Andrew Shadow
Site Supporter
I am curious about why so many of the auxiliary fuse boxes that are sold also have a ground bar included. Does not seem practical to me to run a power wire from a fuse box under the seat to an accessory at the front of the bike, and then run another ground wire the length of the bike all the way back to the fuse block ground bar. What is the advantage of this over simply running the ground wire to a solid engine/frame ground near the accessory that is being added?
I understand that using an existing ground wire is rarely a good option as you risk overloading that ground circuit. I am excluding that option in this scenario and I am assuming that all wiring and connections are proper. If a sufficiently sized wire is run from the accessory to a ground point on the engine/frame you will have a robust ground path back to the battery through the frame and negative battery cable.
The only advantage that I see is that you are adding additional ground carrying capacity back to the battery negative terminal assuming that you wire the ground bar of the fuse block directly to the battery negative terminal as is intended. I don’t see the need for this however. The negative battery cable is sized to handle considerably more load than what can be drawn by the starter motor and all of the other electrical equipment that is powered when the key is turned on and the starter button is engaged. Once the engine is running there is no more demand from the starter motor. This leaves a large unused capacity available in this cable. I would think that this available unused capacity in the negative battery cable far exceeds the capacity being added by running a # 10 wire (what typically seems to be recommended) from the fuse block ground bar to the negative battery terminal. If it isn't wired directly to the battery terminal it is definitely accomplishing nothing.
I cannot possibly imagine adding enough accessories to even approach, let alone exceed, the capacity of the negative battery cable. So why add another ground bar wired directly to the battery?
It seems to me that all it accomplishes is to make the fuse block bigger and more cumbersome without any significant benefit. The only advantage that I see is having a centralized and easy access point to all of the ground connections of your added accessories. I am not sure that this advantage outweighs the disadvantages of a larger fuse block, when space is at a premium, as well as all of the additional wiring that this requires.
What am I missing?
I understand that using an existing ground wire is rarely a good option as you risk overloading that ground circuit. I am excluding that option in this scenario and I am assuming that all wiring and connections are proper. If a sufficiently sized wire is run from the accessory to a ground point on the engine/frame you will have a robust ground path back to the battery through the frame and negative battery cable.
The only advantage that I see is that you are adding additional ground carrying capacity back to the battery negative terminal assuming that you wire the ground bar of the fuse block directly to the battery negative terminal as is intended. I don’t see the need for this however. The negative battery cable is sized to handle considerably more load than what can be drawn by the starter motor and all of the other electrical equipment that is powered when the key is turned on and the starter button is engaged. Once the engine is running there is no more demand from the starter motor. This leaves a large unused capacity available in this cable. I would think that this available unused capacity in the negative battery cable far exceeds the capacity being added by running a # 10 wire (what typically seems to be recommended) from the fuse block ground bar to the negative battery terminal. If it isn't wired directly to the battery terminal it is definitely accomplishing nothing.
I cannot possibly imagine adding enough accessories to even approach, let alone exceed, the capacity of the negative battery cable. So why add another ground bar wired directly to the battery?
It seems to me that all it accomplishes is to make the fuse block bigger and more cumbersome without any significant benefit. The only advantage that I see is having a centralized and easy access point to all of the ground connections of your added accessories. I am not sure that this advantage outweighs the disadvantages of a larger fuse block, when space is at a premium, as well as all of the additional wiring that this requires.
What am I missing?
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