Battery management system for a cordless tool

Abstract

A hand-held, battery powered tool (e.g., nutrunner, drill) includes an output head operatively connected to a motor, a plurality of battery cells, an ON/OFF start switch, a resistance sensor that measures a resistance of the output head to movement, and a controller. When the start switch is ON and the resistance sensed by the resistance sensor does not exceed a predetermined shift resistance, the controller automatically connects the plurality of battery cells to each other and the motor in series. When the start switch is ON and the resistance sensed by the resistance sensor exceeds the predetermined shift resistance, the controller automatically connects the plurality of battery cells to each other in parallel and to the motor.

What is claimed is: 
     
       1. A tool comprising:
 an output head;   a motor operatively connected to the output head;   a resistance sensor that measures the output head's resistance to movement; and   a controller connected to the motor and the resistance sensor, the controller being constructed and arranged to connect to a plurality of battery cells,   wherein the controller is constructed and arranged to connect the plurality of battery cells to each other and the motor in series, and subsequently automatically connect the plurality of battery cells to each other in parallel and to the motor when the resistance sensed by the resistance sensor exceeds a predetermined shift resistance.   
     
     
       2. The tool of  claim 1 , wherein:
 the output head comprises a rotational output head;   the resistance sensor comprises a torque sensor that measures a torque applied to the output head;   the predetermined shift resistance comprises a predetermined shift torque.   
     
     
       3. The tool of  claim 2 , wherein:
 the controller is constructed and arranged to disconnect the motor from the plurality of battery cells when the sensed torque exceeds a predetermined target torque, and   the predetermined target torque is larger than the predetermined shift torque.   
     
     
       4. The tool of  claim 1 , further comprising a fixed ratio transmission disposed between the motor and the output head. 
     
     
       5. The tool of  claim 1 , wherein the controller comprises an electronic control unit. 
     
     
       6. The tool of  claim 1 , wherein the resistance sensor comprises a torque sensor. 
     
     
       7. The tool of  claim 1 , wherein the resistance sensor comprises a force sensor. 
     
     
       8. The tool of  claim 1 , wherein:
 the tool further comprises a start switch having ON and OFF positions, the start switch being operatively connected to the controller; and   the controller is constructed and arranged to connect the plurality of battery cells to each other and to the motor in series in response to the start switch moving into its ON position.   
     
     
       9. The tool of  claim 1 , wherein:
 the tool further comprises a start switch having ON and OFF positions, the start switch being operatively connected to the controller; and   the controller is constructed and arranged such that when the start switch is in its ON position and the resistance sensed by the resistance sensor exceeds the predetermined shift resistance, the controller automatically connects the plurality of battery cells to each other in parallel and to the motor.   
     
     
       10. The tool of  claim 1 , wherein:
 the tool further comprises a start switch having ON and OFF positions, the start switch being operatively connected to the controller; and   the controller is constructed and arranged such that when the start switch is in its ON position and the resistance sensed by the resistance sensor does not exceed the predetermined shift resistance, the controller automatically connects the plurality of battery cells to each other and the motor in series.   
     
     
       11. The tool of  claim 1 , wherein:
 the tool further comprises a start switch having ON and OFF positions, the start switch being operatively connected to the controller;   the controller is constructed and arranged to automatically disconnect the motor from the plurality of battery cells any time that the start switch moved into its OFF position.   
     
     
       12. The tool of  claim 1 , further comprising a plurality of battery cells connected to the controller. 
     
     
       13. A tool comprising:
 an output head;   a motor operatively connected to the output head;   a start switch having ON and OFF positions;   a resistance sensor that measures the output head's resistance to movement; and   a controller connected to the motor, the start switch, and the resistance sensor, the controller being constructed and arranged to connect to a plurality of battery cells,   wherein the controller is constructed and arranged such that when the start switch is in its ON position and the resistance sensed by the resistance sensor does not exceed a predetermined shift resistance, the controller automatically connects the plurality of battery cells to each other and the motor in series, and   the controller is constructed and arranged such that when the start switch is in its ON position and the resistance sensed by the resistance sensor exceeds the predetermined shift resistance, the controller automatically connects the plurality of battery cells to each other in parallel and to the motor.   
     
