I agree good discussion! IF the motors will take the extra voltage
and
it sounds like they will then taking out the charger and replacing it
with a 6 volt battery sounds like the way to go. If you do not want
nor
need the extra voltage just leave it the way it is. Using a modern
controller will make the number of connections less and we can use
larger wire and better connectors than the factory did. The bottom
line
is we may not need the extra battery to make up for all the voltage
drop
in the old system. Has anyone put a voltmeter on the motor connectors
and driven up a hill to see how much it drops under load? My guess
is a
lot. Even on cold days the wire bundles gat warm and the contactor
cabinet is warm, heat is loss. The voltage at the motor is what
makes it
go not the voltage at the battery terminals.
It will be good to have a controller that we can program to set the
acceleration and deceleration! This is going to be fun!
The 36 volt battery charger that charges three 12 volts battery
systems
looks interesting. My E20 wants one!
Steve, yes we need cruise control!
Dwight
Dwight L. Hazen, Indiana University, UITS
Bloomington, In. 47408-7378
812-855-5367 IP phone 317-278-4014
hazen indiana edu http://php.ucs.indiana.edu/~hazen/
Ham Radio wb9tlh arrl net http://wb9tlh.ampr.us
-----Original Message-----
From: Andrew Poush [mailto:agp vt edu]
Sent: Saturday, June 28, 2003 10:33 PM
To: elec-trak cosmos phy tufts edu
Subject: Re: (ET) E12S and a curtis controller??
Wow. I am really pleased with the discussion that spun off my email.
David Roden is pretty accurate in what he says about Mark Hanson's
modifications. I should know because I own one of the two E-15s Mark
modified. And I did my graduate studies in DC-DC power conversion
and
motor control. Mark did use two identical controllers, one for the
drive and one for the PTO. The battery pack is 48V and the
accessories
are tapped off the pack. I can put the tractor in any gear, vary the
speed command so that any voltage from 0 to 48V is applied, and it is
efficient and smooth. I never need to change gears while I mow. I
can
throttle down and switch to reverse in a blink, even if the tractor
is
not quite at rest. I never use the foot brake while mowing since the
reverse is so handy. But my top speed is 4 mph whereas before the
modifications it would have been 10 mph. I don't really NEED the
speed
for mowing and snow-plowing. I just want it for the fun of giving my
daughter faster rides.
David did say that he would trust that since Mark put a second
controller on the PTO that it must indicate that running the mower
deck
at 48V is too risky to attempt. In fact, Mark told me just the
opposite. The mower motors can be run at higher voltage with little
or
no risk. I generally run them at 36V but crank them up when the
grass
gets very thick. I have run them that way for over a year and never
tripped the thermal overload or gotten the motors hot enough that I
couldn't hold my hand on any one of them indefinitely. This E-15 is
a
great ride and I only look forward to it getting better if this kit
Steve's company is developing can be made affordable.
One more feature I would like to see on a controller for the ET is
cruise control. The ability to set a cruise speed and then reduce
speed (or even reverse direction) for maneuvering around obstacles
and
then resume the preset speed would be very useful to me. Currently,
I
can set a speed but cannot resume it after changing speed. The speed
command input to the controller is a slider potentiometer next to the
forward/reverse switch (rather than a foot pedal). I am not sure
that
a foot pedal is compatible with implementing a cruise control cost
effectively. What do you think, Steve? Is cruise control a
possibility?
Andy
PS - I will never go back to a 36V battery pack.
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