Weber and Coulomb's MX-5

Post up a thread for your EV. Progress pics, description and assorted alliteration
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Post by unheardofinstruments » Tue, 17 Sep 2013, 15:48

ooh er... that does look awfully close to complete guys, well done, ?how was it to drive? I have been in some awkward positions making battery boxes and during under dash contortions (unfortunately the electrics in my donor looks like an insane white tailed rat installed the stereo) ...and I never wear undies... lucky I live on a dead end road I guess.

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Post by weber » Tue, 17 Sep 2013, 16:52

unheardofinstruments wrote:?how was it to drive?

Oh we can't drive it on the road. Image It isn't registered yet. Image But our evil twins Maxwell, Faraday and Poundal report a couple of problems that have to be sorted before we call the engineer. One with going, the other with stopping.

The problem with going occurs if the accelerator pedal is pushed too rapidly. Our ICE-like accelerator-backoff regen-braking function determines both torque requests and rpm requests that are sent to the Tritium WaveSculptor (motor controller). When the requested rpm ramps up too rapidly, such that the torque used to get there is limited by the available battery voltage, then the Wavesculptor refuses to go into overspeed (field-weakening) and thereby limits the motor to about 3700 rpm. If rpm requests ramp up more slowly it will move seamlessly into the overspeed region and go as high as we're game to take it (5000 rpm so far). Tritium are looking into this problem.

The problem with stopping is that it doesn't do it quickly enough unless you use a lot of force on the brake pedal. The vacuum boost system seems to be working just fine, and we already upgraded to the largest diameter discs that fit within the standard 14" wheels (250/255 mm). But these were second-hand disks and pads and the disks (rotors) got pretty rusty when we couldn't drive it. So we've ordered new disks and new high friction pads (Hawk HP Plus) from MX5mania, but they were out of stock and won't be here for a couple more weeks.

The Hawk HP Plus pads have a friction coefficient about 25% higher than standard pads, and they do it from cold unlike race pads, but they have the drawbacks of making a lot of dust and possibly squealing when used lightly. Apparently the bedding-in process is critical, and must occur on a freshly-machined disk surface.
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Post by jonescg » Tue, 17 Sep 2013, 16:54

Guys,
I am pleased to see it finally nearing a state of readiness. Don't let the quality drop now that you're on the home stretch - easy to do when you just want it done.
Question about your contactor boxes - why boxes? Seems like an awfully inefficient use of space. Surely they could be packaged better?
Oh, and well done on doing the destructive testing on the heating elements before it was installed. Good to know what might happen Image
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Post by weber » Tue, 17 Sep 2013, 20:13

jonescg wrote: Guys,
I am pleased to see it finally nearing a state of readiness. Don't let the quality drop now that you're on the home stretch - easy to do when you just want it done.
Good advice, thanks. I must admit it is sorely tempting. But I have two brilliant engineers working with me who won't let that happen. Is there some area where you think we might not realise we're letting the quality drop?
Question about your contactor boxes - why boxes? Seems like an awfully inefficient use of space. Surely they could be packaged better?
I'm guessing you're assuming we always have one contactor (and nothing else) per box, based on the photo we posted most recently, which was an unusual case. I don't think you could call the following an inefficient use of space. Image In any case, what did you have in mind as an alternative?

Image
Oh, and well done on doing the destructive testing on the heating elements before it was installed. Good to know what might happen Image
Thanks. I didn't actually expect anything to go wrong with the ceramic elements, having believed the "self-regulating" hype and having previously done successful stagnation testing at 200 Vdc on one half of one element. I was more concerned about how the silicone would hold up. Coming at the end of the day, it was pretty depressing when it went pop with the full (2 halves in series) element on only 360 Vdc.

Now that I think about it, the pop occurred when we had the heater stagnating in a vertical orientation (we had previously been blowing air thru it with a desk fan) so, due to natural convection, the lower half of the element would have been cooler and therefore had lower resistance than the upper half. This would have caused a voltage imbalance between the two halves such that the upper half may have had significantly more than 200 V across it, and it may have reached a significantly higher temperature than it would have when stagnating in the horizontal position it adopts in the car, where natural convection passes through the fins. A good thought.
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Post by jonescg » Thu, 19 Sep 2013, 01:27

I can't think of anything being sub-par specifically - just remembering my own experiences with my first bike. I really rushed it towards the end as Race One was fast approaching. Things like using insulation tape when I should have used heatshrink, or gluing components to a board and soldering wires to each leg instead of paying the $80 and getting a PCB made up. Lots of stuff I did in the name of expedience, resulting in a functional bike which looked pretty ratty. I'm sure you guys won't be travelling that route.

