Battery monitoring arrangement having an integrated circuit with logic controller in a battery pack

Abstract

A battery monitoring device of a battery pack configured for powering a cordless power tool may include an integrated circuit connected to a microprocessor of the pack that is external to the integrated circuit, and which is connected to each of N battery cells of the pack. The integrated circuit may be configured to take, singly or sequentially, a sampled reading comprising one of an individual cell voltage or a total pack voltage for all cells in the pack. The sampled reading is filtered in the integrated circuit prior to being read by the microprocessor.

1 . An arrangement in a battery pack for balancing cell voltages during charging of a plurality of cells of the pack, the arrangement comprising:
 a microprocessor, and   an interface circuit in operative communication with the microprocessor and connected to each of the cells,   the microprocessor directing the interface circuit to periodically measure the cell voltage across each cell of the pack and the total pack voltage,   the interface circuit communicating the measured cell voltage of each cell and at least one of a current average cell voltage for all cells and the measured total pack voltage to the microprocessor,   wherein one of the interface circuit and the microprocessor determine the current average cell voltage by dividing the measured total pack voltage by the number of cells, and,   the microprocessor controlling balancing of each of the cell voltages based on the measured cell voltage of each cell and the determined current average cell voltage.   
     
     
         2 . The arrangement of  claim 1 , wherein
 the microprocessor controls the balancing of cell voltages by comparing each measured individual cell voltage to the current average cell voltage, and   directs the interface circuit to discharge one or more cells which have a measured individual cell voltage exceeding the determined current average cell voltage for a given duration during the charge.   
     
     
         3 . The arrangement of  claim 1 , wherein
 the interface circuit includes a plurality of semiconductor devices, each connected to a corresponding cell in the pack, and   the interface circuit energizes a semiconductor device to enable discharging of its corresponding cell for the given duration, if the corresponding cell has a measured individual cell voltage greater than the determined current average cell voltage.   
     
     
         4 . The arrangement of  claim 2 , wherein the given duration is defined as a time elapsed until the measured cell voltage of a discharging cell has dropped to equal the determined current average cell voltage. 
     
     
         5 . The arrangement of  claim 1 , wherein the periodic measuring, determining of average cell voltage, and balancing functions are repeated throughout the duration of charging to maintain individual cell voltages substantially balanced during charging. 
     
     
         6 . A method of adaptively balancing cell voltages of a plurality of cells in a battery pack during charging of the battery pack, comprising:
 periodically measuring the cell voltage for each cell in the pack;   periodically determining from said measured cell voltages an average cell voltage value,   detecting a voltage differential for one or more cells, the voltage differential corresponding to a difference between a given measured cell voltage and the average cell voltage value, and   balancing cell voltages during charging by discharging those cells which have a measured cell voltage greater than the average cell voltage value.   
     
     
         7 . The method of  claim 6 , wherein said balancing step further includes discharging a cell having a measured cell voltage greater than the average cell voltage value until the measured cell voltage for the discharging cell equals the average cell voltage value.