Battery capacity monitoring system

  • US 5,705,929 A
  • Filed: 05/23/1995
  • Issued: 01/06/1998
  • Est. Priority Date: 05/23/1995
  • Status: Expired due to Fees
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First Claim
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1. A system for monitoring the capacity of the batteries in at least one battery string, each battery comprising a pair of terminals, each battery string comprising connecting straps connecting adjacent batteries of the string, the monitoring system comprising:

  • a plurality of electrical leads, each lead being associated with and electrically connected to a battery terminal of the battery string; and

    capacity testing means associated with each battery string for testing the capacity of each battery in the associated battery string, each capacity testing means comprising;

    i) means for switching between the electrical leads for sequentially selecting the pair of electrical leads associated with the terminals of each battery;

    ii) means for measuring the internal resistance of the battery associated with each selected pair of electrical leads, said means comprising;

    a voltmeter connected between the selected pair of electrical leads for determining the voltage across the terminals of the battery associated with the leads;

    a current testing circuit for applying a load resistance across the selected terminals and for measuring the current between the selected terminals under the load resistance; and

    means for calculating the internal resistance of the selected battery from the voltage across the selected terminals and the current between the selected terminals;

    iii) means for comparing the internal resistance of each battery cell to an internal resistance threshold; and

    iv) means for triggering an alarm condition when the internal resistance of a battery exceeds the limits of the internal resistance threshold.

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