System and method for maximizing battery capacity while in long term storage

Abstract

When in long term storage, battery degradation is avoided by performing battery charge cycles at a voltage level where a change in the battery's voltage divided by a change in the battery's storage capacity is at a minimum, rather than discharging the battery to its minimum storage capacity and then charging to its maximum storage capacity. Further, based on physical and practical limitations, such battery charge cycles can instead be performed within a range or delta Depth of Discharge (“DOD”) and corresponding battery voltage levels rather than at a single voltage level, while still avoiding battery degradation.

What is claimed is: 
     
       1. A method of avoiding battery degradation, the method comprising:
 determining a representative discharge rate for a battery; 
 determining a voltage level where a change in the battery's voltage divided by a change in the battery's storage capacity is at a minimum; 
 determining a representative long term storage time period for the battery; 
 determining a minimum long term storage voltage value and a maximum long term storage voltage value, each as a predetermined function of the determined voltage level where the change in the battery's voltage divided by the change in the battery's storage capacity is at the minimum and each corresponding to limits of a range of Depth of Discharge (DOD) values; 
 determining that the battery is in long term storage; 
 measuring, by a processor, a depth of discharge of the battery; 
 determining that the measured depth of discharge is at or below the minimum tong long term storage voltage value; and, 
 charging the battery to the maximum long term storage voltage value in response to the determination that the measured depth of discharge is at or below the minimum long term storage voltage value. 
 
     
     
       2. The method of avoiding battery degradation of  claim 1  wherein determining the representative discharge rate of the battery is accomplished by disconnecting the battery from any associated electronics. 
     
     
       3. The method of avoiding battery degradation of  claim 1  wherein determining a voltage level where a change in the battery's voltage divided by a change in the battery's storage capacity is at a minimum is accomplished by taking battery measurements during a process of discharging the battery. 
     
     
       4. The method of avoiding battery degradation of  claim 1  wherein determining a representative long term storage time period is accomplished by a manufacturer setting. 
     
     
       5. The method of avoiding battery degradation of  claim 1  wherein determining a representative long term storage time period is accomplished by analysis of battery usage. 
     
     
       6. The A method of avoiding battery degradationof  claim 1 , the method comprising:
 determining a representative discharge rate for a battery; 
 determining a voltage level where a change in the battery's voltage divided by a change in the battery's storage capacity is at a minimum; 
 determining a representative long term storage time period for the battery; 
 determining a minimum long term storage voltage value and a maximum long term storage voltage value, each corresponding to limits of a range of Depth of Discharge (DOD) values; 
 determining that the battery is in long term storage; 
 measuring, by a processor, a depth of discharge of the battery; 
 determining that the measured depth of discharge is at or below the minimum long term storage voltage value; and, 
 charging the battery to the maximum long term storage voltage value;  
 wherein determining a minimum long term storage voltage value and a maximum long term storage value is based on one or more limitation comprising contactor cycle lifespan, charger frequency limits, and charger minimum activation time period. 
 
     
     
       7. The method of avoiding battery degradation of  claim 1  wherein determining a minimum long term storage voltage value and a maximum long term storage value is based on one or more limitation comprising avoiding undesirable noise, efficiency/waste avoidance, measurement limitations, and charger reliability. 
     
     
       8. The method of avoiding battery degradation of  claim 1  further comprising bleeding down any cells in a multiple cell battery that exceed the maximum long term storage voltage value after charging the battery to the maximum long term storage voltage value. 
     
     
       9. The method of avoiding battery degradation of  claim 1  wherein the battery's storage capacity is measured in terms of the battery's storage capacity (“Q”), Depth of Discharge (“DOD”), or State of Charge (“SOC”). 
     
