What is a "Ground"

[posplayr]

Originally Posted by XXXXX
.............. here's the thing i don't always comprehend what im reading but in the link to charging system health there is allot of talk about the ground....... is this talk referring to grounding the battery, r/r, to the frame. is the frame the (single point ground)?

Hi XXXX,
This is actually a very good question. Going by the name "ground" or "earth" as the Brits call it you would be a bit confused.

Keeping it simple and general is not always an easy task, but I will try.

"Ground" generally refers to a point in a circuit which is available as a "return path" to the source of the power.

Generally all ground points are considered to be a zero potential (the lowest voltage in a circuit excluding negative supplies; I don't want to confuse you) . As an example with cars, the frame is generally considered a "ground" because any current that comes from the car battery flows back to the battery via the low resistance path of the frame and is picked up by a frame ground attached to ultimately get back to the the negative side of the battery.

This is traditional and common thinking and generally is accurate enough even when the car (alternator) is charging and it is actually the source of power. Current always returns to the source otherwise it would not be a circuit. So when something is charging the battery, it is actually the source not the battery. Again generally this fine detail doesnt really matter and it is OK to think of the FRAME as the "ground".

However in the case of motorcycles that have SHUNT PM stator charging systems that are very susceptible to connection issues that the specific connection methods for the current paths are just much more important.

The main objective on a motorcycle is to make the R/R terminal voltage (between R/R+ and -) be as close to the battery terminal voltage+/- as possible. This is because the R/R needs to know what the battery voltage is in order to control that value. Even for a 6 wire R/R, the voltage drops on the ground side is still important. The 6 wire avoids high side voltage measurements errors but not low side. This would require a full differential mode measurement which has not been picked up by the industry.

One approach is to put big wires directly between the R/R and battery and this can be OK. A big wire will have no voltage drop, but most of the voltage drop is in the connections so a smaller wire with big connections is probably about as good as a big wire with big connections. All the resistance is in the connections. The main drawback if there is one is that you have altered the OEM current paths relative to the fuse box when you do this. You just have to realize this.

The other approach (using stock OEM and smaller wires) is to take care in the specific path of current flows between the battery and the R/R you can also minimize voltage drops between R/R and battery.

In this context, this objective is what single point grounding is all about. It minimizes voltage drops between the battery and R/R by minimizing the currents that flow between the two. It does this by avoiding current sharing. SPECIFICALLY The ground wire between the battery and the R/R(-) only carries current that was used to charge the battery; nothing else.


When you look at a schematic you will see different types of ground symbols. You have to pay attention to that. On the GS there are ground symbols that represent "FRAME GROUND" meaning the frame is being used as part of the circuit to return current. The are also other ground symbols (for example on the R/R-) which are called "ground" but not connected to the frame.

DISCUSSION: "Where is the current really coming from"
When the bike is off and the battery is the only source of power then all currents return back to the battery. Generally this occurs through a frame/engine/main negative battery ground to get back to the battery(-).

When the bike is running and charging all the current has to get back to the R/R(-). Depending on how you have your grounds setup can have serious impacts to your charging system.


DISCUSSION: "single point ground" In the case of a motorcycle, I have added further discussion on what it does:

1. It collects all currents to a single point so that they can return to the R/R(-) with minimum voltage drops.
2. it minimizes current sharing among the return paths. For example and primarily the battery charging current return (to R/R) from the battery is on a separate wire from all other main current(e.g. coils,lights).
3. The R/R is connected directly across the battery with the lowest voltage drops from other currents not coming through the battery.

You will probably have to read more about electricity to understand the details of a single point ground. Alot of electrical engineers don't actually understand what it is.

Once you are able to visualize how the current must flow to get back to the source(i.e. the R/R-), you will be able to understand how to get the currents to flow with the lowest voltage drops. Voltage drops occur because of current moving through a resistance. If you have a given amount of resistance to live with (in this case an ever corroding contact) then reducing the amount of current in each lead is all you can do. However all currents have to return to the source, to the same place, namely back to a "single point" ground before reentering back into the R/R(-). __________________

[bubby]

Hi XXXX,

Once you are able to visualize how the current must flow to get back to the source(i.e. the R/R-), you will be able to understand how to get the currents to flow with the lowest voltage drops. Voltage drops occur because of current moving through a resistance. If you have a given amount of resistance to live with (in this case an ever corroding contact) then reducing the amount of current in each lead is all you can do. However all currents have to return to the source, to the same place, namely back to a "single point" ground before reentering back into the R/R(-). __________________

i was once told that silver has a lower resistance and higher conductivity but cost more than copper. if this is true would the cost be worth knowing you have the best wires money can buy and does any know where some one might be able to get some. or maybe there are some brands of wire that claim to have a lower resistance, have they been tested? kinda like a try it before you buy it

[Nessism]

i was once told that silver has a lower resistance and higher conductivity but cost more than copper. if this is true would the cost be worth knowing you have the best wires money can buy and does any know where some one might be able to get some. or maybe there are some brands of wire that claim to have a lower resistance, have they been tested? kinda like a try it before you buy it

Unnecessary concern. Copper is fine.

