2018 W213 Voltage Behaviour

[aeg2021]

2018 W213 2ltr Diesel

Just trying to verify normal voltage behavior, when viewed through either the display or via OBD.
Up until a few weeks ago, my car would maintain a voltage of 14.8 at all times while driving.

In the last few weeks however, after about an hour of driving the voltage starts dropping from 14.8 to 13.8 upon acceleration, with the battery losing more and more charge over time until eventually it fluctuates between 13.8 and 14.2.

I captured the behavior here:

I'll also add, when it drops below 14v the car seems to struggle a bit.

Local MB dealers say its normal behavior. As the alternator/belt/regulator/battery are all over 5 years old I'm thinking its one or more of them at fault.

Anyone else with a w213 have this same beahviour?

 

[Blobcat]

Hello and welcome,

What’s the battery like with engine off? Needs to be >12.4v
Alternator should be >14v although with modern electrickery they do strange things at times to reduce load. You have to tell them you’ve put a new battery in so they can adjust the charging.

I’d take a look at the battery first, I expect it’s low and dry. You can with some difficulty get the caps off and refill the cells. This can bring them back to life.