Honda Civic conversion

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Tritium_James
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Post by Tritium_James » Sat, 07 Nov 2009, 02:24

Since we've now got this car out and about, it's about time I posted some photos and info...

It's a 2008 model Honda Civic, brand new (10km on the clock) when we started on the conversion for our client, Deep Green Research. We've just got it running (mostly!) and competed in the recent 2009 Global Green Challenge eco race from Darwin - Adelaide, a touch over 3000km. Here's a shot of it driving near Tennant Creek, and a promo shot I took while stopped at the salt flats near Woomera.

Image

Image

The car performed extremely well, and acheived a 360km run (at 55km/h average) in one charge, giving a consuption figure of 85 Wh/km. The Honda aerodynamics are obviously OK, and our drivetrain is extremely efficient. Image

Specs are:
- Custom 650 Nm (at 400Arms), 4500rpm (at 400Vrms) 3 phase ironless BLDC motor with externally switchable series/parallel windings
- Custom 3.5:1 fixed reduction gearbox (wet sump) to existing Honda diff and drive shafts
- Custom 200 kVA liquid cooled 3-phase motor controller
- 108x series connected 90Ah ThuderSky pack (360V nominal)
- Custom BMS reporting voltage and temp of every cell in the pack at a high rate (CAN bus), and resistive shunts for balancing (~1A) at top of charge
- Custom battery safety controller, handling precharge, cell faults, pack isolation fault detection, and reporting min and max voltages to other systems in the car
- Custom driver controls, interfacing to existing Honda fly-by-wire accelerator pedal, brake switches, direction selection pushbuttons, and reverse-engineered comms to the upper gauge cluster, showing temperature, speed and 'fuel' state on the factory Honda cluster.

Here's a few shots of the engine bay:

Image

Image

Image

The batteries are contained in three boxes, with the bulk of them (96 cells) around (front/back) the rear suspension components, below the back seat and the floor of the boot. The remaining 12 cells are in a box where the ICE radiator used to be. The pack connections are inside the "Danger High Voltage" box, along with the battery safety controller, main contactors, DC/DC converter, charger plug, and connection out to the motor controller. Wiring is 35mm² fine stranded double-insulated 110°C PVC. All DC wiring is in orange conduit, and sealed from the weather.

Here's a keyed photo with some of the items of interest:
Image

A: HV connection box, mentioned above.
B: BLDC motor, designed here in Brisbane by Ultramotive Technologies. Air cooled, 650Nm (peak, 10 second rating), >97% efficient at cruise
C: 3.5:1 fixed reduction gearbox
D: 3x 50uH 400A inductors, as the motor does not have enough inductance by itself (it's ironless) to enable the motor controller to regulate current properly
E: 200kVA 3-phase inverter, designed by us (Tritium), also 97-98% efficient for most of a typical drive cycle area
F: Liquid coolant reservoir for inverter, see also pink tubing in various places in this area

Due to lack of testing so far (quite a rush to get it to the Darwin-Adelaide race), the car is not up to full rated current/torque yet, but we're driving it at around 200A in the motor presently, ie 50% of rated. It drives pretty much like a base-model normal car, and when we have it at 100%, should be moderatly quick. Predicted 0-100 is around 9.5 seconds. It's road-registed in Queensland, however as a two seater only.

Some of you saw it in Adelaide last weekend, on show with the solarcars and other eco challenge cars (including a Tesla). I know I spoke to a few AEVA people, but promptly forgot names, sorry!

It will be at the Brisbane City Council GreenHeart Fair, at the Mt Gravatt showgrounds (1644 Logan Rd), this sunday the 8th of November 2009, from around 9am until 3pm or so. Feel free to come along and have a look.


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Post by woody » Sat, 07 Nov 2009, 03:33

Congrats on the successful run!

That motor looks so tasty wrapped in carbon fibre.

Extremely professional looking work in the Civic.
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Post by coulomb » Sat, 07 Nov 2009, 05:06

Wow!   Image   Image

I see a lot of fat wires coming from the motor; are you implementing series/parallel coil connecting in the high voltage box?

Are there three centre tapped coils or something?

Congratulations! Custom, bleeding edge motor, custom controller, custom gearbox, advanced batteries and BMS, water (yummy bubblegum pink) cooled, advanced interface to stock gauges... there is a lot of technology there!

The motor must rev pretty fast (past the 4500 rpm mentioned) to get highway speed from a fixed 12-15:1 overall reduction to the wheels. Hence the need for the custom gearbox, I guess.

