Charging voltage seems strange
Thread Starter
Junior Member
Joined: May 2020
Posts: 50
Likes: 21
From: Florida
GL350, Audi A3 TDI, VW Beetle TDI
Charging voltage seems strange
I recently did a preemptive primary and auxiliary battery change due to a pending trip. No issues at all but the OEM batteries were approaching 8 years old. My vehicle is a 2015 GL350 with 103,000 miles. I use ScanGuage to monitor several functions and decided to monitor “VLT” after the battery change. What I’m noticing is that upon start, the voltage reading is 14.7V fluctuating +or- 0.1V which seems high. Within 5 to 50 miles, the voltage drops to 12.7V fluctuating +or- 0.1V which seems low. The time/distance for the voltage drop appears to depend on whether from a cold or warm start. I have observed a couple of times the voltage will briefly return to the 14.7 reading. I have driven about 500 miles over the last 9 days with this condition without problems. I do not return home for another week and about another 200 miles for access to tools and scanners. Wondering if I should be worried? Is the alternator going bad? Or is this a fuel saving feature that reduces charging voltage for a fully charged battery?
Super Member
Joined: Jul 2019
Posts: 733
Likes: 298
From: New Orleans
2014 GL450, 1992 W140 300SD, 1993 W140 300SE, 1987 E30 Convertible
Normally people worry then battery dead...
Not normally - Mercedes use on demand charging, where charging is off once computer determine that battery charged.
Not normally - Mercedes use on demand charging, where charging is off once computer determine that battery charged.
Thread Starter
Junior Member
Joined: May 2020
Posts: 50
Likes: 21
From: Florida
GL350, Audi A3 TDI, VW Beetle TDI
Thanks so much arsupisemnet. This is a relief. I was putting a plan together to do an alternator swap when/if I got home from this trip. I guess not needed.
Mike
Mike
