What is the benefit of having dual alternators and why do you need them? They are a $350 option.

 

Good question...I don't know, but with dual alternators the batteries on my fifth wheel get charged pretty fast! Plus it looks cool.

 

I have also heard that on some trucks they install an inverter on one and actually can weld with it.

 

They are good for plowing and using any additional electronics you may add to your vehicle. For $350 it is worth it just to have it in case you need it in the future. IMO, it is not necessary for most types of trailering but it sure does keep the lights in the trailer bright....

 

I lost an alternator at night with the family about 150 miles out of the next city on the road. $350 is a cheap backup it sure less than the tow cost/ headache.

 

i wonder how the alternators are hooked up. do they each charge their own battery and then have an isolator between the batteries?? or does one charge then the other is used when the batteries get real low. does anyone know.

 

if you have 2 batteries does this mean you have dual alternators?

 

No it does not.

 

Straight from the workshop manual;
The dual generator package consists of an Upper (Primary 140A) & Lower (Secondary 120A) generator system. The system is monitored and controlled by the PCM. The Upper & Lower generators are Not interchangeable.
Note: the PCM contols the lower generator by turning it off when the glow plug system is turned on to prevent possible damage (excessive votage) to the glow plugs. As soon as the glow plugs stop cycling the PCM will power up the lower generator.
The generators operate independently of the other. Control is through internal voltage regulators. If one generator fails, the other generator can maintain system performance under light load condition.

The batteries are hooked-up in parallel (positive to positive) with no isolator. The generators work together as a team and supply the necessary power as it is needed to the system.

The Right side (passenger) is the primary battery and the Left side (driver) is the secondary battery.

The battery(s) have three major functions:
1) supply engine cranking power
2) votage stabilizer for the electrical system
3) temporary power when the electrical loads exceed the generator output current

The generator(s) have two major functions:
1) supplies current to the electrical system
2) charges the battery(s)

The dual generators are only availble on the PSD, and are a factory installed option.

For those of you with a single generator on either a gas or diesel engine it is rated at 115A.

If you have dual batteries and one battery goes bad you must replace both batteries at the same time with like type & size. This is do to the fact the batteries are connected in parallel.

Hope this helps

 

wow, thanks for the info blackhat. just what i wanted to know.

 

Why do both batteries have to be replaced, even if they are wired in parallel?

 

When both batteries are wired in parallel the voltage remains the same 12V but the storage capacity and cranking amps are increased. Do to the properties of DC electricity when the batteries are hooked in parallel they always try to have an equal amount of storage between each battery (the batteries always want to be at equal pressure). Therefore the stronger battery is always trying to charge the weaker battery.
Think of DC electricity acting the same way as water. If a series of water tanks are hooked together they will always have an equal pressure and stored amount among all tanks.
A battery must always be recharged at the proper voltage and it must be maintained at full charge at all times. Recharging should be as soon after the battery is discharged as possible. Overcharge the battery and it will be damaged from overheating and burning. Undercharge the battery and it will be damaged by a condition called sulfation. The lead sulfate that is formed on the plate as the result of the chemical action that takes place during discharge will harden over time if the battery is not recharged properly. This sulfation will cause an inability of the battery to receive a complete charge from a properly regulated source, such as an alternator or a converter. The capacity of the sulfated battery will be reduced and if undercharging continues will destroy the battery.
Therefore if two or more batteries are to be connected and charged in parallel, they must be the same size and age and type. If not, one battery or the other may be damaged, do to the effect of equiliaztion.

For a more detailed look, go to this website;
www.surepower.com/ebrochure.asp

Scroll to the bottom of the page an click on "Intro to batteries and charging systems" It is a pdf file with more detail and drawings.

Here is another good link on battery information;
www.uuhome.de/william.darden/carfaq7.htm#multi

Hope this helps

 

BLACKHAT620
This is the best info i have seen on this. I was not convinced that i would need Dual Alts but after reading your post I will get them on my 2005 f350 PSD Thanks again and this is a great site for info

Ron W.

 

I have them on my truck and no problems to date. Charges my trailer batteries just fine while driving along. I'll also have plenty of extra juice in case I decide to wire up an inverter to run misc 120 VAC accessories while driving along.

 

I don't know how many people have thought about alternators in this forum, but an option to dual alternators is a replacement higher capacity and higher efficiency alternator.

I've been keeping a list of mods that I'd like to do and the alternators available at http://www.ceniehoff.com/ seem like really good units.

The Ford dual alternator setup involves an extra serpantine belt ... which is giving problems by some posts ... and isn't available for the 'X, among other things.

These guys are offering more efficient and higher capacity alternators ... which is certainly an option for people wanting more power in their trucks.