     
       14. The tool of  claim 13 , wherein:
 the output head comprises a rotational output head;   the resistance sensor comprises a torque sensor that measures a torque applied to the output head;   the predetermined shift resistance comprises a predetermined shift torque.   
     
     
       15. A method of using a battery powered tool, comprising:
 (a) connecting a plurality of battery cells to each other and to a motor in series; and   (b) automatically connecting the plurality of battery cells to each other in parallel and to the motor in response to a resistance sensor sensing that a resistance of an output head to movement exceeds a predetermined shift resistance.   
     
     
       16. The A method of  claim 15 , using a battery powered tool, comprising:
 (a) connecting a plurality of battery cells to each other and to a motor in series; and 
 (b) automatically connecting the plurality of battery cells to each other in parallel and to the motor in response to a resistance sensor sensing that a resistance of an output head to movement exceeds a predetermined shift resistance,  
 wherein:
 the tool comprises a fastener tightening tool that includes a start switch having ON and OFF positions; 
 the output head comprises a rotational output head; 
 the resistance sensor comprises a torque sensor that measures a torque being applied to the output head; 
 the predetermined shift resistance comprises a predetermined shift torque; and  
 the method further comprises:
 sensing that the start switch is in its ON position, wherein the connecting of the plurality of battery cells to each other and to motor in series occurs in response to the sensing that the start switch is in its ON position; 
 after automatically connecting the plurality of battery cells to each other in parallel and to the motor, automatically disconnecting the motor from the plurality of battery cells in response to the torque sensor sensing that the torque exceeds a predetermined target torque. 
 
 
 
     
     
       17. The method of  claim 16 , wherein:
 the start switch remains in its ON position from when battery cells are connected to each other and to the motor in series until when the motor is disconnected from the plurality of battery cells in response to the torque sensor sensing that the torque exceeds the predetermined target torque, and 
 the predetermined target torque exceeds the predetermined shift torque. 
 
     
     
       18. The A method of  claim 15 , using a battery powered tool, comprising:
 (a) connecting a plurality of battery cells to each other and to a motor in series; and 
 (b) automatically connecting the plurality of battery cells to each other in parallel and to the motor in response to a resistance sensor sensing that a resistance of an output head to movement exceeds a predetermined shift resistance,  
 wherein:
 the tool includes a start switch having ON and OFF positions; and 
 the method further comprises:
 sensing that the start switch is in its ON position, wherein the connecting of the plurality of battery cells to each other and to motor in series occurs in response to the sensing that the start switch is in its ON position; and 
 automatically disconnecting the motor from the plurality of battery cells any time that the start switch moves into its OFF position. 
 
 
 
     
     
       19. A method of using a battery powered tool, comprising:
 in response to sensing that a start switch is in its ON position and a resistance of an output head to movement does not exceed a predetermined shift resistance, automatically connecting a plurality of battery cells to each other and a motor in series; and 
 in response to sensing that the start switch is in its ON position and the resistance exceeds the predetermined shift resistance, automatically connecting the plurality of battery cells to each other in parallel and to the motor. 
 
     
     
       20. The method of  claim 19 , wherein:
 the tool comprises a fastener tightening tool; 
 the output head comprises a rotational output head; 
 sensing the resistance comprises sensing a torque being applied to the output head; and 
 the predetermined target resistance comprises a predetermined target torque. 
 
     
     
       21. A tool comprising:
 an output head;   a plurality of battery cells disposed in a detachable battery pack;   a motor operatively connected to the output head and configured to be powered by the plurality of battery cells; and   a switch configured to be operatively connected to the plurality of battery cells, the switch being automatically switchable between a first configuration, where at least two of the plurality of battery cells are connected to each other in series, and a second configuration, where the at least two of the plurality of battery cells are connected to each other in parallel, based on a sensed characteristic of the tool.    
     
     
       22. The tool of claim 21, wherein the switch comprises an electronic control unit.  
     
     
       23. The tool of claim 21, wherein the switch comprises a mechanical component.  
     
     
       24. The tool of claim 21, wherein the switch comprises an electromechanical switch.  
     
     
       25. The tool of claim 21, wherein the switch comprises a solid state switch.  
     
     
       26. The tool of claim 21, wherein the sensed characteristic of the tool comprises at least one of a sensed voltage requirement, a sensed resistance, a sensed torque, and a sensed force.  
     