Is there air conditioning in there? Power steering? What drives those?

Now I'll be thinking about how to fit that large motor into the next MX-5...
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Post by Tritium_James » Sat, 07 Nov 2009, 14:38

There's another box under the aluminium sheet 'deck' with the series/parallel contactors in it. The motor is physically made with three phases each with two parallel interleaved windings, and the ends of the windings are bought out separately. One set is tied at a star point inside the motor, so only 9 wires coming out from the motor, not 12.

The motor itself weighs 28kg, and the inductors are another 15 or so. It's sized to also be usable as a wheel motor, it will fit inside a 17" rim. Obviously the shaft/mounting arrangement must be changed to use it as a wheel motor, but it's been designed with this in mind.

A FWD diff doesn't provide any further reduction, so it's 3.5:1 to the wheels in total.

No A/C, though there is space remaining for one of the Masterflux units. It currently has a water boiler plumbed into the existing heater pipework to pass the demisting requirement, but I think this will be going when the A/C is installed.

No power steering, and I'm not quite sure how our client convinced Qld Transport to register the car without it, but he has. The steering is quite heavy without it.

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Post by Johny » Sat, 07 Nov 2009, 15:59

Drrroooolll....

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coulomb
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Post by coulomb » Sat, 07 Nov 2009, 16:45

Tritium_James wrote: A FWD diff doesn't provide any further reduction, so it's 3.5:1 to the wheels in total.

Errr... 4.3:1 according to this Honda specifiations page:

http://corporate.honda.com/press/article.aspx?id=4251

(And 4.7:1 for the 6-speed manual, but presumably the client didn't pay extra for that only to rip it out).

But that's presumably the ratio between the output shaft gear and the big gear (called the crown gear on a RWD diff, but it's not crown shaped in a FWD diff) on the carrier of the differential:

Image

So I assume that the custom gearbox essentially replaces the input and output shafts of the original transmission, and drives the big gear on the differential. I don't want to step on any patents or trade secrets, but if you can confirm how that works, that would provide a big clue to the solution of a major problem that plagues most FWD conversions (i.e. how to get significant power through a whimpy OEM gearbox).

I assumed that the 650 Nm and 4500 RPM were after the custom gearbox, but I now presume that's at the motor output. Very impressive torque, and my brain can't wrap around that sort of torque without iron.
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Post by Tritium_James » Sat, 07 Nov 2009, 17:09

We kept this bit:
Image

The new custom box has an intermediate gear to move the centreline of the motor far enough away from the output shafts to not hit it, and also to provide a point for a park brake. You can see this (the bronze insert) in the next photo. The motor pinion obviously isn't in the photo, but when installed, is located in the middle-left area in the box.

Image

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Post by Tritium_James » Sat, 07 Nov 2009, 17:10

And yes, those figures are at the motor shaft. We're getting 2200Nm and 1200rpm at the wheels.

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Post by Electrocycle » Sun, 08 Nov 2009, 01:51

so your top speed will be pretty good :)
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Post by coulomb » Sun, 08 Nov 2009, 02:37

Tritium_James wrote: And yes, those figures are at the motor shaft. We're getting 2200Nm and 1200rpm at the wheels.

Very impressive. But you presumably don't get both at the same time, at least with a 200 kW controller. (And assuming that my maths is good, that would be 276 kW). The 2200 Nm is presumably "in low gear" (windings in series), and the 1200 RPM "in high gear" (windings in parallel).

If you have the power to overcome drag, I calculate 1200 RPM with P195/65 R15 tyres at 143 km/h. Though 4500 RPM / 3.5 is 1285 RPM, so that would be more like 153 km/h.
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Post by Tritium_James » Sun, 08 Nov 2009, 03:26

Yep, that's about right. Torque drops off as speed increases, due to both the motor inductance (not enough voltage available to change the current at the required frequency) and the battery power limitations. I have a curve somewhere, I'll try to dig it up.

The series/parallel changeover point will be around the 70km/h area. It's not automatic yet, that's still on the to-do list.

I think we're getting somewhere in the order of 120 to 130kW out of the system, peak power. The batteries are the biggest limiting factor. The motor itself, as you calculated, is capable of almost 300kW.

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Post by Tritium_James » Sun, 08 Nov 2009, 03:32

Here we go, I think I've posted them somewhere previously...

