Electrically powered bicycle equipment, comprising: - an electric power supply unit comprising one or more secondary cells, - a component having an attachment/detachment seat for removable attachment of the electric power supply unit, the attachment/detachment seat and the electric power supply unit having matching electric contacts (80, 81) that establish electrical connection in the seated state of the electric power supply unit, and characterized in that the electricity powered bicycle equipment is comprising: - at least one latch assembly for retaining the electric power supply unit in the seated state, comprising a slider having a head and a back opposed to the head, one of the electric power supply unit and the component having a sliding seat of the slider, the other one of the electric power supply unit and the component having a retaining seat of the head against a displacement at least in a first way of a retaining direction, in the seated state of the electric power supply unit and in the latched condition of the latch assembly, wherein the slider is slidable in the sliding seat between a fully advanced position wherein the head protrudes from the sliding seat in order to be able to insert in the retaining seat, and a fully retracted position wherein the head does not protrude from the sliding seat, wherein the sliding seat comprises a blind hole, the blind hole and the back of the slider having complementary shapes in a section transverse to the sliding direction, and the blind hole being sized to accommodate the back of the slider in a sliding manner, wherein the back of the slider has a closed-loop peripheral groove, and wherein a ring gasket is housed taut in the peripheral groove, wherein in at least one region (52, 56) of the back of the slider, the peripheral groove has two aligned sections (53, 54) and an intermediate section therebetween, the intermediate section being comparatively deeper than the two aligned sections (53, 54, whereby in the fully advanced position of the slider, a portion of the gasket bridges the intermediate section between the two aligned sections (53, 54), and while the slider moves back, the portion of the gasket is free to curve towards the bottom of the intermediate section of the peripheral groove. - an electric power supply unit comprising one or more secondary cells, - a component having an attachment/detachment seat for removable attachment of the electric power supply unit, the attachment/detachment seat and the electric power supply unit having matching electric contacts (80, 81) that establish electrical connection in the seated state of the electric power supply unit, and characterized in that the electricity powered bicycle equipment is comprising: - at least one latch assembly for retaining the electric power supply unit in the seated state, comprising a slider having a head and a back opposed to the head, - at least one latch assembly for retaining the electric power supply unit in the seated state, comprising a slider having a head and a back opposed to the head, one of the electric power supply unit and the component having a sliding seat of the slider, the other one of the electric power supply unit and the component having a retaining seat of the head against a displacement at least in a first way of a retaining direction, in the seated state of the electric power supply unit and in the latched condition of the latch assembly, wherein the slider is slidable in the sliding seat between a fully advanced position wherein the head protrudes from the sliding seat in order to be able to insert in the retaining seat, and a fully retracted position wherein the head does not protrude from the sliding seat, wherein the sliding seat comprises a blind hole, the blind hole and the back of the slider having complementary shapes in a section transverse to the sliding direction, and the blind hole being sized to accommodate the back of the slider in a sliding manner, wherein the back of the slider has a closed-loop peripheral groove, and wherein a ring gasket is housed taut in the peripheral groove, wherein in at least one region (52, 56) of the back of the slider, the peripheral groove has two aligned sections (53, 54) and an intermediate section therebetween, the intermediate section being comparatively deeper than the two aligned sections (53, 54, whereby in the fully advanced position of the slider, a portion of the gasket bridges the intermediate section between the two aligned sections (53, 54), and while the slider moves back, the portion of the gasket is free to curve towards the bottom of the intermediate section of the peripheral groove.