Removable power supply unit for a vehicle, having a unit body with a length between a first end and a second end along a direction of elongation (I-I), shaped to be introduced into a corresponding receiving compartment of the vehicle, and comprising: - an electrical storage battery, - an output connector, frontally arranged at the first end of the unit body of the power supply unit, having electrical conductors connected to said electrical storage battery, and shaped to releasably engage axially with a vehicle connector and thereby establish an electrical connection with said electrical storage battery for powering vehicle equipment, - a first blanking shutter, movable transversely in the unit body of the power supply unit between a blanking position in which it covers the output connector and a retracted position in which it frees access to the output connector, - a first biasing means biasing said first blanking shutter towards its blanking position, characterized in that it comprises: - a second blanking shutter, said blanking shutters (8, 9) being transversely displaceable in the unit body of the power supply unit between a blanking position in which they each cover a part of the output connector and a retracted position in which they clear access to the output connector, - a second biasing means, said biasing means biasing the blanking shutters (8, 9) towards said blanking position, - a respective shutter cam (21, 22), provided on each of said blanking shutters (8, 9), and shaped to be baised by one or more fixed thrust members provided in the receiving compartment of the vehicle so as to move said blanking shutters (8, 9) transversely away from each other against said biasing means to said retracted position upon engagement of the power supply unit towards the vehicle connector in the vehicle receiving compartment. - an electrical storage battery, - an output connector, frontally arranged at the first end of the unit body of the power supply unit, having electrical conductors connected to said electrical storage battery, and shaped to releasably engage axially with a vehicle connector and thereby establish an electrical connection with said electrical storage battery for powering vehicle equipment, - a first blanking shutter, movable transversely in the unit body of the power supply unit between a blanking position - a first biasing means biasing said first blanking shutter towards its blanking position, characterized in that it comprises: - a second blanking shutter, said blanking shutters (8, 9) being transversely displaceable in the unit body of the power supply unit between a blanking position in which they each cover a part of the output connector and a retracted position in which they clear access to the output connector, - a second biasing means, said biasing means biasing the blanking shutters (8, 9) towards said blanking position, - a respective shutter cam (21, 22), provided on each of said blanking shutters (8, 9), and shaped to be baised by one or more fixed thrust members provided in the receiving compartment of the vehicle so as to move said blanking shutters (8, 9) transversely away from each other against said biasing means to said retracted position upon engagement of the power supply unit towards the vehicle connector in the vehicle receiving compartment.