Sam's Karmann Ghia

Post up a thread for your EV. Progress pics, description and assorted alliteration
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Sawnoff
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Sam's Karmann Ghia

Post by Sawnoff » Tue, 03 Nov 2009, 05:26

Righto! I've been reading this forum for the past 12 months and have been really impressed with the knowledge and the projects that have been shared on the site. I will try not to lower the average with my contributions!

Table of Contents:
1. Donor Vehicle
2. EV plans
3. Big Questions
4. Change of plans for motor


1. Donor Vehicle
The starting point is a 1961 Karmann Ghia. It was bought sans motor and trucked over from Perth about a year ago. Unfortunately the vehicle behind it on the transporter was not tied down properly, so by the time it arrived in Victoria the rear end had been pushed in a bit. Turned out to be a good thing as the insurance payout meant the vehicle ended up being almost free. The Ghia needs a full resotation anyway before it will hold 250 kg of batteries.
Pros and Cons of the Ghia for an EV:
+ kerb weight of about 700 kg without the ICE.
+ compact driveline
+ no power steering
+ no power brakes (is that a good thing?)
+ common mechanicals with VW Beetle (cheap spares)
+ more space for batteries and EV bits than a Beetle
- needs lots of TLC before roadworthy (lots of rust and bog)
(I'll add pics once I work out how...)


2. EV plans
Currently planning
> AC Motor: Azure Dynamics AC24LS motor with DMOC44 controller
> Battery Pack: 320V Li-ion (Thundersky) + BMS
> Charger: Manzanita PFC20
> DC/DC converter: IOTA DLS55-HV
> Main Contactors: 2x Gigavac GX14BC

I am sure there are more economical ways of putting an EV together, but I don't have a strong background in power electronics and am going for bits that will more likely work out-of-the-box without too much experimentation (that will come later, as I learn more of the basics).

3. Big Questions
...?
How many Amps should the HV circuit be rated to?
The AC24LS/DMOC44 spec-sheet says max DC current is 165A, max motor phase current is 250A (when the AC24LS is wired in star @ 312VDC). If I can be sure the most the HV circuit will see is 250A, it will make it a helluva lot easier (cheaper) finding appropriate connectors, switches, fuses etc. But can I be sure?!

What sort of E-stop?
NCOP14 dictates an e-stop that mechanically breaks the HV circuit - but who makes an e-stop that will quickly and safely break 300-600A hot? Doesn't it make more sense to have a LV e-stop wired to the main contactors?

Battery Pack Isolation?
My tendency is to follow the guidlines that SAE have set up for the EV formula racing - Isolate the battery pack and fit a ground fault detector, such as the Bender IR475LY.

Pre-Contactor or not?
I plan on having both POS and NEG main contactors, closing the NEG first. How does the HV circuit - and especially the controller electronics - cope with the inrush current when POS contactor is closed? Would it be better to first close a pre-contactor in series
with a large resistor prior to closing the POS contactor? The pre-contactor could be opened after the main POS contactor had closed. How could/should this be controlled?

There will be more...

Last edited by Sawnoff on Thu, 26 Nov 2009, 18:35, edited 1 time in total.

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Sawnoff
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Sam's Karmann Ghia

Post by Sawnoff » Fri, 27 Nov 2009, 05:31

Vehicle is off to begin restoration of the bodywork this week.
Image

After the feedback on the Azure Dynamics AC24LS motor here (thanks for the feedback) I have been sorting through industrial ACIM options.

My preferences are leaning to the following ABB motor:
M3AA 132SC - 3GAA 131003 BS
Which is a 2-pole motor wound for 220D/415Y, with the following specs
Pn = 11kW
Tn = 36.5Nm
Tm/Tn = 3.4
In = 19.9 A
M = 52kg
Driven at 415V, this should give about 18kW continuous power. There are a couple of ABB motors of similar type that have better power and torque figures, but this is a more compact and lighter unit.

As I understand from other posts, to get reasonable performance I'll need 415 * 1.4 = 580VDC fed into a VFD with a >60kW nominal output. If I have used woody's spreadsheet correctly, acceleration should get to 60km/h in 6.7s and 100km/h in 14s. No rocket, but plenty of time to shift gear Image

I'm still not sure what sort of current I'll need to feed the motor with. Can anyone give me a tip on how to read the spec sheets and determine peak currents - or at least make sure the VFD can supply enough current?

antiscab
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Sam's Karmann Ghia

Post by antiscab » Fri, 27 Nov 2009, 11:51

If the VFD is already rated to 60+kw and you are running at rated voltage an "18kw" induction motor, that VFD will pump out plenty of current.

