Disclosed is a method for determining a value of the state of energy of a rechargeable battery in a vehicle, the battery being connected to an electric consumer; the method including: determining the state of charge as a measure of the present capacity of the battery; and determining the state of energy as an indication of at least the remaining charge and discharge energy of the battery. The disclosed method further includes: calculating and determining the value of the state of energy based on at least one parameter which is related to the operation of the electric consumer and where the at least one parameter varies depending on a mode for operating the vehicle or electric consumer during charging or discharging of the battery. Also disclosed is an arrangement for determining a value of the state of energy of a rechargeable battery in a vehicle.