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Re: (ET) shunt for Alltrax E15 retrofit - what specs, or how to substitute?
Just keep in mind, the Klixon breaker on the motor is not a simple thermal switch. It is a circuit breaker that reduces its trip with increased temp. Typical value is 105 amps nominal. It protects the entire tractor from an overload, not just the motor.
Rob Brockway
E-12M with a curtis controller
Joel Parks nokia com wrote:
My E15 (that I picked up off EBay last month with mower and snowblower) wouldn't move under its own power. Opening up the control box, I found a rat's nest. Actually the previous owner said they were chipmunks, but in any case it was a mess. Lots of wires were chewed and corroded and I didn't know where to start. Since it is a HA (relatively late-model), most of the diagrams I've been able to download didn't relate to my circuit with 5 contactors and different control logic. Somebody's website I saw mentioned a conversion using a Curtis 1204 or some such controller, and I decided new technology was the way to go. Luckily (since I'm not an electrical engineer) before I ordered one of those I found this list and discovered the Alltrax controller. I ordered it last week and started the installation.
I'm nearly done but I've hit a couple of snags. Steve Richardson at Alltrax
answered my questions about the external resistor (1 W 10 Ohm) and diode (3A 100V) shown on their schematic - it turns out I need to obtain those myself.
But the big problem is that my original circuit didn't have a shunt, at least not one I recognized as such. And if it was just a length of wire like Steve said he saw on a E20, then I have no idea which wire it was. Evparts.com lists a pretty good selection of shunts (http://www.evparts.com/shopping/?id=943) under the Renewable section, but I don't know which one to get to match the ammeter in the E15.
Also, I re-used one of the leftover open-frame relays to implement key-switch and seat-switch interruption of the PTO contactor, a feature originally present in my machine and not shown on the Alltrax schematic. Since I have an almost 3-year old around, I thought the safety feature was worth an extra 1/2 hour of crimping and locating the right interconnections to use.
Steve suggested that the thermal cut-out
switch mounted on the drive motor could be rewired in series with the key-switch and seat-switch, rather than in series with the M- lead, this would serve the same effect and reduce the current carried by the thermal cut-out and thus any arcing if the cut-out opens. Using a 18-gauge wire would simplify rewiring for anyone who's removed the chassis wiring. I guess if I do this I'll add an override switch so I can debug which switch is failing (key, seat, or thermal cut-out).
Questions:
Should I get an off-the-shelf shunt for this meter? Or if I'm better off solving my problem the old-fashioned way (fabricating my own shunt), does anyone know the full-scale millivolt input current for the OEM ammeter?
Also, what wire gauges are used for the battery interconnects and for the motor power and PTO connections?
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