Method and system for testing SOC (State of Charge) of flow battery and battery energy storage system

The invention provides a method and a system for testing the SOC (state of charge) of a flow battery and a battery energy storage system.The testing method comprises the following steps: firstly, establishing a function relational expression between the electrolyte viscosity of the flow battery and the state of charge of the flow battery through testing; secondly, respectively measuring a first viscosity value corresponding to the first moment and a second viscosity value corresponding to the current moment of the electrolyte of the flow battery; and finally, calculating to obtain an SOC value of the flow battery corresponding to the second viscosity value at the current moment based on the function relation. The SOC value of the battery is measured by adopting the electrolyte viscosity, which is easy to obtain, of the flow battery, and the method is easy to implement, simple and convenient to operate and low in cost. According to the method, the charge state of the flow battery can be obtained in real time,