Auxiliary battery replacement ordered! (14-BS)

Several models of Mercedes have a 2nd battery - often referred to as the Auxiliary Battery.  It's hidden in the E55 under the cabin air filter in the engine bay.

FYI - The primary battery is in the trunk :)

I was informed of a fantastic deal on the aux battery on Amazon - 50% off!

ACDelco ATX14BS (14-BS) Maintenance Free Absorbed Glass Mat (AGM) Powersport Battery 

Installation was a total breeze, the bolt/washer setup is different from the OEM setup, but now there are no issues with my electronic brakes and/or other 12V items in the car :)  Highly recommend this battery - save yourself about $200 in the process!