt.


That sounds ridiculously frequent, but Tesla has had many gearbox problems, so maybe. The fluid type (which was presumably intended to be "Dexron VI", an automatic transmission fluid) and quantity seem reasonable. I wouldn't trust this information, but it gives you an idea of what it might likely be.

Lubricant suppliers might list the Model S like any other car model, with the corresponding fluids.


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## brian_ (Feb 7, 2017)

I see from other posts that you have changed both drive unit and battery choices. Can you tell us what components you will now be using... and are they still going in a Smart Roadster?


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## Jack-Lee (Mar 29, 2019)

1716/5000

The change to smart forces me to reconsider the components. For this, the existing components must first be sold. If that does not work I have to go back to the polo.
The problem is, in addition to the space, the maximum payload.
The weight of the individual wheels (including driver and full tank)
LF: 193 RF: 178 LR: 250 RR: 250 -> 871kg. The TÜV prefers the further 75kg front passenger, as well as 25kg luggage be carried. But the maximum load is only 1030kg. So I only have 60kg that I can add to the vehicle. Engine, transmission and attachments will most likely weigh only 200kg. With 8x 28kg (+ housing = about 250kg) of batteries and 86kg of motor I would already be over 1100kg.

I think of replacing the Tesla with an EMRAX 208. The controller of the Hyper 9 should work for it, right? The Emrax is a synchronous machine and the controller should work with sinewave.
The disadvantage would be the low maximum speed. Actually, the transmission must be preserved (since this is automated, it will be hard to get this function without engine control unit). However, the maximum output power drops considerably compared to the Tesla. Furthermore, the efficiency drops if you drive the original gear in smaller gears permanently (efficiency of the first gear is only 55% .The 6th gear at 96%)

In order to save weight and space in the batteries, I have to set to maximum energy density. These are currently the Tesla cells.
5 modules weigh about 130kg. With housing so about 150kg at 25kWh +.

The best would actually be a "small Teslamotor" with about 120kW peak power but only 50kg total weight and lower supply voltage ...


PS.Anybody knows a light Diff ? The BMW Diffs wights over 35kg..!


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## Duncan (Dec 8, 2008)

For the weight issue - you could "Certify" a vehicle with a small battery and then accidentally fit a larger one later

My "Certification Plate" says - "Lithium Ion" - no types voltages or capacities


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## Jack-Lee (Mar 29, 2019)

Yea, thats an option. So i could save about 60-100kg. But still close to Max payload


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## Jack-Lee (Mar 29, 2019)

Hi,


the Logicboard is in place and the WLAN are stable


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## brian_ (Feb 7, 2017)

Jack-Lee said:


> I think of replacing the Tesla with an EMRAX 208. The controller of the Hyper 9 should work for it, right? The Emrax is a synchronous machine and the controller should work with sinewave.


It's not that simple. The controller needs to be configured for the characteristics of the motor.



Jack-Lee said:


> The disadvantage would be the low maximum speed. Actually, the transmission must be preserved (since this is automated, it will be hard to get this function without engine control unit). However, the maximum output power drops considerably compared to the Tesla. Furthermore, the efficiency drops if you drive the original gear in smaller gears permanently (efficiency of the first gear is only 55% .The 6th gear at 96%)


I'm not sure that you mean by this. The Smart transmission is automated, but it is not a conventional automatic with a torque converter; it is an ordinary spur gear transmission with motors running a shift drum to move the shift forks, and with a mechanical clutch. A gear transmission can't be only 55% efficient (once the clutch is fully engaged), in any ratio - that would be unacceptably bad. Where did you get this efficiency information?

The most recent Smarts are Renaults, and use a different transmission of a typical dual-clutch design; however, the situation regarding efficiency would be the same.



Jack-Lee said:


> PS.Anybody knows a light Diff ? The BMW Diffs wights over 35kg..!


Do you mean a typical separate final drive, in its own housing with differential and reduction gearing? The lightest units would be from the rear of AWD cars which are primarily front wheel drive... but even then, they're going to be hefty... there is a lot of steel in there. But what would this be used for? Either the original Smart transaxle or the drive unit from an EV both include the differential, so a separate one is not needed.

Are you considering using the Emrax 208 with only the reduction gearing in a final drive unit? I think that performance would be marginal with one of these motors and a fixed gear ratio.


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## brian_ (Feb 7, 2017)

Duncan said:


> For the weight issue - you could "Certify" a vehicle with a small battery and then accidentally fit a larger one later





Jack-Lee said:


> Yea, thats an option. So i could save about 60-100kg. But still close to Max payload


This cheat might get around regulations, assuming that there is never another inspection, but it wouldn't change the parts of the car which are likely to be inadequate, such as suspension, brakes, and even structure.


