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Understanding DC current from battery source...

sao123

sao123

Lifer
Ok so yesterday, I had to jump start my chevy blazer because I left the dome light on and the battery went dead. once it started, I let it run at high rpms for 8-10 minutes to semi charge the battery before I left. I know it was charging, because my alternator guage was reading 16, and a fully charged system runs at 14. However I got 50-75 feet down the road and everything went dead and the car just shutoff driving 35mph down the road. So i went to walmart got a new battery and everythings good... but it got me thinking.

Even if the battery was dead, the alternator should have been enough juice to keep the car running, I know this because I can remove the black terminal off of the battery, while the car is running and the car will stay running. This implies to me that I had some sort of problem with the red side of the battery or the connection to it. Which makes sence because the red connector was heavily corroded. So I must have lost ground contact which is why everything just shut off dead.


So here are my questions...
1 If the red side of the battery (+) is the common ground for the battery, why is it called the hot side?
2 Why when jumping starting a car, do you connect good red to weak red, and strong black to engine block? This seems to imply to me that black (-) is the ground and not the red. Surely the e- are not flowing from + to - on a car battery when its exactly the opposite on every other battery known to man.
3 When connecting up a suped up stereo... once again, why do you connect it to only the red side of the battery and ground the black to the frame of the car?
This all seems to imply to me that the e- leave the black side of the battery, travel through the frame of the car(and the engine block) to their destinations, through some resistance (stereo, wipers, etc) ad then back through the cable into the positive side of the battery?
Very confusing.... someone help?
 
I don't know much about cars....
But I am 99% sure that the BLACK side is the negative side (=should be connected to ground) also on your car battery (it is on every other type of battery I have seen).

So I guess that answers your questions.
 
The positive or "hot" terminal will be visibly marked, either as red or have some kind of cover with a "+" on it. You make your last negative connection when jumping to the frame or block to avoid danger if a spark should appear. This way it will be away from the battery, which produces flammable and toxic gases.

You should not have disconnected the battery with the engine and alternator running. Many alternators can be damaged without a battery connected to them and the same can go for the rest of the electrical system. The power coming from the alternator is not clean, it's rectified 3-phase AC power, which is why it's called an "alternator". The battery acts as a device that smooths out peaks and spikes that could harm electronics in the vehicle.
 
The black side of the battery is definately the negative side of the battery... except... the negative side of the battery has all the electrons waiting to flow to the positive side of the battery(where the electron holes are)... why would you ground the negative side of the battery?

It seems that electrons are flowing from the negative side of the battery, into the engine block, through the spark plug, back through the wire into the distributer, into the spark coil and from there by wire back into the positive side of the battery...
Can someone confirm this?

I read this on an auto site... and I know it is definately incorrect...
Almost everything that is powered electrically in your car is grounded to the frame or the body of the car. These are called "grounding points" and serve to complete the power loop for sending electricity around within the car. Example: current from the positive wiring from the positive terminal of the battery, or fuse box, travels to a light bulb. Once the current has passed through the filament of the light bulb, it passes through the housing of the light bulb and grounds to the frame. The negative battery terminal is also grounded to the frame, which causes the frame to serve as a gigantic piece of wire.
Click to expand...
Remember, electrons do not flow from the positive red side of the battery, they flow to it.




You should not have disconnected the battery with the engine and alternator running. Many alternators can be damaged without a battery connected to them and the same can go for the rest of the electrical system. The power coming from the alternator is not clean, it's rectified 3-phase AC power, which is why it's called an "alternator". The battery acts as a device that smooths out peaks and spikes that could harm electronics in the vehicle.
Click to expand...
I didnt actually do this, but I know it works, because years ago it was routinely performed by mechanics as a test to verify if the alternator is bad or not.
 
The electrons do indeed flow from the negative side of the battery through the external circuit (engine block, etc.) and back into the positive side. For historical reasons, electric current is thought of as a flow of positive charge the other way. For almost every situation, it doesn't matter which way you think about it, but, since most people mean a flow of + when they say current, you will be better able to understand them if you think that way too.

Ground is the name given to the reference level for zero volts. For the past 50 or so years, cars have referenced all voltages to the negative side of the battery, so everything is positive relative to that. Ground doesn't have to do with the current flow, but with the zero voltage reference level.
 
Charge flows from negative to positive, the electrons do indeed go from the negative terminal to the positive one. Current flows from positive to negative. The reason why they're opposite is because the charge carriers are electrons and they're negative. Almost all vehicles are negative grounded, I've never come across a vehicle that wasn't but there are a few "positive grounded" vehicles where the chassis of the vehicle is positive.
 
I have never heard of current as that way. In fact my physics book says:

Flow of Charge

Charge flows when there is potential difference, or difference in potential ?voltage?, between the ends of the conductor. The flow of charge will continue until both ends reach a common potential. When there is no potential difference, there is no longer a flow of charge to the conductor. To obtain a sustained flow of charge in a conductor, a difference in potential must be maintained while charge flows from one end to the other.