As for the contactor boxes you have certainly filled some of them, but I can still see extra space in there Image. I was just thinking since they are hermetically sealed anyway, you could probably just mount them to a chassis and run the 12 V wiring through a wiring harness back to the controls. Since you have so many separate boxes of cells I can see that a neat, self-contained unit isn't always practical.

Don't stop now!
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Post by weber » Thu, 19 Sep 2013, 04:30

jonescg wrote:Things like using insulation tape when I should have used heatshrink, or gluing components to a board and soldering wires to each leg instead of paying the $80 and getting a PCB made up. Lots of stuff I did in the name of expedience, resulting in a functional bike which looked pretty ratty. I'm sure you guys won't be travelling that route.

Certainly not! Image We'll make sure all our ratty stuff like that is well hidden. Image
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Post by coulomb » Mon, 23 Sep 2013, 04:38

Completing the DCU wiring

Here I am completing the DCU wiring:
Image   Image

As you can see, we're using a rather technical method of assembly here; it's based on this thing called the offcut of masonite. [ Edit: it's actually MDF. ] I don't think we even cut it to size; Weber found one that seemed about the right size and told me to use that. It has the sound deadening behind it, so we can just drill holes in the thin wood, and put electrical tape behind it. It all gets covered by a piece of metal that covered the original engine ECU (the only ECU in this 23 year old car). The plan is to use 2 or 3 self tapping screws to hold the masonite to the floor of the car, using spacers. [ Edit: We'll use my Sili-Cone (TM) technique, since tape by itself will peel off with time. ]

You can see the two Driver Control Units (DCUs), one for each half pack, and two relays with diodes for logic and back-EMF protection. The relays control a group of contactors that we're calling the battery contactors. These link the various ELV strings of cells into one half-pack.

I believe that this is where I received some nasty bruises to my ribs:
Image

You can rest assured that the week after, I always had a comfortable Bananas in Pyjamas (TM) pillow between my ribs and the door sill.

We used this professionally drafted circuit diagram:

Image

and also this spreadsheet of connections:

Image

Image

We've updated the DCU firmware to drive the various sets of contactors. As always, the firmware is freely downloadable; there are instructions earlier in this build thread. Just today Weber got the DCU code all working, so we can now charge without the key in the keyswitch, and it's not possible to drive off when one of the chargers is powered up.

The heater is working well enough for registration, or we certainly hope so.

We've had the tachometer moving, and a few changes to the gauge1 constants should have its scale correct.

Edit: as always, use the right mouse button and "View image" for a more readable version of the larger images.
Last edited by coulomb on Mon, 23 Sep 2013, 06:00, edited 1 time in total.
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Post by Renard » Mon, 23 Sep 2013, 18:57

coulomb wrote:

As you can see, we're using a rather technical method of assembly here; it's based on this thing called the offcut of masonite. [ Edit: it's actually MDF. ] I don't think we even cut it to size; Weber found one that seemed about the right size and told me to use that. It has the sound deadening behind it, so we can just drill holes in the thin wood, and put electrical tape behind it. It all gets covered by a piece of metal that covered the original engine ECU (the only ECU in this 23 year old car). The plan is to use 2 or 3 self tapping screws to hold the masonite to the floor of the car, using spacers.


MDF down on the floor? It had better not get wet at all. Or have I not understood the structure correctly?
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Post by BigMouse » Mon, 23 Sep 2013, 23:39

Renard wrote:MDF down on the floor? It had better not get wet at all. Or have I not understood the structure correctly?


Personally, I think wood products of any kind should be outlawed for EV conversions right in the NCOP14. Wood (in the form of MDF or otherwise) tempts too many people because it's easy to shape, but it's completely unsuitable to use in cars, especially around electricity. Whenever I see plywood floors on battery boxes in EV album, I cringe.

Have another look at that mdf after a year of moisture variations and vibration and see what condition it's in.

Plastic (HDPE, Delrin, or similar) or aluminium would be better options in my opinion. Find a plastics retailer or sign shop near you, most of them sell offcuts and could recommend a particular type for that application. Some are more brittle than others for example.

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Post by 4Springs » Tue, 24 Sep 2013, 03:20

BigMouse wrote: Personally, I think wood products of any kind should be outlawed for EV conversions right in the NCOP14. Wood (in the form of MDF or otherwise) tempts too many people because it's easy to shape, but it's completely unsuitable to use in cars, especially around electricity. Whenever I see plywood floors on battery boxes in EV album, I cringe.

