Battery Gas Gauge

Abstract

Full capacity determination in a battery gas gauge. Operations include measuring instantaneous open circuit voltage levels during an open circuit time interval for a specific battery cell and correlating such measurements to estimate values. Such estimated values may then be correlated to associated relative state of charge levels. Finally, a full capacity calculation can be made based on the associated relative state of charge levels. A plurality of full capacity determinations may also be made and compared to each other to assess the reliability of such determinations.

1 . A method comprising: 
 measuring a first and a second instantaneous open circuit voltage level of a battery cell of a battery cell circuit during a first and a second time interval, respectively;    correlating said first and said second instantaneous open circuit voltage levels to a first and a second relative state of charge level of said battery cell, respectively; and    calculating a first full capacity level of said battery cell in response to a difference between said first and second relative state of charge levels.    
     
     
         2 . The method of  claim 1  further comprising: 
 correlating said first and said second instantaneous open circuit voltage levels to a first and a second estimated value, respectively.    
     
     
         3 . The method of  claim 1  further comprising: 
 opening of said battery cell during said first and second time intervals and interrupting charging of said battery cell during a charging mode    
     
     
         4 . The method of  claim 3  further comprising: 
 updating said first and second estimated values in response to a charging current level before said interrupting of said charging of said battery cell.    
     
     
         5 . The method of  claim 1 , wherein said first time interval is associated with a first capacity level of said battery cell and said second time interval is associated with a second capacity level of said battery cell, and wherein said calculating operation further comprises dividing a difference between said first and second capacity levels by said difference between said first and second relative state of charge levels to obtain said first full capacity level.  
     
     
         6 . The method of  claim 3 , further comprising: 
 storing said first and second estimated values and said first and second relative state of charge levels; and    updating said first and second estimated values and said first and second relative state of charge levels in response to additional openings of said battery cell circuit at additional time intervals associated with said first and second capacity levels.    
     
     
         7 . The method of  claim 1 , further comprising: 
 measuring a third instantaneous open circuit voltage level of said battery cell during a third time interval;    correlating said third instantaneous open circuit voltage level to a third relative state of charge level of said battery cell; and    calculating a second full capacity level of said battery cell in response to a difference between said second and third relative state of charge levels.    
     
     
         8 . The method of  claim 7 , further comprising: 
 calculating a third full capacity level of said battery cell in response to a difference between said first and third relative state of charge levels, and comparing said first, second, and third full capacity levels to assess a reliability of each of said first, second, and third full capacity levels.    
     
     
         9 . The method of  claim 1 , wherein said first estimated value is representative of a first theoretical open circuit voltage level and wherein said second estimated value is representative of a second theoretical open circuit voltage level.  
     
     
         10 . An electronic device comprising: 
 a storage medium having stored therein instructions that when executed by a machine result in the following: 
 measuring a first and a second instantaneous open circuit voltage level of a battery cell of a battery cell circuit during a first and a second time interval, respectively;  
 correlating said first and said second instantaneous open circuit voltage levels to a first and a second relative state of charge level of said battery cell, respectively; and  
 calculating a first full capacity level of said battery cell in response to a difference between said first and second relative state of charge levels.  
   
     
     
         11 . The electronic device of  claim 10  wherein said measuring said first and said second instantaneous open circuit voltage levels comprises opening of said battery cell during said first and second time intervals and interrupting charging of said battery cell during a charging mode  
     
     
         12 . The electronic device of  claim 10  wherein said measuring said first and said second instantaneous open circuit voltage levels comprises correlating said first and said second instantaneous open circuit voltage levels to a first and a second estimated value, respectively.  
     
     
         13 . The electronic device of  claim 12 , wherein said instructions that when executed by said machine also result in updating said first and second estimated values in response to a charging current level before said interrupting of said charging of said battery cell.  
     
     
         14 . The electronic device of  claim 10 , wherein said first time interval is associated with a first capacity level of said battery cell and said second time interval is associated with a second capacity level of said battery cell, and wherein said calculating operation comprises dividing a difference between said first and second capacity levels by said difference between said first and second relative state of charge levels to obtain said first full capacity level.  
     
     
         15 . The electronic device of  claim 12 , wherein said instructions that when executed by said machine also result in storing said first and second estimated values and said first and second relative state of charge levels, and updating said first and second estimated values and said first and second relative state of charge.  
     
     
         16 . The electronic device of  claim 10 , wherein said instructions that when executed by said machine also result in: 
 measuring a third instantaneous open circuit voltage level of said battery cell during said third time interval;    correlating said third open circuit voltage level to a third relative state of charge level of said battery cell; and    calculating a second full capacity level of said battery cell in response to a difference between said second and third relative state of charge levels.    
     
     
         17 . The electronic device of  claim 16 , wherein said instructions that when executed by said machine also result in calculating a third full capacity level of said battery cell in response to a difference between said first and third relative state of charge levels, and comparing said first, second, and third full capacity levels to assess a reliability of each of said first, second, and third full capacity levels.  
     
     
         18 . The electronic device of claim of  claim 10 , wherein said first estimated value is representative of a first theoretical open circuit voltage level and wherein said second estimated value is representative of a second theoretical open circuit voltage level.  
     
     
         19 . A battery gas gauge circuit comprising: 
 a switch network for coupling to a plurality of battery cells;    an analog to digital converter (ADC) coupled to said switch network, said ADC configured to receive an analog signal from each of a plurality of battery cells via said switch network and convert each said analog signal to an associated digital signal; and    a processor configured to: 
 control said switch network to couple terminals of said one of said plurality of battery cells to said ADC;  
 receive, from said ADC, a first digital signal representative of a first instantaneous open circuit voltage level of said battery cell during said first time interval and a second digital signal representative of a second instantaneous open circuit voltage level of said battery cell during said second time interval;  
 correlate said first digital signal to a first relative state of charge level of said battery cell and said second digital signal to a second relative state of charge level of said battery cell; and  
 calculate a first full capacity level of said battery cell in response to a difference between said first and second relative state of charge levels.  
   
     
     
         20 . The circuit of  claim 15 , wherein said wherein said processor is further configured to: 
 measure a third instantaneous open circuit voltage level of said battery cell during said third time interval;    correlate said third instantaneous open circuit voltage level to a third relative state of charge level of said battery cell; and    calculate a second full capacity level of said battery cell in response to a difference between said second and third relative state of charge levels.