Why Have a Fuse Box Ground Bar?

[Andrew Shadow]

All this talk about ground loops, resistance, volts, and wires makes my head spin. How about a good ole oil thread?

jeez this thread is kinda nutzo interesting fun, what about an oil

I am only trying to broaden your horizons and am laying the ground work for the day you are all riding electric motorcycles and won't be able to discuss oil threads anymore. You will already be up to speed and prepared to debate which colour of electrons move faster.

 

[mello dude]

Cheers

 

[st11ray]

I am only trying to broaden your horizons and am laying the ground work for the day you are all riding electric motorcycles and won't be able to discuss oil threads anymore. You will already be up to speed and prepared to debate which colour of electrons move faster.

They will still need lubricants, so the oil threads won't be going anywhere.

 

[Al st1100]

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?

these are designed for the DIY and some of them do not understand ground or as the say in the UK earth. Most accessories come with 2 long wires that go to the battery and have a inline fuse.

 

[HairyHeffalump]

I have installed the Eastern Beaver PC8, too. Yes it does allow me create an 12V negative ground bus bar, just like you must in boats, but it also has other benefits. The PC8 has relay driven and an unswitched supplies and an earth cable going through dedicated pure copper wiring back to the battery terminals. This allows no extra physical connections to the battery posts making them less of a weak point in the electrical system and also does not allow galvanic action with other inaccessible components on the engine/frame. Copper wiring has minimal voltage loss. All of my accessories are therefore connected to the PC8 which makes adding, deleting or amending them easy and accessible.

In addition, because the power distribution is at the PC8, so are the respective accessory fuses; otherwise all accessories at the front of the bike must necessarily be fused and/or earthed inside the nose to protect wiring which can be a a PITA if you have problems. By having a separate ground return for accessories, including audio, you will minimise interference.

I take the attitude that the bike's wiring is designed to only handle what the bike is designed by Honda to do; any thing you add must have its own wiring to support it. Therefore the only electrical common components are the battery, alternator and main positive and earth tails (assuming the battery terminals, alternator terminals and tails can handle the current). The alternator is rated as 740W which at 13.5V output gives a current of about 55A at 5,000 rpm starter capacity is 100A at 12V so I would reckon that the positive and earth tails are deliberately over spec'd and will take anything you throw at them.

 

[SMSW]

They will still need lubricants, so the oil threads won't be going anywhere.

Probably will become grease threads.

You will already be up to speed and prepared to debate which colour of electrons move faster.

Now there is a topic we can sink our teeth into.

 

[dwalby]

You will already be up to speed and prepared to debate which colour of electrons move faster.

Now there is a topic we can sink our teeth into.

I can't wait for the discussions on which way the electrons flow.

 

[spiderman302]

The electrons flow the other direction if you are riding on left side of the road......

 

[Larry Fine]

I can't wait for the discussions on which way the electrons flow.

I know, I know! Pick me, pick me!

 

[spiderman302]

N-fets require a positive drive and P-fets require a negative drive ??, What were they smokin?
Electron's flow negative to positive and the holes go the other way.......
What is this about a valence ring?.....

 

[SMSW]

Electron's flow negative to positive and the holes go the other way.......

You got it wrong, Spidey, the holes go AWAY.

 

[Al st1100]

The electrons flow the other direction if you are riding on left side of the road......

how silly... its north to south and here is the proof

 

[spiderman302]

Conventional current flow is the "holes" moving from positive to negative. I think it is just an old school binary explanation of the atomic structure.

The holes cannot go away. If you can do that then let's turn lead into gold...........

North to South? Not, if you live below the equator...

 

[Larry Fine]

The real bottom line is that fuse-block manufacturers add them because they believe the bars help sell fuse-blocks.

 

[mello dude]

Conventional current flow is the "holes" moving from positive to negative. I think it is just an old school binary explanation of the atomic structure.

The holes cannot go away. If you can do that then let's turn lead into gold...........

North to South? Not, if you live below the equator...

N-fets require a positive drive and P-fets require a negative drive ??, What were they smokin?
Electron's flow negative to positive and the holes go the other way.......
What is this about a valence ring?.....

Jeez.... And I thought the VFR Forum guys were crazy....

 

[Andrew Shadow]

The real bottom line is that fuse-block manufacturers add them because they believe the bars help sell fuse-blocks.

This is the most convincing response I have seen so far!

 

[Andrew Shadow]

I can't wait for the discussions on which way the electrons flow.

Or if they flow at all.

 

[Larry Fine]

Or if they flow at all.

Actual electron movement is very slow, but the effect moves at almost the speed of light.

Imagine a garden hose filled with marbles, and you force another one into one end. The result is that a marble pops out of the other end immediately, but not the one you added at the first end.

 

[ST Gui]

The real bottom line is that fuse-block manufacturers add them because they believe the bars help sell fuse-blocks.

And it works especially for those who have the need and can make use of the ground bar. As on boats for instance. That's the real bottom line. It's up to the buyer to make an informed choice.

 

[Andrew Shadow]

As on boats for instance.

I thought the same thing and doing it any other way on a boat never occurred to me and I have never seen it done any other way on a boat. Curiously enough, while researching something else, I found that there seems to be a small fringe element who believe that ground bars wired directly to the battery are not the proffered method on a boat either. They believe that the negative wires should be routed to a solid connection on the engine block to make a connection back to the battery and, if necessary, upgrading to a lager size negative battery cable. This seems ridiculous to me on a boat. However, it did make me wonder if there was a difference between the two methods, based on some scientific/physics principle, on a vehicle that does have a mass of conductive metal readily available that can be used as a ground path. I didn't really find an answer looking through all of the B.S. that one has to wade through when researching something like this on the internet so I asked the question here.

It's up to the buyer to make an informed choice.

Thus the point of my starting this thread- to solicit the information. Plenty of varying responses of having successfully done it both ways have come about which is proof that sometimes there are no bad answers- the way that they are acted upon decides if the outcome is good or bad.