A method for determining a state of health of a rechargeable battery includes: determining a change in charge within an upper border and a lower border of a charging state window, the change in charge being determined by summing up current values measured within the charging state window; determining an actual state of health by scaling the change in charge with the width of the charging state window and dividing by an initial charging capacity of the battery; and determining an average state of health by calculating a sliding average of the actual state of health with at least one previous determined state of health.