Super Capacitor Super capacitors have very large capacitance (typically from 0.1 to 50 F), small sizes, and very long charge holding times, making them useful in non-battery backup power applications.

The charge holding quality of a super capacitor is measured using the circuit in Figure P7–81. The switch is closed for a long time (say, 24 hours) and the capacitor charged to 5 V. The switch is then opened and the capacitor allowed to self-discharge through any leakage resistance for 24 hours. Suppose that after 24 hours the voltage across a 0.47 F super capacitor is 4.5 V. What is the equivalent leakage resistance in parallel with the capacitor?

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5V + 100 Super capacitor FIGURE P7-81 RL