Due to the monomers difference caused during the production process, the inconsistencies of Lithium batteries in remaining capacity can affect the service life of battery packs and cause damage or even explosions. A new modular equalization circuit, composed of improved DC-DC converters with the adaptive equalization control strategy based on ant colony system (ACS), is proposed to enhance the performance of battery packs. The equalization circuit has the advantages of simplicity and easy implementation. It achieved the controllability of bidirectional energy equalization and current size. First, the circuit’s structure and working principle are introduced. According to ACS, the simulation model of this balancing circuit with four batteries in series is built. The simulation results showed that equalization time is shortened by about 60% compared with the traditional control strategy. Then, a small-scale experimental circuit with 8 batteries was built to verify the simulation results, and the batteries were balanced under charge, idle, and discharge states, respectively. The experiment results verified the correctness and feasibility of the method.