| 摘要 |
PURPOSE:To enhance greatly the cycle life characteristic of a plate by maintaining the rapid electric-discharge and regulate the early reduction in capacity of the plate by converting chemically only the lower part of the plate in an aqueous weakly acidic, neutral-salt or alkaline solution, and adding dilute sulfuric acid after that. CONSTITUTION:In a chemical conversion process carried out by feeding current to a plate after pouring dilute sulfuric acid used as an electrolyte after the plate is inserted in the container, before adding dilute sulfuric acid, below 10% of the theoretical capacity of electricity is fed by adding an aqueous solution with an acidified degree of over pH 3 until a part of the plate is immersed, and thereafter the usual chemical conversion with added dilute sulfuric acid is carried out. Although there is an active part in the upper part of the plate, differently from such a conversion that is carried out by feeding current after the whole of a plate is immersed in an aqueous neutral-salt or alkaline solution, the rapid electric-discharge characteristic naturally decreases as the part of the plate immersed in the solution is increased, and the slow electric-discharge life tends to deteriorate as the part immersed in the solution is decreased. Therefore, it is preferred that 1/5-3/4 of the plate is immersed in the solution. In addition, in order to prevent any marked reduction of the slow electric-discharge capacity although depending upon the depth of immersion, it is preferred that the quantity of electricity fed to the plate in the preliminary chemical conversion is suppressed to around 0.01-10% of the theoretical capacity of the plate. |
