Power output question...

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Richo
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Power output question...

Post by Richo » Sat, 15 Aug 2009, 21:57

http://www.teslamotors.com/performance/ ... torque.php

I was looking at this the other day.
The bit that interest me was the power curve doesn't really resemble an AC induction Image
Maybe it really is a hybrid of PM and Induction...

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Power output question...

Post by EV2Go » Sat, 15 Aug 2009, 22:20

Richo wrote:
EV2Go wrote:While many on the guy forum think their EVs are quick, many haven’t driven in a seriously quick street car to compare

That's a bit of a broad statement.

Also I don't think ZEVA did a dyno before he started upgrades on the MX5.
So I doub't he will be doing one soon Image
Not really... Zeva mentioned owning a 265rwkw Skyline, which is getting there but I would call that a quick street car but not a seriously quick street car.

If it runs 10's down the quarter or quicker you have a seriously quick street car. Can't claim I owned one because I never managed to get it to the track after the upgrades and before mine was totalled, but if it didn't crack 10's it was a shoe in for low 11's.   

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Power output question...

Post by acmotor » Sat, 15 Aug 2009, 22:43

Richo,
Yes but the tesla graph is of the motor not the rear wheels.
True, one should be able to extrapolate but...
Is there a normal dyno kW/kmph graph ?

The torque curve looks fairly normal AC induction to me Richo ?
As with prius, the v/f is probably modified above nominal voltage thus the shape may not overlay a spreadsheet.
I don't get flat torque. It is controller boost and current limit dependent but the theory is a flat line most of the way.
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Power output question...

Post by Richo » Sat, 15 Aug 2009, 22:58

there are some nice you tube videos but no plots that I saw
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Power output question...

Post by acmotor » Sat, 15 Aug 2009, 23:41

I'm thinking to tow another vehicle with an EV with a load cell in the tow rope so you can set/hold various speeds and thus calculate kW to the road. I recall Mal's dyno attempt with the electrolux wasn't very informative.
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Post by woody » Sun, 16 Aug 2009, 00:54

Mal's dyno issues I think were that the dyno is a very light load, so acceleration is quick - quicker than his acceleration ramp...
Plus the queue of rev heads waiting behind him...
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Power output question...

Post by Tritium_James » Sun, 16 Aug 2009, 19:12

Here's a graph from a run I did this morning in the Porsche. I did two runs (up and back) and they were identical within my measurement error. Data is logged from on-board telemetry and should be accurate. 0-100 in 4.9s. Australia's quickest EV? 0-100 in 9.8s. Oops. My software was logging at 1 second intervals, not 0.5s. It's much less exciting than I first thought!

Image

The nameplate power on the system is 150kW, although the batteries (Optima Yellowtops) fall over quite badly under load and I don't think it's making it to 150kW. I'd estimate (from eyeballing V and I gauges) closer to 130kW going into the controller. From there it's a fixed 10.1:1 reduction to the rear wheels.

It's down one battery at the moment, so that lops a bit off the top speed, but even with a normal pack it tops out at 125km/h or so. So I'd imagine the 1/4 mile time is fairly lousy.
Last edited by Tritium_James on Tue, 18 Aug 2009, 16:58, edited 1 time in total.

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Power output question...

Post by acmotor » Sun, 16 Aug 2009, 20:42

That's great TJ. Image Image Image Image

Now honestly, when do you get time to eyeball the V and I gauges when your doing 0-100 in 4.9 ?   Image

Can you put emotor RPM on that graph scale too ?

I'd expect the voltage shortfall only has effect above say 80kmph ?

Are there more specs on the EV ?
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Post by Tritium_James » Sun, 16 Aug 2009, 21:08

It's a first gen AC Propulsion system, so the tech specs are on their site somewhere.

Motor rpm is directly proportional to speed, where 12000rpm = 128km/h.

It's full torque out to about 7000rpm (75km/h) where it hits full power, then constant power from there out to top speed.

On a wide flat straight street, with no traffic (cough: closed, too) the car doesn't actually feel that quick. You get a shove in the back off the line that isn't really that strong compared to lots of ICEs, but it just keeps going and going. It feels kind of like an aircraft taking off, you just keep getting pushed along faster and faster.

Where it does feel fast is driving in normal flowing traffic at 50 or 60km/h, and stepping on it. It JUMPS. Lots of cars are quick 0-20 or so - but this one does 50-70 in the same time as it does 0-20. Not many cars are still in first gear at 70km/h Image

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Power output question...

Post by acmotor » Sun, 16 Aug 2009, 21:16

OK so pack voltage only starts to limit things about 75kmph then.

I like the description of the acceleration !    AC direct drive (well single ratio gearbox anyway)
You can keep telling us about the acceleration all day. I can hear it again and again and.... Image
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Power output question...

Post by Electrocycle » Sun, 16 Aug 2009, 21:36

having gone for a ride in this car the other week, I can definitely confirm the seamless acceleration :)
It doesn't feel super fast off the line, which is partly because of the single ratio, but also because you don't have a torque converter or clutch there to boost the launch power like in an ICE car.
Geoff's go kart feels much faster off the line, but where the go kart runs out of steam the Porsche is really starting to get going :)

It's very different to ICE cars doing a similar 0-100 time. Usually they launch very hard, have trouble maintaining traction, then have to do a gearchange in the middle of the run - with traction difficulties again :)

Thanks again for the demo James!
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Power output question...