As someone who has used quite a lot of wood in my conversion, I'd point out the benefits:
Cheap, light, strong, flexible, low conductivity of both heat and electricity, easy to work and readily available. Most wood is waterproof. If it isn't then you can paint it. Also quite resistant to chemical spills (in my experience, no hard data on that claim though!).
So what makes it competely unsuitable? Because it is flammable perhaps?

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Post by BigMouse » Tue, 24 Sep 2013, 04:36

4Springs wrote: As someone who has used quite a lot of wood in my conversion, I'd point out the benefits:
Cheap, light, strong, flexible, low conductivity of both heat and electricity, easy to work and readily available. Most wood is waterproof. If it isn't then you can paint it. Also quite resistant to chemical spills (in my experience, no hard data on that claim though!).
So what makes it competely unsuitable? Because it is flammable perhaps?
Wet wood is a surprisingly good conductor of electricity. I've read about people who've had wood start steaming from current flowing through it when wet (don't remember where I read it, but it was definitely in an EV).

Wood changes shape and size when exposed to moisture and humidity, especially over many humid/dry cycles.

Mounting holes quickly get elongated enlarged due to vibration and changes in shape due to humidity and temperature.

I've never come across waterproof wood. Plywoods and particle board are held together with water soluble adhesives. Even straight timber absorbs water from the cut edges. Painting helps, but it is an incomplete seal and still doesn't address the hole elongation issue.

Wood absorbs chemicals and it's impossible to get them out once they've soaked in. Organic fibers don't like solvents. Anything chemical that would effect a paint coating on the wood would also effect the wood itself, likely much faster.

When trying to present EVs as the way of the future to the general public, the presence of wood in a conversion makes it appear very "backyard", low-tech, and old. When's the last time you saw wood in a car other than as purely cosmetic trim? It conjures up images of old boats, Pre WWII airplanes, or cars from the early 1900's.

Also, it's flammable. ;-)

In my opinion, for the amount of effort that needs to be put in to making wood suitable, you might as well do it with a more suitable material.

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Post by BigMouse » Tue, 24 Sep 2013, 04:38

EDIT: Please delete double post. Forum had a hiccup while trying to post my reply above.
Last edited by BigMouse on Mon, 23 Sep 2013, 18:41, edited 1 time in total.

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Post by weber » Tue, 24 Sep 2013, 05:07

Rather than have the slightest hint of un-quality, I have just spent the last several hours making and installing a replacement backing board made of 3 mm clear polycarbonate, which can be seen in this photograph (if you look really carefully).

Image

And yes, I'm aware there's still some supporting of wires needed. Image

However I would like it noted that the previous backing board was 3 mm melamine-coated MDF. I told Coulomb this when I saw he had described it as "masonite". Melamine is hard, waterproof and fire resistant. And there was no voltage on it greater than (an appropriately fused) 12 volts. And there was no way it was going to get wet.

This board, containing the "twin brains" of the MX-ϟ, is installed where the original ECU was installed, at the end of the passenger footwell, at a 45 degree angle where the floor curves up to become the firewall. A metal cover goes over it, and then the carpet, so you don't even know anything's there.
Last edited by weber on Mon, 23 Sep 2013, 19:22, edited 1 time in total.
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Post by jonescg » Tue, 24 Sep 2013, 05:43

Polycarb is the shiz. It doesn't shatter (unlike acrylic aka Perspex) it's non conductive (unlike aluminium) and it's arc and flame retardant (unlike Delrin). Delrin burns like crazy, so don't use it in battery packs - go for Polycarb.

Downside of polycarb is the HCl that is released when it's exposed to an oxidizing flame. But it takes a thread nicely, drills nicely and is easy to bend. WIN.
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Post by BigMouse » Tue, 24 Sep 2013, 05:59

I agree, polycarb is a much better choice. The ECU spot seems like a handy location.

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Post by weber » Tue, 24 Sep 2013, 06:33

BigMouse wrote: The ECU spot seems like a handy location.

Yes. It has allowed us to repurpose wires in the existing loom for almost every 12 volt signal we need. Here's what the cover looks like.

