Electrical storage cell life extender

The useful life of an electrolytic battery cell commonly employed in a series string as a backup power source is significantly extended by maintaining the polarization of the positive plates of such a cell at a predetermined level relative to a reference electrode of similar composition in contact with the cell electrolyte. While the cell is being supplied with the usual float charging voltage, a controller circuit senses any variance of polarization below the desired level and meters a minute input current to the positive plates with a resulting increase in the polarization over a substantial time period. The slow biasing of the polarization effects a passivation of the surface of the plates which deters the penetration of oxygen to the plate metal and prevents the deep destructive formation of expansive metal oxide.