Interesting problem
 

Alittle history on my 2007 Mercedes S550 which has 167k miles on it. I replaced the front starter battery as well as the rear main battery in July of 2020. As about a month ago the car started having issues actually starting which caused by a failing starter. Since the car sat for couple of weeks the battery completely drained. Right before I had it towed I put the car on a trickle charge so that I can’t put the car in neutral to get it on the flatbed. I picked up my car from the mechanic and he said that the battery was completely drained and that he had to charge it. I drove the car home after picking it up from the mechanic which was about 30 mins or so from my house. After parking my car on my driveway I went out to unlock the car with my remote. Well of course the car wouldn’t unlock so I used the valet key to unlock it. Once in the car I was able to start the car right away with the key. While the car was idling I noticed that the battery voltage was 13.3 and when I pressed the gas it got all the way up to 13.9. I suspect when of the battery cells went bad and thankfully I have the pep boys receipt for it and it has 48 month warranty. Just want to ask anyone else think of what it could be besides the battery ?
https://cimg9.ibsrv.net/gimg/www.mbw...4ca429af3.jpeg

Likely it's the battery.

I am thinking it’s the same but hoping that it’s just that it hasn’t been driven on a consistent basis .