I would totally agre with graystreak's explanation. As he said an alternator will only put out the amount that is being drawn never more never less, unless the maximum capacity has been reached.

A good example would be your house a radio might only use .5 amp, but the circuit that it plugs into has 15-20amps available. If it had to take 15-20 it would blow up everytime you plugged it in.

 

seabisquet says max inrush current is 12 to 14 volts, this is true but thats really inrush voltage not inrush current. the max inrush current could be as high as what ever batterty amperage is, say 500 to 700 amps@12vdc. i agree with 100% about the alt ony putting out what it needs to keep battery charged but no more than 75 amperes [ with a 75 amp alt]. it could put out less in the case of a failing alt or extreme high heat conditions. none the less it is just not worth the chance of burning up electronic is it?

there is a major differance between voltage and current, voltage is the amount of power and amperage is how hard it hits.i also feel that if your regulator failed on the overvolt side you would definatly hit the battery with more voltage but the amperage would decrease and the battery would probabably be able to dissapate the overcharge through geting hot and boiling out the electrolite. once of course the electrolite is gone your battery is probably shot.

 

"I agree with your synopsis..I'm not real sure it would even "spike". It may shock the system, but without capacitors it would only have the inrush of what charge was in the battery. My .02'

The quote above is what I typed, and it says charge...not amperage.

It might be that this thread is becoming too argumentative instead of being productive in nature.

 

It's not argumentative - it's just a discussion of terms. And even arguments can be informative.

Voltage isn't power - it's electrical "pressure". The higher the voltage, the more current will be pushed through resistance. It's like water pressure pushing through a partially-closed valve. The higher the pressure (potential/Voltage), the more flow (current/Amperes) you'll get thru a given restriction (resistance/Ohms). The open air gap of a spark plug has REALLY high resistance, so it take a REALLY high voltage to push even the tiny bit of current through it to get a spark to jump. Lightning works at MUCH higher voltage because it has to jump ~2,000 feet and it gets a LOT more current flowing.

Electrical "power" is usually measured in Watts (or KiloWatts), but is often measured in horsepower (usually for electric motors).
Watts = Volts x Amperes , so a light bulb rated at 12V to burn 120W would pull 10A.
Volts = r (resistance/Ohms) x i (current/Amperes) , so the bulb has 1.2 Ohms resistance.
Since the alternator is actually going to put out ~14V, the bulb will actually pull ~12A and burn ~163W of power when the engine is running, which is ~0.2 hp that it takes from the engine.

Visteon offers a nice online utility for unit coversion.

 

Many types of voltage exist such as longitudinal, gradient, ripple and phosometric (measured with a duh, phosometric meter) The most well known definition of voltage as a Science is 'Electromotive Force'. Basically it's a mathmatical theory that can be proven out (in most cases) depending on the makeup of the circuit.

Voltage, also called electromotive force, is a quantitative expression of the potential difference in charge between two points in an electrical field. The greater the voltage, the greater the flow of electrical current (that is, the quantity of charge carriers that pass a fixed point per unit of time) through a conducting or semiconducting medium for a given resistance to the flow. Voltage is symbolized by an uppercase italic letter V or E. The standard unit is the volt, symbolized by a non-italic uppercase letter V. One volt will drive one coulomb (6.24 x 1018) charge carriers, such as electrons, through a resistance of one ohm in one second.
Voltage can be direct or alternating. A direct voltage maintains the same polarity at all times. In an alternating voltage, the polarity reverses direction periodically. The number of complete cycles per second is the frequency, which is measured in hertz (one cycle per second), kilohertz, megahertz, gigahertz, or terahertz. An example of direct voltage is the potential difference between the terminals of an electrochemical cell. Alternating voltage exists between the terminals of a common utility outlet.

A voltage produces an electrostatic field, even if no charge carriers move (that is, no current flows). As the voltage increases between two points separated by a specific distance, the electrostatic field becomes more intense. As the separation increases between two points having a given voltage with respect to each other, the electrostatic flux density diminishes in the region between them.

However, in the real world it's only a theory. I've seen (high) voltage do many weird things in my 30+ years as a Industrial Electrician.

Wayne

 

You're the only person I've ever heard describe voltage as direct or alternating - those terms are used to describe current. The reason is that voltage CAN'T change unless charged particles move, which is USUALLY accomplished by current flowing.

Also, your term "electrostatic flux" is contradictory; "flux" is the synonym of "flow", and "static" is their antonym. The term used in Physics is "electric field strength". "Flux" is only used to describe magnetic fields, which are distinct from electric and gravitational fields (the only other 2 types of field).

The types of voltage you mentioned are only different in the way, location, or the time period that they're measured - the voltage being measured is always the same physical phenomenon.

Voltage doesn't always imply that there is any flow of current - they're related, but not interdependent. 2 charged particles that are separated exhibit electrical potential (voltage), but no current ever has to flow. That's called "static" electricity.

Voltage doesn't physically "produce" an electric field - those 2 phenomenon ARE interdependent; one can't exist without the other. And an electric field doesn't only exist "between" 2 charged particles - it's spherical, so it exists all around each of them.

The physical definition of an electric field is "an altered space in which a charged particle experiences a force". The definitions of magnetic & gravitational fields are almost the same, except they refer to magnetized particles and particles with mass, respectively.

 

Hi guys, this discussion reminds me of Science class!! Man I hated that class. At least I'm learning something here.

