Hey "JINGLES". Good to hear from you again. AC and DC are just alike in this respect. They both need a completed path from the source, to the load, and back to the source. In a single circuit situation. The current flow will be the same on both sides of the circuit. It is possible that there my be some diffrences because of the load. But I only have an "applied" understanding of this theory. But you can use a clamp-on meter on either side of the circuit and see the same results. You are correct about the diference in flow between AC and DC. Direct Current flows continusly in one direction. Alternating Current cycles from a positive flow to a completly oppsite negitive flow @ 60hz ( us standard ). Now for the battery cable theroy. I'm going to use my experience to take an educated guess here. So let the rebuttles fly! There are seperate ground cables on the battery. One to the block for the starter. And one to the frame for electrical devices. Since neither one will carry the full load. They do not have to be as big as the positive cable. Both of them together should = the larger power cable.
How did I do?

P.S. Thank you for the complement.

 

You are entirely deserving; and I believe you are correct about current. The total current should be the same at all points in a simple DC series circuit; but the voltage will vary (drop) after each different device/resistor. Most of the modification/added circuits we are adding to our JKs are simple DC series/parallel circuits; which do have varying currents after each parallel device/resistor. However, the total current is still the same before and after the total load (devices/resistors). So I agree with your description of the negative cable at the battery being only one component of the total negative "pathway" back to the battery. Add up all of the conductor sizes (circ. mils) running directly from the negative terminal to the engine, chassis, and body; and you'll probably exceed the circ. mils of the positive cable. That being said, I still want to know why the negative battery clamp and oftentimes the negative terminal itself are smaller than the positive side? Carry-on

 

I should have known and mentioned about the voltage drop after the load. I have seen and studied a lot of information on electrical theory over the years. But the older I get. The more that I seem to forget. Once again you force me to rely on my training and intuition to provide you with some type of logical answer. The truth may only be held in the minds of the engineers that design these systems. The first thing that crosses my mind is; are these fittings adequately sized for the load. Since we have all ready established that the current is the same on both sides of the circuit. And the smaller fitting is apparently sized to fit the load. Then the larger fitting would not having an impact on the circuit. The only thing that I can come up with related to the size difference would be some type of referance to polarity. Something like the different size slots in your standard recepticale. If there are any further explinations, I would be interested also.

 

Here is my understanding of the + and - cable sizes and terminal sizes.

Ground can found on most metal surfaces in a vehicle. As I mentiuoned before when you install lights you can run just power to the lights and ground them to nearby metal. When the lights are energized the power will flow from the battery to the light bulb, across the filament to the black wire, to the ground point, through the fender and finally across the lug to the negative cable and back to the battery. That negative lead is sized to carry the maximum sustained predicted current.

The positive lead is larger for safety reasons. From the battery you would have a wire to a relay or switch to the device. Since every device/circuit has its own "direct" line to the battery, the positive lead is larger.

Heat also factors into the discussion here. There are numerous threads discussing amperage in a given wire AWG. Since the positive wires distribute power they have to be larger so they don't over heat and burn through the insulation or melt or just spontaneously combust. The ground path is mostly made up of the frame. You would need a bolt of lightning to over heat that. The short wire from the fender lug to the battery can handle the brief spikes in demand without getting hot.

AC receptacles are easy. Hot, Neutral and Safety ground. The Hot is the smaller blade. The Neutral (aka Ground or Return) is the bigger blade. The Safety Ground is always the sideways D. You want a BIGGER (Neutral) GROUND than power (Hot). That way if the contacts corrode or don't make good contact there is more "opportunity" for the Neutral to make contact. Less possibility for the Safety Ground to act as the Neutral and less possibility of the device external metal parts being energized.

 

I did electronic theory when I joined the Air Force and forgot everything about it. Sadly. However, by reading a bunch on the interweb and these posts it seems that you can ground anything to anywhere on the main body of the jeep. Because technically a jeep is a tub of metal sitting on metal rails. Everything except doors, hood, tailgate. Am I right in saying that? Make sure to have metal on metal contact and you should in theory be okay. Unless struck my lightning of course.

 

Yes Vernnz. The ground has to be sized according to the predicted load of the OEM system.Plus maybe a little oversuze for safety. But there is no way that you can predict what different Jeepers will install on our vehicles.

All currents that flow away from the source have to return to the source. So the current carrying fittings have to be rated to carry those flows. Therefor both outfeed and infeed only have to be sized equal. Ony oversize would have no impact. Any undersize would have problems.


Your theory on the ground is acceptable. However, like I previously stated, oversizing is unnecessary. The size does matter though. It hast to be properly sized.

Maybe the contact area does have a baring here. But the main reason for the different size slots is to insure proper polarity. On some devices the neutral is not considered to be dangerous. So it would be desirable to make sure that all devices are plugged in correctly.

Yes you can ground small load devices and be O.K. But some people have fried their Jeeps electronics by ground larger load devices like sterio amps, power inverters, winches, ect. Yes the Jeep frame will cary a tremendous amount of current. But that current still has to make the complete path back to the battery ( source ). And the conductor from the battery to the frame is not very big.

 

Polarity is mainly nec for lamp sockets; to avoid shock. Hot wire in lamp cord must go to socket switch (if present); which controls the energy to the socket center/bottom contact. The NUT wire goes to socket threaded shell; which is the part of the socket more easily contacted with the hand, when changing bulbs. Safety is increased; because one must insert finger/tool to the bottom of socket to reach potential shock. The shell is relatively safe in this wiring configuration.

 

I remember reading a post in which the poster had mounted a winch using the frame as the ground path. Apparently, the bonding strap from frame-to-body either failed/melted, or was a loose connection. Hundreds of amps were looking for a path back to the battery. They found one.... The rear flex/steel brake lines fried! The current was flowing from the frame thru the brake lines to the drive-train, to the engine/starter ground strap, and to the battery; but the brake lines couldn't handle the current, and melted.
So, it's a good idea to run a separate ground wire to the battery, for those high amperage loads. The smaller device loads can either use a separate ground wire back to the battery; or one could add larger gauge bonding straps from batt-to-body and from frame-to-body; and ground the device at the frame or body
Separate/dedicated ground wires can make it easier to troubleshoot non-op circuits. This is one reason I like the "power distribution center and switch systems".

 

Agreed, but there are a lot of other reasons to maintain proper polarity. Some motors will run in the oppsite direction when the polarity is reversed. Some electronic equipment will let go of the magic smoke if the polarity is reversed. Double insulated tools ( that do not have a ground ) depend on proper polarity to keep the user safe. And it's nice to know that the polarity has not been reversed when working on electrical equipment.