Coagulation of charged aerosols is investigated by developing a sectional numerical model for both particle size and charge distributions and accounting for electrostatic dispersion. Symmetric bipolar charging increases the coagulation rate when particles are highly charged. Asymmetric bipolar charging results in a faster decrease in the particle number concentration, but does not actually result in larger particles as the decrease in number concentration is dominated by the electrostatic dispersion and not by the coagulation of particles. The performance of a simpler model in the literature is evaluated by comparing its predictions against those of the above sectional model. The simple model is most accurate for initially mildly asymmetric bipolar aerosols at short residence times.