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Vehicle battery discharging indicator

  • US 4,803,417 A
  • Filed: 12/22/1986
  • Issued: 02/07/1989
  • Est. Priority Date: 12/22/1986
  • Status: Expired due to Fees
First Claim
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1. In a motor vehicle powered by an internal combustion engine including a storage battery having an open-circuit emf dependent upon battery conditions, an electrical load, and a unidirectional current source supplying current to the parallel combination of the battery and the load, the current source normally providing sufficient current to the battery and the load to impress upon the battery a voltage greater than the open-circuit emf of the battery thereby causing the battery to charge, wherein the battery discharges when the voltage impressed upon the battery is below the open-circuit emf of the battery, a method of indicating when the battery is discharging, comprising the steps of:

  • a. measuring a first voltage of the battery before cranking the engine each time the engine is started;

    b. storing the first voltage as a reference voltage value, the reference voltage value representing the open-circuit emf of the battery compensated for the battery conditions existing when the first voltage is measured;

    c. measuring a second voltage of the battery after the engine is started, the second voltage having a value less than the open-circuit emf of the battery when the battery is discharging;

    d. comparing the second voltage with the stored reference voltage value; and

    e. indicating that the battery is discharging when the second voltage is less than the reference voltage value.

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