Post by Tritium_James » Wed, 19 Aug 2009, 02:37

Oh man, this is really embarrassing! I've just discovered a major flaw in my test, which makes the Porsche much less interesting. My software, which I thought was logging to disk at 0.5s intervals, is actually logging at 1s intervals. So that fantastic 4.9s 0-100 time is actually a very boring 9.8s. Bummer.

I have to say this does agree more with what the car feels like. So where I said "off the line, it doesn't feel that quick" I guess the (new) numbers show I was right! Dammit!

Guess I'd better fix that graph...

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Power output question...

Post by Electrocycle » Wed, 19 Aug 2009, 03:46

hehe well that makes more sense :)

it does really keep accelerating nicely all the way out to 100 though.
Time for the lipo :)
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Power output question...

Post by woody » Wed, 19 Aug 2009, 15:09

Good news for Zeva :-)
Who's got the fastest 0-100 EV(s) now?

Tesla (Unregistered) 3.9s
Mustang ?
Bikes ?
Kearon + Jaron's Formula V
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Power output question...

Post by Tritium_James » Wed, 19 Aug 2009, 15:25

The civic we're working on (with the BLDC motor) might do 0-100 in 6s (simulations say so), but I think it's going to have wheel slip issues with the front wheel drive and rear-biased battery placement.

Going to be hard to beat the Tesla anytime soon methinks.

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Post by Johny » Wed, 19 Aug 2009, 15:25

Thanks for admitting it TJ. I have been trying to use what data I had on the Porche and motor to model it in woody's spreadsheet and I had to do all sorts of fudges to get close to the figures you posted - mainly lightening the car. Now it makes more sense. What is the weight of the Porche in it's current configuration (apologies if you have posted it somewhere). Image

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Post by Tritium_James » Wed, 19 Aug 2009, 15:40

Yeah it seemed cockeyed to me too. It's really hard to estimate when you're actually driving the thing, in a pedal-to-the-metal sprint like this you're too busy hanging on, watching for other traffic, watching V and I gauges, etc, etc to count seconds reliably. It's also deceptive in the smoothness of the acceleration doesn't have the usual cues that a 'fast car' has, no surging through gearchanges for example.

I don't have the exact weight for the car, but I think it's around the maximum possible for that vehicle, somewhere near to 1600kg. It's not a light car.

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Post by Johny » Wed, 19 Aug 2009, 16:19

To get the 9.8S at 100k/h using AC150, I have to give the controller 590 Amps at 336 VDC for a 1600kg car.
I get this graph.
Image

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Power output question...

Post by acmotor » Wed, 19 Aug 2009, 17:57

Image

At least 0.2sec faster than a gen 3 prius !

Ditch the lead acid !

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Power output question...

Post by Richo » Wed, 19 Aug 2009, 18:43

woody wrote: Good news for Zeva :-)
Who's got the fastest 0-100 EV(s) now?

Tesla (Unregistered) 3.9s
Mustang ?
Bikes ?
Kearon + Jaron's Formula V


Do you think they would allow the registration of a converted vehicle to do 0-100kph in under 4secs.

I could imagine my AC motor wound for 200kW output.
Then through a 2.2:1 reduction drive.
The BMW would just do 0-100kph in under 4secs.
AND pull 1G while doing so!
Nah they'd never pass it at the registration office.
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A bike perhaps.
Somone build an eV superbike.
Please.
Preferably in WA Image
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Power output question...

Post by Tritium_James » Wed, 19 Aug 2009, 18:47

I want (among other things) a converted Ariel Atom. Yes, I've seen the wrightspeed car, something like that would do nicely. It's 0-100 in ~3s. I'd rather my motor controller in it instead of the ACP setup though!

Richo, of course they'd pass your BMW at the registration office. The rewound motor nameplate says 22kW! Image

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Power output question...

Post by woody » Wed, 19 Aug 2009, 18:58

I was planning on having a "normal" mode and a "Woody" mode for my EV. So you give it to them in "Normal" mode.
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Post by acmotor » Wed, 19 Aug 2009, 19:43

What about the 'normal for woody' mode. But then what is normal woody ? Image
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Post by woody » Wed, 19 Aug 2009, 20:07

I don't think anyone on this forum is in any danger of being normal.

I'd thought of a 1200cc mode, 1500cc mode, Lotus mode to give the same peak torque at each RPM as a factory motor + gearbox. This could be done with an external uC between potbox and VFD. The same uC could also do the speedo / tacho.

Way OT, here is the circuit diagram for the whole Cortina, including a bunch of options I don't have (Pass Lamp, Long Range Lamp, Reversing Lamp, Heater) :
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Power output question...

Post by bga » Thu, 20 Aug 2009, 00:37

Hmm,

Typical car circuit diagram. It'd make more sense if they didn't try to economise on paper Image

Then again, it's gets one in the right frame of mind for chasing wires in the loom.

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