Detection method of state of charge of flow battery

A detection method of a state of charge of a flow battery, comprising:

• providing a flow battery, wherein the flow battery includes a negative electrode electrolyte;
• executing a preliminary step, wherein the preliminary step includes:
• providing a detection device, wherein the detection device includes a light source and a receiver;
• a fixed distance is maintained between the light source and the receiver;
• the light source emits a light with a single wavelength;
• after the light passes through the negative electrode electrolyte, the receiver receives the light and outputs a signal;
• the single wavelength of the light is between 750 nm and 1100 nm;
• operating the flow battery with at least one full charge and full discharge in a time interval;
• obtaining a waveform according to the signal which is corresponding to a plurality of measured values and a plurality of time values in the time interval;
• defining a plurality of state of charge (SoC) values according to the waveform and obtaining a curve corresponding to the plurality of measured values and the plurality of state of charge values;
• and
• executing a detection step, wherein the detection step includes detecting the negative electrode electrolyte by the detection device and outputting the signal by the detection device, thereby obtaining a value according to the signal;
• through the curve, one of the plurality of state of charge values corresponding to the value is obtained.