Passive battery balancing refers to consuming the excess energy of high-energy batteries first. Generally, high-energy batteries are discharged by means of resistance discharge, usually releasing electricity in the form of heat, so as to obtain more charging time for other low-energy batteries. The advantages of passive equalization are low cost and simple circuit design. The disadvantage is that the capacity of the low-energy battery cannot be increased due to the battery with the least residual charge, which is a waste of the heat generated by the discharge of electricity.