A combustion apparatus has a built-in storage battery and has circuitry which restores a sufficient amount of stored electrical energy in the storage battery when the amount of electrical energy stored in the storage battery is lowered below a required level. A thermoelectric generator element is heated by combustion heat produced by a burner to generate a thermal electromotive force. A manual operation of a slide button causes an associated multi-contact switch to repetitively turn ON and OFF, such that a coil in a booster circuit boosts a voltage generated by the thermoelectric generator element. The boosted voltage is applied to an oscillator circuit in the booster circuit, so that the booster circuit is driven to boost the voltage from the thermoelectric generator element as well as to start powering the oscillator circuit and a storage battery. Consequently, a sufficient amount of stored electrical energy is restored in the storage battery.