     
       10. A battery management system configured to avoid battery degradation, the battery management system comprising processing logic configured to:
 determine a representative discharge rate for a battery; 
 determine a voltage level where a change in the battery's voltage divided by a change in the battery's storage capacity is at a minimum; 
 determine a representative long term storage time period for the battery; 
 determine a minimum long term storage voltage value and a maximum long term storage voltage value, each as a predetermined function of the determined voltage level where the change in the battery's voltage divided by the change in the battery's storage capacity is at the minimum and each corresponding to limits of a range of Depth of Discharge (DOD) values; 
 determine that the battery is in long term storage; 
 measure, by a processor, a depth of discharge of the battery; 
 determine that the measured depth of discharge is at or below the minimum tong long term storage voltage value; and, 
 charge the battery to the maximum long term storage voltage value in response to the determination that the measured depth of discharge is at or below the minimum long term storage voltage value. 
 
     
     
       11. The battery management system configured to avoid battery degradation of  claim 10  wherein the processing logic configured to determine the representative discharge rate of the battery is configured to disconnect the battery from any associated electronics. 
     
     
       12. The battery management system configured to avoid battery degradation of  claim 10  wherein the processing logic configured to determine a voltage level where a change in the battery's voltage divided by a change in the battery's storage capacity is at a minimum is configured to take battery measurements during a process of discharging the battery. 
     
     
       13. The battery management system configured to avoid battery degradation of  claim 10  wherein the processing logic configured to determine a representative long term storage time period is configured with a manufacturer setting. 
     
     
       14. The battery management system configured to avoid battery degradation of  claim 10  wherein the processing logic configured to determine a representative long term storage time period is configured to analyze battery usage. 
     
     
       15. The A battery management system configured to avoid battery degradationof  claim 10 , the battery management system comprising processing logic configured to:
 determine a representative discharge rate for a battery; 
 determine a voltage level where a change in the battery's voltage divided by a change in the battery's storage capacity is at a minimum; 
 determine a representative long term storage time period for the battery; 
 determine a minimum long term storage voltage value and a maximum long term storage voltage value, each corresponding to limits of a range of Depth of Discharge (DOD) values; 
 determine that the battery is in long term storage; 
 measure, by a processor, a depth of discharge of the battery; 
 determine that the measured depth of discharge is at or below the minimum long term storage voltage value; and, 
 charge the battery to the maximum long term storage voltage value;  
 wherein the processing logic configured to determine a minimum long term storage voltage value and a maximum long term storage value is based on one or more limitation comprising contactor cycle lifespan, charger frequency limits, and charger minimum activation time period. 
 
     
     
       16. The battery management system configured to avoid battery degradation of  claim 10  wherein the processing logic configured to determine a minimum long term storage voltage value and a maximum long term storage value is based on one or more limitation comprising avoiding undesirable noise, efficiency/waste avoidance, measurement limitations, and charger reliability. 
     
     
       17. The battery management system configured to avoid battery degradation of  claim 10  wherein the processing logic is further configured to bleed down any cells in a multiple cell battery that exceed the maximum long term storage voltage value after charging the battery to the maximum long term storage voltage value. 
     
     
       18. The battery management system configured to avoid battery degradation of  claim 10  wherein the battery's storage capacity is measured in terms of the battery's storage capacity (“Q”), Depth of Discharge (“DOD”), or State of Charge (“SOC”). 
     
     
       19. A method of avoiding degradation of a battery, the method comprising:
 determining a voltage level where a change in the battery's voltage divided by a change in the battery's storage capacity is at a minimum;   determining a minimum long term storage voltage value and a maximum long term storage voltage value, each as a predetermined function of the determined voltage level where the change in the battery's voltage divided by the change in the battery's storage capacity is at the minimum and each corresponding to limits of a range of Depth of Discharge (DOD) values;   determining that the battery is in long term storage;   measuring, by a processor, a depth of discharge of the battery;   determining that the measured depth of discharge is at or below the minimum long term storage voltage value; and,   charging the battery to the maximum long term storage voltage value in response to the determination that the measured depth of discharge is at or below the minimum long term storage voltage value.    
     
