Weber and Coulomb's MX-5

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Post by weber » Fri, 21 Oct 2011, 14:34

A bicycle bell mounted at the front grill with a piece of string going back to the driver? Image
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Post by evric » Fri, 21 Oct 2011, 14:37

What about a loud-mouth person walking in front with a white flag?..
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Post by Johny » Fri, 21 Oct 2011, 14:43

weber wrote: A bicycle bell mounted at the front grill with a piece of string going back to the driver? Image
Get real - it's an ELECTRIC car. Feed the battery pack into a doorbell:
DING DONG!

Edit: Hmmm - maybe more like DING dong. (The dong is the spring recovery.)
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Post by bladecar » Fri, 21 Oct 2011, 15:35

I noticed no air line on the air pipe at a couple of 'service' stations recently. I later asked did they not supply air anymore and he said that they keep the hose inside and you only have to ask for it.

That makes me think that they are protecting the line and gauge, but also they have an idea of whether you have bought something when you want to use the air.

With an electric car, this could become significant in the future if you get to use the air when you buy petrol.

I'm still toying with the idea of getting a nitrogen bottle for future use (since the Blade comes with nitrogen in its tyres). With a 3 month interval between nitrogen loss, I've yet to determine the cost of renting a bottle. With a few vehicles to keep track of, it might be worth it to have long intervals between fills instead of low tyre pressure (if the truth be told)

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Post by Jeff Owen » Fri, 21 Oct 2011, 16:38

Most EVs already have an onboard compressor (vacuum pump). With a couple of valves, hose and gauge, a "service station" is not required. Combined with a can of puncture repair spray, the spare tyre can be eliminated.

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Post by Electrocycle » Sat, 22 Oct 2011, 03:18

bladecar wrote: I'm still toying with the idea of getting a nitrogen bottle for future use (since the Blade comes with nitrogen in its tyres). With a 3 month interval between nitrogen loss, I've yet to determine the cost of renting a bottle.


these guys: http://www.atomicgas.com.au/ will sell you a bottle outright, and do refills by swapping.

They don't have any distributors in Qld yet unfortunately. (I'm one in Sydney)
They sell on Ebay too, and might be able to send one to Qld, but is possibly not worthwhile if it'll be difficult to get refilled
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Post by EClubman » Sat, 22 Oct 2011, 17:55

Seriously?
Nitrogen in your tyres is an expensive scam.
Compressed air is 80% Nitrogen, and is free at your local servo.
It will make bugger all difference to the following:
Rate at which tyres deflate over time.
Rate at which tyres oxidise over time.
Amount of extra Oxygen available to burn stuff in a fiery crash.
Fuel or Energy consumed per km.

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Post by Electrocycle » Sat, 22 Oct 2011, 19:07

the main benefit seems to be more pressure stability at different temperatures.
Varying moisture levels, etc in normal air can cause larger differences in tyre pressure in different conditions.
For a road car it's not that important - but people use it in race cars for more predictable control over tyre pressure.
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Post by weber » Sat, 22 Oct 2011, 19:41

Jeez guys,

This is our build thread. Enough's enough. Please start a thread elsewhere to discuss petrol stations and tyre inflation. Apart from Jeff Owen's little gem, what they even have to do with EVs escapes me.
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Post by bga » Thu, 27 Oct 2011, 16:44

Hi Weber & Coulomb.

I had a power steering pump that sounded a bit like that. The return oil cooler flexi line had become loose at the radiator and was sucking a bit of air (as well as dripping) It made the oil frothy like a milkshake and caused horrible noises to come from the pump, like it was about to eat the gear and self-destruct.

I was wondering if the horizontal orientation could be a factor.
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Post by weber » Sun, 30 Oct 2011, 22:30

The Brisbane AEVA convention at Parliament House on Friday and festival at King George Square on Saturday were a great success. Many thanks to all those who helped make them so, particularly our wonderful organisers Simone, John, Graeme and Don.

