Mazda MX-6 build thread (EV conversion)

[thingstodo]

I spent some time doing a bit of troubleshooting. The contactors both appear to click, but it's hard to tell. Touching each of the contactors as they cycle I still can't be sure.

I check bus voltage while the contactors are cycling. There is no bus voltage. It's weird. It was always 5V before, or 9V. Now it's 0V? That's shown on the interface module. I have that sinking feeling again ...

Tomorrow I will disconnect the contactor coils and cycle them at 12V, check for resistance. If they are damaged, I'll get the new ones ordered. If they are not, I need to troubleshoot the controllers with Netgain .. or just send both the controllers in to get repaired. The one controller has a primary contactor output that has failed. This second controller, the one that took the high current and the overheat, may have the same thing or something different ... but Netgain should be able to tell pretty quickly with their test rig instead of wasting time figuring it out with me .. in the case that the controller is not turning on the contactors properly.

[freebeard]

Andrew looked at the driveway and figured out that the noise that we heard, that sounded like the supports were still dragging ... was the FRONT TIRES SPINNING ALL THE WAY DOWN THE DRIVEWAY. I had dug grooves in my gravel driveway!

Wow. Try it again in third gear. What's the overall reduction? Is it in the range of 6—10 to 1?

My new favorite thing is EVTV, and he was saying there that the biggest part of each build is the battery box[es]. You're planning to replace it all with new construction, aren't you?

[thingstodo]

Originally Posted by freebeard

Wow. Try it again in third gear.

I'd LOVE to ... but the controller won't power up on the high voltage pack.

The contactors have been checked and operate from 12V as they should.

This weekend I hope to get my garage cleaned up enough to *MAYBE* get the car inside. It's -10C (about 14F) and I can only work outside bare-handed for a few minutes at a time.

What's the overall reduction? Is it in the range of 6—10 to 1?

According to the attached manual page, my final drive ratios are:
first 4.105 * 3.307 = 13.575:1
second 4.105 * 1.833 = 7.524:1
third 4.105 * 1.233 = 5.061:1
fourth 4.105 * 0.914 = 3.752:1
fifth 4.105 * 0.717 = 2.943:1

So second is in the range you asked about. Third is not quite in the range.

Other pertinent info - 14 inch tires
11 inch netgain motor has a redline of about 5500 but I'd like to run it 3500 rpm or so at 65 mph. That appears to be 4rth gear

My new favorite thing is EVTV, and he was saying there that the biggest part of each build is the battery box[es]. You're planning to replace it all with new construction, aren't you?

Awesome - I've been watching EVTV for years.

One of the reasons that I built the box and supports from wood first is that I expected it to be a challenge. The aluminum build will be *MUCH* easier the second time around, when I have a bit of a template set up from wood (although I will be making a bunch of changes during the battery box rebuild)

My wife thinks I'll need to do version 2 in wood first, then in aluminum

[Astro]

Originally Posted by thingstodo

Remove the shroud from the motor. That's the part that is rubbing on the axle as it rotates.

Move inside the car. Interface module is inside now.

Run the motor up in neutral (100A is too low, even for neutral!)

Duplicate the test with 300a maximum on the motor. It runs fine

Put the car in 3rd gear, then run up the car. I didn't check the speedometer

Mazda MX6 Day 125 Video 036 Nov 1 2014 - YouTube

I am struggling with that 100Amp figure in Neutral.
I have no first hand experience but that seems like WAY more current than should be required to spin up a flywheel.
The display in the cabin said 386V, if that is correct and the current was 100A then isn't that 38.6 kilowatts?!?!
At 386V i would have expected only a few amps being required to spin the motor in neutral.
Maybe somebody else with a similar set up could comment on the neutral spin up current requirement but my guess is something is holding that motor from spinning or else a lot of that power is going somewhere other than the motor.

[thingstodo]

Originally Posted by Astro

I am struggling with that 100Amp figure in Neutral.
I have no first hand experience but that seems like WAY more current than should be required to spin up a flywheel.
The display in the cabin said 386V, if that is correct and the current was 100A then isn't that 38.6 kilowatts?!?!

Yes, that would be. The pack voltage is 386V but the current from the pack is 0 - 2 amps. The output voltage to the motor is much lower, 5 - 7 VDC at 100 amps. 500 - 700W to spin up the transmission means a slow accelerate.

At 386V i would have expected only a few amps being required to spin the motor in neutral.

The current from the pack bounces between 0 and 2 amps. Consistent with 500 - 700W

Maybe somebody else with a similar set up could comment on the neutral spin up current requirement but my guess is something is holding that motor from spinning or else a lot of that power is going somewhere other than the motor.

The numbers make sense to me, but I'd be happy to hear anyone else's experience!

[thingstodo]

Check contactors by connecting to the 12V battery (controller is disconnected)

12V - the primary contactor closes, resistance is 0.1

12V - the secondary contactor closes, resistance is 0.1

So the controller appears to be the problem .. sigh!

Next time I will check the outputs from the controller. The first controller has a failed primary contactor output (I think) so I'll check on that first. Then work through the second contactor output, then the precharge sensing

It's cold outside. I may need to clean up a space in the garage so that I can work inside.

[Astro]

Originally Posted by thingstodo

Yes, that would be. The pack voltage is 386V but the current from the pack is 0 - 2 amps. The output voltage to the motor is much lower, 5 - 7 VDC at 100 amps. 500 - 700W to spin up the transmission means a slow accelerate.
...

I didn't realise that the voltage to the motor was being reduced. 500W sounds a bit better than 38600W.

[thingstodo]

Not really an update - cleanup of the garage to make a workspace for the car is going slowly.

No new tests, no new video

[thingstodo]

Day ... 469! ... of the Mazda MX-6 conversion (sigh!)

The wooden supports for the batteries were removed. I've been working on an aluminum base for the battery box for several months now, a few minutes at a time. It is going to be very strong.

The first layer of 4 inch square tube is done. It is bolted to the car floor and the rear axle supports. The second layer is almost done. The batteries will lay on top of the second layer. The vertical supports (that will keep the batteries from sliding around) have me scratching my head - how to bolt them in (to both layers) after everything else is bolted together and into the car. I have issues fitting wrenches into the space.

Lastly is the cover, which will keep the batteries from moving in case of a roll-over.

There is no big rush. I missed summer driving season again. The batteries need heating to function in winter. And my netgain industrial controller is still dead. No progress there. I may use a P&S Cougar controller temporarily (after I am done bench testing). I need to test whether the car is driveable with 500A for acceleration, 125A for continuous output. And whether I can cool the controller to maintain 125A continuous output.

I'll post a few photos in the next couple of weeks.

Here is a video for first spin of a different DC motor with the Cougar controller. https://youtu.be/aex9fFwmFis

[thingstodo]

Finally got around to editing this video with the pictures

https://youtu.be/v-mlagw5s48