We propose a physical process to use a Schwarzschild black hole as a rechargeable battery and nuclear reactor. As a rechargeable battery, it can at most transform 25% of input mass into available electric energy in a controllable and slow way. We study its internal resistance, efficiency of discharging, maximum output power, cycle life and totally available energy. As a nuclear reactor, it realizes an effective nuclear reaction "α + black hole→ e+ + black hole" and the kinetic energy of positrons can reach GeV. This process amplifies the kinetic energy of α-decay hundreds of times. Since some tiny sized primordial black holes are suspected to have an appreciable density in dark matter, the result of this paper implies that such black-hole-originated dark matter can be used as reactors to supply energy.