Aerosol charging has been subject of research for a long time. The theoretical charge limits, the charging mechanisms and experiments of charging of aerosol particles have been reported in literature, in several research fields. In the applications different kinds of chargers are used, resulting in different amount of charges on the same aerosol particle. We are interested to find the highest charge level that can be achieved with a (corona) charger. In this paper a robust method to compare electrical aerosol chargers is presented. This model makes the charging theories more transparent and is not dependent on assumed values of for example Ni t. The particle charging equations, known from aerosol technology, are combined with basic physical models known from electrical engineering. The model is experimentally tested with a corona needle charger and with results from literature.