Speed-Torque:
Image

Speed-Power:
Image

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Post by coulomb » Sun, 08 Nov 2009, 16:25

Tritium_James wrote: I think I've posted them somewhere previously...

Yes, I happened across it yesterday: part way through "Direct to wheel motors", starting about here.

It must be nice to have a motor that other components haven't caught up to, and yet not hog up too much space or weight.

So this motor would be like a 195 SSSS frame (195 is non standard, standard is 180 or 200). The "SSSS" is my attempt at guessing what they'd call a really, really short frame   Image
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Post by Electrocycle » Sun, 08 Nov 2009, 16:59

don't forget it's axial flux, and permanent magnet!

Not much in common with the usual industrial motors
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Post by coulomb » Sun, 08 Nov 2009, 20:53

I've seen the Civic in person now. The bonnet seems much less cramped in real life than the above photos seem to suggest.

Image     Image

There isn't much ground clearance at the back; TJ says he didn't have anything to do with that part. Personally I'd have increased the clearance by 20 mm and taken the hit in boot space (it's pretty much as original now). 96 90 Ah Thunder Sky cells are split between this rear battery box and the one under the rear seat.

Alas, the total weight was too much to have it registered as a four seater (as is, without suspension and/or brake upgrades). So even though the original thick rear seat had at one point been replaced with a thinner one, it wasn't allowed to be registered like that. I suggested smaller cells, e.g. 60 Ah, but of course then the battery power limit is even worse. This vehicle could have benefited from (even) more advanced batteries.

Image     Image

You can see that it's really been to the Global Green Challenge (formerly World Solar Challenge)! The gearbox buttons are the only non-standard thing about the dashboard / interior. At present, the low to high gear change is manual, but I'm told a little work on the software will fix that.

Image     Image

The motor is serial number 001! Image   You can see winding letters engraved on the motor. There are 5 thick orange leads at the front, and 4 more at the back. One extra black one at the bottom carries wiring for the hall effect position- and temperature- sensors. Above some 8-12 km/hr, the hall effect position sensors aren't needed, as back EMF gives better positional information. The motor position is modelled to within 5 degrees. I was surprised to learn that this motor sees sine waves (modulated by square PWM, of course), not square or trapezoidal waveforms, above the ~ 12 km/h minimum where back EMF is sufficient.

Above at the right is a view of the custom gearbox, and what I assume is the filler cap. The differential of the Civic is designed to be completely immersed in oil, and the large gear throws oil to (originally) the far reaches of the gearbox. Note also the blue temperature stickers.
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Post by coulomb » Sun, 08 Nov 2009, 21:02

coulomb wrote: So this motor would be like a 195 SSSS frame (195 is non standard, standard is 180 or 200). The "SSSS" is my attempt at guessing what they'd call a really, really short frame   Image

Actually, per a flyer from the Green Day, the diameter is 402.5 mm. So that's pretty close to a 200 frame.

Also, the flyer states the weight as 40 kg (not 28 kg as TJ states above). But maybe the flyer is including the inductors in "Total Mass". It is forced air cooled, and actually has an orange air filter (visible in the first under bonnet photo). Ick! A consumable in an EV!   Image   Still, for that power (almost 300 kW, if you can get the electrical power to it), I'd put up with that.
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Post by HeadsUp » Sun, 15 Nov 2009, 04:23

very kind of you James to let me borrow the car now the challenge is finished

got a few errands to run

i can bring it back in about 2019 if thats okay ?



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Post by Richo » Tue, 17 Nov 2009, 00:44

Tritium_James wrote: We kept this bit:
Image
The new custom box has an intermediate gear to move the centreline of the motor far enough away from the output shafts to not hit it, and also to provide a point for a park brake.


Any ideas how much it cost to make the custom box?
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Post by Richo » Wed, 18 Nov 2009, 18:24

Also was it made of aluminium?
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Post by Tritium_James » Wed, 18 Nov 2009, 20:39

Yes, the casing is aluminium. Total gearbox weight is around the 30kg area, of which 10kg or so is the diff.

Probably about $8-9k in parts, the gears alone were around the $5-6k area. That parts cost doesn't include machining time or design time.

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Post by Richo » Thu, 19 Nov 2009, 05:33

wholey moley Image

Well lucky I have 17" rims to bypass the box Image
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Post by Tritium_James » Thu, 19 Nov 2009, 06:06

That's the unfortunate reality of one-off mech bits - they're bloody expensive!


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