The previous battery in my W204 was a Genuine MB battery and from the date stamped on the negative battery post was 7yrs old when it stopped holding a charge. Happened out of the blue no real signs the battery was failing. I had to use my battery jumper to start the car even after long drives on the highway. I ended up getting the same replacement battery at my local MB dealer for around $210 after core return. I later realized Walmart sells the agm H7 batteries with a longer warranty and less money so i'd go with them next time I need one. At the time i never thought to look at Walmart and was looking at all local auto parts store but the MB dealer was actually the cheapest.

I didnt need to do anything special, just removed and installed the new battery. I think I had to reset the clock on the dash but thats about it.

Since then I bought a Noco Genius 5 battery charger/maintainer and will hook it up maybe once a month just to bring it to a full charge and hopefully condition the battery, whatever that means. I dont put many miles on the car and its mostly short trips around town. To make it easier to charge I hard wired the charging cable in the car, positive to the positive battery clamp and negative to the engine bay where the battery ground cable is grounded. I read doing it this way will let the bsm see the battery is being charged. I would have connected the positive to the positive jumping terminal but couldnt figure a good way to do it. When charging i can place the charger in the engine bay then close the hood since i route the extension cord thru the front grill.

 

oh and the metal clamp that holds down the original battery won’t work with many after market batteries. Screws too short. I found longer screws but D***! Getting that in there was a SOB.

 

Take a tape measure and measure up your battery and check if there is any extra room around it. Normally there is no extra space due to the clamp for the battery.

My 2010 E550 has battery in the trunk, my 2012 S550 has the exact same battery under the hood.

On the E I had it first replaced at the dealer only because car was under warranty. Cost me $400 and the problem was not the battery. It was the starter, but that is another story already told in these forums.

Anyway, I bought a new Duralast Platinum battery for the E with the same capacity as the dealer battery. H8 and it fit perfectly. I have had very good luck with Duralast batteries.

Coding new battery to the car is just the dealer trick to scare people from changing their own batteries, in my opinion. There is no way the car can know if the battery is old or new when it is connected in the car other than if the old one was dead. Battery just brings two posts that the car connects to with 12-13 volts between them, that’s it.

 

Electronis Battery Management system on newer models needs the new battery coded in for optimum performance according to web search:

When a battery eventually reaches the point where it needs to be replaced, the electrical system has adapted to operate as efficiently as it’s able to with a battery that isn’t 100% healthy anymore. The electrical system can’t self-diagnose so it won’t automatically detect the presence of a new 12-volt battery. Installing a fresh battery without registering it could set the vehicle into limp mode, shut down electrical systems, or prevent it from starting until registration is complete.

By registering the battery, the charging system re-adjusts to charge at an optimum level again. It prevents overcharging and resets the Battery Management System.

 

Web search? Please cite your sources

 

That's for newer models. The W212 in this forum don't require any battery registration.

 

Are you really serious??!!??!!

The charging system cannot know what quality the new battery is to set to some time period for charging it. It must be able to diagnose the battery as it ages so when you install a new battery of any quality it must be able to know how to charge it without any coding.

 

The W212 does not require battery coding to the car, my 2024 GLS580 does, source, personal experience

 

Yes, My GLS580 requires coding for a battery change, resets the charging algos

 

moving from an h6 (group 48) to an h8 (group 49) is a popular upgrade because you get a much larger "energy tank" and better cold-cranking amps for the same price.

the h8 is about 3 inches longer than the h6, so while the tray usually has the space, double-check that your hold-down clamp can reach the new notch. also, many cars from 2015 and up have a battery management system that tracks the battery's age to adjust the charging rate; if you jump to a higher capacity, you might need to "register" or code the new size so the alternator doesn't undercharge your shiny new agm.