# Little electric EV



## Thomas4200 (May 10, 2018)

Hello,

I'm Thomas 31 years old, i start a project

Car is a "Bellier" model "Formule 85"

See pictures


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## Thomas4200 (May 10, 2018)

I want drive this car by an éléctric motor but now i'm hesitate between a transaxle and a hub motor

For transaxle is difficult to find a gear ratio about i=6, i have find but work with chinese is a little difficult...

see picture of drawing i use for research, if anyone want a drawing or 3d file, tell me 

For hub motor(x2 in traction or propulsion), i don't undersand who the controller(x2) simulate the differential, if anyone can explain me what happen with 2 hub motor ? 

see product i want to buy : https://fr.aliexpress.com/store/pro...60.html?spm=a2g0w.12010612.0.0.f5477442zCbHQi

Have great day

Tom


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## Thomas4200 (May 10, 2018)

Bye bye thermic motor


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## prensel (Feb 21, 2010)

According to the license plate I assume you are from France ?

Before converting anything did you check with the registration offices if they ALLOW the conversion and do you have the required EMC paperwork for the approval ? Without either of these just forget about driving this car on public roads.

Why not get one of these allready electric Peugeot 106 or Citroen Saxo, Berlingo or Partner, they are cheap (under 1000 euro) and easily available in France and will save you a lot of trouble getting it registered


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## Thomas4200 (May 10, 2018)

You have reason, i live in France

i want to make a transformation on this car because this vehicle is in the public domain

This car unloading weight 250 kg and after electric conversion near 350kg

a manufacturer electric car is too heavy for recharge with solar panel or need very big surface

I have a little society in design and programming machine, see this, i have conceive this product : http://www.alicatt.fr/e301.html 

In France the laws are brought

I make this car for hobby and for increase my skills in electric mobility

if you want help me for technical problem, i'm happy 

and if i can help you, i'm happy too 

Have a great day

Tom


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## prensel (Feb 21, 2010)

Hi tom,




Thomas4200 said:


> You have reason, i live in France
> 
> i want to make a transformation on this car because this vehicle is in the public domain


NO it isn't when you replace the combustion engine with an electric motor.
You will loose the cars registration when doing this and you have to apply for a NEW registration. 

But if you keep your battery voltage below 60V you PROBABLY dont have to comply to some EMC requirements but still need to apply for some tests. 

Better check this first before investing time and money in a nice but unusable project.


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## Thomas4200 (May 10, 2018)

thank you for your attention, in the background, you're right but I think that in France it is necessary to provoke a little things for which evolve 

I know that the vehicle will not have the right to drive on the public road

I have already contacted the probate service but in France you know, everything is complicated

I have previously set up a heavy truck camping, I do not explain the folder to write "camping car" on the papers of the car, then to change the engine is not won 

I make this car but i like electric motor, this little car will be run in propriety, not public road 

in France, voltage is complicated after 50v so normaly i must use a 48v system

Can you explain the problem with 2 hub motor et 2 controller, what happen because no differential ?

You have see "who killed the electric car " ?

bye


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## Thomas4200 (May 10, 2018)

Hi,

I have find a video that explain the problem with 2 hub motor

https://www.youtube.com/watch?v=4qf1TkFGSWA

it confirms what I think, it is necessary to cut or slow down an engine according to turns

So i buy product (link in an other post)

and if you want i come to you for explain my solution to drive 2 controllers and 2 hub motor(simulate differential), now i think i had 1 potentiometer (or 2 for security) on steering control and 2 or 4 inductive sensor on support wheel to check problem

Have a happy day 

Tom


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## Duncan (Dec 8, 2008)

No you don't need to do any of that
The road will do it for you!


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## brian_ (Feb 7, 2017)

Thomas4200 said:


> I want drive this car by an éléctric motor but now i'm hesitate between a transaxle and a hub motor
> ...
> For hub motor(x2 in traction or propulsion), i don't undersand who the controller(x2) simulate the differential, if anyone can explain me what happen with 2 hub motor ?
> 
> see product i want to buy : https://fr.aliexpress.com/store/pro...60.html?spm=a2g0w.12010612.0.0.f5477442zCbHQi


I don't see anything in the description which explains how they handle the speed difference between two motors.

With AC (and BLDC) motors, since the motors are turning at different speeds they each need their own controller/inverter, running at different speeds in turns, and coordinated. Curtis Instruments (a popular supplier of AC controllers) includes this feature; they call it "Dual-Drive". In this system, one controller acts as the master, with the accelerator input connected to it; the other controller is the slave, and is connected to the master by a CAN bus cable. There is a sensor attached to the steering which tells the master how tightly the vehicle is turning (and which way), so that the controller knows how the two wheel speeds should be related.



