NOVELTY - A flow battery system (100) comprises a reactor (102); a first pump (104) operably connected to a first electrolyte tank (106) and to the reactor; a second pump (114) operably connected to a second electrolyte tank (116) and to the reactor; a memory including program instructions stored in it; and a controller operably connected to both pumps, and the memory and configured to execute the program instructions to determine a first flow rate through the first pump, determine a second flow rate through the second pump, control the second pump based upon the second flow rate.    USE - As flow battery system (claimed).    ADVANTAGE - The flow battery system provides flow determination without the need for using a dedicated flow sensor; and easily provides state of Charge (SOC) determination without the need for additional equipment.    DETAILED DESCRIPTION - A flow battery system (100) comprises a reactor (102); a first pump (104) operably connected to a first electrolyte tank (106) and to the reactor; a second pump (114) operably connected to a second electrolyte tank (116) and to the reactor; a memory including program instructions stored in it; and a controller operably connected to the first pump, the second pump, and the memory and configured to execute the program instructions to determine a first flow rate through the first pump based upon first pump operating parameters including a differential pressure across the first pump, control the first pump based upon the first flow rate, determine a second flow rate through the second pump based upon second pump operating parameters including a differential pressure across the second pump, control the second pump based upon the second flow rate. The flow battery system also comprises a first current sensor configured to generate a first signal associated with an amount of current used by the first pump; a second current sensor configured to generate a second signal associated with an amount of current used by the second pump; a first speed sensor configured to generate a third signal associated with a speed of the first pump; a second speed sensor configured to generate a fourth signal associated with a speed of the second pump; a first temperature sensor configured to generate a fifth signal associated with a temperature of the first pump; and a second temperature sensor configured to generate a sixth signal associated with a temperature of the second pump.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of the flow battery system.    Flow battery system (100)    Reactor (102)    First pump (104)    First electrolyte tank (106)    Feed line (110)    Second pump (114)    Second electrolyte tank (116)