The layout all depends on the model of car or truck. There is likely a dozen different configurations to secure a battery in an automotive application.
Ron

Agree, two vehicles I owned had the battery under the rear seat, if obtaining a replacement, it had to have a means for the vent to exit the floor of the vehicle.
To operate a jump-start, there were two Clamp points under the hood in the engine compartment.

 

I know that when the Engine is Runinning even if the Car is not Moving this is what Turns the Alternator.

And as the Alternator Turns it Charges the Battery.

And I know how the Alternator works.

So when You Connect the Jumper Cables to the Good Battery Terminals the Jumper Cables also are Touching the Aulternator Cables that are Connect to the Battery as well.

So after You Start the Car with the Good Batter it is the Aulternator that will be Jump Starting the Car with the Dead Battery.

I get all of this but one thing?

But am I Right if You Rev the Engine in the Car with the Good Battery it will not Turn the Alternator any Faster and will not Jump Start the Car with the Dead Battery any Faster?

 

Wrong on atr least one point: The alternator speed is a constant multiple of the engine speed, and so as the engine turns faster, so the alternator turns faster, and is able to deliver more power. That is because mechanical power into the alternator is what drives electrical power out from the alternator. The relationship is direct, but not quite linear.
Thus running the engine of the car with the good battery a bit faster will indeed charge the battery of the car with the dead battery a bit faster, Thus running the engine a bit faster, like at "fast idle" speed, will be able to provide more charge and a shorter time until the car with the weak battery can be started. Note that with a totally dead battery it will take several minutes at least. A weak battery might take a short time, depending on the capacity of the jumper cables. My heavier set of jumper cables will crank a car with a "stone dead" battery, while my set of standard jumper cables will not.

 

Early automobiles had DC generators, the slight down side to these were they had to be revved fairly high if the demand was high.
Alternators on the other hand will output considerable power, even at low RPM's, this was one reason for their implementation over DC.

 

Early automobiles had DC generators, the slight down side to these were they had to be revved fairly high if the demand was high.
Alternators on the other hand will output considerable power, even at low RPM's, this was one reason for their implementation over DC.

In adition, alternators cost a lot less to produce, and are much simpler to regulate.

 

Nobody wants to "wait" for the low/dead Battery to Charge,
this impatience is where the rub comes in.

The Car/Truck with the low/dead Battery likely has some sort of a Charging problem,
( although it could be just a poor connection at the Battery Terminals ),
so the longer the Cables stay connected,
the better-off the person with the low/dead Battery will be.

Just getting the Engine "started" is no guarantee that
it won't die within the next ~10-minutes after the Cables are disconnected.

If You care,
finding-out the reason WHY the Battery is low/dead is the most important part.

It's quick and easy to check the Alternator-Charging-Voltage with any Meter.
If, ( after disconnecting the Cables ),
the Voltage at the Battery is not at least ~13.5-Volts,
they aren't going to get very far.
Of course, maybe all they need to do is get Home.
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My observation has been that the most common cause of needing a jump start is a failing battery. Presently batteries seem to be a weak part of the system, probably because the goal is for folks to replace a car every year. At least that was the plan. Certainly a weak charging system will lead to a low battery, though. But I have also been in a situation where a friend had a very weak battery, barely lit the dome light, and yet with two people to deliver a hand push it would stsrt up nicely when he released the clutch to turn the engine. We rode all over with that car for several weeks before he had enough money to replace the battery. So the charging system was adequate to run the engine very well. So the charging system can carry the load very well, at least without air conditioner running. THAT will kill an engine running on the charging system immediately.

 

My observation has been that the most common cause of needing a jump start is a failing battery.

Also depends on your geographical location, here it can drop to -40°C, at this temp. the oil is pretty much close to solid!
Also low temps play havoc on even a good battery.
My present car is a little better as the oil grade is 0W30.

 

Also depends on your geographical location, here it can drop to -40°C, at this temp. the oil is pretty much close to solid!
Also low temps play havoc on even a good battery.
My present car is a little better as the oil grade is 0W30.

My experience with the weeks of push starting that car, a 1966 Rambler American, was right outside New Orleans, during the time whenit never got below Seventy degrees F. We were so good at it that even in a rainstorm, when his engine stalled at a red traffic light, when the light turned green 2 passengers jumped out and the push start was nearly instant, before the car went even 5 feet we were back inside and rolling down the road. We laughed about that for several miles. That had to have been in 1968.

