Went to start my E220 wagon this morning. First it gave the "display faulty, visit workshop!" message. Then it switched over to something like "longer braking distance, start engine!" and finally "brake defective, stop vehicle!" while beeping a lot. This was before I had even cranked the engine.
Went to start the car to see if the lamps went away, but instead of starting it made a click... then nothing happened. Power windows are not working either. Dashboard display seems dimmed. Headlights, warning lamps, radio and aftermarket DAB adapter turns on. As a side note I have gotten the "battery protection: convenience functions unavailable" quite often as of late. The analog clock also keeps running back and forth.

Is this just a bad battery? Can I get the reduced braking power/increased braking distance/brakes defective, display faulty and battery protection warnings from a bad battery?

EDIT: Fuses look fine. Also remember one time a couple of days ago when the engine cranked slowly and many times before starting.

 

sounds like a severely discharged battery to me. but why guess using the internet? you should be
able to have a shop or auto parts store measure the battery directly for voltage, at rest, as well as
under load/cranking to determine a more accurate state of health.

 

W211 display voltage on cluster. Hopefully with all the messages you can still do it. Search forum for the sequence, but I remember that with key to on, you scroll to mph display and hit button on cluster 3 times.

 

Tried doing that, but seems like the buttons on the steering wheel don't work. Display is also very dim, hard to see anything.

Will replace the battery tomorrow and see if that solves it.

 

Get a voltmeter and check the voltage of the battery. Just sounds like a dead battery that you kept driving. Charging it up might help if you don't drive the car often enough, it won't get charged up enough. Most auto parts stores in the US will charge up a battery for free, not sure about your country.