Abstract: An improved battery structure permitting facilitated replacement of an air supply tube through an air lift pump. The air lift pump includes, as guide means, a funnel portion receiving the inserted distal end of the replacement air supply tube for automatically guiding the distal end downwardly therethrough and into the passage of a depending barrel in which percolation of the electrolyte of the battery is effected by the bubbling of air downwardly through the air supply tube into the barrel. The upper end of the barrel is provided with an outlet tube extending downwardly into the electrolyte, thereby avoiding splashing of the electrolyte, such as against the flash arrester vent of the battery, thereby reducing maintenance and permitting long, troublefree life of the battery. The air supply tube and outlet tube may be formed of a transparent synthetic resin, permitting observation of the air flow during operation.