Methods and apparatus for a battery

Abstract

Various embodiments of the present technology may comprise a method and apparatus to estimate the state of health of a battery. The method and apparatus may comprise utilizing various parameters, such as RSOC, resistance, and voltage, to estimate the state of health of the battery. In various embodiments, the state of health of the battery may indicate the remaining life of the battery.

1 . A management circuit connected to a battery comprising:
 a voltage sensor responsive to an output voltage of the battery;   a current sensor responsive to a current of the battery;   a secondary current circuit coupled to the current sensor and configured to generate a first current and a second current,   wherein each of the first and second currents produce a change in the current of the battery and a change in the output voltage of the battery; and   a logic unit responsive to the voltage sensor and the current sensor, wherein the logic unit is configured to:
 compute the change in the output voltage according to the first current and second currents; and 
 compute an aged internal resistance of the battery according to the change in output voltage and at least one of first and second currents. 
   
     
     
         2 . The management circuit according to  claim 1 , further comprising:
 a memory device responsive to the logic unit and adapted to store:
 a first battery characteristics indicating a relationship between the output voltage and a relative state of charge of the battery; and 
 a second battery characteristics indicating a relationship between an internal resistance and the relative state of charge of the battery. 
   
     
     
         3 . The management circuit according to  claim 2 , wherein the logic unit is configured to determine a baseline internal resistance of the battery according to the relative state of charge of the battery and the second battery characteristics. 
     
     
         4 . The management circuit according to  claim 2 , wherein the baseline internal resistance is an internal resistance of the battery when the battery is new. 
     
     
         5 . The management circuit according to  claim 2 , wherein the second battery characteristic data further comprises predetermined data describing an internal resistance of the battery as the battery ages. 
     
     
         6 . The management circuit according to  claim 1 , wherein the secondary current circuit comprises a first transistor connected in parallel with a second transistor, wherein each of the first and second transistors comprise a gate terminal. 
     
     
         7 . The management circuit according to  claim 6 , wherein the secondary current circuit further comprises a voltage source circuit to adapted to selectively apply a voltage to the gate terminals of the first and second transistors. 
     
     
         8 . The management circuit according to  claim 1 , further comprising a temperature sensor coupled to the logic unit and responsive to a temperature of the battery, wherein the logic unit is configured to adjust the aged internal resistance of the battery according to the temperature of the battery. 
     
     
         9 . A method for determining an aging characteristic of a battery comprising:
 measuring a relative state of charge of the battery;   extracting a baseline internal resistance value from a set of battery data based on the measured relative state of charge;   measuring an output voltage of the battery;   measuring a current of the battery, wherein the current is purposefully influenced by a secondary current;   calculating an aged internal resistance of the battery based on the measured current and the measured output voltage.   
     
     
         10 . The method of  claim 9 , further comprising: estimating the state of health of the battery based on the calculated aged internal resistance and the baseline internal resistance of the battery. 
     
     
         11 . The method of  claim 9 , further comprising generating the secondary current, wherein generating the secondary current comprises applying a voltage to a transistor connected to a positive terminal of the battery. 
     
     
         12 . The method of  claim 9 , further comprising:
 measuring a temperature of the battery; and   adjusting the aged internal resistance based on the temperature.   
     
     
         13 . A system for a battery, comprising:
 a voltage sensor responsive to an output voltage of the battery;   a memory device storing:
 predetermined first battery characteristic data indicating a relationship between the output voltage and a relative state of charge of the battery; 
 predetermined second battery characteristic data indicating a relationship between a baseline internal resistance and the relative state of charge of the battery; 
   a current sensor responsive to a current of the battery;   a logic unit responsive to the voltage sensor and the current sensor and having access to the memory device, wherein the logic unit is adapted to:
 determine a baseline internal resistance of the battery; and 
 compute an aged internal resistance of the battery; and 
   a display unit coupled to the logic unit and adapted to display an indicator related to a state of health of the battery based on the computed aged internal resistance.   
     
     
         14 . The system according to  claim 13 , wherein the logic unit determines the baseline internal resistance of the battery based on the second battery characteristic data. 
     
     
         15 . The system according to  claim 14 , wherein the baseline internal resistance is an internal resistance of the battery when the battery is new. 
     
     
         16 . The system according to  claim 13 , further comprising a temperature sensor coupled to the logic unit and responsive to a temperature of the battery, wherein the logic unit is configured to adjust the aged internal resistance of the battery according to the temperature of the battery. 
     
     
         17 . The system according to  claim 13 , wherein the second battery characteristic data further comprises predetermined data describing an internal resistance of the battery as the battery ages. 
     
     
         18 . The system according to  claim 13 , further comprising:
 a secondary current circuit coupled to the current sensor and comprising:
 a first transistor; 
 a second transistor connected in parallel with the first transistor; and 
 a voltage source circuit connected to a gate terminal of each of the first and second transistors. 
   
     
     
         19 . The system according to  claim 18 , wherein the voltage source circuit applies a predetermined voltage to each gate terminal of the first and second transistors. 
     
     
         20 . The system according to  claim 13 , wherein the logic unit computes the aged internal resistance based on the output voltage and the current of the battery.