Which Alternator

[Dirt Rider]

My truck comes with a 120 amp alternator stock, but is there a cutoff or formula for when I should upgrade? Planning on a total of 4 batteries at some point. 2 in the camper and 2 outside. Load will mainly be a fridge and minor appliances with a seldom used winch and an air compressor. No solar yet but planned for the future.

 

[Vic Harder]

whoa... 4 batteries with what sounds like a small load. If you are looking at upgrading, I wonder if your truck supports dual alternators? Having a dedicated alternator would allow for different battery chemistries to be accommodate easier.

I'd be inclined to go with good battery monitoring first, to see when/if you need more charging capability before investing more $$$.

 

[ntsqd]

I'm pretty sure that 6BT's came with dual alt options, though likely not in the CTD's unless they were bought by a municipality or utility. I want to say that Casa Azul is so equipped as it's 6BT came out of a heavy truck, but I'd need to ping Joaquin about it.

That said, I set up the camper battery charge system for 80A max and those are some pretty heavy cables. Once I put a mere 100W of solar on the camper roof I don't think the alt had much to do.
EDIT: I say this because normally by noon on/near this Coastal Desert the camper batteries were in float according to the TriMetric. The guy who bought our first camper asked me about the VSR. He had noticed that he no longer had the hard starts that he was used to when his truck sat for a while. That little 100W panel and a Morningstar SSD-25 SunSaver Dual PWM controller could keep all of the batteries up.

 

[Advmoto18]

While not answering your question, here is information provided by Ford for their Super Duties with the 6.7 diesel motor.



-The base alternator is still a 157A single unit on the 6.7L.

-Extra Heavy Duty Alternator (220A single unit) is the first possible upgrade:

• Required on any truck with the snowplow package
• Required on any Lariat and up trim truck with the upfitter switches OR 110v outlet

• Required on any XL or XLT truck with the upfitter switches and 110v outlet ordered together

-Dual Alternators (157A + 175A? dual units) is the second upgrade

• Required on any truck with the snow plow package, upfitter switches, and 110v outlet ordered together

(On this upgrade I'm really not sure what alternator combo is used. The order guide states there are 332 total amps, but no combination of the current alternators generates that amount of amperage. Its possible the order guide is wrong and Ford is simply using twin 157A alternators...or, other output alternators were used in the recent past)

-Dual Extra Heavy-Duty Alternators (220A unit + 157A unit) is the top upgrade

• Required on any truck with the supplemental electric cabin heater, since this heater has 3 banks of 50A circuits alone.

As you will note, the use of dual alternators is required for powering some serious electrical energy demands.
I have the Lariat with upfitter switches and 110V AC. It came with a singe HD alternator. I've added a Warn 16.5Ti winch and 4 Rigid lights in the bumper. While winching at night with LEDs on, I noted a significant amperage demand (extreme case for sure as I was winching a car out of a ditch). As such, I installed a second alternator to help with demand. Most diesels have 2 batteries under the hood and most upfits are GTG with a single HD alternator.

I really haven't seen the need for a second alternator for pushing amps to the camper's house batteries. With the Blue Seas ML-ACR installed, I can manually force the alternator to charge the camper batteries; yet, the auto function works as advertised.

More info than you need...just my thoughts and observations.

 

[ntsqd]

Further thoughts:
I would stay away from any of the aftermarket hopped-up alternators. When it fails near Elko, NV what are your options going to be and what are the effects of substituting a lower output alternator to get home going to be?

I would find the highest output optional stock alternator that will fit your truck, and if that is not enough then consider going to two alternators.

On the Gen II CTD's the alt's regulator is part of the PCM (& notoriously known to fail). That means that the alternator is wired for an external regulator. One of my round-tuits is to finally install the Balmar ARS-5 smart regulator. No idea what the Gen I layout is like, but if this is an option then you can have smart charging in addition to greater ampacity.

 

[klahanie]

Dirt Rider, if you go down the battery charging rabbit hole you'll bump into formulas. There's probably one for what you are asking but it could be a long one, dependent on many factors.

From what little I know I'd say you'll want a system that can recharge the battery bank as much as possible, as quickly as possible. I'd look into the charge current recommendations and maximums given by the batt mfr. These may vary by make and will certainly by type.

If we use a traditional bulk charge rate of .2C (20% of the batt AH) and you had 4 x 100 AH batteries that would suggest an 80A current avail for charging as a guideline (plus some to spare for other needs while driving). Whether your oem alt can output and sustain that is another question. Transmission of that current is another requirement, albeit easier. On the surface of it tho, you might be OK.

If you choose a battery bank that can be charged at a higher C rate then a higher output alt could be useful depending on how depleted the bank is and maybe a few other factors I'm forgetting. But if you drive a lot, might be less of a benefit.

If you do choose to upgrade and can do so by adding a second alt that gives you redundancy - that would be a good thing.

 

[Dirt Rider]

Like the idea of a second alternator had not thought of that yet, will have to see what's involved. Also heard that the ambulance and firetruck version was offered with a 220 amp version as well as gen 2 trucks. My truck voltage is regulated by the PCM. Not sure if going to an internal or external regulator will mess with the other systems such as cruise and overdrive as they all work together.

 

[ntsqd]

Like the idea of a second alternator had not thought of that yet, will have to see what's involved. Also heard that the ambulance and firetruck version was offered with a 220 amp version as well as gen 2 trucks. My truck voltage is regulated by the PCM. Not sure if going to an internal or external regulator will mess with the other systems such as cruise and overdrive as they all work together.

That part has made me hesitant as well. Figure since I have the ARS-5 that I ought to at least give it a try and see. Can always revert back. Were I to configure for a second alt I'd for sure use the ARS-5 on it.

 

[Vic Harder]

External regulator would be perfect. ECM would never know that it’s there

 

[Optimistic Paranoid]

A lot of people don't realize it, but the world of high end car audio - the kind of rigs that make the whole neighborhoods shake as they drive through - is heavily dependent on multiple alternator setups to power the insanely powerful amplifiers they use. Do a Google search for IMAGES on "multi alternator setups" and you'll see pictures of two, three, even four alternator setups.

Thus, high end car audio suppliers can be a good source for custom mounting brackets and other hardware and supplies you might need for a project like this.

 

[ntsqd]

Concern is that the ECM may not like the different voltages that a smart regulator will use in normal functioning. The OEM reg function appears to seek to always make the system voltage the same regardless of battery need. No idea how much flexibility the ECM has to compensate. In our case all the ECM does is control the trans, has no engine control functions but does have engine sensors.

I would opt for an OEM dual alt system if one exists. Not a lot of faith in the aftermarket. They usually don't understand or bother with stuff like MTBF evaluations.
The one thing that can really mess with you when doing something like this on a 6BT is that there are apparently many, many different fan idler brackets that place the fan in different locations. So need to find a dual alt. application that is similar to the existing install so that it places the fan in the right spot.

 

[klahanie]

What about keeping the charging segregated. OEM for truck, new externally regulated aftermarket for house. (I think this is what Vic is posting)

If one alt fails the other can charge both battery banks thru a combine switch. Or might the PCM still have an issue with an externally controlled output ?

 

[ntsqd]

What about keeping the charging segregated. OEM for truck, new externally regulated aftermarket for house. (I think this is what Vic is posting)

If one alt fails the other can charge both battery banks thru a combine switch. Or might the PCM still have an issue with an externally controlled output ?

If going to dual alts it is what I'm advocating as well. A manual combine switch is a good idea. At that point so long as it runs and shifts the other stuff won't be as important as getting back.