AC or DC?

AC, DC, amps, volts and kilowatt. It's all discussed in here
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Post by Tonic » Tue, 17 Feb 2009, 21:30

Expertise on tap? ... That would be you gentlemen Image ...
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Post by Richo » Tue, 17 Feb 2009, 21:46

We were looking at some Permanent magnet motors before in another thread.
Unfortunately I was looking at the 100+kW motor which is still in the R&D phase so not available.
Should be more efficient than the Induction motors but a lot more expensive due to the magnets.
So the short answer is NO but the long answer is YES.
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Post by Johny » Tue, 17 Feb 2009, 22:12

I think the "Expertise on tap" nicely sums up the Industrial AC v/s DC question. It means are you comfortable sketching out a quick contactor interlock arrangement or happy to spend hours reading through the drive parameter list looking for that elusive minimum 'something' setting.

I don't know what the time frame will be before the Industrial AC crowd come up with a relatively user-friendly approach but there are a few working on variations of this - be it custom built controllers or documenting how to set up the ones that have been tried. It is unfortunately, slow work. The variations on controllers (and availability) are really the biggest hurdle IMO.

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Post by Nutz » Wed, 18 Feb 2009, 01:22

Not being an academic, I'm liking the "strip the ICE system out, prepare the body, and find a Guru to help design and install the new powerplant" option. Any willing Gurus out there in Melbourne?

Edit; I don't expect charity here either.
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Post by coulomb » Wed, 18 Feb 2009, 04:30

weber wrote:
coulomb wrote: Actually 415/sqrt(2) ~= 293v, the minimum bus voltage needed to generate 415v 3-phase. I may have incorrectly described that as 340v, i.e. 240*sqrt(2).
Er. The minimum DC bus voltage to generate 415 V 3-phase is 415 * sqrt(2) = 587 V, as someone else already said. I presume you meant +-293 V.

Oops. I meant that the amplitude of the flattened sine wave has to be 293v, and of course the output swings plus and minus from the centre tap of the DC supply. So the total DC supply has to be 587v, as you say.

Of course, the outputs will be 415v sine waves, meaning that they have peaks of +/- 587v, so you are getting 1174v p-p from a 587v source, a doubling. Of course, this is because of the push-pull nature of the outputs.

It's still pretty wonderous, considering that you don't need a 240v sine wave (which would require 240 * 2 * sqrt(2) = 678v). Image

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Post by Tonic » Mon, 23 Feb 2009, 22:39

Hi Matt,

The past few weeks has been a real crash course in electronics for me and I do believe I'm getting a good grip of all this stuff. After extensive reading I am quite sure that I want to go 3ph AC, and the Azure Dynamics AC24LS with DMOC445 Drive System will probably be the way I will go (shopping around for prices now {I wish I'd done this six months ago while the Oz$ was a lot higher Image}).

My problem now is trying to understand the situation with batteries. In one of your previous replies you recommended a 40AH 312v (104 cell) TS pack. Is that like 104 qty of the TS-LFP40AHA as shown on the Blade EV website? Coz if it is my maths works it out to be over $5K US in batteries, and surely that can't be correct? Image
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Post by Johny » Mon, 23 Feb 2009, 22:49

Sorry Matt - sounds about right.
The alternative is to go Lead acid and expect only to get 2 years out of them before investing in Lithium (after 2 years) with hope the dollar has picked up by then. You can probably do Lead acid for AU$2000.

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Post by Tonic » Mon, 23 Feb 2009, 23:35

Would running the motor at 156vdc still give me reasonable performance and range (as well as half the battery cost)?
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Post by Johny » Mon, 23 Feb 2009, 23:53

Your range will always be dependent on kWh, not so much voltage. I didn't know that the AC24LS could run on 156V. If you just halve the number of any given TS cells then you are halving your range.

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Post by Richo » Tue, 24 Feb 2009, 02:17

Yeah I don't think it will work with half the voltage.
Too low for the controller.

$5k is cheap for batteries for an eV.
So the short answer is NO but the long answer is YES.
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Post by coulomb » Tue, 24 Feb 2009, 06:27

Richo wrote: Yeah I don't think it will work with half the voltage.
Too low for the controller.

Actually, the AC24LS Product Sheet says you can run the motor in delta (or maybe order a different version that is pre-wired in delta) and run it at 156v. You only get 3/4 the power, but there is no reason you can't run a pack at 312/sqrt(3) = 180v and get the same power as at 312v in wye configuration. Or anything between 144v (minimum recommended nominal voltage in delta) to 240v (maximum recommended nominal voltage in wye). I think they chose 156 and 312 because they are nice multiples of 12v (24v even).

