XLR Port Negative Pin

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  • #1
moriah
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TL;DR Summary
I’m trying to understand the basics of the wiring inside the battery pack of my scooter. It uses a standard 3 pin XLR port, but I’m not sure why the negative pin is not attached to a wire. From my research on forums like this one, I gather that the negative wire can be attached to the ground pin (pin 1), because the return path is somehow synonymous with zero reference level.
Is zero reference level synonymous with the return path of a current, i.e., the negative wire? If so, where a ZRL is being used by a circuit, is the ground pin and the negative pin in a XLR port the same thing?
 

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  • #2
berkeman
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Summary:: I’m trying to understand the basics of the wiring inside the battery pack of my scooter. It uses a standard 3 pin XLR port, but I’m not sure why the negative pin is not attached to a wire. From my research on forums like this one, I gather that the negative wire can be attached to the ground pin (pin 1), because the return path is somehow synonymous with zero reference level.

Is zero reference level synonymous with the return path of a current, i.e., the negative wire? If so, where a ZRL is being used by a circuit, is the ground pin and the negative pin in a XLR port the same thing?
Welcome to PF.

What scooter? Do you have a datasheet for the battery pack? Do you have a wiring diagram for the scooter?

It sounds like they just used an XLR connector for the mechanical convenience and only connected the +/- battery terminals to the two non-ground pins. There is no need for a shield like you might have in audio applications of the XLR connector, so no connection was made to that pin.

https://en.wikipedia.org/wiki/XLR_connector

1634755583480.png
 
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  • #3
moriah
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From what I understand, the ground pin is pin #1. That pin is connected to a wire, and so is pin #2. Pin #3 which stands apart from the other two, is not connected to a wire. It is a Rascal 140 T.
205F566B-2F07-41B7-B2E7-CEC31C1E3B48.jpeg
 
  • #4
berkeman
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Again, it looks like they must have used the XLR connector for robust mechanical convenience. A battery only has two terminals so their choice of how to assign those two connections to the 3-pin XLR connector is a bit arbitrary.

A battery charger connector can involve other connections, if there is an intelligent battery charger circuit (like with cell phones and other USB device charging systems). That does not seem to be what is going on with your scooter, right? :smile:
 
  • #5
Tom.G
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The pinout you describe seems pretty standard. A neighbor has a powered wheelchair that has an XLR connector for charging. The battery is connected to the two outer pins, 1&3 of a 3-pin XLR.

A quick look at data sheets shows Current Rating of 15A to 16A and 50VAC Voltage rating. They seem like a good choice with rating, mechanical strength, and positive, locking mating.

Cheers,
Tom
 
  • #6
moriah
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What would happen if I disconnected the wire from pin 1, and just connected pin 2 and 3 to wires? Because it is most likely a zero reference level ground, I would think that connecting pin 1 would be unnecessary.
 
  • #7
moriah
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No it’s not a smart charger.🙂
 
  • #8
Tom.G
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What would happen if I disconnected the wire from pin 1, and just connected pin 2 and 3 to wires? Because it is most likely a zero reference level ground, I would think that connecting pin 1 would be unnecessary.
You would be modifying a design that you do not understand in an unknown, likely inappropriate, way; with no known benefit.

The wiring diagram you supplied shows connections to all 3 XLR pins. I doubt that the manufacturer would expend both the time and material cost for anything that didn't have a purpose.

If you decide to proceed, I hope you have spare parts on hand -- and the ability to troubleshoot enough to replace the appropriate part(s).
 
  • #9
moriah
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I agree. I’m just going to try to follow the diagram. I’m just wondering how the scooter has been able to operate for so long without the diagram being followed.
 

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