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Replacing the Backup Battery on Mercedes Class B W246

Model: Mercedes Classe B MK 2, W246 - Years: 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019
Part: Battery

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If the display on the instrument panel shows "backup battery fault," it may indicate either a real depletion of the backup battery or, on some models with start&stop devices, a fault in the capacitor located behind the handbrake, which should assist in starting when the main battery begins to deplete.

In the case of the Class B W246, this battery is located in the passenger compartment, on the passenger side, directly under the mat, beneath the carpet lining in the heel area, practically under the glove compartment.


Updated on 1 March 2026 by ScegliAuto


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How to enter the radio code in the Opel Zafira?

In the Opel Zafira, it may happen that the radio locks and consequently requests the appropriate security code, especially after disconnecting or replacing the battery. The code can be found in the documents provided at purchase or through one of the various online recovery services. Once obtained, enter it by following the procedure shown in this tutorial. First, switch on the instrument panel, then press and hold both the "AS" button and the left knob for about 5 seconds. Next, enter the first digit by repeatedly pressing the "1" button, continue with the next 3 buttons, and save the setting by pressing the "AS" button again.

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