The design and modeling of a self-balanced two-outputs battery charger capable to charge two high-power LiFePO4 battery packs is presented. The proposal is based on a four-phase resonant converter which is designed as a voltage-controlled current-source working at constant switching frequency. The output stage consists of two current-doubler rectifiers sharing the same magnetic core with a single primary and two secondaries windings. The structure of the output stage naturally imposes the self-balance-of-charge of both battery packs provided that the coupling between the primary and each of the secondaries has a negligible mismatch. The analysis and design of the proposed charger is fully explained. In order to study the battery charge equalization during the charging process, the long-term co-simulation of the battery model and the envelope model of the resonant converter is developed. The results are obtained considering two 48NPFC50 commercial battery packs with 48 V of nominal voltage and 50 Ah of current capacity.