In this guide, you will learn how to replace the auxiliary battery on Mercedes-Benz S-Class such as S550 S350 S400 S63 AMG from 2008 to 2013.
The early 2006 and 2007 S-Class models have two batteries but no auxiliary battery under the dash. One battery is behind the rear seats, the second battery is in the engine bay.
This guide also applies to CL-Class W216 from 2007 to 2013. Applicable to models such as CL550 CL63 AMG.
There is very little space in the dash which means you may find it difficult to remove the auxiliary battery. If that is the case, remove the panel from under the dashboard. This will allow you to access the auxiliary battery from under the dashboard.
Once you replace the auxiliary battery, the Auxilary Battery Malufaction on the dashboard should turn off immediately. Unless the auxiliary battery is not charged, in which case it may take a few driving cycles for the instrument cluster error message to turn off.