All you need to charge a battery from a capacitor is to have more voltage charged on the capacitor than the voltage of the battery. The size will only affect how much time the capacitor will charge the battery.
Q. Identical dielectric slabs are inserted into two identical capacitor A and B. These capacitor and a battery are connected as shown in the figure. Now, the the slab of capacitor B is pulled out with battery renaming connected. Q. A capacitor cannot be used as a battery because Q.
The capacitor charging circuit is simple: a series resistor R1 to limit charge current through D1 into the capacitor bank C2. If the power-up events are rare, the energy loss on R1 is not substantial and doesn't have undue impact on the energy efficiency of the device.
Supercapacitors need to evolve a lot before they actually replace batteries. Therefore, normal capacitors will not act as batteries. Q. Identical dielectric slabs are inserted into two identical capacitor A and B. These capacitor and a battery are connected as shown in the figure.
A super capacitor normally has a capacitance of between 1 to 3000 farads, which make them good substitutes for batteries! We are going to safely charge 2x 400 farad capacitors in series up to 5.4VDC, and feed that voltage through a DC-DC booster circuit.
To summarize, the charging is only good if the voltage is close to 1.5 volts but capacitors have vastly variable voltage that depends on the stored energy and/or charge dramatically. Normal capacitors store much less energy than batteries because they don't change any chemistry i.e. no "burning".