(ET) Electronic controls part 3

[Kirkvg aol com]

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.