Duncan said:


> No you don't need to do any of that
> The road will do it for you!


With DC (not brushless "DC") motors, you could just connect them to one controller in parallel, but I'm not sure that you would like the result.


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## Emyr (Oct 27, 2016)

Duncan said:


> No you don't need to do any of that
> The road will do it for you!


Yes, but police officers frown at on-street tyre smoking.

It's possible to calculate an ideal speed differential given a known vehicle track, wheelbase and steering angle. The challenge is working out how to manage torque-oriented throttle with speed limiting for the inside wheel, with added complication to detect and accommodate wheel slip.


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## Duncan (Dec 8, 2008)

Hi Emyr

99% of all cars ever sold have an "Open Differential" - which has ZERO control right to left - the road does it all!

Any of the designs involving two motors have more control right to left than an Open Differential

If the OP was making some sort of high performance machine THEN it could be worthwhile looking at some form of torque control

But he is making a low power machine - there is simply NO NEED for anything at all complex

Don't make things more complex than is needed!


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## Thomas4200 (May 10, 2018)

hi Brian and Duncan,

Brian :
Video not explain really the problem so show a system, this video just confirm my think

I have been working with Curtis for several years with little DC controller but I did not know the dual drive, I think it's a good option but it requires to buy the controller at Curtis, i have contact Kelly controller for this function but i have no response for now

But i prefer create an independent system, so if i want i change motor or controller, i can choose in all brand 

So, i will create a little electronic card for receive potentiometer of accellerator and position of steering control and after a little algorithm i control 2 digital potentiometer for drive 2 controller

Duncan : 
my first thought is the same as yours but I prefer to predict the worst, I will try and if it is not necessary, I will not make an electronic card to drive the controllers
Have you an exemple on a forum or web site or video, i can't find on diyelectriccar because i can't find the search barre, if you can help to search in forum it's good, very thanks 

Have a great day Boys and Girl 

Tom


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## Duncan (Dec 8, 2008)

Tom
as I said EVERY open diff car on the road operates with the road making the wheels go at the right speed

This even applied to the days in my youth when I was interested in Twini Mins

A min with an engine in the front and another in the back - again just the road acting to synchronize them


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## Karter2 (Nov 17, 2011)

As Duncan said, you are wasting your effort on totally unecessary complication.
Remember, vendors will be happy to indulge your experimentation since it means more income for them.
I also suspect you are wasting money on those hub motors as well, as the performance will most likely disapoint you.......but that is your choice.!


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## Thomas4200 (May 10, 2018)

Ok Duncan

So why Curtis have created dual drive, for machines that works like a tank or wheelchairs (for invert motors direction)?

You have not send me link about car with 2 hub motor 

I have just one think, I'm in a hurry to try 

if you say true, the electric car is childishly simple to manufacture 

Have a great day

Tom


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## Thomas4200 (May 10, 2018)

Hi Karter2,

i will create electronic card if it necessary, if not i don't create this 

i'm programmer and designer, it is not problem for me 

You think hub motor isnt a good choice, please explain me, do you have experience feedback ? 

see you soon

Tom


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## Karter2 (Nov 17, 2011)

Hi Thomas,
How many electric cars do you know of using hub motors ?
No commercial EVs, and Very few if any DIY cars.
Several projects have tried to use them, but had disapointing results or failed 
Generally, hub motors do not have enough torque for hills, and are difficult to get controllers to work with.
The few that work are expensive.
Your project would be simple, cheap, and effective using modified golf kart components.....either the whole drive package, or just the axle and some other motor/controller system.


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## Thomas4200 (May 10, 2018)

hi Karter2,

Thanks for your observation  it's true

i think hub motor is a very good idea, no gear, no differential, no transmission but the power limit the speed and acceleration, i think this motor have application but not for car like more than 500kg and speed 90km/h

I want to believe in this dream because it's a little slow car

specification of car :
-Max speed :45 km/h
-Max load : 600kg exceptionally otherwise normally 450kg
-Diameter wheel : 460mm 

see my calcul if you want

motor torque is 130Nm (i have demand curve to manufacturer)
(on spécification max torque is 180Nm but curve says 130Nm)

if i want go 0 to 45 km/h in 5 seconds, normally i need 1250N (2.5ms2 X 500kg)

2 hub motors can push 1130N ((130Nm X 2) / 0.23m)

my car normally can run 0 to 45 km/h :

