# Newbe wants to build an EV with hub motors



## dtbaker (Jan 5, 2008)

offroadrover said:


> ...know where parts can be found at a reasonable price?



hub motors that are car size present a number of problems.... low power, balancing multiple controllers, size fitting in existing wheels and around brakes, limited speed/torque without a transmission, and adding a LOT of 'unsprung' weight affecting handling. Your best bet for lowest cost and simple design is to stick to tried and true design of a DC traction motor with adapter to existing transmission.


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## hardym (Apr 2, 2008)

Standard DC is the easiest way to get going. 
The Cheapest way is to purchase an already converted vehicle, like this one

http://www.diyelectriccar.com/forums/showthread.php/sale-1993-toyota-pickup-ev-make-43366.html

Mark.


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## offroadrover (Jul 14, 2010)

Thanks Dan,

I here you about the downfalls but I can’t stop thinking about the advantages. 

1. Massive reduction in overall weigh
2. Reduction in complexity of build (No gearbox, Adapters or differential)
3. Can be converted to 4x4 if power is not enough.
4. More efficient

Unsprung weight is one thing that can not be avoided though.

I contacted someone in the East and got a list of potential motors and prices, please see the attached spreadsheet. 2 motors = 30 kw and 800mn with a theoretical top speed of 105km/h (65 mph). It cost though $$$$

I live in South Africa and EV’s are very rare here so it’s not easy to find and information. I can’t seem to find anyone who has actually built one with hub motors. 

Cheers,

Jason


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## EV-propulsion.com (Jun 1, 2009)

Check our project here- more updates coming real soon.....
http://www.diyelectriccar.com/forums/showthread.php/30kw-hub-motors-evi-43115.html
mike
www.EV-propulsion.com


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## offroadrover (Jul 14, 2010)

Thanks Hardym,

But Im half a world away in South Africa, there is not a big EV following out here so I will have to build my own.

Are hub motors a complete dead end, I know that most of the vehicles that compete in the solar race in Australia use hub motors but have much less power.

I am still looking for someone that has actually built one. 

Cheers,

Jason


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## frodus (Apr 12, 2008)

> 1. Massive reduction in overall weigh


[citation needed]





> 4. More efficient


[citation needed]


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## dtbaker (Jan 5, 2008)

offroadrover said:


> 1. Massive reduction in overall weight


I don't think so.... what do two of the 15kw motors weigh versus a 6"DC brushed motor?



offroadrover said:


> 2. Reduction in complexity of build (No gearbox, Adapters or differential)


less mechanical complexity, but added electrical complexity to match/balance controllers for each wheel. Also performance issues with no gearing having both slow starts and limited max speed.




offroadrover said:


> 3. Can be converted to 4x4 if power is not enough.


I guess, if you wanna spend another $9k on motors... totaling $18k for the same power of a single 9"DC you can get for $1500.



offroadrover said:


> 4. More efficient


marginally... compare the eff rating for these versus a 'normal' traction motor; its probably not that different.



offroadrover said:


> Unsprung weight is one thing that can not be avoided though.


that and lack of gearing will produce pig-slow acceleration.





offroadrover said:


> I can’t seem to find anyone who has actually built one with hub motors.


guess why?!


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## offroadrover (Jul 14, 2010)

Hey Dan, 

You are crucifying me here, I am just trying to find a simpler way to build an EV. If I can get rid of the gearbox, final drive and driveshaft’s I can build a simpler vehicle with more space to put batteries.

The project would be a small light car and initial ideas were to use a Citroën GS from the early 80s. It’s light and reasonably aerodynamic, would have to get rid of that funny rear suspension though. 

Could a motor be bolted directly onto the diff or would the gear ratios be wrong. Where can I find power curves and graphs for the 6”DC brushed motor.

Jason


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## ewdysar (Jun 15, 2010)

offroadrover said:


> Hey Dan,
> 
> You are crucifying me here, I am just trying to find a simpler way to build an EV. If I can get rid of the gearbox, final drive and driveshaft’s I can build a simpler vehicle with more space to put batteries.
> 
> Jason


Jason,

Before you get too defensive, stop and think about it. Do you honestly think that nobody has thought about these alternatives before? The people that work on these cars try all sorts of things, plenty of which don't turn out as well as they hoped. If you've got an idea, and you can't find a single example anywhere on the planet besides expensive, exotic prototypes, it may be because it's really not feasible as a DIY project yet. 

