Car Doctor Q&A: Why Does My Mercedes-Benz Have Two Batteries?

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Maintenance on some luxury cars starts to add up after a while. Sophisticated suspension systems, all-wheel drive and even the charging systems — like the one in this Mercedes-Benz E500 — add extra cost to the maintenance tab. AAA’s Car Doctor John Paul finds out why:

Q: I have a 2006 Mercedes-Benz E500 and was thinking about replacing the battery. After asking around, I was told my car has two batteries. Is this true and why? And if it is true where is the second battery located? I have put many batteries in cars over the years, can I do this myself?

Mercedes-Benz E500 Coupe with AMG Sports Pack

A. Some Mercedes models have two batteries, a main starting battery located in the trunk and a secondary smaller battery located under the hood near the windshield on the passenger side of the car. Essentially there is so much electrical demand on this car it needs two batteries. The charging system for this setup is quite sophisticated to balance the alternators output between the two batteries. In addition some of these cars need to have the various systems re-initialized after the batteries are replaced. You might want to leave this particular battery job for the professional.

Craig Fitzgerald

Craig Fitzgerald

Writer, editor, lousy guitar player, dad. Content Marketing and Publication Manager at


  1. I have a 1998 c230 Mercedes -Benz . my question is, my battery is in the truck, i cant unlock the truck with key because battery control every thing and its dead. can i get in that truck without destroying the lock.

    thank you

  2. Many model Mercedes have two batteries. The one under the hood on the passenger side is the starter battery. It has a habit of showing no signs of aging and will let you down when you least expect it. If ever your car starts with the slightest hesitation, once in a blue moon, replace this battery. The other battery under the floor of the trunk is for all lights, computers and accessories. Before MB put in the second starter only battery the battery that did everything was in the trunk.

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