     
       20. A battery management system configured to avoid degradation of a battery, the battery management system comprising processing logic configured to:
 determine a voltage level where a change in the battery's voltage divided by a change in the battery's storage capacity is at a minimum;   determine a minimum long term storage voltage value and a maximum long term storage voltage value, each as a predetermined function of the determined voltage level where the change in the battery's voltage divided by the change in the battery's storage capacity is at the minimum and each corresponding to limits of a range of Depth of Discharge (DOD) values;   determine that the battery is in long term storage;   measure, by a processor, a depth of discharge of the battery;   determine that the measured depth of discharge is at or below the minimum long term storage voltage value; and,   charge the battery to the maximum long term storage voltage value in response to the determination that the measured depth of discharge is at or below the minimum long term storage voltage value.    
     
     
       21. A battery management system configured to avoid degradation of a battery, the battery management system comprising processing logic configured to:
 measure a voltage of the battery;   start charging the battery in response to the measured voltage of the battery being less than or equal to a minimum long term storage voltage value at which a change in the battery's voltage divided by a change in the battery's storage capacity, a change in the battery's depth of discharge, and/or a change in the battery's state of charge is at a minimum; and   stop charging the battery in response to the measured voltage of the battery being greater than or equal to a maximum long term storage voltage value that is less than a voltage value of the battery in a fully charged state.    
     
     
       22. The battery management system of  claim 21 , wherein the processing logic is configured to repeatedly measure the voltage of the battery and maintain the voltage of the battery between the minimum long term storage voltage value and the maximum long term storage voltage value.  
     
     
       23. The battery management system of  claim 21 , wherein the processing logic is configured to measure the voltage of the battery, start the charging, and stop the charging while the battery is in a long term storage condition.  
     
     
       24. The battery management system of  claim 23 , wherein the processing logic is configured to determine that the battery is in the long term storage condition.  
     
     
       25. The battery management system of  claim 23 , wherein the processing logic is configured to determine that the battery is in the long term storage condition in response to user input.  
     
     
       26. The battery management system of  claim 23 , wherein the processing logic is configured to determine that the battery is in the long term storage condition based on inactivity and/or non-use of the battery for a predetermined period of time.  
     
     
       27. The battery management system of  claim 21 , wherein the battery is arranged as a lithium ion battery.  
     
     
       28. The battery management system of  claim 21 , wherein the battery is arranged as a multiple cell battery, and the processing logic is adapted to bleed down any cells of the multiple cell battery that exceed the maximum long term storage voltage value after charging the multiple cell battery to the maximum long term storage value.  
     
     
       29. The battery management system of  claim 28 , wherein the multiple cell battery includes a plurality of cells connected in series.  
     
     
       30. The battery management system of  claim 29 , wherein the processing logic is configured to measure the voltage of each cell.  
     
     
       31. The battery management system of  claim 21 , wherein the processing logic is configured to repeatedly measure the voltage of the battery, start the charging, and stop the charging maintain the voltage of the battery between the minimum long term storage voltage value and the maximum long term storage voltage value.  
     
     
       32. The battery management system of  claim 21 , wherein the processing logic is configured to maintain the battery between a first predetermined depth of discharge and a second predetermined depth of discharge.  
     
     
       33. The battery management system of  claim 32 , wherein the minimum long term storage voltage value corresponds to a depth of discharge between the first predetermined depth of discharge and the second predetermined depth of discharge.  
     
     
       34. The battery management system of  claim 21 , wherein the battery management system is arranged in an electric vehicle.  
     
     
       35. The battery management system of  claim 21 , wherein the battery management system is arranged in an electric motorcycle.  
     
     
       36. The battery management system of  claim 21 , wherein the battery is arranged as a battery for an electric vehicle.  
     
     
       37. The battery management system of  claim 21 , wherein the battery is arranged as a battery for an electric motorcycle.