- 5.5 s (on flat floor) (1130 = 500 x 2.26) and (12.5/2.26 = 5.5)

- 6s on hill 10% (5.71°) (1130 = 550 x 2.05) (12.5/2.05 = 6)

(I do not consider any friction given the low speed)

You can confirm me this please if you want ? 

i think its possible for my application but i'm not drive 90km/h, if i want that i need more powerfull

I have another doubt, is that the motor hubs are not more fragile because of a direct impact with the road ? what do you think ?

see you soon

Tom


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## brian_ (Feb 7, 2017)

Duncan said:


> 99% of all cars ever sold have an "Open Differential" - which has ZERO control right to left - the road does it all!


While I agree that the same equal-torque behaviour as an open differential should be fine in this case, the above statement is no longer true. While most (but probably not 99%) of currently available vehicles have open differentials, in North America all current production vehicles are required to have electronic stability control, which includes individual braking of left and right wheels. That ability also provides traction control.


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## brian_ (Feb 7, 2017)

Emyr said:


> Yes, but police officers frown at on-street tyre smoking.


While doing a good job of managing torque to the wheels is worthwhile, I don't think this is a concern. If one tire spins, back of the pedal, as with any vehicle not having traction control.



Emyr said:


> It's possible to calculate an ideal speed differential given a known vehicle track, wheelbase and steering angle. The challenge is working out how to manage torque-oriented throttle with speed limiting for the inside wheel, with added complication to detect and accommodate wheel slip.


The calculation is what Curtis includes in the software for their Dual-Drive feature. I don't know what other controllers might include it, because the majority of EV applications do not use individual wheel motors, and because the logic in production EV controllers is not documented.

To be clear about the Curtis Dual-Drive: it is intended for the industrial vehicles which Curtis exists to service, not the DIY EV crowd that also uses their products due to the voltage range which they support. Those industrial vehicles (forklifts, etc) often turn very tightly and should particularly benefit from well-managed side-to-side torque distribution.

Detecting wheel speed is a non-issue with AC (and electronically commutated or "brushless DC") motors, because those controllers inherently know the speed. Synchronous motor detect motor position to maintain synchronization and their output frequency is the motor (and thus wheel) speed; induction motors measure the shaft speed to determine the appropriate inverter output frequency.

Some tire slip is acceptable and even necessary. It's a classic control loop challenge to control it.


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## brian_ (Feb 7, 2017)

Duncan said:


> This even applied to the days in my youth when I was interested in Twini Mins
> 
> A min with an engine in the front and another in the back - again just the road acting to synchronize them


Yeah, that never worked well for anyone who tried it (with Mini, VW, Honda), but it does function to some extent. Intelligent control is much better, but there are few if any dual-engine examples because dual-engine cars make so very little sense. In AWD single-engine cars, passively allocating torque front-to-rear is good enough most situations, but the pursuit of really good performance has led to both mechanical and electronic solutions for torque management, just as it has led to active management of torque side-to-side.

The current most common practice in AWD is to drive one end full-time, and drive the other end through a computer-controlled clutch to actively manage front-to-rear torque distribution. This isn't extreme tech - it's the basic economy AWD SUV from almost every manufacturer.


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## brian_ (Feb 7, 2017)

Duncan said:


> Tom
> as I said EVERY open diff car on the road operates with the road making the wheels go at the right speed...


...except for the ones with traction control and/or electronic stability control, which is everything sold in North America (and presumably in other first-world countries, too) now.


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## Duncan (Dec 8, 2008)

brian_ said:


> Yeah, that never worked well for anyone who tried it (with Mini, VW, Honda), .


Nope you are wrong again! (getting to be a habit)
It worked superbly

The only issue was cost


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## Duncan (Dec 8, 2008)

Thomas

The issue with hub motors is simple 
As a rough approximation Torque is proportional to weight

And a reduction gear is a lot lighter than making the motor 9 times the size

So every car company uses a smaller high reving motor and a reduction gearbox


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## Thomas4200 (May 10, 2018)

Thanks Duncan,

I understand what you are saying

You're trying to convince me to go back to the transaxle 

But is not a bad idea 

I will redo calculations and reflect, and return on forum for explain my conclusion

see you soon

Tom


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## boekel (Nov 10, 2010)

Thomas4200 said:


> Ok Duncan
> 
> So why Curtis have created dual drive, for machines that works like a tank or wheelchairs (for invert motors direction)?


Typically forklift trucks, some with a single rear (steering) wheel turn this wheel 90 degrees, where the driven weels can actually counter-rotate to be able to turn.

