Ian Hooper's RX7 Conversion

Post by **zeva** » Wed, 23 Jan 2013, 19:39

A quick news update..

I sent the first Hairball back for testing/repair late last week. Later that same day I did a test drive around the block and the Zilla tripped out again with the new Hairball, and I had to get it towed home again (fortunately only a short distance this time)

Since then, the same old error has been consistently reoccurring. I don't know why the new Hairball worked for a couple of KMs then stopped - possibly just coincidence, or possibly something in my setup is murdering Hairballs. (Proximity to the power box? It shouldn't be something that can cause damage, but you never know..)

After further discussion with a guy at Manzanita, they've asked me to send the power box back for testing. This is pretty bad news, because (a) I have to take the front battery box out to access/remove the Zilla and (b) round trip postage of a 15kg Z2K will be hundreds of dollars. (Since it's out of warranty I'll probably open the box up myself and do a cursory inspection for loose wires / visible damage first.)

Oh, and yesterday I received the NCOP14 approval from the DoT, telling me I can bring the car in for pit inspection and licensing. Which is a little bittersweet as I begin to disassemble the car again to get the faulty Zilla out!

The trials and tribulations of building EVs.. *sigh*

Post by **EV2Go** » Wed, 23 Jan 2013, 20:30

zeva wrote: Oh, and yesterday I received the NCOP14 approval from the DoT, telling me I can bring the car in for pit inspection and licensing. Which is a little bittersweet as I begin to disassemble the car again to get the faulty Zilla out!

The trials and tribulations of building EVs.. *sigh*

It's a lot like being married, what you gain in one hand you lose out the other

Hang in there (isert picture of kitten hanging in tree here...)

Post by **zeva** » Fri, 05 Apr 2013, 07:41

Hi all,

First, the big news: The RX7 passed its pit inspection today and is officially road legal & licensed!

Not the most trouble-free process, quite a few hiccups along the way, but great to have this milestone done so I can start driving the car regularly!

I've also done up a new blog post covering what's been happening over the last few months leading up to today's licensing. In summary, there's details of what was wrong with the Zilla, some pics from Electrakhana, info about the 12V battery going flat, adjusting the Zivan charger, a problem I had with the speedometer / drive coupling, a bit of info about the licensing process itself, and some plans for future improvements. Here's a direct link to the update: http://zeva.com.au/Projects/RX7/?sectio ... 4April2013

^ What a great picture

Post by **photomac** » Fri, 05 Apr 2013, 15:44

A marvel !!!! And the car too ! Looking forward to not hearing it

How many ideas have you for the ex-exhaust passages under the rear bumper?

Website · Post by **htial** » Fri, 05 Apr 2013, 15:56

That's great news.
Every time I see this RX-7 it makes me want to convert my Skyline.

Post by **Johny** » Fri, 05 Apr 2013, 22:27

Congratulations Ian. A great conversion.

Post by **4Springs** » Sat, 06 Apr 2013, 03:02

Congratulations Ian, looks fantastic, can't wait to hear how it drives!

zeva wrote: I investigated low-voltage cutouts which are designed to isolate the battery automatically if it's voltage gets too low, to avoid over-discharging it. The commercial options all seemed overpriced, so I designed my own. Pictured right is the first prototype – I'll start testing it in the car shortly.

I have the same problem with my (lead acid) 12V battery running flat - mine lasts about 4 days. I'd buy one of those low voltage isolators, for the right price of course!

Post by **zeva** » Sat, 06 Apr 2013, 19:06

I'll get the prototype into the RX7 today and see how it goes. If it works as it should, I'm happy to send one your way for mates' rates

It basically has a comparator holding a power MOSFET closed whenever input voltage is above 12V, with a very slow response rate to prevent it tripping from brief voltage sags when loads kick in etc. The nifty part is that the comparator also disconnects its own power supply when the LV threshold trips so there's no quiescent load (i.e after tripping, the device draws zero power).

It should be able to handle about 50A continuous, 100A briefly. (I used an IPB009N03L which is a pretty amazing little MOSFET - 1 milliohm on resistance!)

Post by **CometBoy** » Sat, 06 Apr 2013, 22:36

Ian very nice and well done!

Ps I have started a new thread on the aux 12 volt issues as I am also interested in clever solutions.

Cheers
Bruce

Post by **zeva** » Sat, 25 May 2013, 23:16

Oh man. I just need to vent..

After the driveshaft coupling came apart again a few weeks back, I had a new extra-beefy one made at great expense. Installed that today, went for a test drive, coupling seems good.. Then the Zilla packs it in again with the same old comms error which I thought was fixed.

