Designing Charging Circuit (XH-HG Capacitor)
XH-HG capacitors, which differ from lithium rechargeable batteries, do not require a resistor for limiting the charging current as long as the maximum charging voltage (3.3 V) is observed. No current-limiting resistors are necessary during constant-voltage charging, but if peripheral circuits or elements may be affected by a rapid fluctuation in capacitor charge current, using a current-limiting resistor is recommended.
Charging circuit example of capacitor
Caution (prohibition of overvoltage)
Using a capacitor with a voltage exceeding the maximum allowable voltage may cause a fatal failure such as leakage or bursting as well as decreased life. Consider voltage fluctuation, ripple voltage, and overshoot to set the maximum charge voltage.
Caution (prohibition of reverse voltage)
Capacitors have polarity. Applying a reverse voltage to a capacitor may lead to leakage or bursting.
Take appropriate measures for the circuit to prevent such an occurence when reverse voltage is applied.
Caution (prohibition of ripple charging)
Ripple (high frequency fluctuation of voltage) in the charging voltage may cause self-heating, extremely lowering capacitor performance. Be sure to charge with stable voltage.
Caution (charge time)
A short charge time (a few hours) may result in insufficient charging. Almost one day is needed for complete charging.
When the charge current is small due to the use of a current-limiting resistor, the charge time takes longer.