NOVELTY - The element has an electric power generation element (10) accommodated in a container (2). Electrolyte solution (3) includes electrolyte accommodated in the container. The generation element contains a separator positioned between positive and negative electrodes and in contact with the solution. Ratio of length of a long side (L1) of the container with respect to height (L2) in the container is set when ratio of cleaner rate of organic liquid along long side direction of the container with respect to cleaner rate of organic liquid along height direction of the container is set.    USE - Electrical storage element e.g. non-aqueous electrolyte secondary battery such as horizontal type lithium secondary battery and winding-type lithium secondary battery, for a vehicle-mounted storage battery system (claimed) used for an electric vehicle and a hybrid vehicle. Can also be used as a laminated type lithium secondary battery, an electrical double layer capacitor and a nickel-hydrogen battery and for a two-wheeled motor vehicle, a portable terminal and a notebook computer.    ADVANTAGE - The element allows ratio of length of the long side of the container with respect to the height in the container to be set when ratio of cleaner rate of the organic liquid along long side direction of the container with respect to cleaner rate of the organic liquid along height direction of the container is set so as to supply the electrolyte solution to the separator in an easy manner, thus reducing generation of partial liquid exhaustion and uneven distribution of the electrolyte solution and accelerating charging/discharging reaction by suppressing that the electrolyte solution depletes, and hence suppressing increase of electrical resistance and fall of output of the battery.    DETAILED DESCRIPTION - The element is a non-aqueous electrolyte secondary battery (1). An INDEPENDENT CLAIM is also included for a vehicle-mounted storage battery system.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of a non-aqueous electrolyte secondary battery.'(Drawing includes non-English language text)'    Long side of container (L1)    Height of container (L2)    Non-aqueous electrolyte secondary battery (1)    Container (2)    Electrolyte solution (3)    Electric power generation element (10)