Morbidly amusing that these two components which have caused so much trouble are among the few things I didn't build myself

It's days like this I find myself questioning why I bother doing conversions..

Post by **EV2Go** » Mon, 27 May 2013, 02:34

Hang in there Ian... Tailshaft issues are almost to be expected with the instant torque, and if you have put in a decent aftermarket one, it should be the end of your problems.

Sorry to hear the Zilla problems are continuing.

Post by **SupraEV** » Mon, 03 Jun 2013, 07:19

Wish I could help you out, but I'm only just starting with my conversion. You're a great inspiration to us EV enthusiasts. You can do it!

Post by **zeva** » Fri, 01 Nov 2013, 22:53

It's been a while since my last update so I thought I'd write up the latest news.

Soon after my last post, I took the Zilla controller out again and bit the bullet - shipping the whole lot back to Manzanita Micro for repair. They were able to reproduce the fault and ended up simply replacing the whole logic board in the power box, which wasn't very expensive ($70 board plus an hour of labour), but the round-trip shipping cost of nearly $500 was a bit painful!

By this time I confess I was pretty annoyed at the Zilla, so resolved to have a go building my own controller for it.

With the front battery pack out, I first took the opportunity to do some road testing of my new 150V motor controllers (shameless plug: MC600SP and MC1000SP) with just the rear cells powering the car.

After verifying these were working reliably, I had a go building a 300V 600A controller based on the same design with IGBTs instead of MOSFETs. It worked well for a few KMs then died spectacularly - a cascading failure of all the IGBTs

I was never sure if the design was going to be thermally adequate for IGBTs since on paper they produce about 3x more heat, and the heatsink housing certainly heated up quickly compared to the MOSFET versions. The other catch with IGBTs is that they don't parallel as well as MOSFETs. Generally have a positive thermal coefficient, meaning their conduction increases as they get hot and are prone to thermal runaway. Seems like IGBT-based controllers are best water cooled.

So it was an interesting experiment, but I decided it was going to be too troublesome to get my own IGBT controller working reliably after all, and about a week ago conceded to just putting the Zilla back in. Since then I've been putting it through its paces and so far so good - touch wood!! I have the Zilla programmed for 1200A motor amps and 500A battery amps, and it's got all the performance one would ever need on public roads, so I'll probably leave it like this for the next month or so until I feel confident to turn it up some more.

I also got some vinyl lettering done for the doors, so people actually know it's an EV! In case anyone else is looking for something similar, I used www.vinyllettering.com.au, and wouldn't hesitate to recommend them. Altogether a very painless process, using their web interface to create the order, pay with Paypal, and a few days later they turn up in the mail. Here's the result:

(Also visible in the background is the new 2.7kW rooftop solar array which more than covers the energy requirements of the car!)

Post by **PlanB** » Sun, 03 Nov 2013, 15:31

The thing with vinyl lettering is is not the ordering or payment it's the sticking it on straight & wrinkle free, nice job.

Post by **jonescg** » Sun, 03 Nov 2013, 17:14

It looks great Ian - we really need to see it at a meeting one of these days. We're at UWA on the 12th of November, so you better bring it along!

I wonder why IGBTs lend themselves to 3-phase inverters more than DC speed controllers? Faster switching maybe?

What was the word on those water pumps you had - can they handle hot water? My motor says not to exceed 55'C but given I will be racing it, I suspect I might be getting hotter than that.

Post by **bladecar** » Sun, 03 Nov 2013, 18:16

Yes, Great car, Ian. I'm very happy to know there are people out there with cars like this, who did it all themselves. One of the most notable cars on the road today

Sure, the new Jaguar advert has a good theme song, but the car was misconceived. It runs on petrol.

Post by **acmotor** » Sun, 03 Nov 2013, 21:50

Great work there hoops !

To be fair to IGBTs, none of the 0.15kW to 1.2MW 3 phase VFDs I work on use parallel IGBTs. But why would you ? power IGBTs usually come in paired modules with diodes or 6pack H bridge modules. Only ever one IGBT in a leg. IGBTs go up to at least 3000V and 4000A presently. So why parallel ? It is not like you are lowering the on resistance as with mosfets. Just use a suitably sized IGBT in the first place.

You are stuck with the on junction voltage with IGBTs but that is part of going to a higher voltage so the switching devices consume such a small portion of the overall power (1 to 2% in most VFDs and that is through 2 series juntions at a time in the H bridge). Once you are above say 200V the IGBT wins hands down over the mosfet.

