Method for performing a diagnostic test of an alternator in a vehicle, test arrangement and vehicle

A method (100) for performing a diagnostic test of an alternator (2), a test arrangement (1) and a vehicle (5) are provided. The method (100) comprises; running (101) an engine (6), providing (102) a signal representative of a pre-determined environmental condition to the alternator (2), providing (103) an output voltage and output current to a battery (3) based on the pre-determined environmental condition, determining (104) at least one of; complete battery voltage, voltage of respective battery cells and current load, comparing (105) the determined battery voltage with a pre-defined reference-voltage representative of the pre-determined environmental condition and outputting (106) an approved test result if the difference between the determined battery voltage and the pre-defined reference voltage falls within a predetermined range.