Matt
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells

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woody
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Post by woody » Fri, 27 Nov 2009, 15:34

Hi Sawnoff,

the spec sheet current will be at nominal output and RPM.
11kW will be about 21 amps at 400V.
More current at less nominal volts, so 21 * 400/ 230 = 35 amps for 230 Volts
for up to 70% of breakdown torque, current is linear with torque, so
up to 84Nm is 1 amp per Nm.
After that the current increases according to the ABB formulas to about 4/3, so maybe 160Amps for 120Nm at breakdown.
This will be a 55kW 415v high overload drive like a Danfoss 5072, Telemecanique atv71HD55N4 etc.
How much torque does the VW gearbox take?

Different cntrollers have different DC volt ranges, from my reading of te telemecanique stuff, it can operate on anything from 300 - 850 Volts absolute, the more the merrier*, so 200-220 lithiums, 50 plus Lead acid...

* higher RPM at peak torque, higher torque above that etc.
Planned EV: '63 Cortina using AC and LiFePO4 Battery Pack

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Johny
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Post by Johny » Fri, 27 Nov 2009, 16:51

To establish optimum controller.

What I do is plug in a nominal controller - say a Danfoss 5042, then play with the controller current and power to see where the diminishing return point is. Once you get to the point where more controller current (don't forget the power field as well) doesn't help, back off the current until you are happy that you could compromise that little bit of acceleration that you have lost. That way you are still slightly controller limited and shouldn't have too much trouble with de-syncing the motor. You are also then getting the lowest cost option that is reasonable.

A quick and dirty while you are playing is to make the power field (k3) equal (k4*505)/1000
that you you only have to fiddle with controller current (k4).

Of course, changing the motor or pack voltage then changes everything again so lock anything you can down first.

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Sawnoff
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Post by Sawnoff » Fri, 27 Nov 2009, 18:11

woody wrote: How much torque does the VW gearbox take?

The stock vehicle produced an ICE peak torque of 80Nm, so I would expect the transmission to be able to cope with up to 150Nm of torque. I plan to program the torque control to smooth out any large step changes or spikes and thus protect the gearbox internals a bit more.
woody wrote: the more the merrier... 200-220 lithiums, 50 plus Lead acid...
The number of batteries has me bit worried. Target range is 100 -160km. 200 TS40AH cells would weigh 300kg. 50 Greensavers (20Ah) would weigh 350kg. I know I'm whinging to the converted...but after adding the VFD (35kg) and the motor (52kg) and other bits (25kg) I may not be allowed to sit in the vehicle without exceeding GVM.
The e-Ghia guy has gone with the Greensavers (see post) - might follow that up.

A few folks on this forum have been testing the 20Ah Headway cells - what was the verdict on those?

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Richo
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Post by Richo » Fri, 27 Nov 2009, 20:50

Greensavers will be out.
You won't get your target range out of them.
So the short answer is NO but the long answer is YES.
Help prevent road rage - get outta my way!

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Richo
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Post by Richo » Fri, 27 Nov 2009, 21:04

Have you got any quotes yet on the 11kW motor?
So the short answer is NO but the long answer is YES.
Help prevent road rage - get outta my way!

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Post by Johny » Fri, 27 Nov 2009, 21:07

Trouble with lead is 50% effective DOD.

At 60km/hr and DOD 80%, I make it that your would get 100km from a 20AH Headway pack (144kg pack, vehicle 950kg) and 140km from a custom 30AH Headway pack (216kg pack, vehicle 1020kg).
At 80km/hr that comes down to 70 and 100km.
I have kind of allowed 106kg for controller, contactors, driver, etc. - not enough but...

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Sawnoff
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Post by Sawnoff » Sat, 28 Nov 2009, 02:20

Richo wrote: Greensavers will be out.
You won't get your target range out of them.
sorry, it was the weight that I was thinking about - if the 350kg of SLA batteries will get into a Ghia, it should be easy to get 300kg of Li-Ion in.
Richo wrote:Have you got any quotes yet on the 11kW motor?
Not yet - I've been weighing up the options until now. I'll start shopping around. I picked the ABB coz they have a good reputation and it can be ordered already wound for the lower voltage.

Thanks for the range estimates, Woody [ed. Johnny]. Looks like the 40Ah TS cells will be the way to go. I'll have fun packaging them...

edit - sorry for mis-atribution of the range estimates, Johnny. I got the small blue british vehicles mixed up!
Last edited by Sawnoff on Sun, 29 Nov 2009, 07:08, edited 1 time in total.

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Post by Lester » Thu, 07 Jan 2010, 16:20

Am interested in above debate re motive power.....I actually think your original idea 320v 40ah AC24LS etc was excellent...given the vehicle. (Regen with those standard brakes will be good but watch the rear wheel braking bias)..... Out of interest I broke up my pack into 4 (6 contactors in all) with a lv cutoff as well as an inertia switch..... seemed the best for safety. The only small problem is the controller takes 30 sec or so to "cold boot" if not permamently connected to power.

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