Since you're interested in using hub motors, you must know that Porsche built production models of a hub drive car back in 1912. There are plenty of discussions about the problems associated with the concept, including this one. Did you think that you had figured out a way to overcome those known issues?

There are plenty of simple solutions for electric drive conversions. The cheaper ones are often heavier and have lower performance and range. the more expensive ones gain perfomance and/or range. If you pose the question as how fast, how far and for how much, it's easier for people to suggest solutions or explain why you may need to adjust your expectations.

Eric


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## Duncan (Dec 8, 2008)

Hi Jason

My partly built machine uses Subaru suspension and a drive-shaft from the motor to the diff

I have deleted the gearbox because I calculate that I will not be able to use the torque multiplication because of traction limitations

If you build light and stick a slightly over-sized motor in you may be in the same situation


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## offroadrover (Jul 14, 2010)

OK Eric,

My daily commute is around 50km (30 miles) to work and back, so I would need an absolute minimum of that plus a safety margin as a range. Also the route is on the highway for about 15km each way and has some steep hills where I would like to maintain 80km/h (45-50mph). It would possible to find a non highway alternative but it would be a similar distance and probably take longer. 

The EV would ideally be build from a small car with a total mass after the conversion of +-1000kg. 

We have a lot of VW Golf I’s running around here but they are expensive as it’s a very popular car, I think you guys call them Rabbits or something. Is there a standard motor, adapter plate and controller for these vehicles. Also what sort of performance can you get out of them. 

Jason


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## EV-propulsion.com (Jun 1, 2009)

I guess you didn't read through the thread, but go to *post 39*, the unit should be going in the car in the next week or two for testing, this is designed for the DIYer, as close as you can come to hub motors economically
http://www.diyelectriccar.com/forums/showthread.php/30kw-hub-motors-evi-43115.html


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## dtbaker (Jan 5, 2008)

offroadrover said:


> Hey Dan,
> 
> You are crucifying me here, I am just trying to find a simpler way to build an EV.



...not trying to shut down innovation; just pointing out the realities of hub motors and why its been tried before, and abandoned. Hub motors work for bikes, but not so good for cars, and brushless DC motors, while very cool, are very expensive.






offroadrover said:


> Could a motor be bolted directly onto the diff or would the gear ratios be wrong. Where can I find power curves and graphs for the 6”DC brushed motor.


you can find curve at the manuf sites.... what you'll find is that if you want both acceleration and highway speed, you need gears.


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## offroadrover (Jul 14, 2010)

I did go though the entire thread, promise. 

The whole idea is kind of changing as I read more on the subject. This project is only due to kick off in July next year (bonus time) so I have time to plan the build. I have a regular gas guzzling 4x4 and the EV is to try reduce the reliance on petrol. 

How much does it cost to convert a vehicle, I know its a broad question but I a talking a ball park figure on a small car capable of 40 miles on a charge if I am prepared to do the work myself? 

Just want to know the budget


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## offroadrover (Jul 14, 2010)

Came across something advertised in a local paper here for a resonable price

8KW DC Motor for sale.
Hitachi TCM electric forklift 48V DC Motor 8KW 

Could this power an EV through a gearbox?


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## dtbaker (Jan 5, 2008)

offroadrover said:


> ...a ball park figure on a small car capable of 40 miles on a charge if I am prepared to do the work myself?


A very reasonable 40 mile sub-compact can be built for $6k-$7k in all-new electronics (8"DC, 400amp curtis controller, etc) plus $1600-$1800 worth of floodies (12 x 8v) at a minimum, but lower cost in the long run if you ante up for about $5k worth of Lithium instead to get better range, better performance, and 3x or 4x the life.


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## dtbaker (Jan 5, 2008)

offroadrover said:


> Came across something advertised in a local paper here for a resonable price
> 
> 8KW DC Motor for sale.
> Hitachi TCM electric forklift 48V DC Motor 8KW
> ...


