Capacitor vs. Battery
Capacitor:
* store energy in an electric field.
* charge stored in a capacitor is proportional to the potential difference between the two plates
* is charged by applying a voltage across the terminals which causes positive and negative charges
* inner resistance is near infinite.
* far lower energy density (compared to battery)
* near instant charge and discharge
* very good at storing charge for short time periods
* manufacturable in nearly any voltage
* charge/discharge cycles near infinite
Battery:
* store electrical energy into chemical energy .
* chemical reaction results in a potential difference between the two terminals
* energy is stored with chemical reactions
* inner resistance is small.
* high energy density (compared to capacitor)
* limited charge/discharge current depending on chemistry and design
* slower-but-steady flow of charge
* voltage determined by chemistry
* limited number of charge/discharge cycles (mostly chemistry dependent)