Hi all,
i've been tinkering with my older E20 (AA model) for a while to
get it to run. Its had more problems than I hoped for (some due
to mice, others due to previous abuse I think):
- bad field diodes (replaced)
- bad current limiting transistor (disabled FW override relay for right
now)
- bad micro switches in speed control (replaced)
- bad motor bearings, motor vibrations (replaced with a good E15 motor for
now)
- bad main disconnect (replaced)
- bad batteries (replaced with used T105s)
- bad charger (diodes blown, charging via external charger)
Anyhow, after fixing all these things the AA still doesn't run nearly
as good as my E20 CC tractor. It simply draws way to much current for
what it does. This was the case with the vibrating E20 motor and didn't
get better with the good E15 motor. D2 speed is basically useless as
the power meter rarely leaves the red zone unless I am going downhill
and D1 ends up being faster or as fast for all intents and purposes.
On my other E20 the D2 speed is still beefy and only goes into the
red if I drive up hill with full field weakening etc.
Yesterday I did a 30 min full-power test (power needle always in
the red, 50% at the far right end of the meter) run in Speed 4-8, to see
what if something heats up. Here the results:
- all battery posts and cables remain cold
- motor armature posts get warm, motor outside remainded cold
- klixon connections on motor got pretty warm, almost too warm to
for more than a second but klixon didn't fire (yet)
(I'd guess it was not long enough)
- all contactor posts on the F and R contactors got warm, one got
to the point where it was almost too hot to touch
- power resistors stayed cold
- FW shunt was sizzling (and smelling :) - didn't try touching it
The performance of the tractor under this condition was mediocre, the
battery voltage on any pair of the batteries almost never dropped
below 11.5V only once did I get it down to 10.5V which was when I almost
stalled the tractor in D2 on a steep incline, speed 4. (I could never do
that
with my other E20). I estimate that I was pulling more than 500A at
this point (based on the power meter being all the way to the right)
which would be over 15kw of power.
Now, please believe me that I usually don't abuse my tractors like this,
I just wanted to stress test it to see if the weak part would reveal
itself
or blow up. But it didn't. I was thinking the one contactor that got a bit
hotter than the others is not the best anymore, but I am not confident
that
that is the sole cause of the mediocre performance.
Wouldn't added resistance (e.g. by a bad connector, bad contactor) not
only
lower the overall performance but also the current flow (due to the
higher resistance?). However I am seeing max. current and I verified that
the
power meter is not way off. Even when running in neutral I have the
feeling that the power spikes e.g. when engaging the motor are higher
than those of my good E20. My next step would be to put a precision shunt
in the system to have an accurate measurement of the current flow. In the
future I may swap the motors (but thats a pain, these things are so
heavy).
Here are two configuration differences between my good E20 and this
tractor that I think may contribute and may skew my comparison:
- the good E20 has lighter AGM/Gel batteries (I think about 150 pounds
lighter)
- the good E20 has an E20 motor
Is the D2 speed on the E15 tractors almost unusable on grass and
small inclines (it works ok, not great, on flat asphalt) or does the
E15 have a different pulley size on the transmission? (I am using
the single E15 pulley on the motor, the belt doesn't slip).
Any other suggestions?
Thanks
Markus
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