US Patent 10128476 Sealed battery

A sealed battery with a battery element housed in a sealed casing. The sealed battery includes a valve brought into a closed state when a pressure of a gas in the casing is less than a first pressure P1, into an open state when the pressure is more than or equal to the first pressure P1 and less than a second pressure P2, and into the closed state when the pressure is more than or equal to the second pressure P2, and a safety mechanism configured to, when the internal pressure reaches a third pressure P3 exceeding the second pressure P2, operate in accordance with the third pressure P3.