Optimized bi-directional balancing method and system

A battery balancing method and system is provided. The system includes a plurality of cells connected in series, a balancer for each cell, a monitor configured to determine a state of charge (SOC) of each cell, and a microprocessor. The microprocessor is configured to perform several functions: to iteratively calculate a SOC error for each cell, based on a theoretical balancing of the Min Q cell and the Max Q cell, until the SOC error is less than or equal to a first threshold; next, to iteratively re-calculate SOC error based on a net charge or discharge time for each balancer until the SOC error is less than or equal to a second threshold; and when the SOC error is less than or equal to the second threshold, to instruct each balancer to physically balance each respective cell based on the respective calculated net charge or discharge time when the second threshold is met.