Had a client with a 2019 G class that was left in their garage for aobut 6 months and the battery went completely, irretrievably flat. Charging didn't recover it. O'Reilly Auto had a Superstart Platinum AGM Group size 49 H8 49PLTJ that matched the OEM Mercedes battery in literally every way except color: terminal location, shape, molding, profile, size, right down to the vent placement and little reinforcement ribs molded into the case.
Easy job to replace it:
Remove the plastic covers from the 4 corner anchors of the cargo top mat
Torx bit removes the anchors
Take care to save the black bushing washers under the anchors that are pushed into the cargo mat
Remove the cargo mat
Remove the battery terminals (-) first, (+) second, wrap the (+) terminal in tape or other insulation against stupid things happening
Remove the battery hold down clamp on the left side, 2 bolts at the base of the battery
Remove the battery vent 90 degree fitting from the battery (right side, top center of the battery). Save that 90, you'll need it for the new battery.
Remove the battery

Installation is the reverse of removal.
No special programming or procedures to get the Mighty G back up to speed.
Happy client, many $$$ saved over the dealer prices. Battery was about $280 all in, might have been an hour to change start to finish including the trip to the auto parts store.
ETA: I'll be installing a charge cord with an appropriate charger for long term storage.

 

I think you need to code the new battery to the car?

 

Perhaps if the replacement battery specs are different than OE, but if the same? My OE battery died at 42 months (about 20 months ago). I replaced it with an Autozone Duralast Platinum H8 -- identical in all respects to OE (even made in Germany). Battery and all electrical systems have been fine. I'm skeptical about the necessity of battery registration, except for its contribution to the dealer's profit.

 

It will work without coding it (obviously), but the coding is done to let the vehicle know how to charge the battery most efficiently and optimally.

As the battery ages, the BMS adjusts its charging methods to extend the life of the battery. Replacing an old battery with a new battery and not coding the car can lead to shortened battery life.

With that being said, I am sure there are thousands of people that didn’t code their car for a new battery and didn’t notice any issues. However if the new battery dies in 3yrs, if it was properly coded to the car would it have lasted 4yrs?…Who knows.

I haven’t had to code any of my Mercedes as I seem to swap them out too soon, but if you are keeping the car a while, imo, it’s worth doing.

Also, any decent scan tool should be able to take care of it for you.


EDIT: I understand your mistrust and hesitation to have a dealer do, I definitely won’t have them do it. It is about a 30 second job.

 

There's no debate that batteries age with use -- their charge capacity and rate of charge acceptance change. Battery charging systems can determine these changing characteristics and adjust charging parameters if this is beneficial to prolonging the battery life and optimizing performance. But why does an intelligent charging system, capable of measuring the charging behavior, need to be told there's now a new battery to deal with?

Many owners don't give their batteries any thought until the day their battery dies. Then, they usually buy a charger and attempt to bring it back to life before coughing up $600 to have a dealer install a new battery and hitting them up another $100 for coding it. When people on this forum ask about chargers, one of the popular recommendations is the CTek MXS5.0 (also privately branded for MB). Ctek's literature promotes its charger as "Features of the MXS 5.0 include diagnosis of battery condition to establish if it can receive and retain charge, patented automatic desulphation step and a special reconditioning step that will revive and restore deeply discharged and stratified batteries."

If your car's battery management system has gradually adapted to the charging requirements of an aging battery, and then you attach this CTek charger that desulphates and reconditions the battery back to much better state, shouldn't there be a coding step required to tell the battery management system that it needs to adjust itself to this new battery state, just like it needs to be told a new battery is installed?

I have designed several portable battery powered instruments that use alkaline (non-rechargeable), nickel-cadmium, nickel metal hydride, lithium and sealed lead acid battery types, including the charging systems for these batteries. Each battery chemistry has its own charge/discharge characterization, and each requires a charging profile that optimizes battery life and charge acceptance. None of these devices ever had to be told when new batteries had been installed in order to work properly and optimize battery life. In fact, several of these instruments were used with interchangeable battery packs of various ages (just like cordless power tools), and swapping out a depleted battery pack for a fully charged battery pack was never a problem, or required the instrument to be told it had to recharacterize the replacement battery before continuing to function.

I remain skeptical about this new battery coding matter, but I could be completely wrong. If anyone can identify a peer-reviewed technical article from a professional trade publication that discusses the merits of battery coding, or identify a patent that describes how intelligent charging systems need to be told when a new battery becomes installed so they can optimally adjust, I would enjoy reading such.

 

Thanks for the input to all who responded. I've placed an order for a ctek charger to install on my client's G and might consider one for my ML if it impresses me.