# Current going into the positive pole of a battery while discharging a capacitor

Please bear with me if this is a fundamental question.

Let's suppose we have an RC circuit, charging a capacitor up to the voltage of a battery of 9V. The capacitor is currently at 9V, we switch the 9V battery with a 3.3V one.

Because of the difference in potential of 5.7V between the capacitor and the battery, does current now flow into the battery?

What are the dangers when this happens? Am I trying to charge it at this point?

• Discharge current I max = ΔV/ΣESR(cap+bat)[mΩ] while Duration Tau=Ccap * ΣESR(cap+bat) Battery is 10kF ~>=50mΩ, Cap is what? 100uF 10mF 1F? ESR? probably harmless unless a dendrite moves and causes internal battery short and starts to heat up, as you toss it in the dirt outside before it reach thermal runaway – Tony Stewart Sunnyskyguy EE75 Jan 20 at 18:33

The possible danger is that the battery is not designed to be recharged, or that the value of $$\R\$$ is not high enough to limit the current to a safe level. In either case there is the possibility of damaging the battery, perhaps causing a fire.