Electric Current

The flow of electric charge is called electric current. In solid conductors, the electrons carry the charge through the circuit because they are free to move throughout the atomic network. These electrons are called conduction electrons. Protons do not move around because they are bound inside the atomic nuclei and are pretty much locked in place. Electric current is measured in amperes (A). An ampere is a flow of one coulomb of charge per second.




EDIT
ok n/m.. I found an interesting article on electricity misconceptions....

pasted here... hopefully this is not some bs from someone who knows nothing about which they are speaking...
Electricity Misconceptions.


Well, what is "current?"
Let's get down to the details of the problem. When trying to understand electric circuits and electrical measurements, we need a simple way to take measurements of the important entity named Electric Current. But won't we first have to figure out how much of the current is composed negative particles going one way, and positive the other? Yes, but ONLY if we want to know EVERYTHING about the electric current. The negative and positive flows are usually not equal, and the speed of the positives in one direction is usually not the same as the speed of the negatives in the other. However, there is a nasty trick we can pull which avoids having to look at the particles at all...

The main effects produced by electric current are magnetism, heating, and voltage drop across resistive conductors. These three effects DON'T CARE about the amounts of positive and negative particles, or about their speed, their mass, charge, etc. If a hundred positive particles flow to the left per second, this gives EXACTLY as much magnetism, heating, and voltage drop as a hundred negative particles flowing to the right per second. (Note: this is because reversing the polarity of the particles reverses the current, and reversing the particle flow direction reverses the current twice! Two negatives make a positive.) Magnetism, heating, and voltage drop together represent nearly every feature that is important in everyday electrical circuitry. So as far as most electrical devices and circuits are concerned, it makes no difference if the current is made of positive particles going one way, or negative particles going the other... or half as many negatives flowing backwards through a crowd of half as many positives.


In other words, the "Ampere" doesn't care about the direction or speed of the flowing particles.


So, to simplify our measurements and our mental picture of Electric Currents, we cut away the unused parts of the picture. We INTENTIONALLY DEFINE the electric current as being a flow of exclusively positive particles flowing in one particular direction. We don't care about the real polarity of the particles. We don't care about their speed, and we don't care about their number. We ignore both the chemical effects and the effects of the velocity and direction moving particles. We ignore the collisions between positive and negative particles. All we care about is the total charge which moves past a particular point in the circuit. The real charges are too complicated to deal with, and the added complexity gets us very little information as long as we're only interested in voltage drop, magnetic fields, and heating.


 
Holes in semiconductors and positive ions (in a solution) flows from positive to negative.
It DOES make sense to define voltage the way we do, a postive voltage just means postive potential energy. This means that when you apply a postive voltage you shift the fermi energy upwards which agrees with what one would expect.
 
Originally posted by: sao123
But won't we first have to figure out how much of the current is composed negative particles going one way, and positive the other? Yes, but ONLY if we want to know EVERYTHING about the electric current. The negative and positive flows are usually not equal, and the speed of the positives in one direction is usually not the same as the speed of the negatives in the other....If a hundred positive particles flow to the left per second, this gives EXACTLY as much magnetism, heating, and voltage drop as a hundred negative particles flowing to the right per second.
Click to expand...

errm, there are no positive particles flowing in a wire.
 
obviously not, but read the whole article... hes not just talking about wires...
WHICH WAY DOES THE "ELECTRICITY" REALLY FLOW?

EDIT
Another quote from same site:


Why is electricity impossible to understand? Because of...
...continuously stating that "current" flows. This tends to convince
everyone of the existence of a substance-like entity called "current," and
steers us away from use of the "charge flow" concept. In any piece of
written text, always test for this by replacing the term "current" with
the term "charge flow" to see how it reads. Most explanations will then
say that "charge flow flows", but some even say that an electron is a
particle of "charge flow" rather than of charge.
 
So here are my questions...
1 If the red side of the battery (+) is the common ground for the battery, why is it called the hot side?
2 Why when jumping starting a car, do you connect good red to weak red, and strong black to engine block? This seems to imply to me that black (-) is the ground and not the red. Surely the e- are not flowing from + to - on a car battery when its exactly the opposite on every other battery known to man.
3 When connecting up a suped up stereo... once again, why do you connect it to only the red side of the battery and ground the black to the frame of the car?
This all seems to imply to me that the e- leave the black side of the battery, travel through the frame of the car(and the engine block) to their destinations, through some resistance (stereo, wipers, etc) ad then back through the cable into the positive side of the battery?
Very confusing.... someone help?
Click to expand...

