To obtain a battery unit which can secure good detection sensitivity of a PTC element in the battery unit having a coin type battery prepared as an elementary battery, the battery unit being excellent in reliability as a result. コイン型電池を素電池とする電池ユニットにおいて、PTC素子の良好な検出感度を確保し、結果として信頼性に優れた電池ユニットを得る。 - 特許庁