[posplayr]

Generally I have seen two Black/White ring lug grounds on any GS harness.

• One of these goes to the battery box bolt as a frame ground.
• One goes to where ever the R/R is mounted or the R/R(-) is connected to return current to the R/R(-).

If the battery box had a component on it that is returning current through the frame then it would also need to be grounded to the frame somehow.

Generally the only things that I can recall return current via the frame (or not through the harness) are:

• mechanical contact points
• Dyna-S
• Spark Plug secondary current (of the spark)
• Oil sensor light
• Gear position indicator
• starter motor
• starter solenoid {unless direct to R/R(-)}
• Ignitor

[jesustheplumber]

lets all plate our connectors in gold! that'll get the current flowing!

[Adler]

lets all plate our connectors in gold! that'll get the current flowing!

No way man, we should use billet... Billet is the best at everything.

[jesustheplumber]

No way man, we should use billet... Billet is the best at everything.

lol.. in all honesty i think gold is second only to silver in conductivity. if i remember correctly aluminum is a very poor conductor.

[bubby]

i found this today at work in my bosses elc book this is the order of metals with the lowest resistance first
Silver
Copper
Annealed Copper
gold
Aluminium

[spchips]

Gold has a higher resistance than copper...

But the reason connectors only are gold plated is that it will always have a true bare metal finish, (not gold oxide). Aluminum, copper, silver, and just about every other metal forms a thin protective oxide patina on the surface. Metal oxides are strong insulators, causing the connection issues mentioned above.

[gearhead13]

They make power lines out of aluminum for the lower weight, the trade off is worthwhile. The aluminum has higher resistance but can be made thicker I guess because of the lower weight. Less strain on the towers too.

[jesustheplumber]

kinda close but still wrong. story of my life.

[posplayr]

I purposely stayed away from the house wiring discussion because it is a marginal analogy at best. An analogy is supposed to be to help understanding GS grounding and I don't think it does.

For house wiring, "ground" is actually a short to "earth" (copper spike into the ground primarily for safety) so it really is an appropriate and "meaningful" terminology. In contrast the AC current return paths (WHITE wire) are the neutral lines, if you think of the hot as one of the 120V phase legs (BLACK or other than WHITE).

The use of the terms ("ground" and "earth") in car electrical is different as these refer to frame return paths to the battery.

So generally in house wiring, "grounds" are safety features so that if there is a short in the equipment, a person is not shocked when they touch the equipment.

In auto terminology the ground is how all normally operating currents returns to the source, e.g. frame return to battery(-).

[posplayr]

The attached diagram shows a simplified wiring diagram with a single point ground. The very effective method of implementing a single point ground is to collect all of the ground wires shown and attached to the R/R(-) return line.

1. Stacked ring lugs with dielectric grease or
2. just soldering them all together

would be very effective.

The single point could also be bolted together at the frame as long as you minimize teh wire between R/R(-) and frame single point.

Here is a simplified diagram showing the connections for a 6 wire R/R. Just omit the Brown wire for a 5 wire R/R. The R/R has doubled up wires for both (+) and (-) so it is actually an 8 wire as shown.



The main benefit of this approach is that the R/R is wired directly across the battery (except for an inline fuse) and the only currents between the battery and R/R are the BATTERY charging currents.

[bubby]

this is AWSOME!!!

so whats the difference in #1 through #4 the mounting plate? or are they different r/r? ... sry im like a sponge but the more i learn the more i want to know

[posplayr]

so whats the difference in #1 through #4 the mounting plate? or are they different r/r? ... sry im like a sponge but the more i learn the more i want to know

On many GS's the starter solenoid and R/R are mounted to the same side plate. One harness ground wire (ring lug) is typically connected to one of the solenoid mounting bolts as the solenoid grounds through it's mount.

You can either leave that where it is (if it is a clean ground) as in #4

or consolidate all of the grounds as they are in #1

To avoid keeping grounds clean in multiple places. They all would join in the same place with #1 , #2 or #3