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Re: [EVDL] too many amps? Easy enough for a caveman to.....

Hello Listers,

This instance brings up a good example how builders
fail to 'see' where their conversions perform at their
best or within the limits of their current batteries,
motor, weight, gearing, etc. - setups. The evcalc and
others that are out there do a pretty decent job of
predicting the performances, but the builders/drivers
arent identifying why something aint working like they
think it should. I think it is because the numbers
start confusing them from info overload. To
counteract this problem I had been working on a simple
graph to illustrate performance ranges as part of a
tutorial (and eventual graph&calc program) At
electricmotorcycles.net .

This graph is intended to show the limits in max
amps/torque/gearing to max voltage/rpm/speed of a DC
setup.
Simplistically, the max 'deliverable' amperage of the
circuit is determined by the lowest max value of the
four elements of all electric vehicles - the
batteries, the controller, the motor, and all wiring.
Combine this with the [email protected] (or going further
[email protected] HP), this range becomes the Y-axis.
Then using the max voltage, as determined by the
lowest max value of the batteries, motor, or
controller, draw the max rpm that the motor can travel
at the rated voltage. Combine this with the gearing
to wheel to speed, this range becomes the X-axis.
http://electricmotorcycles.net/uploads/wordpress/2007/09/4-to-1-gear-ratio-to-torque-to-mph.JPG

This allows the builder/driver to use which ever
evcalc or formulae that she-he-it sees fit to plot
performance for maintaining speed per the setup. OR
(Sorry to use you as an example Michael), the right
gear and speed for the gradient(hill). (Acceleration
is a different graph)
http://electricmotorcycles.net/uploads/wordpress/2007/09/gear-ratio-to-torque-to-mph.JPG

I propose that this graph be used in the future (to
anyone that wants to) for illustrating and explaining
purposes because it is relatively simple and
versatile. i.e. rotating mass can be added into the
evcalc. (I even tried to add heat ranges of the Etek
to ascertain why some were burning up. As well as
predicting CVT performance range limits)

Lyle Sloan


--- Michael Mohlere wrote:

> Paul -
>
> Took your advice and tackled "the hill" with the
> truck in 2nd gear
> going 35 mph the whole way up....no problem. Thanks
> for the advice!
> I received the fuses from mouser in the mail today,
> so will be putting
> the truck back into its original configuration this
> weekend - should
> eliminate the 220 volt charging issue.
>
> Mike
>
> On 10/23/07, Paul <[email protected]> wrote:
> > I'm going to take a guess that the motor rpm was a
> bit low. Lower
> > rpms are great for acceleration (and torque in
> general) but the motor
> > amps will be quite a bit higher than the battery
> amps. The DCP
> > controllers can cut back for either excess battery
> amps (MOSFETs
> > getting hot) or excess motor amps (freewheel
> diodes getting hot.) Its
> > around 3500 rpm that the controller can go full on
> (freewheel diodes
> > not being used, battery amps equal motor amps)
> with your foot to the
> > floor. If your foot is not on the floor the motor
> amps are higher
> > than the battery amps. The DCP 450 can dish out up
> to 625 motor amps,
> > but not for long.
> >
> > You should verify the fan is running full tilt
> before the current
> > starts being reduced. Its supposed to be the first
> line of heat
> > control and current restrictions are the backup
> plan.
> >
> > The DCP 600 should have higher continuous current
> limits. On the
> > other hand, flooded golf cart batteries shouldn't
> really hang out at
> > 250 amps for extended periods of time anyway.
> >
> > Paul Gooch
> >
> > On Oct 22, 2007, at 3:08 AM, Michael Mohlere
> wrote:
> >
> > > My 1981 rabbit pickup (see sig) has a DCP 450
> (Raptor) Controller. I
> > > couldn't resist the urge to conquer a fairly
> major hill....according
> > > to the emeter it was pulling between 200-250
> amps all the way up. I
> > > could tell that the 450 started limiting the
> amps (going into creep
> > > mode) on the way up. My questions is this:
> would upgrading to a 600
> > > allow me to pull more amps longer, or am I
> stressing the system way
> > > too much already by pulling that many amps
> continuously....I'm sure I
> > > will get some slap on the wrist responses, but I
> guess that is how we
> > > learn...
> >
> > _______________________________________________
> > For subscription options, see
> > http://lists.sjsu.edu/mailman/listinfo/ev
> >
>
>
> --
> Michael Mohlere
> My EV: http://www.austinev.org/evalbum/296.html
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>


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