IvanP

I have a facelifted 2013 S550 and preparing for possible battery change. Posts here seem to differ regarding one vs. two batteries (engine compartment and behind rear seat). I have read that some w221 cars have two batteries with smaller starting battery under the hood and larger consumer battery behind the seats and some cars only have one large battery under the hood.
A definitive answer before I start to rip into the lining of the trunk would be greatly appreciated.
In the engine compartment is a rather large battery - 95Ah/850A - part No. A 005 541 10 01

Do I have one or two batteries in this car?

Thank you in advance for any guidance you may be willing to offer.
Regards,
Ivan

ItalianJoe1

The engine compartment battery is a small one. All 221 chassis cars have the large battery behind the panel in the trunk. Some early cars had the smaller starter battery under the hood but that was phased out as it was really unnecessary. That was a carry over system from the 230 SL, which with SBC and so many other systems, it made sense to have a backup starter battery. That system was more hassle than it was worth and Benz got away from it fully after not too long.

Easiest thing to be sure, is pop the hood and ensure you don't have the one up front, but i've never seen a facelifted 221 with a starter battery, and certainly not on a M278 engine car.

DaveW68

2010 to '13 W221's do not have a consumer battery behind the rear seat. They went to the full size battery under the hood which is what you likely need to replace. There is also a small battery under the dash, which I believe is a lithium one.

1975benz

Im going to have to disagree with you regarding All w221 having x2 batts they do upto 2009/ 2010 yes the w221 does have two full size batts one in the trunk and one under the hood but in 2010 that changed and now theres only one large batt under the hood and an aux batt under dash unless you have alot of extra features then there maybe a small batt in trunk but my s350 only has one full size batt but my 2007 s320 i had before did have two full size batts so you are right but up to 2010 then No!!

konigstiger

Starter battery is in engine compartment (OEM 00555411001 replaced by 00198208), should also be additional small backup battery in dash.

IvanP

Thank you Konigstiger,
I appreciate your reply and the diagrams. From your and Dave's responses, I gather that my car's main battery is under the hood and no battery behind rear seats. Saves me the hassle of getting under the trunk lining.
Do you know if all w221 cars have the small battery in dash you mentioned in your post? I had the lower cover and the fuse box on driver side off recently when I was installing Mid City VIM and Remote Starter modules but do not recall seeing any battery in that area, unless it is really hidden. Is there a way to find the exact configuration from the VIN? I purchased the car used so I do not have the data card.
What does the small battery do? Will it serve to keep all the settings intact when the main battery in the engine compartment is disconnected during exchange?
Regards,
Ivan

DaveW68

Yes, your 2013 definitely has the small battery under the dash. And yes, it will keep all of you car's settings while you replace the main battery under the hood. You can get a replacement front battery at Walmart or another parts store for less than half of a MB branded one. And the battery you will buy at those stores will likely be made at the same factory that produced the Benz branded battery. Only the labeling is different.

ItalianJoe1

Yep, our OEM batteries come from Interstate.