'maybe', but not fast.

the typical 8"DC motor used in small cars can put out closer to 50kW. You need about 20hp continuous to maintain 55-60mph and peak of 70-80hp for 'good' acceleration of a 2500# car from a stop... WITH gears.


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## ewdysar (Jun 15, 2010)

offroadrover said:


> OK Eric,
> 
> My daily commute is around 50km (30 miles) to work and back, so I would need an absolute minimum of that plus a safety margin as a range. Also the route is on the highway for about 15km each way and has some steep hills where I would like to maintain 80km/h (45-50mph). It would possible to find a non highway alternative but it would be a similar distance and probably take longer.
> 
> ...


Here's a link to a complete kit to convert some of the older Rabbits/Golfs. http://www.electroauto.com/catalog/dccustkits.shtml#voltsrabbit

You can get an idea of the relative performance that is available. I think that most people here would recommend sourcing the parts and doing some of the fabrication yourself, but this a "one-stop" solution that would get someone on the road. You can see from some of the other posts that there have been some advancements since these kits were designed, but this is a reasonable baseline to work from. You can also see the detailed list of components that need to be considered in a conversion. 

My rule of thumb is that inexpensive conversions made from salvage parts will work, but have limited performance and range. More expensive conversions made from new parts that are intended for EV conversions deliver more performance and/or range. More range or acceleration almost always costs more money. But the corollary of spending more money will not guaranty more performance/range. Each person gets to figure out what budget will fit their personal needs.

Eric


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## vpoppv (Jul 27, 2009)

offroadrover said:


> I am just trying to find a simpler way to build an EV. If I can get rid of the gearbox, final drive and driveshaft’s I can build a simpler vehicle with more space to put batteries.


While this sounds like it is simpler, it really is not. I often say that I "built" my electric car, but that is really a lie. What I, and most others have done, is to CONVERT a car from gasoline engine to electric. There is a big difference between completely changing the working of the car and simply replacing the powertrain. The advantage of using the transmission, among others, is that you can plop in the electric motor using the stock motor mounts. This is also the area where it was engineered to be. Changing the location of the drivetrain presents many more complications, and many more hours of fabrication. Also, the car wasn't specifically designed to have it's powertrain in any other location, which can bring about safety issues that a non-engineer may not be aware of. And more to the point, it will end up being much "simpler" to do what thousands of people have already done, succesfully, than to try to find a handful of people who may have accomplished what you are suggesting. As to the motor you are considering, this would be the place to ask:

http://www.diyelectriccar.com/forums/showthread.php/using-forklift-motor-and-choosing-good-7598.html


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## Duncan (Dec 8, 2008)

Hi Offroadrover

_8KW DC Motor for sale.
Hitachi TCM electric forklift 48V DC Motor 8KW _

That sounds like the motor I am using for my build, mine is 11 inch diameter and weighs 102Kg

I am expecting similar performance to a Warp11
(which is basically a painted up and brush advanced forklift motor)

Don't pay too much attention to the 8Kw you will be over volting and over amping it a little,

I believe that 8Kw continuous power at 48v equates to 24Kw continuous at 150v with burst power of 75+Kw for a minute or so - more if forced cooling is used 

If its cheap - get it before somebody else does!!

Have a look at the "using a fork lift motor" thread at the top of the motor section

Post photos of your motor and the experts will advise


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## umurali2000 (May 3, 2010)

Using Hub motors for EV will create an issue while balancing the wheel. Instead you can try for a differential gear motor.


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## beirao (Jul 19, 2011)

offroadrover said:


> Thanks Dan,
> 
> I here you about the downfalls but I can’t stop thinking about the advantages.
> 
> ...


Hi,

In your post, you have a attach with a .doc of motors of GZ EMOTOR TECHNOLOGY, right? Do you have techinal information about the motors and controllers ? I have a motor EM-2kW and respectible controller, but i haven´t information.

And they have web site? I don´t find nothing...

Thanks!


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## russatt (Aug 30, 2013)

Hi

I am also from SA. Doing a conversion.

Are you still at it?


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