I don’t find anything on this subject, so I ask the professionals here for their opinion. The facts play with a common Varta Silver Dynamic 77Ah 780A in a vehicle year 2000, 1.9L diesel with 120A alternator without electronic snaps like start/stop etc. My knowledge is: -> Rest current if over 12.5V … all good -> Charging current if over 13.5V … all good if I now hold my measuring device at the battery poles with running motor, is indicated for 1sec 13,49V and then immediately 12,79V (without consumer). If I turn on the consumers like light, rear window heating, heating etc., the display falls to 11,77V. That is, every time I go with the measuring ends new to the poles, there is always the 13,49 or sometimes 13,5 or 13,45V for 1 sec and then it falls to the 11 or 12V. What is it? Measuring device? Battery? alternator (which has a brand new controller installed). I miss this 13 coma still something volt permanently, especially if all the vehicles are equipped with a new control unit. the measurement falls to below 12V.