[RReader]

Thanks again for your patient , especially when English isn't your nature language , I appreciate your trying hard to explain this in here .

Battery charger is quite different than the alternator on car , they serve different purpose in reality , and when we connect the Battery charger during programming (I can't believe you'll keep engine running during IstaP programming session ) , the GND of battery charger becomes the GND of that car already , it's not the same really since lots of capacitors are located at output PC-Board side of that charger .

Nowadays most quality battery charger actually decide charging voltage automatically by itself during the charging circle so to have the battery in best capacity , this is what confuse me that BMW want the battery charger to charge the battery with 14.8V , I think what BMW want during the programming session isn't a battery charger but a DC power supply instead , but just let the battery charger decides the charging voltage should be better for the longevity of the battery , by constantly input 14.8v to a car during many hours programming may kill the battery a little every time and make the expensive AGM retired sooner than the battery manufacturer expect , just ask around , isn't that what happened nowadays ?

RReader