Abstract: Recently for lithium-ion batteries in satellites and spaceships , the Battery Management System (BMS) has become essential to enhance life and guarantee safety. However, most of the balance management circuits need complicated cell sensing and duty control modules. Such circuits are too costly to commercialize. In order to reduce the cost, weight, volume and energy consumption of BMS, this paper proposes a new battery management circuit. The designed circuit is passive and small in size. The charge voltage is regulated by increasing the bypass current through an adjustable reference chip. Experimental results show that the bypass current increases linearly if the charging voltage is in the range of 4.05 V to 4.2 V. Also after several charge-discharge cycles, the differences between batteries visibly decrease. The proposed circuit is small in size, low in power consumption and economical, making it ideal for commercial space.