Mercedes-Benz W212 starter battery replacement and charging
How is the W212 starter battery replaced?
1. Take the keys out of the ignition and move the keyless key a couple of metres away from the car. 2. Wait for the systems to go to sleep. 3. Disconnect the negative cable first, then the positive cable. 4. Connect the new battery in the reverse order: positive first, negative last. The battery is in the engine bay on the passenger side in front of the bulkhead, under a plastic cover.
Does the W212 battery have to be disconnected for charging?
No. The battery can be charged with a charger with the cables left connected. Connect the charger to the battery that the car loads, and switch the charger on only after the other connections have been made.
What battery does the W212 have and how much current must a charger supply during a software update?
The original battery can be a 95 Ah AGM battery, and the battery size should be checked from the car before buying. During a software update and diagnosis the voltage must stay above about 12.5 V. A weak charger is not enough, and update attempts can drain the battery.