Matrix charger apparatus and charging method

A charger apparatus and a charging method are provided for charging/discharging battery modules connected in series. The chargers of the charger apparatus are grouped at least into a first charger group and a second charger group. The first terminal of the first charger of the first charger group is coupled to the positive terminal of the i-th battery module of the battery modules, and the second terminal of the first charger is coupled to a first node between the j-th battery module and the k-th battery module of the battery modules, wherein j ranges between i and k. The first terminal of the second charger of the second charger group is coupled to a second node between the i-th battery module and the j-th battery module, and the second terminal of the second charger is coupled to the negative terminal of the k-th battery module.