Which alternator set-up?

[Durango1]

So I am wending my way through ordering a 2018 SRW Ram Chassis Cab in a regular cab configuration. The multitude of choices is a mixed blessing!

As of now: 6.4 Hemi (standard) with upgraded Aisin tranny, 4.44 rear end and dashboard shift-on-the-fly transfer case. Plus all sorts of creature comforts (heated seats, etc.) in the cab for the better half.

My question: The standard alternator is 180 amp. But there is a 220 Amp (195.00) option. Or dual 380 amp alternators can be optioned too. (395.00) So what to do? (I'm trying to "do this right" so money is not a huge issue.)

My current 2500 Ram has the 220 amp alternator and it seems to be OK recharging the dual FWC batteries. Would there be any reason for the dual alternators? We do frequently change camp every day so maybe give faster charging? We will have the standard FWC 160 watt roof top solar panel system too. (I've confessed on here before I am an electrical dummy.)

I throw myself on your combined Sunday morning counsel!

 

[Wandering Sagebrush]

Steve, if it ain’t broke, don’t fix it. Sounds like the 220 ampere alternator is doing the job...

Unless you’re considering some new huge electrical load, why sweat the small stuff. If anything, I would want/suggest more solar for the days you aren’t moving.

 

[CougarCouple]

Morning Durango1
Do you know why they offer a dual set-up. I am curious what they are used for.
Russ

 

[Beach]

I would think 220A should do what you need. I wonder how much load 2 380A alternators adds to that hemi.

 

[ntsqd]

If the second of those dual alts has a totally separate output from the truck's batteries I'd give that some thought. Could wire that second alt directly to the camper batteries with no need for any sort of separator - isolator - relay - etc. If it has an external regulator that is even better because then you can easily employ a marine regulator to do 4-5 step charging of the camper batteries.

Have to keep in mind that it is extremely rare that an alternator is putting out its full ampacity. In a normal vehicle, once start recharging has finished they're loafing along only putting out as few amps as is needed to keep the system voltage within spec.

 

[klahanie]

Would there be any reason for the dual alternators? We do frequently change camp every day so maybe give faster charging? We will have the standard FWC 160 watt roof top solar panel system too.

I ordered them for my Ford and had the pleasure of being told by my dealer, "you're wasting your money. you'll never use them".

My reasons were: faster house battery charging (need large ga wiring), redundancy (alt fails), occasional high load use (electric "rapid heat" cab heater, winch, inverter) and the possibly of ntsqd's idea above.

I think solar (which I don't have) and a large second battery bank could, for the most part and for a while, cover all these concerns.

Would order the 220 atleast tho. If you get dual, and they are both driven by the main serpentine belt, I'd recommend carrying a spare belt as it may not be a dealer common stock item.

 

[Vic Harder]

+ what Thom said. Plus you could look at something like this
Accessories

and dedicate that second alternator to charging the camper batts. I love this idea. As stated earlier, run big cables (2g or better) back to the camper and you could be pumping 100+ A back to the camper. Given that you say you "frequently change camp every day" this might the simplest way to get the batteries back up to 100% in a few hour drive.

 

[ntsqd]

Specifically I went with this even though we have only one alternator:
http://shop.pkys.com/Balmar-ARS-5-H-Regulator-12-Volts_p_1734.html
I've yet to get it installed, should happen between Xmas & NY's.

 

[klahanie]

Prob moot to the OP... the issue I ran into is that my PCM controls alt output. It can be reconfigured for single use but was unsure if the remaining alt could be converted for external control. So I have simply relied on the higher avail output of the oem dual system for charging.

Would a solar charger not handle the absorption and float stages while driving , if indeed a modern vehicle's charging system was inadequate beyond the bulk stage ?

 

[Vic Harder]

Prob moot to the OP... the issue I ran into is that my PCM controls alt output. It can be reconfigured for single use but was unsure if the remaining alt could be converted for external control. So I have simply relied on the higher avail output of the oem dual system for charging.

Would a solar charger not handle the absorption and float stages while driving , if indeed a modern vehicle's charging system was inadequate beyond the bulk stage ?

I'm lucky in that the alternator in my 2002 GMC puts out a healthy 14.2v even when everything seems to be fully charged, and I've seen 30A or so even at idle.

"Modern vehicles" might be set up differently. That said, if you are not getting that, you could use a DC-DC unit like the Ctek d250 to up the voltage to your camper batteries.

