RE: (ET) E12S and a Curtis controller??

["Hazen, Dwight L" <hazen indiana edu>]

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.