Some months ago we decided that the MX-ϟ should at least look finished for the festival and be able to be driven there, even if not allowed to do so due to not being registered. But the closer the festival approached the more obvious it became that we were a long way short of our goal.

Over the past few weeks, family and friends have given a great deal of their time to try to achieve this aim. My parents Margo and David Keenan put in many hours, as did my son Hunter Keenan and wife Janelle Briggs. Jeff Owen (Newton) and Dr Mike Van Emmerik (Coulomb) who were already contributing so much to this project redoubled their efforts during this period. I must also thank their wives Raewyn Owen and Margaret Van Emmerik for freeing them up to work on the MX-ϟ.

This all culminated in one last concerted effort by Coulomb and myself starting immediately after the Convention on Friday. Newton, who had his own vehicle to prepare, turned up at about 10 pm and the three of us worked into the wee hours of Saturday morning.

It's all a bit of a blur but think it was around 1 am that I was crimping up the last high voltage cable while Coulomb was booting up the software and Newton was lowering the car off its stands from under us. Coulomb did some very clever stuff adapting the existing wiring loom and fuel-cutoff relay to control the contactors for battery pack breakup and controller precharge from the ignition keyswitch, so we hardly had to run any 12 volt wiring.

The last problem that could have killed the whole thing was a software problem. Coulomb eventually solved it by rebooting Microsoft Windows. Sound familiar?

I hasten to add that Windows is not in any way involved in the actual driving of the car, but only in allowing us to communicate with the Tritium controller to configure and monitor it. Image

Coulomb and Newton left for home about 1:30 am to grab a few hours sleep before the festival. I continued working to put all the covers back on, clean and tidy things up, add warning stickers, pack things for the festival etc.

When the tow truck driver arrived at 7:00 am I had just finished washing and drying the car, having been up all night. When he asked "Does this one go?", it gave me enormous pleasure to say "Yes, it does" and then, for the first time in two and a half years simply turn the key and drive her, even if it was only up the ramp onto the back of the truck.

And it gave me great pleasure again, when I rolled her off the back of the truck at King George Square and Simone asked if I needed a push, to be able to say "No. It goes!" and to drive the MX-ϟ slowly through the square and into her display space for the day.

The photo below shows the MX-ϟ in King George Square with the beautiful Albert Street Uniting Church in the background (thanks Jeff). That's me in the white shirt.

Image

But below is my favourite photo of the day. This girl, about 12 years old, was apparently on a dare from her friends (who were behind and to the left of the camera position) to get into the driver's seat. She only made her moves when she knew Coulomb (green shirt) wasn't looking, and she kept turning around and grinning at her friends. But she didn't know about me.

Image

I had some surprise visitors for the day, my cousin Laurie who I hadn't seen for 30 years and my Uncle Rick who made it just in time to see me drive the the MX-ϟ back onto the truck to go home.

And once home, although all I wanted to do was sleep, I was glad to learn that mum had organised a party and invited all helpers. It really was something that deserved to be celebrated. The champagne flowed and toasts were made.

But I wasn't the only tired one, so it wound up at around 8 pm and I hit the sack. Hard.

[Edit: Grammar and added aftermath]
Last edited by weber on Mon, 31 Oct 2011, 05:14, edited 1 time in total.
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Post by Johny » Mon, 31 Oct 2011, 13:48

Fantastic effort MX-5 team! You're right weber - priceless photo.

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Post by a4x4kiwi » Mon, 31 Oct 2011, 14:45

Brilliant effort! I wish I could have been there!
I love how the family really helped out and celebrated your success!
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Post by woody » Mon, 31 Oct 2011, 15:15

Great Work! Nothing like a deadline to motivate you :-)
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Post by coulomb » Mon, 31 Oct 2011, 15:40

The movie of the MX-lightning driving onto the tilt tray truck at the end of the festival (only because it isn't registered; it would have been capable of driving the 7 km to and from the laboratory even without a BMS).