As for the solar charger handling things while driving, from what I have seen the answer is "yes and no." If I disconnect my alternator charging system from the camper batteries (via switch in my truck's console) then the solar is doing its bit for sure. If connected, then the alternator may try to charge a fully charged camper battery, which would not be good long term.

In practice, what I have seen in my truck is that on warm days, the alternator is putting out just enough voltage to trickle about .2 A to the camper. When it is cold out, the voltage in higher from the alternator, and it is overcharging the camper batteries with about 3-4A even though they are fully charged.

So no, the solar charge controller can't stop the (relatively dumb) alternator from over charging the camper batteries.

In practice, I watch the guages (aftermarket that I installed in the cab console) to let the alternator do its bit during bulk and then when the batteries are around 98%, disconnect them and let the solar finish the job.

On the other hand, having them connected while the truck is parked for days at a time lets the solar array charge both the camper and truck starting batteries perfectly. So I no longer have to worry about my starting battery!

 

[ntsqd]

Prob moot to the OP... the issue I ran into is that my PCM controls alt output. It can be reconfigured for single use but was unsure if the remaining alt could be converted for external control. So I have simply relied on the higher avail output of the oem dual system for charging.

Would a solar charger not handle the absorption and float stages while driving , if indeed a modern vehicle's charging system was inadequate beyond the bulk stage ?

The PCM on our truck is the same. However, it is a known failure mode and I have been carrying a old style external regulator & pigtail as a trail spare.

The good news is that PCM control means that it is an externally regulated alternator, that makes going to a more sophisticated multi-stage charging regulator fairly easy. The potentially bad news is that the PCM may not like those different charging voltages. In our case all it does is shift the trans, the engine is purely mechanical.

With a second alternator it won't matter to the PCM if a multi-stage regulator is used to charge the camper batteries because the PCM will never see that alt's output.

 

[klahanie]

I'm lucky ...

Vic, thanks for your posts on this subject. Informative, as I have no monitoring. I have measured 14.5v at the house batt but at what current IDK. As an aside, sometimes in the morning after camping and before driving off, I activate the trucks user selectable BCP feature (battery charge protect, assoc'd with PTO) which maintains a charge to the truck batts partly thru raising engine idle rpm. I'm always surprise by how short the period is before the idle drops to normal (with both truck and house batts combined) and I assume returns to "normal" voltage. So I'm thinking the alts are replenishing much of the house batteries fairly quickly. And I know there has been a draw down because we often hear a low voltage warning from the camper inverter (heated blanket).

In practice, I watch the guages (aftermarket that I installed in the cab console) to let the alternator do its bit during bulk and then when the batteries are around 98%, disconnect them and let the solar finish the job.

I like this !

If the alts can charge the house batts to the high 90s percent range, that's fine for me. Add a periodic top with a 120v or solar powered smart charger and the batts will be happier. Like yours I suspect during long drives the alts are overcharging the house batts a bit. Here smaller ga wire would be better.

btw the "modern" was not a dig at all. Circuitry and management systems are increasingly complex and sophisticated (to me). I'm more familiar with the Ford product than the 2018 RAM of the OP. So for eg ... this may be both a bad example and old news ... Ford now advises against connecting new circuits to the neg batt terminal to avoid confusing the (hall-effect ?) sensor located there - used for determining the charging profile.
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...
The good news is that PCM control means that it is an externally regulated alternator, that makes going to a more sophisticated multi-stage charging regulator fairly easy.
...
With a second alternator it won't matter to the PCM if a multi-stage regulator is used to charge the camper batteries because the PCM will never see that alt's output.

Thom, good point and info. The PCM is "external" - hadn't thought of it as such. I'll look into it again, out of interest.

I wonder tho if, in my case, duals rated at 320A vs a single aux rated at 120A wouldn't still be the better choice for me as I've been ok with a mostly "bulk stage" type of charging.

I agree with the principal and benefit of it but over time I have grown less concerned about optimal battery charging. A condition likely to change when I go solar ...

 

[Durango1]

My Ram salesman tells me the dual alternators do not have an external regulator. Given that I am A) an electrical dummy and certainly don't want to mess with the electrical complexities of a new vehicle and C) the 220 amp alternator has been OK with my current Ram I think I'll just stay with 220 amps.

Thanks for the great advice.