2007 S80 Battery drain problem Topic is solved

[Skymongrel]

My son's 2007 S80 (150k) battery died the other day. The battery is only two years old so I charged it and monitored voltage. It didn't hold a charge, dropping to below 12v overnight. I went down the rabbit hole of looking into parasitic drain, specifically the alarm siren and SiriusXM radio module.

My model year doesn't have the radio module, and although pulling the fuse for the alarm siren module seemed to work initially, it disabled my radio and heater controls. And then the battery still dropped to 12v ( I did charge battery on a charger). I tested the alternator and it would bring battery voltage up to 14.6 or so. So I figured that the battery was bad even though its not to old!

Thinking about it; my son doesn't drive the car much at all. His work is five minutes away and only a couple time a week. The way I figure, the car never got a chance to fully charge the battery and shortened its life. I installed a new battery (H6 or Group 48 size) and a trickle charge devise (Noco Genius1) to maintain charge and hope this solves the problem ( I could still have a drain issue).