A radiation-resistant nuclear battery combining betavoltaic and photovoltaic techniques was demonstrated using Ce-doped Gd₃Ga₃Al₂O₁₂ single-crystal scintillator. The present device comprising 1mm thick Ce-doped GGAG single-crystal scintillator and Si-based p–i–n diode produced an electric power output of 48 nW with a short-circuit current of 490 nA and an open-circuit voltage of 0.18V using a 3 mCi ¹⁰⁶Ru source. Long-term radiation stability test carried out for more than 4000 h revealed that there was no significant reduction in the output of beta-photovoltaic device (with scintillator), whereas there was 68% reduction in the output power for the betavoltaic device (without scintillator). The electron beam irradiation of 1mm thick Ce-doped GGAG scintillator up to a dose level of 5 MGy using 10 MeV electron beam indicated a power degradation by 4% suggesting a reasonably long battery life (~15 years) with ⁹⁰Sr-⁹⁰Y source.