In this paper, a resistance-compensated phase-locked battery charger (RC-PLBC) mathematical model is built, and its s-domain transfer function is also derived. The stable, safe, and nonovercharging conditions of the RC-PLBC are discussed, and many criteria are proposed. After that, a complete design procedure is presented for designing a fast and safe RC-PLBC. A prototype of RC-PLBC is designed and realized to verify the charging performance. Comparing with a typical PLBC, the charge speed of the proposed RC-PLBC is improved by 18%, and the safety is held on.