Abstract: An energy storage device may include a housing and a fluid access aperture extending through a sidewall of housing that is used to fill the device with electrolytic fluid. In some examples, the fluid access aperture may define a length extending through the housing that is greater than a major width that extends across a cross-sectional area of the fluid access aperture. In some additional examples, the fluid access aperture may be angled relative to an axis that is substantially orthogonal to the housing. Depending on the situation, such example fluid access apertures may prevent electrolytic fluid from escaping from the energy storage device while the fluid access aperture is being sealed.