 

2 passengers jumped out and the push start was nearly instant, before the car went even 5 feet

I rue the disappearance of the crank handle for emergencies!
One nice advantage was if stuck in a icy rut with no traction, first gear with the ignition off and hand crank'er out

 

Let Me See if I have this Right?

The more You Rev the Engine the Faster the Alternator will Turn.

The Faster the Alternator Turns will put out more Power.

But the Car with the Dead Battery will only Take whatever it needs.

So You can Rev the Engine and make the Alternator Turn as Fast as it can go but this will not Charge the Car with the Dead Battery any Faster.

Is this Right?

 

So You can Rev the Engine and make the Alternator Turn as Fast as it can go but this will not Charge the Car with the Dead Battery any Faster.

Is this Right?

Pretty much. A bad battery can also kill the alternator.

 

Let Me See if I have this Right?

The more You Rev the Engine the Faster the Alternator will Turn.

The Faster the Alternator Turns will put out more Power.

But the Car with the Dead Battery will only Take whatever it needs.

So You can Rev the Engine and make the Alternator Turn as Fast as it can go but this will not Charge the Car with the Dead Battery any Faster.

Is this Right?

It depends on the Car or Truck that is giving the Jump.
Most Trucks, and Luxury-Cars, will have a fairly serious Alternator,
usually with a Capacity over ~100-Amps,
on the other hand, small "Economy-Cars" may only have a wimpy ~65-Amp Alternator
which struggles just to barely keep-up.

The "take what it needs" comment only applies to "Battery-to-Battery-Charging",
which can be extremely slow.
When an Alternator enters the equation, the Alternator-Output now makes all the difference.

The Big-Alternators are much more likely to be able to maintain the
maximum ~14.5-Charging-Volts at idle,
but the cheaper Cars, with the wimpy-Alternators,
will definitely benefit from holding the engine at
a Fast-Idle-Speed of around ~2000-RPM to produce their maximum Alternator-Output.
Higher than around ~2000-RPM will just get the Engine hot and
make the Electric-Radiator-Fans kick in,
which will soak-up every bit of Output-Current that the wimpy-Alternator can create.

Make sure the AC is turned OFF.
Make sure all exterior-Lights are turned OFF, (unless you're in traffic).

The key here is PATIENCE,
hook'um-up, get comfortable, AND WAIT.
Charging takes time, ~5-full-Minutes should be considered the absolute minimum-Charge-time
if You actually want to impart a reasonable Charge into the Dead-Battery.

If the Car with the Dead-Battery,
has a dead Battery because of a defective Charging-System,
they are not going to make it very far,
unless the Battery has a "Full-Charge" on it,
and a "Full-Charge" could easily take over an Hour.
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A car alternator produces around 1/2 the rated amperage at idle. You can look at datasheets and pulley ratios are typically 2:1 or 3:1. So an engine idling at 800RPM the alternator might be at 1,600-2,400RPM, and will charge at a low rate.

This winter, also note a dead car battery has a higher freezing point and frozen battery will never take a charge, and is a hazard for hydrogen build up apparently. I have to bring those into the house to thaw out and then charge.

 

Let Me See if I have this Right?

If the Car giving the Jump Start has a Good Alternator and it is Rated at 100 Amps this is Telling Me that if the Cars Engine is Turning the Alternator Fast or Slow the Alternator will still put Out 100 Amps.

Do I have this Right?

 

NO!, The 100 amps is what the aternator is capabe of delivering at maximum output. That is at some higher RPM, not at idle.

 

From the rating of the rectifier bridge typically fitted, they do not come close to 100A!
Maybe momentarily!

 

From the rating of the rectifier bridge typically fitted, they do not come close to 100A!
Maybe momentarily!

Many "Large-Frame" Alternators will handle substantially over ~100-Amps continuously.

Way back in the '80's I maintained a fleet of 20 Stretch-Limousines,
some of which idled at over ~80-Amps for up to ~6-hours at a stretch, with ~200F under-hood temps,
with no failures in 2-years of service, ( equipped with Internal "Dual-Diode-Packs" ).

The custom "MechMan" Alternator in my Truck has been measured at over ~150-Amps for several minutes,
( when charging a completely dead Optima-Spiral-Wound Gel-Cell Battery with
extremely low Internal-Resistance ),
but it normally runs right around ~130-Amps with 4-Electric Radiator-Fans on "High", and
with the AC-Blower on "High" as well,
but this set-up also has 4 Auxiliary 3-Phase-Bridges and Internal "Dual-Diode-Packs",
so I guess I'm actually not making a fair comparison.
Still going strong after ~5-years.
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Does the TS now have enough information???