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Post by weber » Mon, 31 Oct 2011, 16:54

Thanks guys. Yes, there's nothing quite as important as a supportive family in anyone's life. I probably wouldn't have even been in a position to start such a project without that background. And thanks to you three guys Johnny, Mal and Woody, plus ACMotor, Richo and others, for all the great support and advice you've given Coulomb and me over the years.

I'd also like to take this opportunity to thank those who may not have been much involved in the madness of the past month or so, but made significant contributions to this project in the past, in particular my friend and former employer Ross Pink (Mho) for advice and the example of his industrial-AC based eVan, my friend and former co-worker Warrick Beatie (Pascal) for the beautiful adapter plate and the design of the taper-lock flywheel, and James Kennedy of Tritium Pty Ltd for advice and support above and beyond that expected of any component supplier.

And also thanks to those who may feel they only contributed one day of their time, but every bit counts when you're running up to a deadline: my Uncle Dudley Ford and my co-teacher (Photovoltaics) David Chaplin. I will always be able to point and say "There's the part you made." Thanks.

Thanks also to my sister Anne Keenan for wonderful food, and her boyfriend John for assistance in reassembly and advice re hydraulics.

Now we just have to get back to finishing that Battery Monitoring System and installing the rest of the batteries and contactors so we can get her registered.

For more of the MX-ϟ and the EV festival in general, see Coulomb's wonderful photographic record beginning here:
http://forums.aeva.asn.au/viewtopic.php ... 575#p34764
Last edited by weber on Thu, 03 Nov 2011, 09:20, edited 1 time in total.
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Post by weber » Mon, 31 Oct 2011, 18:13

In case anyone has the urge to show the above story and photos to someone else, I've made a tiny URL that is hopefully easy to remember.
http://tinyURL.com/mxlightning
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Post by weber » Wed, 02 Nov 2011, 00:11

bga wrote: Hi Weber & Coulomb.

I had a power steering pump that sounded a bit like that. The return oil cooler flexi line had become loose at the radiator and was sucking a bit of air (as well as dripping) It made the oil frothy like a milkshake and caused horrible noises to come from the pump, like it was about to eat the gear and self-destruct.

I was wondering if the horizontal orientation could be a factor.

Hi bga,

I tried earlier unbolting it from its mounting and holding it in my hands as it was running, mainly to see if the mounting was causing or conducting the noise. It wasn't. But at the same time I tried tilting it at various angles. That made no difference either. And we don't have an oil frothing problem. But thanks for the thought.

The major noise turned out to be a mechanical resonance of the motor casing. It rings like a bell, and this resonance happens to be excited by the no-load speed when powered at a very specific voltage around 12 volts. By using a PWM buck converter operating at 20 kHz or more (to avoid adding its own noise), and turning the voltage down to 11 V or less, we avoid this resonance.

It is still noisier than I would like, but acceptable. I'll look for a late model Astra pump in future, or a vane pump rather than a gear pump.

We will implement the "stealth" option by providing the driver with a knob to turn the PS pump speed down even further -- all the way to zero if desired. Of course then the driver will need to use the "armstrong" power steering. Image
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Post by coulomb » Fri, 04 Nov 2011, 23:03

We suspect noise on the 12 V (auxiliary battery) system is the cause of our BMS communicatoins problems. We can hear a distinct buzz on the AM radio in key-switch ON position which is not pressent in auxiliary position. There is also 1-2 volts peak to peak of noise measurable by DSO at the cigarette lighter.

The MX-ligntning video has been posted; see this post.
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Post by coulomb » Sat, 05 Nov 2011, 02:13

It turns out it was the set of EV200s we have installed (6 at present, 20 in the final design). Just one doesn't seem to upset the BMS comms much, but 5 or 6 of them (we use one to bypass the pre-charge resistor) does.

Well, it upsets comms from the last BMS to the netbook, and we likely have to fix this before we can find any other noise issues, if there are any.

