[juld0zer]

Yeah fully charge the battery before load testing but based on your measurements i wouldn't hesitate to replace the battery. BMWs are sensitive to weak batteries. Not so much the N55 but N54 cars would do lots of strange things with a weak battery.

The DME will assess the condition of the battery using the IBS if it is present and working properly. If the IBS is absent or disconnected, the DME will use its own internal measurement to determine charging regime but it will be at a fixed failsafe voltage.

On late model BMWs like ours which have IGR (intelligent generator control with brake energy recuperation), it is NOT rare to see the idle voltage at or slightly below 12V. This is where old school guys will get caught out.

Another thing is, if your alternator has lost communication with the DME then it is possible the alternator is not putting out anything. It is not like a conventional alternator. These only have two connections - the BSD line and the positive cable.