I don't really understand alternators:
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Post Fiend
Joined: Jan 2009
Posts: 6,521
Likes: 11
From: Greenwood, SC
I don't really understand alternators:
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?
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?
Post Fiend
Joined: Jun 2003
Posts: 5,983
Likes: 2
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?
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?
Post Fiend
Joined: Jun 2003
Posts: 5,983
Likes: 2
Thread Starter
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Post Fiend
Joined: Jan 2009
Posts: 6,521
Likes: 11
From: Greenwood, SC
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.
I'm just curious, hope y'all don't mind.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
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...
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...
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Postmaster
Joined: Sep 2006
Posts: 2,598
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From: Maryland
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.
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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.
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.
Senior User
Joined: Feb 2007
Posts: 474
Likes: 0
From: Colorado
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.
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.
Postmaster
Joined: Sep 2006
Posts: 2,598
Likes: 5
From: Maryland
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.
Senior User
Joined: Nov 2013
Posts: 163
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From: Albany NY
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
Cross-Country
Joined: Feb 2014
Posts: 61
Likes: 0
From: Las Vegas
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!