Sevcon also has this function in their controllers.


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## brian_ (Feb 7, 2017)

Duncan said:


> The issue with hub motors is simple
> As a rough approximation Torque is proportional to weight
> 
> And a reduction gear is a lot lighter than making the motor 9 times the size
> ...


All true, and excellent points 



Thomas4200 said:


> I understand what you are saying
> 
> You're trying to convince me to go back to the transaxle
> 
> But is not a bad idea


Yes and no. In that post Duncan is making a good argument for using a reduction gear between the motor and the wheel, but that argument is still valid whether you have

a motor (plus reduction gear) in each hub, or
a motor and reduction gear for each wheel, but mounted to the vehicle's structure and connected to the hub by a jointed shaft, or
one motor and reduction gear shared between the two wheels of one axle, with power distributed between the wheels by a differential (which can be done in a transaxle).

There are other reasons not to use motors mounted at the hubs, even with reduction gears. The most obvious is the high unsprung weight, which hurts ride and handling. That might not matter with this low-performance vehicle.

There are other reasons not to use separate motors for each wheel. Primarily this is the higher cost of two small controllers versus one larger one, and two small motors versus one larger one, and two small reduction gear sets versus one larger one.

The advantages of separate motors are typically not important to DIY EVs:

better control of individual wheel torque without using individual wheel braking or a complex active differential (most builders are not attempting to reach a modern level of control, so they don't attempt any kind of individual wheel control)
avoidance of energy lost to individual wheel braking for torque control (which is not an issue for most since they don't do any individual wheel torque control)
elimination of the weight and complexity of the differential (which is not a problem with a plain open diff)
potential to leave the centre line of the vehicle between the wheels free of any hardware (not important except for some specialty applications such as a low-floor hauler)


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## brian_ (Feb 7, 2017)

Duncan said:


> It worked superbly
> 
> The only issue was cost


Not really. Vehicles such as the 2CV Sahara has so little power that the distribution front-to-back didn't matter. High-power examples such as the 1980's VW "Golf" (with almost no Golf parts) hillclimb car are almost undriveable in many situations. Somewhere in-between are the various Minis, Hondas, etc.; at very best, they maintain a constant front-to-rear ratio and so are comparable to a traditional centre-differential AWD system... but while that traditional system was great a couple of decades ago it isn't good enough by current standards.

In cost-is-no-object scenarios (such as Group B rally cars) twin engines have not been used because they don't work well. The twin engine cars are all novelties. They could be done well now, taking advantage of computerized management of both engines and transmissions, but no one bothers.

A recent example of how front-to-rear distribution matters is the Volvo XC90 T8. It is a plug-in hybrid with the engine in a parallel hybrid system driving the front, and electric-only drive to the rear. As the vehicle shifts between power modes the front-to-rear distribution changes, in a way which is noticeable and unsettling to test drivers... because it really does matter how power is distributed.

None of this is very relevant to the topic of this thread, because this is not a high-power vehicle needing sophisticated control of power to the wheels, and isn't even being considered for AWD.


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## brian_ (Feb 7, 2017)

Thomas4200 said:


> ... if you say true, the electric car is childishly simple to manufacture


An EV is certainly *mechanically* simpler than an engine-driven vehicle. 
In practice they are not simpler to manufacture. Most EV manufacturers build their EVs and engine-powered cars on the same production lines, with little difference in manufacturing complexity (other than the engine itself)... and the EV costs more due to the battery and high-power electronic components (mostly the inverter).

Many of the same issues apply regardless of the power source, and are disregarded by do-it-yourselfers who don't yet understand much about automotive design. Examples include the effect of unsprung mass on suspension performance (an issue with hub-mounted motors), and mass distribution (often problematic in conversions which pile battery packs in one end of the vehicle).

The mechanical complexity of an engine is to some extent replaced by electrical complexity and battery management in an EV.

Some of the simplicity of a typical DIY conversion is only by comparison with a modern vehicle. If you compare a straightforward EV conversion to the cars you can find in a car dealer's showroom, the DIY EV looks simple. If you compare the same EV conversion to a 1960's gas-engine car, they are not so different, because neither one has anti-lock brakes, traction control, stability control, and sophisticated suspension.


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## evric (Oct 26, 2008)

Thomas4200 said:


> Hi,
> 
> 
> So i buy product (link in an other post)
> ...


Hi Tom,

You say that you will be running the car on 48Volts. The minimum voltage for the QS Motor is 60Volts.

Eric


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