Does your Mercedes vehicle have one battery – or two?

In Automotive Diagnostics, Vehicle Maintenance by HomeTowne Auto Repair & Tire


Do you own a Mercedes or BMW?  Then it’s important to know if the model of your vehicle has one battery – or two.

The Mercedes S550 is one model that has two batteries; one to start the engine, and another – called the auxiliary battery – to run the car.

We recently had a Mercedes S550 in the shop that was experiencing some battery issues and wouldn’t start.

“If the auxiliary battery dies, the power locks don’t work, all of the accessories that work with without the key won’t work…but the car will still be able to start,” said HomeTowne Master Technician Keith Clausson.

One of the benefits of having a two battery system is that if your car’s main battery goes dead, you still have the ability to work the locks and get into the vehicle. But, it can also sometimes be a challenge for drivers to identify the problem if they’re not aware of the two batteries.

“Nine times out of ten that battery will give you a warning when that fails, with an indicator on the dash, this one did not. So we just had to go in and test, and see why it wasn’t working,” said Clausson.

If you’re experiencing a problem with your Mercedes or BMW vehicle, and you’ve changed the main battery but there are still issues, make sure you’re checking the panel with the relay boxes in the trunk, to look at the rear auxiliary battery, or bring it into the shop for a diagnosis.