Batteries, and how they're connected to the car

[dhong089]

I was always intrigued when I found out how batteries were connected to the car.

I always thought that the battery would be connected to various connectors in order to supply the power. Basically I thought there would be lots of wires running from the battery to the components. However, the negative terminal of the battery is simply attached to the frame of the car itself. Thus when the battery begins to let the electrons flow, I presume the car-components (radio, blower motor, fan, etc) receive their power from the frame, via the battery.

How wild! I never imagined that cars operated like this! Ever! Can someone explain how this works? I mean, if water or something touches the frame, wouldn’t it be dangerous? The process just seems so “primitive,” yet advanced at the same time. I had a bit of a mind explosion today when I removed my battery from my car today.

[cooljess76]

Every electronic component is grounded to the chassis. The negative cable is nothing more than a ground. The positive terminal is the power source. Electrical current can only flow through a component if it has a positive charge going in and a ground going out. Now if a positively charged wire touches a ground(bare metal connected to the chassis or one of the many brown ground wires connected to the chassis) then you'll have whats called a "short". Now almost all of the electrical components on our cars are fuse protected. This means there's a fuse in place to protect the components from overload in the event that the amperage exceeds the specifications of the component. If you look at the fuses themselves, you'll see a wire or strip of metal inside of it. The thickness of the metal determines the fuses amperage rating. If you follow the positive cable, you'll see that it goes to the fuse block first, with exception of the starter and alternator as those have built in fuses. From there, prescribed power is regulated to each individual component. The components, will all have either a ground wire attached to them or they'll be mounted directly to the chassis itself which is connected to the negative termial of the battery. When you're working on live positively charged wires, the reason you don't get shocked is because you're not grounded and the current cannot pass through you. Same as an electrical component that is not grounded. Now if you were to touch a ground while simultaneously touching a positively charged wire, the current will pass through you. As for water touching the frame and shorting something out, well this would require the water to touch the chassis(ground) AND the power source or positively charged wire at the same time in order to complete the circuit and short out that particular component. For instance, the chassis could get wet and the fog lights could get wet. As long as the water isn't one continuous connecting element allowing continuity to flow from the grounded chassis to the positively charged light, it won't short out. Now if you took a component with a circuit board, say your stereo for example, and you opened it up while it was energized, If you took a drop of water and droped it onto the board where the water was touching a positively charged wire or component AND a grounded component, that circuit would short out and likely blow a fuse. Hope that makes sense.

[dhong089]

I think I have some major problem with understanding the basics of electricity…

Here’s how I always thought; please tell me if I am understanding this correctly. The negative terminal has excess electrons (thus having a negative charge). The positive terminal has a deficiency of electrons (thus having a positive charge). When a conductor is attached from the negative terminal to the positive terminal, the electrons find a path to flow. The theory is that electrons will flow from negative to positive (unless you’re using the conventional theory where positive flows towards negative). But as long as understanding that anything with excess electrons will flow towards anything with a deficiency of electrons, it doesn’t really matter if you say “ + flow to –” or “- flows to +”

Thus I don’t understand when you say that the Positive terminal source is the “power-source” while the negative terminal is just the ground. Isn’t it the other way around? Or am I missing something here?! : (((

Also, I’m having a major problem understanding exactly what “grounding” really means. I know trucks that are transporting huge tanks of gasoline have some kind of “ground,” meaning that they have some connection from the tank to the ground (usually a grounding-strap). This is to prevent static electricity sparking the gas, because friction can cause static (the wheels contacting the ground would be the cause of the unwanted static). So the grounding-strap let’s the accumulated charge constantly discharge in order to prevent a spark.

So in general, “grounding” is just a source for electrons to “escape” to.

So isn’t the positive terminal the “Ground”? Because the negative terminal (with excess electrons) can only permit the flow of electrons if there is a positive terminal. Gah I’m so confused right now, it’s not even funny…. It would be great if anyone can clear this up : (

[cooljess76]

I have to admit, I'm not an expert and never really understood this topic completely myself. hopefully someone else can shed some light

[familytruckster]

Conventional labeling and actual electron flow are opposite...

If you touch the chassis, you are not interrupting the flow, since it goes the path of least resistance, and bodies are not very conductive....

The grounding on buses/trucks is to get rid of the excess electrons built up by static electricity..Same with Grounding rods etc...


I understand all of it, but have a hard time explaining it....

[xxxJohnBoyxxx]

The battery does flow negative to positive but the negative is called the "common reference point" in this type of system. It does not matter if electrons touch outside surfaces from the positive or negative as long as they are not invloved in the electrical loop (Battery positive to chassis). If you take a negative or positive and separately touch it to a outside source like the street it won't matter because it is not in the electrical loop of DC (direct current). You all are confusing DC with AC current

AC is totally different since it is alternating current and without a proper "ground" your electrons will have a chance to flow through you or any object that is a earth ground. AC current without a proper ground will give you a good shock since the electron alternate flow it is not direct from negative to positive like a battery or DC current.

I can explain AC in more detail but I'm not a total expert, and I'm not toally sure I'm, 100% on the above but this is what I can offer.

Best, John Smith

[dhong089]

Thanks guys. I understand now that simply touching the chassis will not induce a shock. I also learned a new lil' thing about AC current, thanks JohnBoy.

I'm still confused when people say that the negative terminal is the "ground." I simply just don't get it! But I guess I'll just forget about it and continue living my life hahaha