Industry News

# Three key parameters of shunt

2020-04-25

A shunt in a power cell PACK is essentially a resistor that detects the value of the current flowing through.Because the current value is not easy to monitor, most of the current is converted into voltage, that is, when the current through the resistor voltage drop, voltage value detection, can be calculated through the current value, according to U=IR.

This method requires the shunt to have enough precision, and the resistance value should be as small as possible with the temperature change, and the temperature rise should not be too high, so the following three key parameters are derived:

1.Accuracy

As we all know, the resistance value will change with the change of service environment and temperature, but if the range of change can be controlled well, that is, the accuracy is high enough, can meet the current monitoring requirements.At present, the accuracy (the deviation of resistance value from standard resistance value) of shunt includes ±0.1%, ±0.2%, ±0.5%, etc., which is related to the application environment of current detection of shunt.

2. temperature

In the application environment of the battery system, the temperature requirement is generally -40℃~+85℃. In order to ensure that the heat generated by the shunt does not affect the use of surrounding components, the temperature rise control value, such as 100℃, should be guaranteed.

3. warm drift

The smaller the temperature drift, the better its stability.To characterize the performance of shunting ratio [(r1-r0) /R0] changing with the change of temperature T, the unit can be expressed as X%/℃, such as shunting ratio of 0.2%/℃, means the temperature change of 1℃, resistance value deviation is 0.2% of the nominal value.

The current method of testing the temperature coefficient is to keep the resistance value in an incubator at a high temperature (above 100℃) for more than 30 minutes, according to the formula [(r1-r0) /R0]/(t1-t0), where R0 is the nominal resistance and T0 is the room temperature.