Method of calculating the input current drawn by a power converter

The invention relates to a method and apparatus for calculating the input current being drawn by a power converter. The power converter may be connected to and charging a battery and the method includes the steps of measuring the current and voltage being supplied to the battery, along with the frequency at which the power converter is operating. The voltage being supplied to the power converter may be calculated using a pre-determined relationship with the current and voltage being supplied to the power converter and the frequency of operation. The voltage being supplied to the converter may then be used to calculate the current being drawn by the converter.