From,
__what I read, it seems that if you don't want duel batterys.
You'll need to wire both alternators into one high amp regulator.
But this is rather a expencive choice, as well a wiring fright for some.
It is much more affordable, & easier to do duel batt.
All I can say is, make your choice. & live well with it.

 

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Nine years later, & I'm looking to do the same thing in a related sense.
I retract my statement from back then about the dual batt.'s.
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So far, if one is using identical Alt.'s it's not an issue.
But for mismatched Alt.'s, things like isolating the positive Batt. leads on the Alt.'s is required. So not to suffer from having "lazy' Alt. syndrome within the sys.

ATM I'm working to verify that just running blocking diodes on the Batt. leads of the Alt.'s is all that is needed for a simple dual sys. & won't fry the batt.

 

Not quite true

Ideally you want to to run external regulator alternators and use one regulator to control the field of both alternators together. This is the way it is commonly done in twin engine aircraft.
If you use two alternators with two separate regulators you need a paralleling unit to keep the two alternators together, ( no two regulators, internal or external will run perfectly together).
otherwise the one that runs the slightly higher voltage will win out and the other unit will not produce any amps until the higher unit becomes overloaded and can no longer keep up.

You would have been better off sticking to the external regulator alternators and using one regulator as you can get aftermarket high load regulators for running multiple alternators.

 

I used to work on Emergency vehicles. we had some one ton chevys with dual alternators. they had a diode put in between the regulators to keep them from backfeeding the other and giving it a false reading. that is probably all those modules are.

 

That would be for regulator isolation. With each alternator feeding one battery bank. There likely was a switch in side the vehicle that allowed the operator to switch between regulators either normal operation with each regulator handling one bank (usually start and house power so to speak) or able to switch both banks on to one regulator automatically, that is how aircraft are done two alternators two regulators normal operation is off one or the other regulator with the other as a back up, that whole redundancy thing. Would make sense for emergency vehicles also

 

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All I know is I'm going to be trying to run two different Alt.'s
(both Ford of course).
& I'll need to drop a schlocky (blocking) diode at each Alt. Batt. lead cable to separate them.
But still looking for those diodes to purchase & how to install them.

Have found another possible option from a company called perfect switch,
Battery Isolators | Solid State Relays
but alas they fall waay outside my current funding for this project idea.
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There is also the idea of installing a switch on the wires that feed the fields to the Alt.'s, so it could be possible to just "turn-off" the Alt. I don't need at that time saving wear'n'tear & maybe fuel too.
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There is also the possibility to install some Mosfet's instead of schlocky diodes.
But still looking into that as well…
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I'll be continuing to research this.
Till' then, feel free to aid in my research on doing this boneyard style. On the cheap that is.
_

 

You do not "need" the blocking diodes if both alternators are powered from the same source. Blocking diodes are needed if you have the alternators powered from different sources (IE twin engine install or separate drive belts), the reason for this is if one alternator were to stop (lets say the drive belt were to break) The one that was running would send DC current back to the field windings of the other which could burn it up. The diode bridge is used to separate the charging currents of two alternators are to ensure that current from one cannot flow to the other but both can charge the batteries.

But with two alternators running off the same power source it is not necessary, but the safe thing to do is to wire through diodes which will ensure a malfunction with one does not affect the other. This not necessary if an external dual alt regulator is used as malfunction in one will not affect the other.
The cheap solution for a an external regulator that can handle 2 alternators is an old school mechanical regulator as they have much higher amp capacity than their electronic counter parts..

 

True.

But, I'm still researching all the possibilties & configurations on multi-Alt. systems with a singular drive. (Engine)
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I'm also looking into kill switch's for the excite wires for each Alt. as of means to save fuel & safety, that of course would require blocking of the Batt. feed with diodes.
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The making of this system is still in the design stage. So redundancies & safeties are still being thought out. All on shoestring budget no less.
I'm learning what I can & doing all the work, funding by myself. Aside from the helpful advice I get here that is.
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I'm thankful for all the good advice & any support I get from here.