My charging voltage is 15.2 volts, constantly verified by 3 gauges. It's my understanding the voltage regulator is located within the Powertrain Control Module (PCM). I don't drive the truck that often but the batts go low and it barely cranks after a week of sitting still. Does anyone know what the voltage values are supposed to be? I think 15.2 is the very high end of the scale but it seems to keep it that high always, I have cleaned cables and applied dielectric grease on batts and cables. I do haul a slide in camper that has a built-in voltage inverter but the camper is off the truck for the winter season. !5.2 VDC and low batts.

 

Had that same issue with 2012 Ram 3500 ST.Everything relies on the battery voltage when in sleep mode.Log story short,bought a Battery Tender, from any parts store near you.Just follow instruction on pkg & plug in.Ground the unit on the engine block.Blinking green light means 80% charge solid green means full charge.Reason I added this,because most people don;t read instruction,Battery Tender is easy to use and keeps both of my batteries up 100% for months,Mine sit for long periods as well.Just a thought.........................