Capacitor Discharging Rate

Hi , Can we replace battery with capacitor?? I know that energy stored in a battery is far greater than in the capacitors ,but still can we some how convert a charged capacitor into a temporary battery?? So the Question is how to control the discharge rate of capacitor? Is this have something to do with RC Time constant?

Changing the resictance would be an obvious way to go.

Changing the resictance would be an obvious way to go.
Is there some IC or something like that for slowing the discharging rate exponentially?

See "ultracapacitors" for some applications where the batteries are replaced by capacitors.

From what I seen, the voltage decreases a lot more sharply during discharge than in a battery.

• davenn
CWatters
Homework Helper
Gold Member
Batteries approximate to a constant voltage source, a capacitor doesn't. For a capacitor..

Q=CV
I = CdV/dt
so
dV/dt = I/C

So the voltage "curve" depends on the load current. If you discharge at a constant current the voltage falls in a straight line. If it's a constant resistance load you get the classic exponential curve.

If the load must get a constant voltage (not all need that) then some sort of voltage regulator, perhaps a switching type, can be used to provide it.

You don't always need a voltage regulator. The motor in an electric car for example doesn't necessarily need a constant voltage but it does need some form of speed control. It may well be possible to build one control unit that accepts the variable voltage from a capacitor and outputs whatever the motor requires.

• Hamza Abbasi and davenn