Image
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Post by Jeff Owen » Tue, 24 Sep 2013, 07:59

BigMouse wrote: Wet wood is a surprisingly good conductor of electricity. I've read about people who've had wood start steaming from current flowing through it when wet (don't remember where I read it, but it was definitely in an EV).
Why would you want to have a current flowing through wet wood? Obviously, for this to happen a fault would have to occur and the result would be far less dramatic with wood than if this happened with a metal or carbon fibre structure. Maybe we should ban these materials from EVs.   
Wood changes shape and size when exposed to moisture and humidity, especially over many humid/dry cycles.
With proper design and epoxy coating, this is simply not correct.

Mounting holes quickly get elongated enlarged due to vibration and changes in shape due to humidity and temperature.
This could only occur with bad design and/or poor workmanship.
I've never come across waterproof wood. Plywoods and particle board are held together with water soluble adhesives. Even straight timber absorbs water from the cut edges. Painting helps, but it is an incomplete seal and still doesn't address the hole elongation issue.
Epoxy resin is very effective in waterproofing wood. You wouldn't expect a steel car body to be durable without paint, why would you expect wood to survive without suitable protection. Marine and exterior plywoods are made with waterproof glues. As I stated earlier, hole elongation is just poor engineering or workmanship.
Wood absorbs chemicals and it's impossible to get them out once they've soaked in. Organic fibers don't like solvents. Anything chemical that would effect a paint coating on the wood would also effect the wood itself, likely much faster.
I am not sure what chemicals you are referring to, but it is just common sense not to expose wood, or any other material, to damaging chemicals.
When trying to present EVs as the way of the future to the general public, the presence of wood in a conversion makes it appear very "backyard", low-tech, and old.
Not all of us feel the need to try and present EVs as the way of the future. And for some of us, our cars are "backyard", low-tech and old. What's wrong with that.

When's the last time you saw wood in a car other than as purely cosmetic trim?
Last night in the Singapore F1 Grand Prix. Formulae One cars contain wood. Morgans are also still built with a structural wooden frame.
It conjures up images of old boats, Pre WWII airplanes, or cars from the early 1900's.
Plenty of new boats, including high performance racing boats are built from wood. The WW2 Mosquito bomber was built from wood and was faster than the Spitfire fighter. Wood has certainly been used structurally in cars more recently than the early 1900s. Marcos and Morgan are marques that come to mind.   
Also, it's flammable. ;-)
It may well be, but I had some machining carried out in Brisbane by a company that supplies to at least one of the airliner manufacturers, and their new building was built with laminated timber full span beams. The reason given was that insurance was cheaper as timber beams perform better than steel ones in the event of a fire.
In my opinion, for the amount of effort that needs to be put in to making wood suitable, you might as well do it with a more suitable material.
I disagree.
Last edited by Jeff Owen on Tue, 24 Sep 2013, 07:37, edited 1 time in total.

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Post by BigMouse » Tue, 24 Sep 2013, 16:48

I was responding to the reply above mind regarding conductivity and chemical resistance. Obviously you wouldn't want current to flow through wood.

I guess I'm approaching my EV conversion with a different philosophy. There's nothing wrong with doing a "backyard" low-tech, old EV conversion, as long as it's safe. My first one was exactly that with an old forklift motor and used batteries (though I still didn't use any wood).

I don't think Weber and Coulomb are aiming for such a conversion though.

Speaking of Weber and Coulomb, sorry for the sidetracking.

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Post by weber » Fri, 27 Sep 2013, 01:03

This is the last contactor box for the MX-5. It's the "B2" contactor box, which is the main contactor box for the "B" half-pack. It will be installed under the bonnet.

It contains the "MID" contactor which will separate the two half-packs any time we don't require traction, including during charging. This doesn't matter very much at the moment since the two half-packs are in parallel, but when we go to the series configuration this will be important to avoid exceeding the charger insulation rating. It's coil is driven in parallel with the motor-controller precharge contactor's coil, so it's considered a TRACTION contactor. The other two are BATTERY contactors.

One is the contactor that breaks the under-bonnet battery box into two ELV segments. The designations WHT and GRY refer to the colours of the two Anderson connectors for those two segments.

The other is the "B-" contactor which is the negative main contactor for the "B" half-pack. The positive main contactor "B+" is in contactor box B3 at the rear of the car, close to the most positive terminal of the "B" half-pack.

Image Image
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Post by coulomb » Sun, 29 Sep 2013, 14:48

The MX-5 had a brake update today in preparation for the registration test on Tuesday. It has new rotors and pads all around.

Image   Image

As you can see, the new rotors are lovely and shiny. Made in Australia; let's hope we can still buy locally made car components in a few year's time.

