I'm curious about how the alternators work and thought y'all would be great help.

As I understand it, the greater the demand for electrical current is, the harder it becomes to spin the alternator (rotor/magneto/spindle/stator, I dunno what it's called).

My question is, how? There are no points of physical contact in there, right? Why does greater current demand equate to friction in the alternator? Or, am I wrong and it does not require more HP to spin an alternator in high demand?

So, does it require more HP to spin it when you are drawing high amount of voltage/current?

I suppose it's the same as a portable generator. I can hear the load on mine when the air conditioner kicks on in the camper. Why? Isn't it just a spinning magnet?

 

subscribed, I enjoy learning new things, great question.

 

I'll do my best. The rotor (moving part) spins within the stator (the stationary part). Moving a coil of wire rotor through a magnetic field (what the stator gives when conducting a 'field' current) is what generates current.

As electrical demand increases, field current is raised and it is this magnetic field increase, which makes the rotor harder to turn.

Does that help?

 

More detailed info: HowStuffWorks "How Alternators Work"

 

Much obliged.

Any body know if there's real benefit to ordering the dual alternator set up? I assume ford still offers it.

 

Anyone know how much horsepower is required to run the alternator? Like, hp drain at minimal demand, hp drain with all the lights and heat on? Curious about the range, like 2 hp normally, 8hp at high demand.

I'm just curious, hope y'all don't mind.

 

Years ago my brothers and I were tooling around in Dad's 72 Dodge Dart. Steve was driving and noticed we were getting low on fuel and started to really panic. Suddenly, he reaches over and turned off the factory AM radio. ???

To save fuel! Never laughed so hard in my life. In theory it could drag on the alternator, I suppose. And we DID make it to our destination...

 

The high output alternator uses no more than 5.5 hp at full output. There is a much greater potential for HP draw with the dual alternator setup.

 

Another good question and good topic. There are a lot of factors.
Maybe someone here works with these formulas every day.

1 mechanical HP is 745.7 watts. 100 watts would be 0.134 HP.
Also have to factor in an alternator isn't 100% efficient but I don't know how efficient one is at proper operating specs. 70%...idk???
Even good computer power supplies are only rated for 80% efficiency.

How many watts is that supplemental heater? That would be a good place to start for the high load.

 

Some else measured the current output at the 125 amp rapid heat mega fuse. Current draw on the alternator at startup was 80 amps from the cab chassis and an additional 80 amps when rapid heat kicked in. At Idle that HD200 amp alternator is maxed out, likely only producing 160 amps at idle. Time to upgrade to a 250A billet aluminum unit - better yet, this 360 Amp unit http://www.americanpowerinc.com/imag...-EF67-12WV.pdf

 

Any truck with rapid heat comes with a 275 amp alternator. I think the heat element is 1500 Watts = 125 amps. I ordered my truck with the rapid heat and the dual alternator 375 amp (I think) setup.

 

There are two alternator options beyond the standard 157 amp. You either get the 200 amp HD or the 357 Dual setup. 1500 watts/14.2 volts = 105.63 amps. If your alternator is only putting out 12 volts, you are in deep doodoo! A healthy alternator should measure 14.2-14.4 volts.

If we use Kper05's 0.134 hp per 100 watts, the 200 amp alternator should max out at 3.86 hp and the 357w dual alternator at 6.89 hp based on 14.4v output. Any way you look at it, the alternator is not a huge HP draw.....maybe 1-2% of the HP that the 6.7 is capable of. Although at idle it could be as much as 25% of the available power.

 

My opinion: There is a benefit, whether it's prudent to make a change is another thing. BTW The load on the engine is insignificant (in regards to single or dual).

Advantages:
More available current (if you need it)
Redundant system if one fails (it'll get you home)
Less wear due to working less. The alternator can be viewed the same as your engine; if it has an easy life it has less wear, if it is operating at the top of it's range it has more wear (higher temps, brush/slip ring and bearing wear).

Disadvantages:
An extra part to fail. Even though combined they are working less than a single unit and theoretically can last longer because of this, they are still spinning and wearing in regards to brushes, slip rings and bearings. Not to mention unexpected or premature failure of electronics (regulator and rectifier diodes).

https://www.fleet.ford.com/truckbbas...ml/Q-160R1.pdf

It is offered and is not a difficult modification.
You keep the original 200amp alternator and add a 157 amp alternator. Bolt on the below parts and have Ford program the PCM

Single alternator to dual alternators:
Alternator Assembly:
Primary: 200 amp BC3T-10300-BA
Secondary: 157 amp BC3T-10300-EC
Alternator Belt for dual alternators:
BC3Q-8620-GA
Alternator Fasteners:
W715092-S437: M10 x 92 mm (lower alt bolt) Qty 2
W715094-S437: M10 x 40 mm (upper alt bolt) Qty 2
Secondary Water Pump*:
BC3Q-8501-BB
Wiring Harness:
BC3Z-14305-F

 

What about doubling the odds of an alternator seizing up and taking out your serpentine belt?

 

absolutely.

Man, I remember the days where a GM 10SI alternator for a car was like 42 amps and if you needed a "High Output" you would get the 63 amp. A 100 amp alternator on a car was amazing, The ford insta-clear windshield cars had like a 125amp alternator. Now we got 200amp on a pickup truck and we're looking for more!