State of charge calculator for multi-cell energy storage system having cell balancing

摘要

An arrangement for monitoring the current or state of charge (SOC) of an energy system (230) having one or more series-connected strings (S₁, S₂, . . . S_n) of battery cells (C₁, C₂, . . . C_n). The battery cells each have respective dissipative devices (D₁, D₂, . . . D_n) selectively connectable in parallel therewith for balancing cell voltages in the string. The dissipative devices are of predetermined, typically equal, impedance value. The voltage across each cell (V_c1, V_c2, . . . V_cn) may be separately monitored, such that by dividing the monitored voltage across a cell by the impedance value of a dissipative device connected in parallel therewith, the dissipative current is determined. A summation of all of the dissipative currents yields an error value, which error value is then removed from the measured gross current (I_bat) flowing through the combined battery cells and dissipative devices to yield a corrected value of current (I_batnet). A corrected SOC value (Q_net) is obtainable in a similar manner.