[primoV8]

I posted this over at a dedicated Infiniti forum and pretty much echoes what marctronixx has mentioned about the battery current sensor.

The ECM controlled alternator could be part of this problem.
The battery current sensor attaches to the negative battery. With the harness unplugged and ignition ON, signal wire should have an output of at least 5V. You can either de-pin or cut the wire; I cut the wire and spliced on bullet connectors so when I would bring the truck in for annual emmissions (NYC), I would connect it back on so it wouldn't trigger a DTC for the battery current sensor.
Why do this? The alternator now works as a traditional charging alternator. My Northstar battery is always a constant 14V+, even with the A/C running. Even at rest, the lowest I've seen the battery voltage was around 12.9V. We all know a weak or failing battery can throw in a mix of electrical issues so this DIY wouldn't hurt ruling out the ECM controlled alternator being a possible cause of this issue.

 

[primoV8]

...The solution with tiny aluminum foil (shield) under current sensor doesn't work for me. I put 4-5 wraps on negative cable and still low charging voltage during driving.

Adding foil won't do anything for the battery discharging issue. Nissan is definitely aware of this issue but refuses to acknowledge their ECM controlled alternator is causing these premature discharges of the vehicle's battery.

One of the first mods I did when I first got my Z62 was cutting the signal wire (5V output) on the battery current sensor. It's been over 3 years and 50K+ miles since I did this mod and no battery/charging issues.

 

[primoV8]

On my ‘14 QX80, the signal wire for the ECM-controlled output on the battery current sensor is a blue wire. It’s likely the same for your truck. Easy to rule out with ignition on and a multimeter on hand. It’ll be the only wire with an output of at least 5V.

The only DTC that will appear when scanned is a P1550 for battery current sensor. What I did, since NYS has annual emissions/inspections, I spliced in bullet connectors. When my truck is due for inspection, I reconnect the wire and the P1550 DTC is eliminated. Once inspection is done, I disconnect it.

 

[primoV8]

@iervoline4, thanks for being honest about not having any automotive knowledge. With that said, the last thing you'd want to accidentally do is damage the IPDM and end up having to replace it. That will be very costly.

Take a look at the negative battery terminal. Bolted on the negative terminal is the battery current sensor which has a pigtail connector that plugs into that sensor. There are two ways to go about it this but to be on the safer side of DIY'ing, here's what you can do. Unplug that connector from the battery current sensor. Tape off the pigtail that you've just unplugged. Now the alternator will run like a traditional alternator and not rely on the ECM to say when and if to start charging the battery.