The update went reasonably smoothly, except that one of the pistons was stuck. This took some time and frustration to fix.

The theory is that the poor braking performance may be the result of that dark film on the rotors, which looks like a coating of graphite. This coating may have gone away with regular use, but as it was, it was unlikely to have impressed the engineer.
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Post by coulomb » Sun, 29 Sep 2013, 15:14

The wiring of the DCUs is now complete:

Image

It may look like a jungle of wires and optic fibres, but it's a vast improvement over what it was. The silicone over the diode leads is due to a brain spasm on my part. I forgot that Weber had already installed a neat polycarbonate sheet under the metal cover, so nothing (like the diode leads) could short out. It's mostly removed now.

The second purple lead now goes up to a CAN-ethernet bridge, which we found fits nicely between the air conditioning evaporator and its blower, behind the glove box, which is right above the DCUs in the passenger side foot well.

We like to keep this bridge so we can run a netbook (small laptop) and get telemetry from the motor controller. As it turns out, this came in rather handy very soon.
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Post by coulomb » Sun, 29 Sep 2013, 15:38

With the brakes recently updated and a registration test coming up soon, we really needed to test the MX-5 on the road. We obtained a dealer's plate for the weekend. Thanks to Jeff Owen for bringing them over in his EV. I think that's 4 EVs at the Weber Wigwam, including a small scooter that has mysteriously appeared since last EV day.

Image   Image

We're both wearing our MX-lightning caps, even though it's night time. Hey, we're geeks, OK? There is the standard driving crew on the right: one driver and one computer operator. Weber didn't want to bring the computer, but I thought it would be handy. Well, it turns out we have a new gremlin, which means we have to reset the motor controller now and then to clear some serious errors. We suspect the auxiliary battery, since some errors popped up while still in the garage doing heater testing; the high 12 V load of the blower motor may have caused the 12 V system to glitch. It could also be because we're now feeding the Driver Control Units (DCUs, like Electronic Control Units but programmable) from a different source, so they are "always on". This allows us to charge with the keyswitch off. It's nice now that when we want to charge, we can just plug in the charger, and it starts charging (no reaching down to a tiny toggle switch in the passenger foot well any more).

Image   Image
After consulting multimeters measuring auxiliary battery voltage and charge current, we decided that for reasons unknown, the DC/DC (a 15 V 15 A adjustable MeanWell power supply) wasn't putting much current into the auxiliary battery. We'd let it run low again today, due to a misunderstanding; it must have gone down to about 9 V since the contactors started clattering. (The contactors would drop out because the voltage was low, the auxiliary battery would recover a little, and/or the economisers would work a bit harder, so the contactors would pull in, and the cycle would repeat several times per second. With half a dozen contactors connected (one half-pack only so far), it got our attention. Before today's incident, the auxiliary battery had run low many times before, since for a lot of that time we didn't have the DC/DC running. So we know that the auxiliary battery was weak. It looks like one DC/DC wasn't enough.

Jeff Owen suggested using the second DC/DC. It's wired in on the extra low voltage side, but not on the haz voltage side. The B pack is there, but two of the contactor boxes are not wired in yet. There are a few hours work needed to get those finished, and we've never charged the B half-pack, and we've never paralleled the two half-packs. So could we do something dodgy and temporarily wire the B side contactor box (for DC/DC, charger, and heater) to the A half-pack? It would mean sacrificing some crimp connectors (since we don't know the final length, and in any case the final length would not reach), and we're running low on those, so what to do? Jeff spotted some yellow 8 mm crimp connectors. These are designed for up to 6mm diameter wire (about 4 mm^2, from memory). Our wire is 16 mm^2 (that thin because of our relatively high voltage). We finally decided to use about a quarter of the strands, peel the rest back, and tape over it all. This would be completely unacceptable for traction wiring, but this only had to handle the less than one amp of the DC/DC, and the less than 5 amps of the heater. This had the advantage of being able to use the second heater core without messy clip leads in the 12 V auxiliary box as well. So we did that; Weber managed to squeeze two extra lugs onto the busiest contactors in the busiest contactor box.

At first there was no improvement. Of course! This DC/DC was never used, so it was never adjusted for voltage. So they would not be sharing current properly. It turns out that the second DC/DC didn't have a 20 A fuse on its output either. So we adjusted the voltage of each DC/DC to as close to 14.00 V as we could. We ended up within about 3 mV.

At last, we could run the headlights, power steering pump, coolant pump, and heater blower at the same time, and not have terrible voltage sag. So that's one more problem out of the way.

