Original battery
 

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Car has been having issues starting lately. It's my 2012 E550 4matic. I'm guessing this is the original battery since it's a Varta and made in Germany and I doubt replacements are shipped across the Atlantic.

Car won't start, but I put my jump pack on and it fires right up without taking juice from the pack. After 6 jumps my pack still shows 100% and isn't to the 75% level yet.

Leaning toward a new battery but since I only drive a mile and a half to work it may not be getting a good recharge cycle. I've got it on a charger to see if it improves.

I would definitely replace the batteries. You do not want to be stranded somewhere.

Just purchased Gold 3yr warranty battery from Advance auto, dropped right in, no problem. Was actually a longer battery than my original. Paid about $120 after online coupons and same day pickup / install at store.

+1, it's time after 5 years. Shorter trips means shorter life on these batteries and 'smart' alternator.

A strong battery on full charge is the best thing you can have in these cars, and is probably one of the cheapest fixes you will spend money on.

My ride will be 4 years old at the end of December I plan on changing out all the batteries even tho I have just reached 12,000 miles. do not want problems .

Yes, that is a very smart move. Why wait for problems that will crop up with a lot of them attributable to simply a weak battery.

The 1998 Varta made in Spain lasted in our MB for 13 years. Couple of members reported 17 years.

WoW! That's incredible.

Take a picture of the post. The one in my 2008 is almost 10 years old. It has a month and year code stamped on either the positive or negative terminal. The 2011 had the battery replaced by the previous owner so maybe they just don't last as long as they used to.

For a cheap battery charger, there's the Schumacher SC3 8amp battery charger, around $30 on Amazon.

Batteries seem to have reverse technology.
They last less and less each year.
Few years back Kirkland batteries had 100 months pro-rated warranty. Not anymore and most common you can buy is 36 months replacement.
Than Jay Leno is still washing 100 years old battery on his fire truck.

So it cut my picture off when I posted it. The terminal is engraved 31/11 so I'm guessing it's from the 31st week of 2011 (August) which is consistent with the age of the car. I charged it up Wednesday night and haven't had any problems with it.

I spent Thursday changing the front and rear breaks on this car which I'll post some pics of in a new thread. I noticed something odd while working on it with the hood open. I had the cabin airbox off and I could see the climate control fan running. This stopped as soon as I opened the passenger door. The car had been off for at least an hour. Between Wednesday night and Thursday afternoon I only moved it in an out of my garage to give myself more space on the one side of it while changing the brakes. Is it normal for the interior fan to run while the car is off? I wonder if there is something creating drain. Before I had issues with it starting, my parking sensors, and other systems were giving me errors, which seemed to go away with a good charge.

I almost took the car in because the AC wasn't cooling as well as it should, but decided to wait since I the weather is getting cooler. I hear what sounds like air occasionally hissing from behind the dash, possible AC coolant or a vacuum leak? Are these issues related? Is it time for a new S-class?

At any rate I've got first world problems here.

The operation of the blower fan when the car is off is completely normal. It is the evaporator coil drying procedure so your A/C doesn't smell like feet. LOL
Opening the door will cause it to stop. I do not know what the actual programmed run time is, but I have had it come on, then turn off, then come on again. whatever....
The only hissing noises I have heard was my old 2010 with airmatic letting go of some air. pssssshhhh noise, or a brief popping fart noise.
These cars are noisy!

Fan running for 1 hr is not normal.
When we don't have good description how drying program works, it has to be only few minutes and the only way for cabin blower to run for max 1/2 hr is use REST program.
From forum replies I notice that lot of those cars might have problems with door switches.
The car should go to sleep 20 seconds after closing the door. Other members report their Bluetooth still working after 1 hr, what indicate the car did not go to sleep till battery saver clicked in.

My E550 doesn't have airmatic, but that's the sound. My wife's E63 you can hear the air going out and see it lowering after it's parked; if it gets locked its immediate but if not it can take a while, often just as we are getting ready to drive it again.

I'm not sure if either car is going to sleep properly or not. I've wondered if I keep my keys to close and they "activate" it. My key fobs don't last but few months in fact last time I changed them all 4 keys I got the replace battery within 2 weeks in both cars; which could have been bad batteries. I haven't changed them and its been a month. I frequently get a key not detected message when I try to start the E550 often after I've just unlocked the doors.

I think the two 212's keep each other up talking to each other in German.

Ha! Hilarious. I wouldn't doubt that they like to communicate with each other. Your key proximity may be the issue and you should definitely make sure they are far enough away. I got at least a year from my 2010 keyless Go batteries, and my 2014 batteries have been in the fob for over 6 months now with no warning. I always lock my car and it's in the garage.

My September 2010 built 2011 E350 is now on its 3rd battery. It would seem as if 2-3 years is the max life for a battery in one of these cars.

Does it matter if ECO mode is used or not? Does that wear the battery out more?

ECO is using smaller battery and the size usually is shorter-lived than the bigger brothers.
Battery use is whole science for those like boodocking in RV, so thank the manufacturer that in car it is all automatic. First batteries hate to be discharged below 50% of its capacity. Not happening in car unless there is failure.
Than battery needs to be "topped off" for long life, meaning low current charging for long time. Most of the time cars are driven on significant distance, so unless you have 1 mile commute, you don't need to worry about it.
Than battery has a number of charge/discharge cycles, but that goes in thousands, so unless you start your car 100 times a day - you don't have to worry about it.
Modern cars have more gadgets to run, but then modern electronics are more battery-saving.
We had 1999-2000 MB models sitting for 5 weeks with alarm on and they started on their own power.
I read on W211 section that lot of those cars stay awaken for strange reasons and that is definitely what can kill the battery.
So from time to time, close your car and stay for 20 seconds observing if all the lights and displays go off. If not- start checking.

My most recent MB purchase
 

It has a Varta battery in it which I'm having some issues with not knowing its age and has no stickers on it.. Is there a way to find when it was produced? It is German
and found this out as Varta batteries are now made in the USA by Johnson Controls.and marked as so. Battery life recently is horrible and Johnson makes most of them.
Had a new one in my Suburban in January and it was dead in August, made by Johnson. Just a fair warning!.

The oem batteries typically have the week and year stamped on the post of the battery.

Battery life has been bad lately because most newer cars have new charging algorithms that don't fully charge the battery so they can get slightly better gas mileage on their CAFE ratings. I recommend getting a battery charger that's under 10 amps and giving the battery a good charge once in a while as a fully charged battery will last longer than one that isn't fully charged up all the time.

So both of the E cars eventually ended up getting new batteries. The E63 got a warrantied battery a month after I originally posted this. It was interesting the dealer could see every charging/discharging event in the log. Basically given that my wife and my commutes are less than 2 miles, and most of our driving is the same it's difficult for it to recharge and battery life suffers. The E550's battery I kept going for another 6 months. I gave it a good charge every once in a while and it was mostly happy. It needed jumped one day in the Chic-Fil-A parking lot and I'd had enough. So the 2012 E550 original battery lasted 6.5 years and the 2016 E63 2.5 years.

Each battery has to have manufacturing date code stamped on it somewhere, but the coding is different between manufacturers, so google your battery how to translate the codes.
Lately I fired up my ScanGauge on 2014 diesel for DPF monitoring and as side gauge I display car voltage.
The car has variable charging programs, but main point is that in the morning, on car who was driven day before, warm weather, so no electrical load - the car still takes over 6 miles of charging at 14.5V before computer switches to 13.7V maintaining voltage. My diesel fires up in 1/2 second, so the battery is never much discharged.