Battery state of charge indicator

  • US 4,949,046 A
  • Filed: 06/21/1988
  • Issued: 08/14/1990
  • Est. Priority Date: 11/19/1985
  • Status: Expired due to Term
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First Claim
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1. A combination of a battery and a device for indicating a state of charge of said battery, comprising:

  • a Ni-Cad battery including input/output terminals;

    a current sensor operatively connected to said input/output terminals and arranged to provide an output indicative of magnitude and direction of a current flow from said Ni-Cad battery;

    a voltage sensor operatively connected to said input/output terminals and arranged to sense a potential difference subsisting across said input/output terminals;

    timing means arranged to provide a time signal;

    data storage means for storing an indication of a state of charge of said battery; and

    computer means for determining said state of charge of said battery operatively connected to said current sensor, to said voltage sensor, to said timing means, and to said data storage means, said computer including;

    means for computing from the output of the current sensor and the timing means a signal representative of a change in a state of charge of said battery over a period of time,means for supplying to said data storage means a signal representative of said change in said state of charge of said battery to update stored data on said state of charge of said battery to provide an indication of the current state of charge of said battery,means for monitoring an output signal of said voltage sensor and, when the monitored voltage reaches a predetermined maximum value to reset said data storage means to indicate that said battery is fully charged and, when said battery is fully charged and when said monitored voltage reaches a predetermined minimum value, to reset said data storage means to indicate that said battery is fully discharged, andmeans for comparing the state of charge indication immediately before it is reset at one of said predetermined maximum and minimum values with the state of charge indicated by the voltage sensor when the indication is reset when the battery is one of fully charged and fully discharged, respectfully, and to use the results of this comparison to vary at least one parameter to tailor said at least one parameter to the connected battery.

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