Secondary cell replacing method

Abstract

In a pre-replacement process, a replacement battery module is provided with a memory effect before being dispatched, by performing at least one of the process of performing a cyclic charge/discharge operation on the replacement battery module while limiting the width of SOC change to an intermediate range, and the process of setting an initial SOC and then letting the replacement battery module stand for a predetermined time in an environment of temperature above normal temperature. This pre-replacement process substantially eliminates the difference between the voltage characteristic of the replacement battery module yet to be used and the voltage characteristic of a battery module having a history of use, thereby achieving a uniform voltage characteristic of a battery pack as a whole.

What is claimed is:  
     
         1 . A secondary cell replacing method for replacement with a replacement cell, comprising: 
 preparing a replacement cell provided beforehand with a memory effect; and    replacing a secondary cell of a battery pack formed by electrically connecting a plurality of secondary cells in series or parallel, with the replacement cell.    
     
     
         2 . The method according to  claim 1 , wherein a secondary cell of the battery pack is reclaimed as a to-be-replaced cell, and only if a cell characteristic of the to-be-replaced cell fails to meet a predetermined reference after a predetermined process performed on the to-be-replaced cell, the to-be-replaced cell is replaced by the replacement cell provided beforehand with a memory effect.  
     
     
         3 . The method according to  claim 1 , wherein a secondary cell of the battery pack is reclaimed as a to-be-replaced cell, and if a cell characteristic of the to-be-replaced cell meets a predetermined reference after a predetermined process performed on the to be-replaced cell, the secondary cell is incorporated into a battery pack, and the battery pack is then provided for use.  
     
     
         4 . The method according to  claim 1 , further comprising performing a cyclic charge/discharge operation so as to impart a memory effect to a secondary cell.  
     
     
         5 . The method according to  claim 4 , wherein the cyclic charge/discharge operation is performed while a width of change in an amount of charge present in the secondary cell is limited to an intermediate range of a capacity of the secondary cell.  
     
     
         6 . The method according to  claim 5 , wherein the intermediate range is a range of 20% to 80%.  
     
     
         7 . The method according to  claim 1 , further comprising setting an initial amount of charge present in a secondary cell to at least 40% and then letting the secondary cell stand for at least two weeks while keeping a temperature of the cell above a normal temperature so as to provide the secondary cell with a memory effect.  
     
     
         8 . The method according to  claim 1 , further comprising: 
 reclaiming a secondary cell of the battery pack;    performing a predetermined process on the secondary cell;    determining whether a cell characteristic of the secondary cell meets a predetermined reference based on a result of the predetermined process; and    replacing the secondary cell with the replacement cell provided beforehand with a memory effect if the cell characteristic of the secondary cell fails to meet the predetermined reference.    
     
     
         9 . The method according to  claim 1 , further comprising: 
 reclaiming a secondary cell of the battery pack;    performing a predetermined process on the secondary cell;    determining whether a cell characteristic of the secondary cell meets a predetermined reference based on a result of the predetermined process; and    placing the secondary cell back in the battery pack if the cell characteristic of the secondary cell meets the predetermined reference, and then providing the battery pack for use.    
     
     
         10 . The method according to  claim 1 , wherein the second cell provided beforehand with the memory effect substantially identical to a memory effect possessed by a to be-replaced secondary cell is prepared as the replacement cell.  
     
     
         11 . The method according to  claim 1 , wherein agreement of a voltage characteristic of the replacement cell with a voltage characteristic of a cell having a history of use is made possible by imparting the memory effect to the replacement cell.  
     
     
         12 . The method according to  claim 1 , further comprising overcharging the battery pack to at least 100% of a capacity of the battery pack after replacing one of the secondary cells of the battery pack with the replacement cell.