     
       27. The tool of claim 26, wherein the tool further comprises a sensor configured to sense the characteristic of the tool.  
     
     
       28. The method of claim 21, wherein the tool comprises a fastener tightening tool.  
     
     
       29. The tool of claim 21, wherein the switch is further switchable to a third configuration where the at least two of the plurality of battery cells are disconnected from each other.  
     
     
       30. The tool of claim 21, wherein the switch is further switchable to a third configuration wherein the switch is in an open state.  
     
     
       31. The tool of claim 21, wherein the switch comprises a network of switches.  
     
     
       32. The tool of claim 21, wherein the switch comprises a plurality of switches.  
     
     
       33. The tool of claim 21, wherein:
 the switch comprises a series/parallel switch;   the tool further comprises a start switch having ON and OFF positions, the start switch being operatively connected to the series/parallel switch; and   the series/parallel switch is constructed and arranged to automatically disconnect the motor from the plurality of battery cells any time that the start switch moves into its OFF position.    
     
     
       34. The tool of claim 21, wherein the characteristic of the tool comprises a characteristic of the motor.  
     
     
       35. The tool of claim 21, wherein the detachable battery pack comprises a single detachable battery pack that houses the plurality of battery cells.  
     
     
       36. The tool of claim 21, wherein:
 the tool comprises a tool component that is separate from the detachable battery pack;   the tool component includes the output head and the motor; and   the characteristic of the tool comprises a characteristic of the tool component.    
     
     
       37. The tool of claim 21, wherein the tool further comprises a sensor configured to sense the characteristic of the tool.  
     
     
       38. A method of using a battery powered tool wherein the battery powered tool comprises a plurality of battery cells disposed in a battery pack that is detachable from the tool, the plurality of battery cells being in either a first configuration wherein at least two of the plurality of battery cells are connected to each other in series or a second configuration wherein at least two of the plurality of battery cells are connected to each other in parallel, the method comprising:
 automatically switching the at least two of the plurality of battery cells to the first configuration or the second configuration based on a sensed characteristic of the tool.    
     
     
       39. The method of claim 38, wherein the automatically switching between the first configuration and the second configuration is performed by a switch.  
     
     
       40. The method of claim 39, wherein the switch comprises an electronic control unit.  
     
     
       41. The method of claim 39, wherein the switch comprises a mechanical component.  
     
     
       42. The method of claim 39, wherein the switch comprises an electromechanical switch.  
     
     
       43. The method of claim 39, wherein the switch comprises a solid state switch.  
     
     
       44. The method of claim 39, further comprising automatically switching the plurality of battery cells to a third configuration, where the switch is in an open state.  
     
     
       45. The method of claim 39, wherein the switch comprises a network of switches.  
     
     
       46. The method of claim 38, further comprising sensing the characteristic of the tool via a sensor in the tool.  
     
     
       47. The tool of claim 38, wherein the sensed characteristic of the tool comprises at least one of a sensed voltage requirement, a sensed resistance, a sensed torque, and a sensed force.  
     
     
       48. The method of claim 38, further comprising automatically switching the plurality of battery cells to a third configuration where the at least two of the plurality of battery cells are disconnected from each other.  
     
     
       49. The method of claim 38, wherein the tool comprises a fastener tightening tool.  
     
     
       50. The method of claim 38, wherein the characteristic of the tool comprises a characteristic of the motor.  
     
     
       51. The method of claim 38, wherein the detachable battery pack comprises a single detachable battery pack that houses the plurality of battery cells.  
     
     
       52. The method of claim 38, wherein:
 the tool comprises a tool component that includes an output head and a motor operatively connected to the output head and configured to be powered by the plurality of battery cells;   the tool component is separate from the detachable battery pack; and   the characteristic of the tool comprises a characteristic of the tool component.    
     
     
       53. The method of claim 38, wherein the sensed characteristic is sensed via a sensor that is part of the tool.