Here is how the system is supposed to work: voltage regulator is commanded by the DME over LIN bus-a few simple devices are connected, including the IBS. DME is supposed to evaluate the information from IBS and send commands to the voltage regulator. In case of something wrong the DME must send a message to the CCC/CIC to display a low voltage, but somehow this doesnt happen on N62 equipped cars.
I know this exact same problem occurs on a specific Mercedes 4 cylinder engines. No charging and no warning.