Battery Charge Strategy Using Discharge Cycle

Abstract

A battery management system for a vehicle includes a controller programmed to charge a battery at a predetermined charge rate. The controller discharges the battery for a predetermined time in response to a terminal voltage of the battery exceeding a predetermined voltage limit that results in a reduced charge rate. After discharging for the predetermined time, the controller resumes charging at the predetermined charge rate. A current magnitude during the discharge and the predetermined time may be based on factors including the predetermined charge rate, a battery temperature, and a charge current magnitude during charging.

What is claimed is: 
     
         1 . A battery management system comprising:
 at least one controller programmed to charge a battery at a predetermined charge rate and, in response to a terminal voltage of the battery exceeding a predetermined voltage limit that results in a reduced charge rate, to discharge the battery for a predetermined time and resume charging after the predetermined time at the predetermined charge rate to reduce battery charge time.   
     
     
         2 . The battery management system of  claim 1  wherein the predetermined voltage limit is a battery charge voltage limit at which constant voltage charging is initiated. 
     
     
         3 . The battery management system of  claim 1  wherein the predetermined charge rate is at a predetermined current. 
     
     
         4 . The battery management system of  claim 1  wherein a discharge rate magnitude during the discharge is less than a magnitude of the predetermined charge rate. 
     
     
         5 . The battery management system of  claim 1  wherein a current magnitude during the discharge and the predetermined time are based on one or more of a battery temperature, a battery state of charge, and a battery impedance. 
     
     
         6 . The battery management system of  claim 1  wherein a current magnitude during the discharge and the predetermined time are based on a charge current magnitude during the charge. 
     
     
         7 . A vehicle comprising:
 a battery; and   at least one controller programmed to charge the battery at a predetermined charge rate and, in response to a terminal voltage of the battery exceeding a predetermined voltage limit that results in a reduced charge rate, to discharge the battery for a predetermined time and resume charging after the predetermined time at the predetermined charge rate to reduce battery charge time.   
     
     
         8 . The vehicle of  claim 7  further comprising at least one electrical load, wherein the at least one controller is further programmed to command operation of the electrical load to discharge the battery for the predetermined time. 
     
     
         9 . The vehicle of  claim 7  wherein the predetermined voltage limit is a battery charge voltage limit at which constant voltage charging is initiated. 
     
     
         10 . The vehicle of  claim 7  the predetermined charge rate is at a predetermined current. 
     
     
         11 . The vehicle of  claim 7  wherein a discharge rate magnitude during the discharge is less than a magnitude of the predetermined charge rate. 
     
     
         12 . The vehicle of  claim 7  wherein a current magnitude during the discharge and the predetermined time are based on a battery temperature. 
     
     
         13 . The vehicle of  claim 7  wherein a current magnitude during the discharge and the predetermined time are based on a charge current magnitude during the charge. 
     
     
         14 . A method comprising:
 charging a battery at a predetermined charge rate;   discharging the battery for a predetermined time in response to a terminal voltage of the battery exceeding a predetermined voltage limit that results in a charge rate less than the predetermined charge rate; and   resuming charging the battery after the predetermined time at the predetermined charge rate to reduce a battery charge time.   
     
     
         15 . The method of  claim 14  further comprising terminating the charging when a state of charge of the battery exceeds a predetermined state of charge indicative of a fully charged battery. 
     
     
         16 . The method of  claim 14  wherein the predetermined voltage limit is a battery charge voltage limit at which constant voltage charging is initiated. 
     
     
         17 . The method of  claim 14  wherein the predetermined charge rate is based on one or more of a state of charge of the battery, a temperature of the battery, and an impedance of the battery. 
     
     
         18 . The method of  claim 14  wherein a discharge rate magnitude during the discharge is less than a magnitude of the predetermined charge rate. 
     
     
         19 . The method of  claim 14  wherein a current magnitude during the discharge and the predetermined time are based on a battery temperature. 
     
     
         20 . The method of  claim 14  wherein a current magnitude during the discharge and the predetermined time are based on a charge current magnitude during the charge.