In BMS applications, the shunt is used to measure the total current of the battery pack, so its detection accuracy is very important, so we need to understand what factors affect the detection accuracy of the shunt.

Factors affecting accuracy: Directly from Ohm's law I=V/R, it can be seen that the main factors affecting the accuracy of current sampling are resistance R and voltage sampling value V, so the following two factors are mainly analyzed. Factors affecting the sampling voltage V: the sampling value of the voltage is obtained through ADC, so the sampling accuracy can be further improved by selecting a high-precision ADC and adding a filter circuit with purpose. This is not the focus of this paper, so it will not be expanded.

Equivalent inductance: One of the electrical parameters of the shunt is inductance, which refers to the equivalent parasitic inductance at the alloy (the following figure is from the official website of ISA). The inductance of a type of shunt in the following figure is less than 3nH, and basically the parasitic inductance of the shunt is in the order of several nH.

In theory, for constant current, the parasitic inductance has no effect; However, when the current changes, according to Faraday's law of electromagnetic induction, induced electromotive force will be generated at both ends of the inductor, which will be superimposed into the voltage V actually collected, thus leading to measurement errors. The greater the inductance, the greater the induced electromotive force, so the size of the inductance should be limited. In addition, in order to eliminate the error caused by inductance, RC selection of sampling filter circuit is also very important, so it is not expanded.