Message is due to a low battery condition so you took the correct first step. Since this failed you now need to check charging system and if this seems fine move on to check if something may be draining battery (i.e.: module, etc.) by not powering down after ignition shut off.

 

thanks!
the new battery got so drained out, the battery tester could not recognize it
Used e charger/maintainer. It took a few hours to come up to 6.8 volt, which the tester could recognize.
after disconnecting the charger, it went down again - below 6.5
I am thinking car-shop

 

Definitely check your alternator. I had a car in yesterday that had the same problem. She had her rear battery replaced at Christian Brothers about a week ago, and as she was driving the same warning came on her command, along with almost every dash warning light, the seats would not move. Every electrical device had a low power code, even with the car on running @ 2,000 rpm the battery voltage was low. I replaced the alternator, cleared the codes and test drove for about 40 min, double checked for codes and battery voltage, everything was fine.

 

I am not a mechanic, so, do you think I will be able to replace the alternator myself.

 

I don't even know how to check the alternator

 

So this warning came up while driving or just parked?

 

both, driving and not driving

 

Sometimes I’ll be working in the garage and click on the CD player and after 3 or 5 minutes it’ll turn off... then I’ll cycle the key and seems fine after that... it’s been that way for 4 yrs... I bought it new 2015

 

no this would not drive. the new battery is so drained, there is no light anywhere in the car, let alone car lights; even doors would not open, except with the mechanical key

 

Ohhh I see...

 

Is this a good alternator for S550
Bosch AL0844N New Alternator

 

Current MB part # 013154050287. Bosch equivalent AL0846N or AL0844N: 100% New Alternators | Bosch Auto Parts

 

either of them would be fine, right?
844 is smoothers, so, maybe easier to fit?

 

smather, not smoother

 

smaller (there you go)

 

Here is a quick clip on how to check if your alternator is working.

Keep in mind that you are checking the main battery in the trunk, not the starter battery. My shop Forman let me use his load tester that has “Snapon” stamped on it so is expensive. He said using a multimeter is fine too.
Replacing the alternator does not require any special tools, I used the following:
17mm socket, long breaker bar for the belt tensioner, E10 and 12 sockets, 10mm socket for the radiator bar, a little pick or screw driver, and coolant to top off what a spilled. Oh and at least two cans of brake cleaner to clean coolant off any pulleys if it spills.
BUT....it is a pain in the behind, everything is tight and the bolts are a pain to get too. Even with a lift it took me a while, but part of that is be a I am very cautious and don’t want to damage anything (the plastic bits in the engine compartment gets brittle over time).
the WIS instructions are accurate, you can buy a copy off ebay for under 20.00.

 

Thanks!
I have a 2010 s550 4Matic.
The only battery I found is the one under the hood.
I am not sure if it has 2 batteries!?
Nobody seems to know.

 

Ahh, yes I forget that almost every different year of every different model....is different lol. So if you have two batteries, the one in the trunk will be smaller and if an OEM battery is installed it will be labeled “starter battery”. This is my starter batter on the passenger side. Other models way have the main battery on the drivers side.

 

Thanks. I'll check the trunk

 

10 S550 4m should have one battery in engine compartment and backup battery in dash for transmission shifter. As it concerns the charging system and possible battery drain if alternator is fine (either one previously discussed is compatible) need to have someone pull fault codes using MB diagnostics and/or identify module not shutting down causing possible drain.

 

This is the only battery I found, and which drains.

 

Can you tell me where the other is. I assume I should replace that one as well, right?

 

thanks. i think i got it

 

If you want to proactively, see attachment.

 

Thank you so much!