The invention concerns a device and method for checking the state of an accumulator with energy reserve that is connected to a fluid system. According to the invention, the fluid system is first of all pressurized and this fluid is maintained at an operating pressure P.sub.F for at least a time .tau. so as to ensure the stabilization of this fluid system. Then the pressurisation of the fluid system is stopped and the time .DELTA.t taken by the system to pass from a predetermined pressure P.sub.1 to a predetermined pressure P.sub.2, with P.sub.2