As the power density of lithium-ion batteries continues to increase and high-power fast-charging technologies emerge, the development of battery thermal management systems has become an important and challenging area of research. In this study, a direct-cooling thermal management system for multi-box battery packs using roll-bond cold plates was presented, and the performance of the system was experimentally investigated under different operating conditions. The experimental results show that at a charging rate of 0.5 C and a compressor speed of 2400 r/min, the average coefficient of performance (COP) of the system can reach 5.83, the maximum dimensionless loss coefficient of the cold plate is 6.27%, and the maximum temperature difference between the cold plates is 1.90 ℃. Notably, the temperature difference between the plates escalates with increasing compressor speed and the thermal load on the cold plate, reaching a maximum value of 3.99 ℃ during the tests. Concurrently, the COP of the system showed a decreasing trend with the compressor speed, reaching a maximum value of 7.41 throughout the duration of the experiments.