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(ET) Electronic controls part 3
- Subject: (ET) Electronic controls part 3
- From: Kirkvg aol com
- Date: Sat, 8 Apr 2000 04:16:13 EDT
- Sender: owner-elec-trak cosmos5 phy tufts edu
To all: I "borrowed" 6 Trojan T145 batteries out of a Toyota electric
truck
that my students converted about 5 years ago and dropped them in my E-20
today. I then took it out and ran in for a few minutes and everything
seemed
OK. So I decided to really test it out and hooked up the mower and went
out
and cut about a half acre of grass. I was surprised at how low the power
usage meter stayed. While mowing it usually ran at about !/3 in the green
or
less.It has been a couple of years since I used it but it seems like it
ran
close to the yellow most of the time then. I plan on taking current
readings
in the future to check the calibration on my meter. I stopped after about
10
minutes and felt the motor, controller and my field transistor. The motor
and
controller were very cool but my transistor was pretty warm/hot. But what
the
heck I wasn't about to stop now so I continued on cutting grass like a mad
fool. Everything seemed to work fine until I hit a pretty good sized bump
and
the seat shifted (I had pulled the pins and set the seat plate on a couple
of
boards on top of the bateries because the batteries were too tall) and the
seat plate shorted out two battery terminals and arced pretty good! Anyway
after throwing the seat off as I jumped ship I repositioned the seat and
continued on mowing.
I got comfortable with how it was working so I started to play around with
the potentiometer that controls the field transistor and it definetly
increased the starting torque and allowed the motor to reach a higher rpm
as
I switched it from low resistance to high resistance. But I think that I
must
not have the pot right because as I turned it further toward the higher
resistance end I saw a wisp of smoke come out from under the dash in that
location and the ET slowed down. I must have smoked the pot (that doesn't
sound quite right) because the transistor cooled down and I lost almost
all
of my starting torque and reverse. The current draw also went up as I had
to
give it more pedal to maintain speed. So I decided I had better not push
my
luck any further so I parked it and put the charger on it.
All in all I think today was a huge success. I was able to mow about a
half
acre the first time out. The speed varied smoothly with throttle changes.
The
power usage seemed good. Even my wife was impressed! And that is not easy
to
do!
I hope to check out the field circuit on Sunday and based on what I find I
hope to modify it soon. Life is going to get busy once spring break is
over
this weekend so I probably won't get much "play" time till June. But I
will
update as progress is made. Thanks for all of the interest! Kirk
P.S. - Once I have a little more seat time I will post my observations
concerning speed stability, motor braking on downhill slopes,
driveability,
etc.