horrible

I replaced the rear battery because it went dead.
Car stays in the garage and I keep a trickle charger on the rear.
Never had trouble with the starter battery but it sure acts strange!
Car would not start so I jumped it.
My wife used it to go visit 90 mi away and I gave her the jumper take with her.
She never had a problem with it starting.
3 days later car starts. Go get gas.
Car won't start.
Same day drive two hours on Interstate stop to eat. Car won't start. Turns over very little then stops.
Jump again. Starts right up!
Continue on Interstate for another hour.
Shut car off twice,starts right up?
Shut off,sits all night,starts right up.
I'm going to replace it because now I can't trust it.
It just seems very strange no warning lights. Everything works fine!
I've read on this forum that once they go they go quick.
Not this one! It's an MB battery and I've had it for 6 years so I guess it's time.

Rudeney

6 years of service is getting your money;s worth out of a battery. MBZ batteries used to last that long and more, but the last few I've had have been no better than any regular battery, lasting about 4 years at best. Personally, I like the Advance Auto "Platinum" AGM batteries. I've had very good results with them. My C240 that stays parked for weeks at a time would always start right up, and that battery is now over 4 years old.

F1BHP

What did you replace the rear battery with. The rear battery charges the starter battery through a DC to DC converter so if you didn't replace the rear with the correct Mercedes AGM battery this will cause charging and starting problems.

horrible

I replaced the rear with an AGM battery from Advance Auto Parts before the starter battery started acting up.
Where is this converter your talking about located?

bobterry99

The Starter battery is charged through the converter by the alternator. It is not necessary to use an AGM battery for the rear Systems battery, though it is generally preferable.

It is located in the right side of the trunk behind the paneling.

I suggest you have your Starter battery tested. Autozone will do it for free.