This post suggests a small 22 uF capacitor across the coil/economiser:

http://electric-vehicle-discussion-list ... 41517.html

Unfortunately, this will increase the already high inrush current (3.8 A per contactor), so we might use an inductor as well. But that will increase the turn-off voltage spike. Some experimentation will be needed.

Perhaps this is a disadvantage of a high voltage design with many ELV breakup contactors. Perhaps no-one has attempted to run 20 EV200s with economisers in one vehicle before.

[ Edit: This post also mentions the problem: Are EV200 Contactor coil leads polarized. ]
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Post by Nevilleh » Sat, 05 Nov 2011, 12:03

Congratulations on your achievement in making it to the show and I am pleased to see you are well on the way to tracking the source of interference in your BMS. I tried mine on the road yesterday and it works just as well as in the shed, so I am very relieved that motor controller noise doesn't affect it. All my contactors are just simple 12V solenoids, so no problems there.
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Post by Renard » Sun, 06 Nov 2011, 16:17

"It turns out it was the set of EV200s we have installed (6 at present, 12 in the final design). Just one doesn't seem to upset the BMS comms much, but 5 or 6 of them (we use one to bypass the pre-charge resistor) does. "

Thanks for uncovering this possible problem, nobly serving as voluntary minesweepers.

I checked my EV200s and indeed found a 20kHz pulse with associated higher frequency ringing. The ringing was eliminated, and the pulse amplitude reduced, by the addition of a few uF of capacitance across the coil leads.
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Post by coulomb » Sun, 06 Nov 2011, 17:03

[ Actually Weber posting: ]

I must point out that the EV200 noise is not the problem with our BMS comms, as we did not have any EV200s in place when we first noticed the comms problems, and at that time the problems only occurred when the motor was being driven or regenerating.

The EV200s only cause a problem when the netbook, which we are using to communicate with the BMS, is being powered from a DC-DC converter plugged into the cigarette lighter socket. And I note that we are not currently using isolated comms from the last cell as we were when we first noticed comms problems.

On a completely different note: A number of people commented on how shiny the MX-ϟ was at the festival and assumed we must have spent some time polishing it just before the festival. In fact all I did was wash it with dish-washing detergent and water, then hose that off and dry it. In fact the gloss dates from 2.5 years ago! Although of course the car has been under cover most of that time.

2.5 years ago I used a two stage product called "Liquid Glass" which I can't recommend too highly. There I go, giving away our secrets again. Image

This post was actually from Weber. I guess I'll have to learn to log out when I use one of Weber's computers to make AEVA posts. - Coulomb
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Post by coulomb » Sun, 06 Nov 2011, 17:29

Renard wrote: The ringing was eliminated, and the pulse amplitude reduced, by the addition of a few uF of capacitance across the coil leads.

Thanks! I'm guessing we could put through-hole capacitors inside the economisers:

Image

They could possibly go across one of the ovalled capacitors, or using two of the three holes circled in yellow, depending where the tracks go. I'm thinking about 10uF 35 VW tantalum capacitors, although ordinary electrolytic capacitors might be more surge tolerant.

The advantages of putting the capacitors there are that they are close to the source of the problem, and are after the SMD inductors (the two large components under where the 12 V lead comes in). That way, the inrush current should be no larger than before.

The disadvantage is that we have four contactors pretty much buried inside two tightly packed contactor boxes, and it will be a pain removing the boxes and the contactors from the boxes to get at the economisers.

Edit: capacitors have two leads Image
Last edited by coulomb on Sun, 06 Nov 2011, 06:32, edited 1 time in total.
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Post by bga » Sun, 06 Nov 2011, 19:56

Hi coulomb,

I will likely have the same problem.

Those boards in the EV200 are not very big.

Would it be possible to quarantine the power supply for the contactors so that all the noise can be caught before it gets out onto the 12V bus?

I was thinking a Pi filter on the battery side between the ground and +12 lead to the contactor drivers.

BTW, well done for getting the car to a drivable state.
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