Method and system for charging multi-cell lithium-based battery packs

Abstract

A method and system for charging multi-cell lithium-based batteries. In some aspects, a battery charger includes a housing, at least one terminal to electrically connect to a battery pack supported by the housing, and a controller operable to provide a charging current to the battery pack through the at least one terminal. The battery pack includes a plurality of lithium-based battery cells, with each battery cell of the plurality of battery cells having an individual state of charge. The controller is operable to control the charging current being supplied to the battery pack at least in part based on the individual state of charge of at least one battery cell.

What is claimed is: 
     
         1 . An electrical combination comprising:
 a battery charger operable to provide a charging current;   a battery pack electrically connectable to the battery charger over a positive terminal and a negative terminal, the battery pack including a plurality of lithium-based battery cells and a control circuit, each of the plurality of battery cells having an individual state of charge, the battery pack operable to communicate with the battery charger in a serial manner over a sense terminal, wherein the battery pack communicates information related to the individual state of charge of at least one of the plurality of battery cells to the battery charger; and   a switch operable to control the charging current from the battery charger to the battery pack based on the information related to the individual state of charge of the at least one of the plurality of battery cells, the switch operable to be controlled between an ON state and an OFF state to control the charging current.   
     
     
         2 . The electrical combination of  claim 1 , wherein the switch includes a field-effect transistor (“FET”). 
     
     
         3 . The electrical combination of  claim 2 , wherein the control circuit is operable to control the switch. 
     
     
         4 . The electrical combination of  claim 1 , wherein control circuit includes a microcontroller. 
     
     
         5 . The electrical combination of  claim 1 , wherein the battery pack communicates information related to the state of charge of each of the battery cells in the plurality of battery cells to the battery charger. 
     
     
         6 . The electrical combination of  claim 1 , wherein the battery pack communicates information related to the state of charge of fewer battery cells than a number of battery cells in the plurality of battery cells. 
     
     
         7 . The electrical combination of  claim 1 , wherein the plurality of battery cells is connected in a series-parallel configuration. 
     
     
         8 . The electrical combination of  claim 1 , wherein the plurality of battery cells is connected in series. 
     
     
         9 . The electrical combination of  claim 1 , wherein the switch is located in the battery pack.