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Do we know what the logic is in how these function? Do they always split the load? One work at a time depending on the demand?

Is it a smart (variable voltage) alternator? If so, any recommendations on where to grab an ignition hot as a signal wire, from the engine bay? In the cab?

I'm wiring up a popup camper with LiFePO4 batteries and a DC-DC 50a charger
 

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Do we know what the logic is in how these function? Do they always split the load? One work at a time depending on the demand?

Is it a smart (variable voltage) alternator? If so, any recommendations on where to grab an ignition hot as a signal wire, from the engine bay? In the cab?

I'm wiring up a popup camper with LiFePO4 batteries and a DC-DC 50a charger
Dang, they let anyone in here... :wink2:

But... Thats a good thing.. I'm wondering the same thing as i am doing a similar thing! :)
 

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A lot depends on how your truck was optioned. I have the 440 dual amp system. I do know that the vehicle computers control when the alternator turns on, cause if you don't have that option, and just add an alternator, it won't produce any voltage until you have the computer flashed to recognize the extra alternator.

As for hot leads, best place is the VSIM module and AUX switches that you program via your dashboard.
Here is a link to RAM's Upfiter Guide that has links to several areas you will find useful.
 

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A lot depends on how your truck was optioned. I have the 440 dual amp system. I do know that the vehicle computers control when the alternator turns on, cause if you don't have that option, and just add an alternator, it won't produce any voltage until you have the computer flashed to recognize the extra alternator.

As for hot leads, best place is the VSIM module and AUX switches that you program via your dashboard.
Here is a link to RAM's Upfiter Guide that has links to several areas you will find useful.
Thanks!

What he's asking (I know, because we've chatted and i'm planning the same thing he is) is where to tap into the alternator hot circuit to trigger the DC/DC charger that will be going to the aux battery bank.

We both ordered the duals as a factory installed option.

The DC/DC chargers (or most isolators for that matter) are triggered once they get to "X" voltage and turned on by the alternator once it starts working.

This is pretty easy to setup with a single alternator, mine was super easy in my last truck.

But with the dual alternators its not as straight forward.

So..... We will have dual alternators charging the truck batteries, thats easy and all setup from the factory.

But we will have a battery bank in our campers what we also want to charge from the alternator(s).

So trying to figure out... Is one a main always charging, and one just kicks on if needed? Or???
 

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Discussion Starter #5
I’m assuming the factory dual batteries are always connected in parallel and never isolated from each other or the charging system. If this is the case then I can put a fused lead from either battery positive and wire it to the DC to DC charger. And using the bodybuilders guides I can locate a blunt cut ign+ and use this for a signal wire.

This sound correct to you guys?
 

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I’m assuming the factory dual batteries are always connected in parallel and never isolated from each other or the charging system. If this is the case then I can put a fused lead from either battery positive and wire it to the DC to DC charger. And using the bodybuilders guides I can locate a blunt cut ign+ and use this for a signal wire.

This sound correct to you guys?
Been lurking because I ordered a 3500 pickup with dual alternators, but I did look at a few things in the builders docs.

There's also a high current power point (300A) 8mm post mounted on the driver side battery. Assuming you have the aux switches and/or VSIM, you could put an ignition source on one of the aux switches too as a backup disconnect for the signal wire.
 

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Been lurking because I ordered a 3500 pickup with dual alternators, but I did look at a few things in the builders docs.

There's also a high current power point (300A) 8mm post mounted on the driver side battery. Assuming you have the aux switches and/or VSIM, you could put an ignition source on one of the aux switches too as a backup disconnect for the signal wire.
Good info! Thanks for sharing!
 

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The RAM Body Builders guide will answer all your questions and curiosities. They also show how to downgrade to a single alternator. Strange idea, but to each their own.:confused013:

But as for a tap point, here is another suggestion from the BBG.

From just watching my volt gauge and comparing to my last 2013's single alt volts readings, I would guess that the system is smart enough to adjust the alternators outputs to the demand. My truck gets to 13.3-5V within seconds of a very cold start, and within a minute I see over 14V. That's with the grid heater sucking the life out of the system, a triple heat element interior cabin heater, headlight, the 12" display and the 2 fuel heaters. Plus all the other stuff that typically kicks in on a vehicle.
 

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The RAM Body Builders guide will answer all your questions and curiosities. They also show how to downgrade to a single alternator. Strange idea, but to each their own.:confused013:

But as for a tap point, here is another suggestion from the BBG.

From just watching my volt gauge and comparing to my last 2013's single alt volts readings, I would guess that the system is smart enough to adjust the alternators outputs to the demand. My truck gets to 13.3-5V within seconds of a very cold start, and within a minute I see over 14V. That's with the grid heater sucking the life out of the system, a triple heat element interior cabin heater, headlight, the 12" display and the 2 fuel heaters. Plus all the other stuff that typically kicks in on a vehicle.
Thanks, the BBG is amazingly helpful for most things, but it lacks in some things, such as this alternator confusion.

It also lacks in any info whatsoever on how the dual tanks work. Luckily a member here schooled me on their function recently.

This is my first diesel, and its not even in my possession yet, just reading and waiting! :)
 

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Waiting is the hardest part. Been driving a Cummins RAM since 2004, so feel free to ask as questions pop into your head.
I got the dual Alt for mine because of the weak output from the single alt my previous ones had. (The 220Amp is at max alt speed, which is about maybe 80Amps at idle).

As for your alternator charging strategy, I have plugged in my fifth wheel RV with a really dead battery, started the truck, and the RAM was able to run the truck and recharge the RV battery quick enough to where I could raise the RV landing gear to hitch up to the truck within minutes. Hope that gives you an idea on the output.
 

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Never realized there was any kind of problem keeping the batteries charged with the basic alternator. Sure could understand the need if you have major draws from towing or some kind of aftermarket electrical loads. My old Cummins never gave me an issue and so far, no hint of a problem with the new one.

Good to read the comments and experiences here.
 

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Most of my RAM battery charging issues happen during Nov-March when temps are between -20F and +35F. Even this 2019 cranked just a hair slow last week when it was -5F, but it did fire up and the volts went to 13.3V. As usual by time I was at the end of my street, 14.2V was displayed.
Dual Alt's rule...:grin2:
 

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Most of my RAM battery charging issues happen during Nov-March when temps are between -20F and +35F. Even this 2019 cranked just a hair slow last week when it was -5F, but it did fire up and the volts went to 13.3V. As usual by time I was at the end of my street, 14.2V was displayed.
Dual Alt's rule...:grin2:
Do not doubt that is the case. Here in south Florida I read of freeing temperatures somewhere. At my hunting camp in Georgia there are mornings like that. Reminds me of why I live in south Florida.

Would imagine that short runs would tax the batteries and a greater charging amperage would be useful.
 
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