Post by **zeva** » Mon, 04 Nov 2013, 05:51

jonescg wrote: I wonder why IGBTs lend themselves to 3-phase inverters more than DC speed controllers? Faster switching maybe?

It's more to do with efficiency at various voltage levels. Up to about 200V, MOSFETs win hands down. You'll probably find all controllers rated up to 200VDC will be MOSFET based, including 3 phase ones from Curtis, Kelly etc.

But as voltages ratings go up, MOSFET on-resistance seems to go up quadratically, while IGBT voltage drops increase linearly at best (vs device voltage rating). So for controllers rated to 300V+, which includes pretty much all industrial and high performance 3ph controllers/inverters, IGBTs end up being more efficient.

Also as Tuarn says, you can get single IGBTs with very high power handling, or in half bridge / even 3ph bridge modules, which simplifies design and construction.

One reason to parallel is because TO-247 packages still offer the best bang for your buck, at about 10c per amp (but only handle ~50A each). Also small devices in parallel can usually be switched faster than big single devices, which reduces switching losses. For interest, Zillas use TO-247 IGBTs, but they use IGBTs with closely matched performance, and a copper heat block instead of aluminium (significantly better heat conduction, at much greater expense) and water cooling of course. OTOH AFAIK Solitons use two or three large IGBT modules.

jonescg wrote: What was the word on those water pumps you had - can they handle hot water? My motor says not to exceed 55'C but given I will be racing it, I suspect I might be getting hotter than that.

Not sure but you can have one as a freebie and just see how it goes. I'll try to remember to bring one when I'm out your way this week.

Post by **acmotor** » Mon, 04 Nov 2013, 10:24

zeva wrote: .........TO-247 packages still offer the best bang for your buck,......

Clearly !

You are right about the thermal management. In an EV, the space and weight of an 'industrial' heatsink is an issue so working with fluid cooling is a good move.

Post by **Richo** » Tue, 05 Nov 2013, 20:33

Some of the latter designed 3-phase modules are all die bonded in a small package.
So getting the heat out is a right PITA - water cooling(good one) is the ONLY option and this puts the price up substantially.

Post by **zeva** » Thu, 02 Jan 2014, 03:37

Hi all, FYI I've just added a quick update to the build blog, covering the installation of the new CAN-based BMS and EVMS - direct link to the post here:

http://www.zeva.com.au/Projects/RX7/?se ... 2014Update

Pic of the new BMS modules

Post by **zeva** » Tue, 20 May 2014, 22:34

The RX7 gained a new addition today - a new display module for my EV Management System, aka the EVMS Monitor V2, which talks over CAN bus to the EVMS Core and BMS modules for providing instrumentation to the driver. It's something I've been working on for the last month or two, to replace the somewhat "agricultural" looking EVMS Monitor V1 which used a 20x4 character LCD display. This one uses a 3.2" TFT full colour touchscreen - much prettier / more modern, more space for text, and support for graphs etc. And it was about an order of magnitude harder to interface with a microcontroller, of course.. Anyway here are a few pics.

Display installed in the space where the gear shifter used to be. I 3D-printed a panel the same size as the old Monitor to make the swapover easy, but as you can see it is bigger than it needs to be for the new Monitor.

This is the main page shown when the system is powered up (driving or charging). Sorry about the picture quality, it's hard to get a good shot of a bright screen in a dark cabin!

This is the "BMS Summary" page, showing min/max/avg cell voltages, and a little graph at the bottom showing all the cells at a glance, which looks pretty boring here because all 88 cells are within a hundredth of a volt..

And there's a "BMS Details" page where you can cycle through all the BMS modules to view individual cell voltages:

I'll be putting it through its pages in the RX7 over the coming weeks to make sure there are no software bugs left, but so far so good.

In other news, Tim at EV Works says he has a shipment of Headways arriving in the next week or two, so I'll be purchasing another 264 of them to finally install the last 8kWh of the battery pack in the car, taking it up to 25kWh total. It'll be good to get another 40km or so of range (having only 80km has occasionally been inconvenient). But it'll also give the car another 50% power, which could be a whole lot of fun. Seeing the video of the ELMOFO Radical on the race track last Sunday has given me renewed interest to get the RX7 into some motorsport too!

Post by **Johny** » Tue, 20 May 2014, 23:04

Looks great Ian. It needs some black metal heads on those screws though (picky).

Post by **zeva** » Wed, 21 May 2014, 00:49

Hah, I was thinking the same thing while I was screwing them in.. I didn't have any suitable black screws handy, but I'll get some.

Post by **Bluefang** » Wed, 21 May 2014, 01:11

Awesome looking battery display. It looks perfect and built into the car settings better then alot of OEM items

.