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Battery state of charge monitor

  • US 5,444,378 A
  • Filed: 07/23/1992
  • Issued: 08/22/1995
  • Est. Priority Date: 07/13/1988
  • Status: Expired due to Fees
First Claim
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1. An apparatus for monitoring the state of an electrical energy source comprising:

  • a current sensor for producing a first signal related to the magnitude and direction of the current flowing to or from said energy source; and

    a low power operational amplifier having a capacitive element in the feedback path for integrating the first signal on a continuous basis as the current flows to and from said energy source, and thereby charging the capacitive element at a rate proportional to the magnitude of the sensed current when the current flow is in one direction and discharging the capacitive element at a rate proportional to the magnitude of the sensed current when the current flow is in the opposite direction, the amplifier having a supply voltage input operatively connected to the energy source for energizing the amplifier and a minimum drain current that is less than 1.05 mA, the capacitive element having a capacitance greater than 0.01 farad.

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