The invention refers to a system and method for assisting the start of an electrically powered vehicle comprising a battery and processing means configured to: a) receive a sequence of voltage measurements by a sensor connected between the high voltage terminals of the battery and a chassis, b) compare the sequence of voltage measurements received from the sensor with previously established voltage patterns, wherein each voltage pattern is formed by a sequence of voltage values, and wherein each voltage pattern is associated to an insulation resistance value, c) select the voltage pattern whose voltage values are closest to the voltage values of the sequence of voltage measurements received from the sensor, d) establish the insulation resistance value of the battery from selected voltage pattern, e) enable starting of the vehicle if the insulation resistance value obtained exceeds a predetermined insulation resistance threshold value that ensures the insulation of the battery.