So yes, you could go as low as 144v nominal (call it 45 cells), but 45 cells at 40AH would not be enough in Thunder Sky cells to meet peak battery demand. I wouldn't ask more than 5C from TS cells for acceleration (their pulse rating is 10C, but that seems like for a second or so, not the minute it might take to accelerate up a hill). 5C times 40A is 200A, which at 45 cells, could be as little as 45 * 2.5 * 200 = 22.5kW (Edit: assuming sagging to 2.5vpc at 5C), barely enough to maintain 100kph in a small vehicle. Also, the range would be low, perhaps 25km (less with highway speeds). So for the low voltage, you'd need larger cells, and lithium costs about the same per kilowatt-hour. You would save on BMS, but lose on thicker cables and higher current contactors, etc.

If you don't need much range, 45-56 60AH cells might do it, though Blade EV (according to the web site) skips that size (next size above 40AH stocked is 90AH).
Last edited by coulomb on Mon, 23 Feb 2009, 19:33, edited 1 time in total.

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Post by antiscab » Tue, 24 Feb 2009, 06:34

the AC24LS will either run off a 312vdc battery pack when the motor is wired in wye, or off a 156v battery pack when the motor is wired in delta.

performance on either is much the same.
have a look at the datasheet

and yes, johny is correct. range needs kwh which costs money.

when i said 104, i did indeed mean number of cells.
the AC24LS has slightly more power when run at the higher voltage in wye.
run at the higher voltage in delta, and it has *alot* more power.

40AH cells would be fine with 104 cells, but not with only 52 cells.

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Post by Johny » Thu, 26 Feb 2009, 17:27

I hadn't seen these before:
108V AC Motor and Controller kits
They also appear to carry SepEx motors and controllers for regen braking with DC.

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Post by Richo » Thu, 26 Feb 2009, 17:49

40kW going to enough?
So the short answer is NO but the long answer is YES.
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Post by carnut1100 » Thu, 26 Feb 2009, 18:02

can you run two motors off the same controller?
I would like to do something like having two motors, one for the front wheels and one for the rear to give AWD traction for snow, black ice, and gravel roads, the kind of conditions around where I live...

Would it be more efficient to run both motors all the time, with each having little work to do while cruising, or have one running all the time and the other only coming in when accelleration is required or when wheelslip is detected?

I would prefer to build something with AC and direct drive, no gearbox.

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Post by Johny » Thu, 26 Feb 2009, 18:06

No, you would need 2 controllers if the motors are not hard-coupled. But two controllers means they can be smaller and gives you very good possibilities for traction control under accel and braking.

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Post by Tonic » Mon, 02 Mar 2009, 21:13

After serious reflection on both my (lack of) knowledge in this field and with the resources I am willing to put into my first EV project, I have now decided to buy the 203-06-4001 from EV Motors. This will give me more money for the batteries which I will need to buy and thus give me greater range capabilities (and to get me up Mt Tamborine on the way home from work!). I want to order the motor this week. What else do I need to get? Will a controller come with the motor? If not where should I get one? Is there anything else that I need to think of at this point? Please help guys.
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Post by Johny » Mon, 02 Mar 2009, 21:23

Hi Tonic - no the motor won't come with a controller.

What voltage are you planning on running?
Are you going to use the gearbox?

Regardless, you will need (major parts):
--------------------------
Motor
Controller - it looks like you need a 600 Amp controller
Emergency cut-off switch
Main circuit breaker
Cable
DC-DC converter
Heater-demister
Batteries

And lots of little bits...

Lots more to come but they're the main bits - did I miss anything?
The controller looks like the next big decision and purchase.

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Post by Tonic » Mon, 02 Mar 2009, 21:32

Hi Johny,

To get max hill climbing power I guess I will run the motor at 120V. I intend to keep the gearbox that comes in the Excel as it is still in great condition and uses three of the mounts in the engine bay - which should make the motor easier to install and secure.

Some of the parts you have mentioned I should be able to buy at the local Jaycar store just down the road (I hope). I've already spoken to a couple of the guys there and they are interested and happy to help out where possible in getting whatever I need. I don't think that they supply controllers however (although I will need to confirm this). Is there a good site for getting controllers (or any other necessary parts) that I can look at now that you are aware of?
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Post by Johny » Mon, 02 Mar 2009, 21:53

Hi Tonic.
Great on keeping the gearbox - good move. It also saves you need a "reversing contactor" so will save you money and give you a few options when driving.