[ Edit: Added text re caps, squeezing lugs into busy box ]
[ Edit: blanked plate ]
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coulomb
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Weber and Coulomb's MX-5

Post by coulomb » Sun, 29 Sep 2013, 16:13

Finally, with legal plates, Weber and Coulomb were able to drive the MX-5 on bitumen for the first time:

Image   Image

It's a bit dark to see, but the front wheels are on bitumen there. Of course, the MX-5 has been on short test drives before, but driven by our evil twins.

The second photo shows the tacho working; I forgot to mention this in previous posts. It was wired up days, but never seemed to work, so Weber tasked me to research some possibilities. It looked like it might need a pull-up resistor, and the Tritium DCU has one, but maybe it needed a stronger one. It turned out that there is a bug in the standard DCU code for driving the tacho, which causes a 6.5536 second delay from first pulses to the tacho actually moving. (Real Hackers (TM) will recognise that number; the tacho runs on a 10 kHz timer). It's an easy fix. There is still an issue with jerkiness of the tacho, which is worse for us because we have a 4 cylinder donor vehicle.

So what was the first drive like? Well, terrible, actually. There was the reset gremlin, the brakes didn't feel much better, and the power was anaemic.

We received a clue about the first problem accidentally. When attempting to adjust the brake vacuum setting, we turned off the water pump so we could hear the vacuum pump. (The power steering pump was off by then too). Somehow, we did the next drive without the cooling pump turned on, and discovered a new motor controller limiter: "sink". When this label came up, we initially thought for a moment what this might mean, then both exclaimed together "Oh s#1+!". Sink likely stands for "heatsink over-temperature". We had forgotten to re-connect the coolant pump after fiddling with the vacuum pump. A minute under the bonnet fixed that.

The IGBT temperatures had been climbing up into the sixties, which I thought I hadn't noticed before; this should have been a clue. But it was interesting that we didn't get any motor controller errors up to that point, and they started again as soon as the coolant pump was running. The coolant pump is close to the motor controller. So maybe some spikes are getting from the coolant pump to the motor controller, possibly through the 12 V system. Maybe the weak auxiliary battery is allowing more glitches through by being a higher impedance.

As for the second problem (brakes not feeling much better), this is only to be expected with new brake pads. Only driving them and using the brakes a lot will bed them in. Already, with a few heavy brakes (thanks, Jeff!) and driving around Weber's hilly area (in the foothills of Mount Coot-tha), they do seem to be improving a little already. Weber is confident that the engineer will be happy with them.

The third problem was fixed at the start of the last run. Weber asked me to check what the vehicle mass was set to. It was 30 kg; this is a figure we use when testing the motor in neutral. We set it to 1000 kg (roughly right for a 1300 kg car in third gear), and found that the power was considerably better (we were getting peaks of over 50 kW from the motor controller), and this is all we can expect from a single half-pack and the limits we have set. With over 50 kW electrical, you can start to feel the potential of the MX-5. It raised a half-EV grin from one half-pack Image

[ Edit: added that the reason for the "sink" limiter was that we forgot to re-connect the coolant pump. ]
[ Edit: technical edit by Admin to close an unclosed font size tag ]
Last edited by rhills on Wed, 11 Nov 2015, 09:07, edited 1 time in total.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

Renard
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Weber and Coulomb's MX-5

Post by Renard » Sun, 29 Sep 2013, 16:17

coulomb wrote:
After consulting multimeters measuring auxiliary battery voltage and charge current, we decided that for reasons unknown, the DC/DC (a 15 V 15 A adjustable MeanWell power supply) wasn't putting much current into the auxiliary battery. We'd let it run low again today, due to a misunderstanding; it must have gone down to about 9 V since the contactors started clattering.


Perhaps because we've grown up with large lead-acid ICE batteries, we EVers are a bit too casual about 12V supplies with our much smaller auxiliary batteries. It seems that at least 30A of DC/DC capability is needed. (My DC/DC is 450W, and copes OK but I suspect a smaller unit would be problematic.)
Renard

Renard
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Weber and Coulomb's MX-5

Post by Renard » Sun, 29 Sep 2013, 16:32

coulomb wrote: The IGBT temperatures had been climbing up into the sixties,
Unless your drive was long or hard, I'm surprised by this, since my controller never goes over about 35. It suggests that the coolant circulation is critical. Or perhaps there is something else in your set-up causing abnormally high currents. Did you also observe current or power levels?
Renard

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