A dumb electrical question (please educate me)

[trularin]

Once you get reference down, electrical ( minus a large amount of electronics ) is a matter of pressure, volume and resistance.

You car runs on 13.8 Volts. That is the pressure. You alternator puts out 14 Volt or more of pressure OF 65 to 150 Amps. Amps are the volume.

The resistance to the flow of the Amps is called...you guessed it Resistance.

Okay, relative to ground, all of your readings with your voltmeter are made with the black lead connected to ground ( your reference ). On the battery not running, 12 to 13 volts. Running will be from 12 to 15 Volts ( the alternator is trying to push more Amps back into the battery ).

If you read the voltage at say the fuel pump, it may be lower because the long wire getting to the pump has some resistance in it.

These are general concepts that may be helpfull.

[RedBarchetta]

Originally Posted by AKDreamer23

If the batt connection was loose, you would see the fluctuance in the headlights when you come to idle and brighter with RPM.

HTH

That's pretty much what I was experiencing (on the headlights).

Originally Posted by trularin

Once you get reference down, electrical ( minus a large amount of electronics ) is a matter of pressure, volume and resistance...
These are general concepts that may be helpfull.

That all makes sense to me, but I still can't compute the end results due to a loose connection (ground) all the way back at the battery. I always understood that the sole function of the battery was to start the car. Once the car is started, the charging system takes over and it is essentially not needed once the car is running. But the fluctuating headlights (getting brighter with RPM) would dictate that my previous understanding is completely wrong.

I use an Optima Red Top battery and (I believe) it's a 65amp alternator (it has several wires off the back). The battery is fairly new.

[Tommy]

The battery is more than for starting the car. Think of it as a large reservoir of electrons than can be drawn on any time the alternator is not producing enough to meet your car's needs. That can happen at low RPM when the alternator is producing little or no electrical output, and it can happen when very high loads (e.g., headlights, electric fuel pump, electric fan, windshield wipers, stereo, etc. all on at the same time) exceed the capability of the alternator.

[Ronbo]

A lot of people don't realize the battery is your main filtering device for your car's electrical system. Alternators don't by nature supply "clean" power to the system. Alternators produce "pulsed" DC (actually AC run through diodes).

Lots of things on your electrical system produce noise, especially inductive loads like motors and your ignition coil. The battery absorbes all this.

[RedBarchetta]

Originally Posted by trularin

You car runs on 13.8 Volts. That is the pressure. You alternator puts out 14 Volt or more of pressure OF 65 to 150 Amps. Amps are the volume.

Holy shiat! I just re-read all the posts and now this finally makes sense!

When I was experiencing that off-idle stumble, essentially what was happening was there was not enough volume of electrons to fire the MSD. It was too low an rpm for the alternator to put out sufficient volume to generate the proper spark, so the system really needed the battery at that point to supply the necessary level of juice. Once I got to higher rpms, the alternator was then supplying enough volume to compensate for the loose negative battery cable condition. Hence the stumble/cutting out immediately went away.

Teacher, do I get an 'A' for today?