The NERattler v. 3 can charge an external capacitor, or battery, while running on very low input voltage and powering an external circuit. This is similar to the functioning of some of John Bedini's motors, using essentially the same circuit, but at self-resonance and with no moving parts.
Here I show the Rattler running the Ring Oscillator on 3 v input, while at the same time charging an external 260 uF capacitor to 150 volts. On raising the input power to 5 volts, the capacitor quickly reaches its voltage limit of 250 VDC, so I stopped the charging, but it would have reached nearly 400 volts. With 12 volts input I can get a cap up to voltages that are truly dangerous and scary.
This circuit also oscillates with very low voltage, depleted single AAA batteries, enough to get the external cap up to 30 volts or so. Then all the energy that was in the battery can be discharged in a millisecond by shorting the capacitor !!