W211 2005 Mercedes E200 Kompressor 1.8 163 hp battery (?) problem (?)

[nikow211]

hi, new member here, my name is Nick and I am from Limassol, Cyprus. I bought 2 years ago a mint condition top notch garaged W211 E200 kompressor with 163 hp automatic. the car had only one owner, an elderly cypriot fella who bought the car brand new from UK back in 2006 and the car has only 90.000 km on the clock. it has been double checked on the MOT. he goes at the same MOT the last 14 years and the mileage is the same. so, the car inside and outside is brand new condition, very happy for my purchase and the only thing that is broken is the sensor of the outside temperature which shows constantly +85 degrees Celsius.
so when i bought it didnt have a battery and the owner told me that i will need a brand new one because the old was alredy 6 years old. we managed to start the car, i drove it on the highway and got home. the other day i had a warning on the dashboard about the "comfort mode won't be available right now" or something. i went to my technician and said that the alternator was making noise and need to be replaced. we replaced the alternator with a brand new one out of the box (BOSCH) and changed both batteries with VARTA. no problems ever since. affter that i discovered some videos on the internet about hidden menus and i experimented a bit. i switched on the voltometer of the car by pressing three times the button on the dash and i was a bit confused. i had only diesel cars by now and all of them had 13.3 in idle and 14 + something when the car was driving.
mine shows 12.8 volts in idle and 13.7 in running. is it normal for gasoline? the technician said that the voltage regulator was on the alternator and is brand new. both batteries are brand new. i took a voltometer tonight from a colleague at work and put it on the car battery itself. it shows the same voltage.
all youtube videos are with diesel w211 and can't understand if it is normal.
other than that the car starts like a charm, no errors are shown and my commute is very short. about 10 km every morning.
thank you for your patience and excuse my poor english.

 

[190]

It may be because your car has a so called "smart alternator" which in general driving will only charge at a higher voltage in certain circumstances such as when the engine is on the overrun e.g. descending a hill with your foot off the throttle. Try measuring the charging voltage while driving the car and see how the voltage varies.

 

[nikow211]

In idle it stays in 12.8 volts. When rpm goes up, meaning when i drive it stays constantly in 13.7 volts.doesnt matter headlights or not ac on and everything it stays on 13.7 no less no more. The same in idle. I checked it i pressed every electric thing to work and stays in 12.8 in idle. My question is isnt it low for such a car? It is not diesel i know but still...