ESR, short for equivalent series resistance, is one of the most important parameters of super capacitor, which is the resistance component in an equivalent series circuit of inductance, capacitance and resistance of ultracapacitor. DC ESR evaluation is complicated and requires special equipment, most customer only evaluate AC ESR to select product. Main test procedures for AC ESR evaluation are as following:
1.Arbin instrument integrated test procedure
The curve shows the Arbin instrument integrated test procedure. The tester generates continuous 10 pulses applied on the capacitor. At current amplitude setting, IIR, the pulse current changes between I0 – IIR and I0 + IIR. I0 is the offset of the current, i.e. the average current during IR measurement, usually I0 is zero. Pulse Width. T1 is adjustable from 1 millisecond to 100 milliseconds per different requirement. The data points are picked up at P2 at the end of T1 and P3 right before the current rising, as shown in the curve. An average over ten pulses is adopted. and then calculate the internal resistance by the following formula.
ESR = Average {(voltage at P2-voltage at P3) / (2IIR)}
2.AC 1kHz impedance Test
Using a 4-wire connection, connect the impedance tester cables to the terminals of the device. Set signal amplitude such that RMS current is between 1 – 10 mA, set signal frequency 1kHz. AC impendence is calculated as the ratio between effective AC RMS voltage and AC RMS current across the terminals of the device.
AC ESR = Vrms / Irms
SPS adopts Arbin instrument integrated test procedure and 6 steps procedure ( described in previous chapter) to evaluate all product ESR before delivery.
About SPS
Supreme Power Solutions Co., Ltd. (SPS) is a leading manufacturer of ultracapacitors, as well as a provider of ultracapacitor energy storage systems and technological solutions. Our products have wide industry applications, such as new energy vehicles, wind turbines pitching control systems, trams and subways, smart grid, micro grid, heavy duty machineries, intelligent instrument, etc. We support more than 180 Chinese customers, and our products are exported to 23 countries and territories.
