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

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

This application is a divisional of U.S. application Ser. No. 11/239,286, filed Sep. 30, 2005, which claims priority to U.S. Provisional Application Ser. No. 60/615,201, filed Oct. 4, 2004, the entire contents of which is hereby incorporated by reference herein.

1. Field of the Invention

The present invention generally relates to a method and device for monitoring battery cells of a battery pack configured for powering a cordless power tool, and to a method and arrangement for balancing cell voltages during a charge.

2. Description of Related Art

Cordless products or devices which use rechargeable batteries are prevalent throughout the workplace and home. Rechargeable batteries may be used in numerous devices, from computer products and/or housewares to power tools. Nickel-cadmium, nickel-metal-hydride battery and/or lithium-ion cells may be used in these devices. Since the devices use a plurality of battery cells, the battery cells may be ordinarily packaged as battery packs. These battery packs may be coupled with the cordless devices so as to secure the pack to the device. The battery pack may be removed from the cordless device and charged in a battery charger or charged in the cordless device itself, for example.

An example embodiment of the present invention is directed to a battery monitoring device of a battery pack configured for powering a cordless power tool. The device may include an integrated circuit connected to a microprocessor of the pack that is external to the integrated circuit, and 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.

Another example embodiment of the present invention is directed to a method of monitoring battery cells of a battery pack that is configured for powering a cordless power tool. In the method, a first serial data command may be received from a microprocessor of the pack to take a voltage measurement from channels connected to one or more of the cells. The voltage measurement may be embodied as a differential voltage value measured across an individual cell or a differential voltage value measured across all cells to reflect a total pack voltage. The voltage measurement may be stored in a capacitor and filtered so that the capacitor charges up to an average of the differential voltage value for a given cell or across all cells of the pack. A second serial data command may be received to connect the capacitor to a buffer amplifier so that the microprocessor can read the average voltage value off the capacitor.

Another example embodiment of the present invention is directed to an arrangement in a battery pack for balancing cell voltages during charging of a plurality of cells of the pack. The arrangement may include a microprocessor and an integrated circuit in operative communication with the microprocessor and connected to each of the cells. The microprocessor may direct the integrated circuit to periodically measure, throughout the duration of charging, the cell voltage across each cell of the pack and the total pack voltage in a sequential manner. The integrated circuit communicates the measured individual cell voltage and a current average cell voltage for all cells to the microprocessor. The measured total pack voltage is automatically divided by the number of cells within the integrated circuit to determine the current average cell voltage. The microprocessor controls balancing of each of the cell voltages during the charge based on each measured individual cell voltage and the determined current average cell voltage.

Another example embodiment of the present invention is directed to a method of adaptively balancing cell voltages of a plurality of cells in a battery pack during charging of the battery pack. The method includes continuously monitoring cell voltages for each cell in the pack in a sequential manner, and detecting a voltage differential for one or more cells. The voltage differential may be represented as the difference a given measure cell voltage exceeds a current average cell voltage value calculated from the continuously monitoring step. Cell voltages may be balanced during the charge by discharging those cells having a detected voltage differential, until a measured cell voltage for the discharging cell has dropped to equal the average cell voltage.

Another example embodiment of the present invention is directed to a battery pack configured to monitor voltages of cells therein, the battery pack operatively attachable to a cordless power tool. The battery pack includes a microprocessor and an integrated circuit in operative communication with the microprocessor for monitoring cell voltages of at least N individual cells and total pack voltage during discharge of the pack, based on commands received from the microprocessor. The battery pack includes a motor control semiconductor device operatively controlled by the microprocessor. As the battery pack is engaged to a cordless power tool, and upon an initial actuation of a trigger of the power tool, the microprocessor directs the integrated circuit to sequentially measure the individual cell voltages of all the cells. The microprocessor may energize the motor control semiconductor device to enable battery current to flow to a motor of the power tool, if the determined individual cell voltages are acceptable as compared to a given voltage threshold.

The example embodiments of the present invention will become more fully understood from the detailed description given herein below and the accompanying drawings, wherein like elements are represented by like reference numerals, which are given by way of illustration only and thus are not limitative of the example embodiments of the present invention.

FIG. 1 illustrates a block diagram of a arrangement for monitory battery parameters in accordance with an example embodiment of the present invention.

FIG. 2 is a flow diagram illustrating data flow between the microcontroller and ASIC of FIG. 1, in accordance with an example embodiment of the present invention.

FIG. 3 is a block diagram illustrating components and terminals of an example battery pack in accordance with an example embodiment of the present invention.

• Provisional Patent
• Utility Patent

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