Re: More Dolphin information

["Christopher Zach" <czach@computer.org>]

Hm. The times I was looking at the computer display (and not at the road),
it was reading 60-80amps at steady state driving. Since I couldn't watch all
the time, I saved a hundred seconds of telemetry to disk while on the
highway; the 60-70amp levels I was seeing looked to me to be a bit on the
low side.On the other hand, the VW bugs had like 20-30hp and were able to do
highway speeds. Maybe it has something to do with the two-stage nature of
the motor (max torque < 3600RPM, then it shifts to max speed or something
like that).

Yes, I did mean the floor seems to be 250 volts on the pack or 10 volts per
battery. Is that a high enough do-not-exceed to prevent batteries from
reversing? What would be the signs of a reversed battery in a string?

Thanks for the other driving comments; sounds like coasting (or being in D
where regen is limited to 10%) is the best way to go. The regen works really
well when you come off the highway; drop it into L and it's like tossing an
anchor out the window.

This is *fun*

Chris


----- Original Message -----
From: "Seth" <vze3v25q@verizon.net>
To: <ev@listproc.sjsu.edu>
Sent: Sunday, June 30, 2002 9:50 PM
Subject: Re: More Dolphin information


> One note: I think you mean 250V and 10 volts per module. Or 1.67vpc.
>
> 1)
> 200 battery amps at 250V is 50kW. Or about 67hp at the motor assuming
> 100% efficiency. 67 x.85 (motor/ contorller eff.) x0.97 (gears) is about
> 55 hp to the tires. Are you sure you can pull 200A at highway speeds? If
> it is geared correctly you should be above base speed and I suspect the
> battery current will fall below the peak. I suspect you will draw max
> current between 25-35mph, but this is just a hunch. So I would expect
> you to draw something like 120-160A at highway speeds. Assuming the peak
> is 200A at base speed.
>
> 2)
> Regen is not 100% efficient, ther are motor, controller, cabling and
> battery losses involved in putting energy back into the motor. Coasting
> doesn't incur those losses. So coast if you can, regen as long and
> slowly as you can if you need to slow down (don't tailgate and do plan
> ahead) and use the brakes as little as is practical and safe.
>
> 3)
> Slower up hills is a mixed bag. *Mostly* slower is better. But if you
> are going really slowly (perhaps 10-15 mph), then you can be in a less
> efficient mode for the motor, despite drawing less current and having
> less air drag. The dynamic range for AC induction is good, but not
> infintite and the efficiency can fall off at either end. Current AC
> drives and energy systems make *single gear ratio* AC drive EVs a
> compromise between range, starting torque, battery mass, motor
> efficiency and top speed.
>
> Seth
>
> Christopher Zach wrote:
> >
> > The Dolphin controller appears to have two cut-off's. The system will
not
> > draw more than 200amps at a time from the batteries, and the system will
not
> > draw the batteries below 350 volts (10.0 vpc).
> >
> > Typical highway motoring currents are around 60-70amps at 290-300 volts.
> > Flooring it doesn't seem to do much more than drive the amps up to
150-200;
> > the same results can be gotten by gently accelerating and going for
accel on
> > downhills. This might be a limit of the single gear concept.
> >
> > Is there a "tip list" for optimal EV driving anywhere? One question I
have
> > is which is better: A bit of regen (which slows you down with your foot
off
> > the pedal) or coasting (putting the car in neutral)? Is it better to let
> > speed decay a bit on hills, or keep speed constant with some power?
> >
> > Chris
>
> --
> vze3v25q@verizondotnet
>
>
>