The controller really is going to be the next BIG decision. It is very important as to how the car actually drives. Your post should start attracting attention very soon and you should get comment from people running various brands. Your motor can also be overvolted to 144Volts so keep your options open on the controller. Adding 2 more batteries to your 120 volt system may come to be just-that-bit-extra that you need and it would be a shame if the controller couldn't handle it.

I will be very surprised if Jaycar can help with much of the big stuff but it's good that you have interested people there.

Kelly are one of the controller brands, some people like them, some don't.
Kelly

I am looking through my stuff now as I think there are better controllers out there.

Also check the links on the AEVA home page. The various state home pages have other links.


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Post by Johny » Mon, 02 Mar 2009, 22:22

Here is the other controller I saw recently:
LogiSystems Controllers

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Post by lithbattboss » Mon, 02 Mar 2009, 23:14

Tonic wrote: Hi Johny,

To get max hill climbing power I guess I will run the motor at 120V. I intend to keep the gearbox that comes in the Excel as it is still in great condition and uses three of the mounts in the engine bay - which should make the motor easier to install and secure.

Some of the parts you have mentioned I should be able to buy at the local Jaycar store just down the road (I hope). I've already spoken to a couple of the guys there and they are interested and happy to help out where possible in getting whatever I need. I don't think that they supply controllers however (although I will need to confirm this). Is there a good site for getting controllers (or any other necessary parts) that I can look at now that you are aware of?


Hi Tonic,
If you are planning on driving up Mt Tamborine on a regular/daily basis you will want to invest in the best performance lithium batteries you can afford. You will kill lead acids very quickly with the sort of current demanded from them for steep hill climbing. I believe Shaun Williams is on his 3rd set of lead acids in electric echo before slowly making the change to high discharge lithium.
http://www.electric-echo.com/lifepo4/index.shtml
From the last time I spoke with Shaun I recall being told a set of lead acid batteries in his car would typically last just over 12 months. When you consider the terain and hills around Upper Mt Gravatt where Shaun lives it doesn't even compare to Mt Tamborine.

As others here have already suggested it would be wise to increase the voltage to 144V (or even higher if possible) so as to keep the current as low as possible. This will also allow you to reduce the cable size   (less copper).

As far as Kelly controllers go, from what I have heard they are are really good company to deal with and they provide excellent service. If you read some of the e-bike forums you will see this for yourself. A company I have supplied my LiFePO4 cells to in Austria for the world's fastest production e-bike (all european designed and built) is using a programmable Kelly controller and so far the performance has been floorless (top speed of 97kph during testing from a 36V battery pack).
Last edited by lithbattboss on Mon, 02 Mar 2009, 12:19, edited 1 time in total.
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Post by Tonic » Tue, 03 Mar 2009, 22:46

OK. I just need to confirm the maths to ensure that I'm not going to get this wrong (sorry if it appears like a stupid question). Image

If I'm running the DC motor at 144V do I require 48 x 3V LiFePO4 batteries? (Qty = Total Voltage / Voltage per Battery).

Also, are Chinese / Taiwanese batteries good or bad in general?
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Post by Johny » Tue, 03 Mar 2009, 22:59

Correct. 3V per cell so 48 cells.
To my knowledge all Lithium (at least all that are used in EVs) cells are made in China, but yes, there are good and bad.

Thundersky appears to be the cells most often used in EVs.
There are 2 main types of Lithium cells - low current and high current.
Have a read of the batteries topics.

Depending on your motor/controller combination and thereby battery current you will probably need about 500 Amps continuously rated pack. That means something like 90Ah with 6C rating.

These people have attracted woody and my attention but you would be the first to try them in Oz:
EVPST Batteries

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Post by woody » Tue, 03 Mar 2009, 23:13

Your maths/electronics is good.

There are a few other things to consider:

The common controller (Curtis, Kelly) components have a voltage limit of 200V. Ask the supplier/vendor of your controller how many they recommend.
LiFePO4 are about 3.2 nominal and 3.65V when fully charged, up to 4.2 while charging.
The commonly available chargers only go up to a certain voltage.
Non-prime numbers can be arranged more ways.
Yuo might want a spare or two, or four to replace the 12V battery.

I have heard this is why some people have 40 (zeva), 42 (kearon), 45 (rod dilkes) cells.

Check out EV Album cars with Thunder Sky for numbers of cells and controllers.

As for good/bad - I think most customers are happy with their Thunder-Skys, they have an Australian distributor. They did piss off a few of their early customers with one group buy (see Wikipedia).

The other brands (EVPST, HiPower, ToPower) - I don't think they have been widely used in EVs.

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