MWmp5

Where can I buy an Auxiliary Battery(besides dealer), what is part number, and can anyone tell me for sure where it is in a 2011 E350. Is definitely not in the trunk, the main battery is under the hood just in front of passenger side firewall.

thefisch

The aux battery for a 2011 should be behind the drivers side dash panel. Search on here there are threads with instructions on how to change it yourself. Looks very easy. You should be able to use any battery that matches the size, connections and voltage/amp specs.

MWmp5

Tried a search can't find it, help

thefisch

Well I see you found the right thread but gave up before you read down to the 8th post. There is a pdf in there of the instructions I was referring to.