Introduction/newbie questions

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WayneG
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Post by WayneG »

Hi Folks,

Firstly just want to say hi and introduce myself. I'm planning an EV conversion for a daily commuter, so I have some newbie questions...

I'm looking for something light and fun. I would like it to be quick off the line, a 0-100 of around 5 seconds. In saying that I probably don't need to reach 100km/h but would be nice if it could. At this stage I'm looking at a Datsun 1000/1200 ute as a donor, they weigh around the 600-700kg mark. I was thinking mounting the motor under the tray would be better to keep weight over the rear wheels for more traction. I don't plan on having a gearbox at all.

My round trip to work is roughly 30kms so a range of 50 should be enough. So I guess I'm after suggestions on motor and battery selection. The Kostov motors seem like good value but I'm not sure what size I need, a K9/17R? To keep the car as light as possible I realise I will need to use Lithium cells, but unsure what voltage and how that affects acceleration.

Thanks in advance.
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Gabz
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Post by Gabz »

being from newie you should go see john from catavolt http://www.catavolt.com.au/ and old mate from solar power australia / elmofo http://www.elmofo.com.au/

both on the same street in Warners Bay

just for newie cred varley group is in tomego http://www.varleygroup.com/site/index.cfm
Last edited by Gabz on Wed, 15 Jul 2015, 18:37, edited 1 time in total.
Corporate Member Recharging NSW Pty Ltd. http://rechargingnsw.com.au/
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jonescg
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Post by jonescg »

Lots of good advice here on the forum. If you want performance at a reasonable price I can strongly suggest lithium cobalt pouches. The DC motors aren't as efficient as AC, but they are still much cheaper.

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Richo
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Post by Richo »

jonescg wrote:The DC motors aren't as efficient as AC, but they are still much cheaper.

Not to be picky but AC motors are comparable on price - it's the controller that's the costly part.
WayneG wrote:At this stage I'm looking at a Datsun 1000/1200 ute as a donor, they weigh around the 600-700kg mark.

Yep that would be a good choice.
Most of the cars around that era would be similar.
Escort, Corolla, Mightyboy, Mira
WayneG wrote: I was thinking mounting the motor under the tray would be better to keep weight over the rear wheels for more traction.

Doable but involves more engineering certs as you would need new motor mounts.
WayneG wrote: I don't plan on having a gearbox at all.

The only time you would keep the box is if you cant get the power or mechanically it's cost prohibitive.
For the older RWD cars I doubt the box would ever be needed.
WayneG wrote: My round trip to work is roughly 30kms so a range of 50km should be enough.
So I guess I'm after suggestions on motor and battery selection

So as a ball park figure a 10kWh minimum battery pack - the more the better (depends what fits / weight limits).
WayneG wrote: The Kostov motors seem like good value but I'm not sure what size I need, a K9/17R?

K9 sounds about right ~60kW.
WayneG wrote: ...unsure what voltage and how that affects acceleration.

Until you sort out your motor/controller choice best not to worry about the battery.

The CURRENT will affect your acceleration
The VOLTAGE will affect your top speed.

Typically your pack voltage is determined by your motor controller.
As an estimate for the K9 you would want 140-160V DC.
So a 10kWh pack will mean cells that are 60-70Ah.
And if you had an INPUT power of 85kW and 10kWh pack you need cells rated for at least 8.5C.
The bigger the pack the lower the C rating can be.

So the short answer is NO but the long answer is YES.
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Johny
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Post by Johny »

Hi Wayne and welcome to the forum.
Richo summed it up nicely.

Assuming you mount most of your battery pack on or under the rear tray, you will have lots of weight in the back for traction.

I mounted my motor on a cradle that mounted on the original engine and gearbox mounts. The motor was placed where the transmission used to be, as far back in the tunnel as possible.

Once you pin down the donor car you can figure out what weight distribution you want. Too much in the rear will make it hard to get approved and have bad steering ramifications.

I found it hard to get enough weight up front to get close to the original weight distribution (which was a bit front heavy in my case).
WayneG
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Post by WayneG »

Hey Gabz, I see you're in Maitland. I'm actually more that direction than Newie these days but I figure more people know where Newcastle is.

Thanks Richo for the detailed reply, but now I have more questions Image How do I know a certain motor will draw enough Amps to give me the performance I am after? Do those graphs tell you somehow? Is 64Kw and 600A the absolute max of the K9? I've found some calculators online and I don't think 64Kw will do it for me.