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## Jack-Lee (Mar 29, 2019)

Hi, 

ive found this : https://www.schaeffler.com/remoteme...mposia_1/downloads_11/6_getriebesysteme_1.pdf

On the second Side you could see the efficency with low tourqe. 



And i think i could match the Emrax with a Diff and kick out the smart gearbox (The shifting times are so fu** long..)


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## brian_ (Feb 7, 2017)

Jack-Lee said:


> ive found this : https://www.schaeffler.com/remoteme...mposia_1/downloads_11/6_getriebesysteme_1.pdf
> 
> On the second Side you could see the efficency with low tourqe.


The strange graph does show low first-gear efficiency, and efficiency is lower in any gear set at low loading, but it doesn't show efficiency in any other gear, making me wonder what the purpose of the testing was, and what method might have been used. One problem is that this is a review article, with no supporting data provided (I'm still looking for the reference journal from Verein Deutscher Ingenieure - The Association of German Engineers). I fed the document to Google for translation so I could read it for context, and while it provides no explanation of why there would be so much loss in a low-gear ratio, it does include something which translates as "Losses arising from the EKM and the slippage strategy are included"; it looks like "EKM" probably means electronic clutch module. There is no slippage once moving with this type of transmission, and no slippage at all in an application with an electric motor, so I don't think this low efficiency is valid.



Jack-Lee said:


> And i think i could match the Emrax with a Diff and kick out the smart gearbox (The shifting times are so fu** long..)


Yes, the Smart transmission is infamous for slow shifting. If you can take manual control of it, you could shift it only when you want, and it would probably be much more tolerable.

With only one ratio, the Emrax looks like a poor choice. Most EV motors are configured and rated so that they can produce their maximum rated power over the whole speed range from about one-third of their top speed, all the way to nearly their top speed; the Emrax data shows that maximum power is only available near maximum speed. If you choose the gear ratio so that the motor runs 6000 rpm at your target highest road speed, and that speed is (for instance) 100 km/h, then at 50 km/h it will have only half of its rated power available... which won't be quick.


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## brian_ (Feb 7, 2017)

Jack-Lee said:


> In order to save weight and space in the batteries, I have to set to maximum energy density. These are currently the Tesla cells.
> 5 modules weigh about 130kg. With housing so about 150kg at 25kWh +.
> 
> The best would actually be a "small Teslamotor" with about 120kW peak power but only 50kg total weight and lower supply voltage ...


A lower supply voltage will limit the high-speed performance of the motor. This is why production EVs which need the motor to work effectively over a broad road speed range with a single-speed transmission typically use 360 V (nominal) or higher battery packs.

If you really like the Tesla Model S/X modules, and want the lower system voltage only because you can only carry 5 of these modules, it might help to know that these modules can be modified from 6S to 12S, doubling their voltage (and of course cutting their amp-hour capacity in two). This means they won't work with the stock BMS wiring, of course, but it can give you 225 V (nominal) from five modules.


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## Jack-Lee (Mar 29, 2019)

The alternative : I could use the newer 120Ah BMW I3 Battery.
With 6 Packs (72S 1P) the Voltage could high enough.


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## brian_ (Feb 7, 2017)

Jack-Lee said:


> The alternative : I could use the newer 120Ah BMW I3 Battery.
> With 6 Packs (72S 1P) the Voltage could high enough.


If I understand correctly, that would be essentially the original battery plan, with the same number and dimensions of modules, but double the capacity due to the cell upgrade from the original i3 to the i3s. The ~270 V nominal pack voltage might be enough for sufficient high-speed performance, depending on the motor and gearing.


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## Jack-Lee (Mar 29, 2019)

Not double, but nearly 50% more from 94 to 120ah. The 270v should work, i had 185/50 r15 tires and wont drive faster then 110-120kmh.


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## Jack-Lee (Mar 29, 2019)

Need to sell the Motor and battery to buy other components...


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## Jack-Lee (Mar 29, 2019)

The Battery is sold and i buy a Smart ED4 Battery-Assamble.
120kg for all three Blocks (17,6kWh). Little bit higher (175mm instead of 150mm from the BMW I3 Blocks) and with 430x355mm Groundaera a little bit larger Modules. I hope i could squeeze them under the rear trunk, above the Engine. 

"Fleck Elektromobile", a lokal EV Workshop, means the Roadster get +49kg empty Payload after his convertion. He use a heavy 60kg asynchronmotor with only 30kW and 10kWh LiFePO4 (wight about 110kg). So my Setup with ED4 Battery and Tesla should weight the same and i had no problem with "overweight"


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## Jack-Lee (Mar 29, 2019)

Anybody knows a potent Onboard-Charger? Search vor 22kW or something.


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## Jack-Lee (Mar 29, 2019)

New painting ist finished


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## Jack-Lee (Mar 29, 2019)

Hi,
I See a few smart conversions, but.. how they trick the ECU? Without this ECU i had much errors on the tacho.


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