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Electric EZGO Electric EZ GO Marathon, Medalist, TXT and RXV. |
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07-28-2020, 11:04 AM | #1 |
Gone Wild
Join Date: Jul 2012
Posts: 527
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New XCT controller adjusting alltrax toolkit
I have a ezgo pds converted to 48v. I just purchased the xct 400pds and the hd solenoid from scottyb (Thanks JohnnyB for all of the help diagnosing and getting what I needed). I have a stock motor, but I do not have the speed sensor plug (I do but the wires have been cut) I was planning to connect the speed sensor, but now I am not sure that I really want it. It is my understanding that it will allow the regen braking and some recharging of the battery? I don't necessarily want this. I had the alltrax dcx model prior to this, and I understand that I shouldn't over rev the motor going down a big hill. Honestly, I am tempted to get an aftermarket motor for this cart, but see no reason now because my stock motor is fine. However, if I happen to blow the motor up, it would give me an excuse to get another motor....
So, my questions: 1- Am I missing any other benefits of the speed sensor that I may want? 2- If I want to maximize speed and torque (push the limits of this stock motor) what all would I need to adjust in the tool kit? I appreciate any and all help! |
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07-28-2020, 11:26 AM | #2 | |
Techno-Nerd
Join Date: Jun 2011
Location: West Virginia
Posts: 19,654
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Re: New XCT controller adjusting alltrax toolkit
Quote:
2. Attached is a screen print of my settings for max performance. The max RPM for a stock PDS motor should be 6500RPM. The throttle rate isn't shown, but the lower the %, the softer the takeoff. |
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07-28-2020, 11:55 AM | #3 |
Gone Wild
Join Date: Jul 2012
Posts: 527
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Re: New XCT controller adjusting alltrax toolkit
AHH, so the speed controller maximizes the torque and speed? So, I am curious, but not very smart.... when you say "optimize the dynamic field mapping" what does that mean in simple terms? Thanks again!
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07-28-2020, 12:44 PM | #4 |
Techno-Nerd
Join Date: Jun 2011
Location: West Virginia
Posts: 19,654
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Re: New XCT controller adjusting alltrax toolkit
The relative strength of the magnetic fields generated by the moving electromagnet (armature windings) and the stationary electromagnet (stator or field windings) determine if the motor has a lot of low end torque with a low max RPM or little low end torque with a high max RPM, or something between those two extremes.
The speed/torque curve of a series wound motor is more or less cast in stone by the number of turns of wire placed in the moving and stationary windings. The same is true for a sepex (separately excited) motor, but the speed/torque curve can be altered by altering the amp flow through the stationary (field) windings and this can occur while in use. This is called field mapping. In other words a cart with a sepex motor can have a torque motor to take off with and then transition to a speed motor to reach higher top speed than it would have otherwise. |
07-28-2020, 01:07 PM | #5 |
Gone Wild
Join Date: Jul 2012
Posts: 527
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Re: New XCT controller adjusting alltrax toolkit
Ok, so if I am understanding correctly, If I connect the speed controller up and enable it in the alltrax toolkit: It will allow it to send the amps to the necessary place during "take off" and change it during the course of the drive in order to reach the maximum speed?
So if I disable it all together, (this is how I currently have it) Is there just a set formula that the controller is sending a certain percentage of amps to both parts of the motor? Thanks! |
07-28-2020, 06:23 PM | #6 | |
Techno-Nerd
Join Date: Jun 2011
Location: West Virginia
Posts: 19,654
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Re: New XCT controller adjusting alltrax toolkit
Quote:
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07-28-2020, 06:34 PM | #7 |
Happy Carting
Join Date: Dec 2007
Location: Southern California
Posts: 73,358
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Re: New XCT controller adjusting alltrax toolkit
I see zero benefit to disabling the Regen brake feature in the PDS cart except your lazy but doesn't have to crawl under the cart and connect the wires
Do you know exactly what happens when an electric motor grenades at full speed and how potentially dangerous that event can be? JB can tell you what happens. |
07-28-2020, 07:24 PM | #8 | |
Techno-Nerd
Join Date: Jun 2011
Location: West Virginia
Posts: 19,654
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Re: New XCT controller adjusting alltrax toolkit
Quote:
Attachment-2 is what my stock PDS motor looked like after I went down a hill with my foot on the floor to see how fast my cart would go. The armature was spinning over 8000RPM when it exploded and welded itself to the field coil shoes, seizing the motor. Fortunately, both rear wheels locked up and I was able to to keep the cart out of the barbed wire fences on both side of the road as is slide to a stop from over 33MPH. The DCX400 was smoking when I lifted the seat to see where all the arcing noises were coming from, but the short burnt itself open before anything caught on fire. Ironically, the AN250 fuse did not blow. Had to replace both the motor and the controller. The flat spots on the rear tires are still noticeable when I drive on smooth pavement, but there's not much of that around here, so it isn't much of an issue. The replacement controller was another DCX, but I went to the XCT when they came out. Now I have my motor RPM limited so the cart will only do 25MPH. |
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07-29-2020, 07:50 AM | #9 |
Gone Wild
Join Date: Jul 2012
Posts: 527
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Re: New XCT controller adjusting alltrax toolkit
Yikes! Ok, I will not be lazy, and I will connect the speed sensor. I didn't understand the benefits, but I appreciate ya'll explaining to me. So, with my stock motor, 48v and xct400 controller will I have enough "juice" to turn the motor 6500 RPMS on flat ground? Or, will this only come into play when I am going down hill? I have 22x11x10 tires. Also, what speed should I expect? I only got about 25 mph with what I had and the dcx400 controller, but I think my dcx controller was throttled down (maybe). Thanks again.
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07-29-2020, 10:58 AM | #10 | |
Techno-Nerd
Join Date: Jun 2011
Location: West Virginia
Posts: 19,654
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Re: New XCT controller adjusting alltrax toolkit
Quote:
If your tires are truly 22" tall (the numbers embossed on sidewalls are very approximate and the true height can be off by an inch or more in either direction), then there is a mathematical speed gain of 22.2%, but that speed gain will not be fully realized since the increased tire height also induces an effective 18.2% torque loss where rubber meets road. If the tires are the low pressure type (max inflation pressure of 10PSI or less) than there is even more speed loss. You say the cart had a top speed of 25MPH with a DCX controller and a 48V battery pack and the theoretical top speed for that combination with 22" tires is about 39MPH, so the top speed was considerably below optimal. I suspect soft tires, but could have been the field map loaded in the DCX, or it could be an excessive mechanical drag the cart has. (Dragging brake shoes, bad or stiff bearings, wind shield, rear seat, etc.) A sepex motor's max RPM is determined by the mechanical load, the voltage applied to the armature and how much the field is weakened by the field mapping. In other words, some field maps have a higher max RPM than others, but that is more or less a moot point since a stock PDS motor should be RPM limited to 6500RPM or less and even that max doesn't really come into place since your motor is only reaching about 4750RPM at 25MPH with 22" tall tires. ------------- Your cart might be a little faster with the XCT and better field mapping, but for the most part, whatever was holding it back with the DCX, will still be holding it back, so your motor will not reach 6500RPM on level pavement. However, it could reach up to 35MPH going downhill, which is scary in a short wheelbase, narrow track, vehicle with rear wheel only mechanical brakes, whose stock high center of gravity has been further raise to clear oversized tires, so the max RPM in the XCT probably ought to turned down to a safer speed. (5000 maybe) |
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