An electrical battery for multi-cellular interconnection in series, parallel or series and parallel has a protrusion and a recess, such as a tongue and a groove, extending on outer surfaces of the sidewalls of the battery case such that when a protrusion of one battery is slid into a recess of another, the two batteries are electrically connected by the portions of the protrusion and the recess that are made of electrically conductive materials connected to the voltage producing elements inside the case. The battery further includes hollow plug-in posts and plug-in pins at the top and the bottom of the case that are connected to the voltage producing elements of the battery so that when the plug-in pins of one battery are inserted into the plug-in posts of another, the two batteries are in electrical interconnection. The battery also includes an electrolyte recirculation, gas purging, and automatic watering systems.