BATTERY PACK FOR CORDLESS POWER TOOLS
First Claim
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1. A battery pack of a cordless power tool system including a power tool and a charger, the pack removably attachable to the tool and charger, the battery pack comprising:
- a housing,a plurality of battery cells within the housing,a battery electronic control unit within the housing for controlling the charger during a charge of the cells, and for controlling a field effect transistor (FET) during discharge operations to control current to a motor of the power tool,a first voltage monitoring unit for monitoring one or both of individual cell voltages and total stack voltage in the pack during charge and discharge operations, anda second voltage monitoring circuit for separately monitoring individual cell voltage to detect any cell reaching an over-voltage condition during a charge.
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Abstract
A battery pack which includes a battery pack electronic control circuit adapted to control an attached power tool and/or an attached charger. The battery pack includes additional protection circuits, methodologies and devices to protect against fault conditions within the pack, as the pack is operatively attached to and providing power to the power tool, and/or as the pack is operatively attached to and being charged by the charger.
141 Citations
37 Claims
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1. A battery pack of a cordless power tool system including a power tool and a charger, the pack removably attachable to the tool and charger, the battery pack comprising:
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a housing, a plurality of battery cells within the housing, a battery electronic control unit within the housing for controlling the charger during a charge of the cells, and for controlling a field effect transistor (FET) during discharge operations to control current to a motor of the power tool, a first voltage monitoring unit for monitoring one or both of individual cell voltages and total stack voltage in the pack during charge and discharge operations, and a second voltage monitoring circuit for separately monitoring individual cell voltage to detect any cell reaching an over-voltage condition during a charge. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. An electronics module of a battery pack for powering a cordless power tool, the pack including a plurality of lithium-ion battery cells therein, the module comprising:
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an integrated circuit which includes a first voltage monitoring unit for monitoring individual lithium-ion cell voltages and total stack voltage of the lithium-ion cells during charge and discharge operations, a microcontroller external to and in communication with the integrated circuit, a discharge FET for controlling one of current and power output from the battery pack to control a motor of the tool, wherein the microcontroller selectively controls the discharge FET so as to control current to the tool motor, a second voltage monitoring circuit for separately monitoring individual cell voltage during a charge, and a fuse in a charge return line to the module. - View Dependent Claims (25, 26, 27)
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28. In a battery pack having a controller providing pulse width modulation (PWM) control of a field effect transistor (FET) in the pack to control current to a motor of a power tool, the FET having a duty cycle and a fixed switching period for each on and off state in the duty cycle, a circuit for performing current limit processing in the pack, comprising:
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a comparator, which is fed a reference voltage level from the controller representative of a current limit for the pack at a negative input thereof, a current sensor for measuring, with the FET on, instantaneous current flowing through the FET during each given switching period and sending a shunt voltage representative of the measured instantaneous current to a positive input of the comparator, wherein, if the shunt voltage equals or exceeds the reference voltage level in the given switching period, the comparator generates an output signal to the controller to turn off the FET for the remainder of the switching period.
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29. In a battery pack providing pulse width modulation (PWM) control of a field effect transistor (FET) therein to control current to a motor of a power tool, the FET having a duty cycle and a fixed switching period for each on and off state in the duty cycle, a method for performing current limit processing in the pack, comprising:
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setting a reference voltage level representative of a current limit for the pack, and during each switching period of the FET with the FET on, comparing a shunt voltage representing measured instantaneous pack current to the reference voltage level, and turning off the FET for the remainder of the switching period if the shunt voltage equals or exceeds the reference voltage level in the given switching period to reduce power out of the pack.
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30. A battery pack of a cordless power tool, comprising:
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a housing, a plurality of battery cells within the housing, a controller within the housing for controlling a field effect transistor (FET) during power tool operations to control current to a motor of the power tool, and a driver circuit that supplies a drive signal for switching the FET during power tool operations based on a control signal received from the controller, wherein the controller periodically monitors a supply voltage of the driver circuit for comparison against a reference voltage level and, if the supply voltage falls below the reference voltage level, the controller inhibits the drive signal so as to turn off the FET.
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31. A method of detecting a faulty driver circuit in a battery pack of a cordless power tool system, the driver circuit supplying a drive signal for switching a FET to control current to a motor of the power tool, the method comprising:
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periodically monitoring a supply voltage of the driver circuit, comparing the supply voltage against a reference voltage level, and inhibiting the drive signal so as to turn off the FET, if the supply voltage falls below the reference voltage level.
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32. In a cordless power tool system having a battery pack attached to a power tool, a method by which a controller in the battery pack detects a short circuit in the power tool upon tool startup by trigger actuation of a tool trigger, comprising:
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turning a FET in the pack on for a fixed duration upon trigger actuation, measuring current in the pack during the fixed duration, wherein if the measured current does not exceed a set current limit in the pack during the fixed duration, the pack determines that the tool does not have a short circuit, else the tool is determined to have a short circuit and the controller turns off the FET to place the pack in a shutdown mode.
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33. A battery pack of a cordless power tool system an attachable to a power tool, the power tool includes a power diode between power terminals in the tool and in parallel with the tool motor, the pack comprising:
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a housing, a plurality of battery cells within the housing, a controller within the housing for controlling a field effect transistor (FET) in the pack during power tool operations to control current to a motor of the power tool, a detection circuit for detecting an open diode condition in the power tool upon the power diode failing open or becoming disconnected during power operations, and protecting the FET by generating an interrupt in the controller to turn the FET off. - View Dependent Claims (34)
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35. A secondary circuit for providing over-voltage protection for battery cells of a battery pack in a system including the pack and a battery charger, the pack having a pack microcontroller in communication with a charger microcontroller of the charger during a charge, one of the pack or charger microcontrollers providing primary cell over-voltage protection during the charge, the secondary circuit comprising:
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a first circuit in the pack detecting a cell over-voltage condition of one of the cells and generating a signal reflective of the condition, and a second circuit in the charger sensing the signal to generate a disable signal in the charger to interrupt the charge current. - View Dependent Claims (36, 37)
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Specification