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Discussion Starter · #1 ·
I just got a 2020 Laramie Longhorn with the Ecodiesel....had a 2015 before and loved it. On the long drive home (1300 miles!) I noticed that the voltage was varying a good bit on the electric system....it would usually average in the 12.7 to 12.9 range, but then would drop off to at times to as low as 12.3 for a second, and then shoot up to 14.7 or so for a few seconds, then back down to 13.0 or so for awhile then back down to 12.8 or so....in other words, very erratic from what I typically see in a vehicle. I thought it had a faulty voltage regulator, so, I took it to the local RAM dealer.....they actually called FCUSA and talked to their technical folks.....what they were told was that for this motor, that is perfectly normal and was designed that way, along with the AGM battery, to improve fuel economy in these models. Put another way, only run the alternator when absolutely necessary. Hmmm, OK, well proof is in the pudding, so, for any other 2020 GEN 3 engine owners, what does yours do? Let's share and compare to see if this is indeed normal or not.

Thanks for listening and let me know what you think? For those with GEN1 or GEN2 engines, this is not supposed to happen, it's just the new GEN3's from what I was told......
 

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2015 Outdoorsman EcoD CC w/6.4' 4X4
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It seems odd that the voltage would fluctuate that much.
I do know the alternator voltage is controlled by the Intelligent Battery Sensor which is on the negative battery terminal. It take into account current draw, temperature, voltage etc to determine how the battery gets charged.
 

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Discussion Starter · #3 ·
Yeah, that's what I thought to......but FCUSA is saying that it's designed to be that way.....if it's designed that way, then all of them should do it (of the Gen3's) so that's why I'm trying to gather input from other owners.....we'll see!
 

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I know the hardcore hypermiling guys will install shut off switches for their alternators and marine batteries to help with fuel economy. If FCA is doing that with the computer I find that pretty intriguing. On the old geo metro, shutting off the alternator netted about 3-4 mpg gains. I don't think it would be that much on a large truck but it would improve economy and lessen the drag in the engine, while increasing the strain on the battery. I'm going to look into this a bit more and see if there is anything documented about it.
 

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2016 Ram 1500 Ecodiesel 4x4 CC Laramie
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One of the " FEATURES" of the GDE tune is constant 14v charge from the alternator, gen 1 and gen 2 stock did the same thing where you would notice battery voltage drop to 13v while driving, I am gde tuned and noticed the battery reads 14v constant as long as the engine in running..

I wouldn't be surprised if FCA took it to next level with the gen3 in order to achieve better mpgs.
 

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2015 Bighorn, CC, 6'4", 4x4, 3.55
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I think this battery/alternator strategy is common on all vehicles today, it will likely be harder to find a vehicle that doesn't do this (short of aftermarket tunes like GDE which shut it off). The first time I remember hearing about it was on the GM trucks likely around the 2007 redesign, so it's not new.

A newer, but similar, idea is using pulse width modulation on the fuel pumps for the hemi trucks (it was added in 2013 IIRC). the pump output is controlled by PWM based on engine parameters. In situations where less fuel is required, the controller turns down the fuel pump. pumping less fuel saves electricity which saves the battery/alternator which puts less load on the engine and increases economy.

Idk if this is used on the EcoD also, but I hope not given what we know about the HPFP
 

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2020 Limited ED 3.92 33gal
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My bone stock 16 was alway around 14v, my 2020 does seem to fluctuate around 12.8-14.7. I’ll ask about when I do my first oil change. But I’m not concerned about it.
 

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I just got a 2020 Laramie Longhorn with the Ecodiesel....had a 2015 before and loved it. On the long drive home (1300 miles!) I noticed that the voltage was varying a good bit on the electric system....it would usually average in the 12.7 to 12.9 range, but then would drop off to at times to as low as 12.3 for a second, and then shoot up to 14.7 or so for a few seconds, then back down to 13.0 or so for awhile then back down to 12.8 or so....in other words, very erratic from what I typically see in a vehicle. I thought it had a faulty voltage regulator, so, I took it to the local RAM dealer.....they actually called FCUSA and talked to their technical folks.....what they were told was that for this motor, that is perfectly normal and was designed that way, along with the AGM battery, to improve fuel economy in these models. Put another way, only run the alternator when absolutely necessary. Hmmm, OK, well proof is in the pudding, so, for any other 2020 GEN 3 engine owners, what does yours do? Let's share and compare to see if this is indeed normal or not.

Thanks for listening and let me know what you think? For those with GEN1 or GEN2 engines, this is not supposed to happen, it's just the new GEN3's from what I was told......
This is really been "bugging" me. Thanks for info.
 

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2020 Ram 1500 Laramie ECO 3:92 4X4 33gal tank
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I noticed the same thing today on mine. Although I never put the battery voltage on the display and looked at it all the way home. But I did today when I got my first CEL. Scanned the code and it was a P225D. Cleared the code and hoping for the best.
 

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Today I drove my 2020 EcoDiesel and watched the charging system to try to understand it a little better. The only time I saw 14V was when the truck wasn't under load, i.e., turning off the cruise and coasting or when going down a hill. Here's a picture documenting the highest voltage reading.



 

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The system had similar charging characteristics regardless of running empty or towing. 13.0v was the lowest charging number that I saw. In this photo, I'm towing in 7th gear cruising along at 1,900 RPM. For the most part, the charging system stayed between 13.0v and 13.2v the vast majority of the time.

 
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