Question #1 - the red side is called the "Hot Side" because it has the highest voltage potential above chassis ground. The output of the alternator connects to the Red terminal and maintains the battery voltage above the static voltage (usually about 13.2vdc).
Question #2 - on a car that won't start, you connect their Red to your Red so that their battery and alternator will impose a higher voltage than your dead battery can provide. If your battery is merely discharged, then your working alternator will begin charging and you will eventually be back to normal. If your battery has a problem internally, then it can act normal for a few minutes and then quickly go dead. The most common problem is an internal high resistance connection between battery cells. When there is little or no current flowing out of the battery, a high internal resistance is barely noticeable. Because of the equation V=I*R (voltage = current times resistance), as the current from the battery goes up, the voltage dropped across the bad connection goes up, and your battery's output voltage drops by that exact amount. 10amps across a 1 ohm connection will drop your 13.2vdc battery to 3.2vdc. Normally, the internal resistance of a battery is in the thousand's or hundredth's of an ohm. Most "bad batteries" have high internal resistance. A battery with low internal resistance (a "short") will sometimes explode from internal heating. It isn't common.
Question 3 - when connecting a high power stereo, you connect directly to the highest potential point (the red terminal) so that there are minimal connections between the battery and the amplifiers. Every connection, every foot (or meter) of wiring adds resistance and therefore reduces available voltage and power for that stereo. Using a power lead that has to go through small gauge wires and then the ignition switch before reaching your amplifier means reduced voltage under high current draw conditions. Subwoofers and their amplifiers draw HUGE amounts of current, so they need direct connections and large capacitors to keep the voltage high and steady.

ps, running the car with the battery disconnected can destroy the voltage regulator because it will sense Zero volts and therefore try to raise the voltage up and up and up in a futile attempt to charge the battery. Something will eventually burn out.
 
Originally posted by: sao123

You should not have disconnected the battery with the engine and alternator running. Many alternators can be damaged without a battery connected to them and the same can go for the rest of the electrical system. The power coming from the alternator is not clean, it's rectified 3-phase AC power, which is why it's called an "alternator". The battery acts as a device that smooths out peaks and spikes that could harm electronics in the vehicle.
Click to expand...
I didnt actually do this, but I know it works, because years ago it was routinely performed by mechanics as a test to verify if the alternator is bad or not.
Click to expand...

Years ago, the average car didn't have 50+ microprocessors, electronic voltage regulators and electronic ignitions. Wires, relays, and filaments are a whole lot less susceptible to bad power than silicon.

/frank
 
If there is not enough electricity consumption in the car, then the alternator power will be able to create a high voltage in the installation. This is what is more dangerous (even if it comes in spikes or long flowing currents)
 
just to talk about a few things here:

Originally posted by: sao123
Ok so yesterday, I had to jump start my chevy blazer because I left the dome light on and the battery went dead. once it started, I let it run at high rpms for 8-10 minutes to semi charge the battery before I left. I know it was charging, because my alternator guage was reading 16, and a fully charged system runs at 14. However I got 50-75 feet down the road and everything went dead and the car just shutoff driving 35mph down the road. So i went to walmart got a new battery and everythings good... but it got me thinking.

Even if the battery was dead, the alternator should have been enough juice to keep the car running, I know this because I can remove the black terminal off of the battery, while the car is running and the car will stay running. This implies to me that I had some sort of problem with the red side of the battery or the connection to it. Which makes sence because the red connector was heavily corroded. So I must have lost ground contact which is why everything just shut off dead.
Click to expand...

If replacing the battery was the solution, the battery was the problem, simple as that. The alternator charges the battery, which in turn the car runs off of (basicly). Batteries can fail. They can short out, run out of water, or cells fail, causing the alternator to be useless because it is trying to charge a dead (or shorted out) battery.

So here are my questions...
1 If the red side of the battery (+) is the common ground for the battery, why is it called the hot side?
2 Why when jumping starting a car, do you connect good red to weak red, and strong black to engine block? This seems to imply to me that black (-) is the ground and not the red. Surely the e- are not flowing from + to - on a car battery when its exactly the opposite on every other battery known to man.
3 When connecting up a suped up stereo... once again, why do you connect it to only the red side of the battery and ground the black to the frame of the car?
This all seems to imply to me that the e- leave the black side of the battery, travel through the frame of the car(and the engine block) to their destinations, through some resistance (stereo, wipers, etc) ad then back through the cable into the positive side of the battery?
Very confusing.... someone help?
Click to expand...

As stated several times above, the red is the hot positive and the black is the negative or ground. Take any basic wiring/electronics classand the normal convention states that the negative is ground, possibly system ground, chassis ground(like a car) or ground ground(like in a house).

And yes, as stated also above, just about every car you will ever see is negative ground. The old cars sometimes did have positive ground though. I can personally attest to that. I was helping out getting a friend's old WWII Dodge command car (think really big willies jeep) started. Went to jump it with a battery charger, and almost blew out the voltage regulator after connecting the clamps. Turns out it was a 6-volt battery (that was my stupid mistake for not looking) and it had a positive ground (my terminals were backwards). The friend almost killed me for almost killing his relic.
 
I had a similar problem a couple years ago and it took me forever to find out what the problem was. It turns out I had a crack in my distributor cap, which I discovered by accident when I saw sparks near it when looking at the engine while it was running. That thing drove me insane for months - would start sporadically and randomly die - then it was fixed with $4 and 5 minutes of time.
 
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