 

Guys, the fact remains that even if the battery had a million amperes to send through the system, the ONLY amperage ACTUALLY running into the system at ANY given time is the exact amount required by the components wired directly into the system and NOT on a switched circuit (unless the switch is "on", duh). The battery does not discharge at any greater rate just because you connect something to it UNLESS what you connect to it actually draws from it. And even then it will only flow the amperage required to make that component function. If the full amperage capacity of the battery was pushed through the system no mater what the load, every fuse and circuit breaker in the vehicle would blow the instant you turned it on. Amperage is flow rate and flow rate is determined by what the components "PULL" through the circuit. (The only way to "force feed" electrical components is with a capacitor or a good lightning bolt)! The amperage RATING of an alternator, battery, circuit panel, etc. is the amount of amperage the power supply CAN provide if its needed i.e. 75 amp alternator or 700-800 amp battery. The amperage rating does NOT mean that that much aperage is being FORCED down the circuits at all times.

By the definitions given by some people, if you connected one dashboard lamp (you know tiny little wedge based things) and nothing else to the battery to see if it worked, the full 700-900 amperes would be shot down the circuit to that one lamp! Uh, that just doesn't happen because thats just NOT how it works! The total amperage released by the battery at the time of connection to that lamp would be something far less than a single ampere. Will that lamp burn brighter than it would if it were wired into the rest of the system? Heck yeah, but thats because direct wiring it, eliminates the resistive qualities of the rest of the system...i.e. wiring, connectors, switch contacts, etc. NOT because there are 700 amperes pumping into it.

As I said before, electricity doesn't build up like water in a sink. A more accurate comparison is that the battery is the water supply and every component (lamp, motor, solenoid, relay...NOT switches) in the system has its own faucet and opens the valve only as much as it needs to, to function. Open enough faucets, too far and you will exceed the flow capacity of the system. Or in electrical terms, the amperage draw will exceed output capacity and fuses will blow and circuit breakers trip (provided the fuses and breakers are properly sized for the components on that circuit).

 

The only way to "force feed" electrical components is with a capacitor or a good lightning

this is exactly the spike im talking about, the battery amperage at disconnect or reconnect.

alternating current is the current that is in your home and direct current is in your car. ampererage has nothing to do with type of current. ac sends power out on the hot wire and what ever is not used is sent back and gotten ridden of to ground, dc voltage flows from the negative terminal of the battery, powers all of the devices and is sent back to the battery on the positive side. you can have the same current draw in a circiut whether the circuit is ac or dc voltage. dc current and voltage is just a more stable voltage than alternanting current.there is no cycling on a dc power source where ac electricity cycles, at least here in the USA at 60 cycles per second.

 

this was a very informative discussion but now i think everyone who thought they had a clue is totally confused. what should our next discussion be about?
it really was great to hear everyones interpretation of elactrical theory. i feel that i have learned alot during this discussion and i will definatly take into account all that was said.


bob

 

I have a 89 351w and it is doing the same thing ..i think it is because the batt that i have in it is to small or getting old.let me know ..i might just spring for one of them really good batt's and give the old truck a treat..lol

 

Its only a "spike" if the voltage through the circuit is higher than the components in the system are designed to handle...Otherwise its no different than turning the switch on. If the sudden flow of electricity to the compnents in the circuits from mere battery voltage was enough to damage them, you would run that same risk EVERY TIME you started the truck.

 

so do you think a new batt would help out ?

 

A capacitor won't "force" any more current thru a circuit than it normally pulls. It just stores it in a way that allows small amounts to flow out faster than the chemical storage in a battery, thus keeping the voltage more steady. (Specifically, it's stored in an electric field.) Lightning pushes more current because of its extreme high voltage (pressure).
Yes, amperage IS current.
The AC in your home comes in on 2 wires @ ~120VAC each, for a total of ~240VAC across both of them. Since we've already established that a circuit doesn't pull the current it's not using, we know that there's nothing to "send back & get rid of". The current that you're using flows to ground thru 120V loads to complete the circuit, and thru the other 120V line on 240V loads.
You're right about the direction the electrons flow.

 

Steve,
I am surprised, given your knowledge, that you have never heard of the term 'alternating voltage'. Following are examples of such, and all voltages forms are not the same regardless of where they are measured..as I take it that you would infer.

ripple voltage: 1. In a dc voltage, the alternating component that is residually retained from rectification of ac power, or from generation and commutation. 2. In a dc voltage, the alternating component that is coupled into a circuit from a source of interference.

Alternating Voltage: Alternating current (AC) is current which flows back and forth along a conductor. (In contrast, direct current (DC) is current which flows in one direction only.) Alternating current is the result of an "alternating voltage" (force) pushing electric charges back and forth.

It is basically a loop of wire rotating between the poles of a magnet. This curve is called a sinusoidal waveform. It has the formula:

where
v is the voltage,
t is the time,
sin is the function that gives the curve its wave shape,
A is called the amplitude and is the maximum height that the curve reaches,
W is called the angular velocity and describes how rapidly the curve oscillates (it is actually the rate of rotation of the generator measured in radians per second), and
Then there is the phase angle. It determines the shift of the wave left or right. A shift of 360 degrees (or 2 radians) is a shift of one complete cycle and any smaller shift is a shift of less than one cycle.
When v is positive (at the top or crest of the wave) this means that the upper terminal has a greater voltage than the lower terminal. And when v is negative then the lower terminal has a greater voltage than the upper terminal. An oscilloscope is capable of displaying such waveforms.

If a circuit is connected to the terminals then the resulting current will alternate in direction as well, flowing first one way through the circuit, then reversing itself and flowing the opposite way. AC has several important advantages over DC. Among them are ease of generation, efficiency of transmission and safety of use.

Again, I feel this thread may have got out of hand, and I apologize if I have added to that problem.

Wayne