Thanks also Johny. Utilising the transmission mounts and tunnel space for the motor makes a lot of sense.
Last edited by WayneG on Thu, 16 Jul 2015, 15:24, edited 1 time in total.
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Adverse Effects
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Post by Adverse Effects »

if your not going to run a GBox you may need to change the diff in the car you want to convert to a Higher raito to get the best value for your $ in the final outfit
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Post by bladecar »

"...to get the best value for your $ in the final outfit"

I'm not sure what that means.
Getting the best value for your $ is simply a judgement call but how does the right diff become a $ judgement. It would be a case of matching motor and power characteristics to road speed. Because the $ enters less into an EV than getting the vehicle that suits you best. Unless you never intend to have an EV.
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Post by Johny »

I think adverse was pointing out that with no gearbox the diff ratio is going to play an important role in the final performance (IE value for $) of the vehicle.
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bladecar
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Post by bladecar »

Yes, I can't say anything against the comment but feel that it's the least likely way of describing why you want to change the diff. If Adverse changed the diff in his diesel ute, it would be to get a different performance and not to improve the dollar value of his ute.
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Richo
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Post by Richo »

The diff can be changed later to improve the acceleration.
WayneG wrote: Thanks Richo for the detailed reply, but now I have more questions Image

Well that's what the forum is for - just ask away Image
WayneG wrote: How do I know a certain motor will draw enough Amps to give me the performance I am after?
Do those graphs tell you somehow?

The graphs provided by DC motor manufacturers tend to be closer to the continuous rating.
To get peak values most of the graphs need extrapolation.
WayneG wrote: Is 64Kw and 600A the absolute max of the K9?

Probably not but the more you push it the more wear you will get.
It says 600A for 20secs.
So what current would it take for 5 secs?
Don't know but I doubt 60kW will turn into 100kW if you get my drift.

WayneG wrote: I've found some calculators online and I don't think 64Kw will do it for me.

Calulators?!?
Do they allow you to put in motor constants.
If not then the data could only be used as a guide.
If you are looking at it from an aerodynamic point of view a lot of the older cars dont have these figures listed.

In my case I had to physically do a roll down test to get the losses from the car.
Then I had to enter in motor modelling data and combine the two to get realistic values.
You may be right 60kW may not be quite enough.
It would be difficult to know for sure without some calcs.

But dont forget the way a 60kW electric motor will "feel" more like an 80kW motor.
This is due to the electric motors higher torque response at lower RPM than a regular petrol car.

In comparison there is a BMW with 9" direct drive here in Perth and even though it's not setting new performance records it is a 1200kg car that used to have 80kW.
You have nearly half the weight and probably started out at around 40-50kW.

What would be next option 11" motor at $3k - could you justify it?
So the short answer is NO but the long answer is YES.
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4Springs
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Post by 4Springs »

I describe my destructive testing of a Kostov K9/17R here: BrumbygoBoom
The K9 with 800A controller was a bit underpowered for my roughly 1400kg ute. The K10 with 1000A controller is much more like it.
Not sure what my acceleration is now, I have not been game to push it too hard in case something breaks.

If you want to accelerate that quickly without a gearbox you'll need to consider your gearing carefully. Mine is zippy in 2nd but can only go to 80kph before I hit the motor's top RPM spec of 5600. In 3rd it can reach 110kph but is not so quick off the mark.
I tend to use 3rd gear for most things. I almost never use 4th. Sometimes I use 2nd in town if I want to be quick off the mark at the lights. I don't use 1st and I'm careful in reverse because of the low gearing - it tends to jerk into action. This would be better with a better controller such as the one Zeva offers.

I use 48 LFP cells to provide the voltage. 130AH cells so about 20kWH pack. This gets me about 100km in range.
As a thought exercise I could use 48 x 60AH cells. In theory this would give me 46km range, but because of the reduced weight it would probably be around 50km. If your vehicle was lighter it would go further and of course accelerate better!

Do you have the performance graphs for the motors you are considering? I found them confusing to interpret but I think I got my head around them in the end. There is a bit of conversation about them here: MotorStuff

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Adverse Effects
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Post by Adverse Effects »

something like a UQM Powerphase 100 Motor and Inverter and between 90 to 100 CALB CA60FI 60Ah LiFePo4 Cell would give you a nice little Dato1200 and it would go real nice you may even be able to drop drop down to CA40FI CALB LiFePo4 Cell if you limmited the amps in the controller a bit

but that is all in a world where anything is possible and cheep
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Post by WayneG »

Richo wrote:Calulators?!?
Do they allow you to put in motor constants.


No I was purely trying to get an idea of required HP/Kw based on vehicle weight and gearing. See it here.

Anyway, thanks everyone for your input. I think I have enough to go off and research. Might just be easier and cheaper to buy a Leaf or MiEV!
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Post by bladecar »

Owners of Leafs and MiEV's here seem to like them.

A cheap one (as they are at the moment) could be a good way to go.

My car is not a major manufacturer one but still gets me where I
want to go most of the time and when it doesn't, I'm gradually learning how it works, which is a major goal for me (given enough time).

I think a certain amount of independence should be part of EV ownership. A fork in the path of transport should mean that the old is not necessarily good enough, depending on what has annoyed you the most about the established systems.

I was just driving past the servo with 1.45 on the sign (if you follow the silly supermarket games.) We've greatly reduced our visits to the servo, and then it's often to buy milk.
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Post by reecho »

I-Miev's are a good starting point for a toe in the water experience. Originally i was planning on a conversion, but the ex-lease I-Miev's came up at a price that pretty much matched the conversion cost, with a full warranty and all the mod cons like AC, power steering and windows...etc. The sticking point for me is that i would be keen on modding the Miev (such as adding a Brusa charger) and maybe replacing the LEV50 batteries for the updated LEV50N cells, or even go the Voltron Evo route with pouch cells, but the car still has MMAU warranty for another 4 years.
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bladecar
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Post by bladecar »

reecho,

It's good, isn't it, that you have what you want and a sticking point is that you have to wait to make it better :)
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Post by reecho »

Yes.......although some people just cannot wait..... :-)

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Richo
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Post by Richo »

WayneG wrote:I was purely trying to get an idea of required HP/Kw based on vehicle weight and gearing.
See it here.


Yeah I wouldn't use that calculator as a basis for anything.
Oh except an ROV with an "ideal" motor on a planet with no atmostphere Image

I'll plug in some data into my calcs to come up with something more realistic.
Even if you dont want it anymore.

WayneG wrote:Might just be easier and cheaper to buy a Leaf or MiEV!

Yep it IS easier and cheaper.
But not better Image
So the short answer is NO but the long answer is YES.
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Richo
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Post by Richo »

Ok So here is a rough write-up.

Initial Requirements:
0-100kph in ~5 seconds
Direct drive

Required Specs:
102kW Peak @ 3000RPM
326Nm @ 3000RPM
Weight 730kg
Rim Size 185/60R13
Rolling resistance 90N
Drag coefficient 0.42
Frontal Area 1.8m2
Diff ratio 4.11
No wind
No slope

Here is what the power graph looks like
Image

And here is the 0-100kph times
Image

Now things to note.
Most of the values I got from a Datsun wiki site.
Frontal area and rolling resistance are ESTIMATED.
Changing the rim/tyre combo wont really affect it - legally same OD.
There are other diffs ratios avail like 4.8:1 etc which could improve 0-100 times.
The motor used specified is an industrial, of course, 160 frame (11kW plate rating) weighing 90kg.
But in terms of motor cross referencing (DC v AC) it should weigh around 90kg unless you change to a permanent magnet.
Last edited by Richo on Mon, 20 Jul 2015, 16:11, edited 1 time in total.
So the short answer is NO but the long answer is YES.
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Adverse Effects
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Post by Adverse Effects »

so kind of like what i listed up a bit :-)
Last edited by Adverse Effects on Mon, 20 Jul 2015, 16:42, edited 1 time in total.
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Richo
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Post by Richo »

Yep it seems a workable solution.
Not too sure if I like their terms of use for an USD$8k system.

If I was purely after the 0-100 time I'd be trying to optimise a 7.5kW induction motor (132 frame) with the 4.8:1 diff to give 100kW@100kph.
That would be ~6secs - not quite the 5secs but still pretty reasonable.
That brings the motor down to 60kg.

Either way it's still around 100kW.
So the short answer is NO but the long answer is YES.
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Adverse Effects
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Post by Adverse Effects »

Richo wrote:Not too sure if I like their terms of use for an USD$8k system.


oww i was just posting them as links to "a item list" not buy it from there but evtv dose supply with the battery's all the connection straps , bolts , and nordlock washers in the price
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Post by WayneG »

Wow thanks again for the extremely detailed reply's (especially Richo). Didn't expect this kind of response, really appreciate it!

The UQM motor and 100 CALB cells are just a bit out of my budget. I don't exactly have one, just didn't want to spend quite so much. But I guess with my goals I don't have much choice. Initially I thought a 5 sec 0-100 would be real easy to achieve with such a light vehicle, along with a tiny 50km range...

Does 2nd hand stuff come up for sale often? Does anyone buy stuff from the states directly? Shipping would be expensive I imagine.
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Richo
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Post by Richo »

Adverse Effects wrote:oww i was just posting them as links to "a item list" not buy it

It is a good find regardless of terms.
There wouldn't be many places selling UQM motors+controllers.
So the short answer is NO but the long answer is YES.
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