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Cranking system performance indicator

  • US 4,731,601 A
  • Filed: 12/08/1986
  • Issued: 03/15/1988
  • Est. Priority Date: 12/08/1986
  • Status: Expired due to Term
First Claim
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1. In a cranking system including an internal combustion engine requiring a minimum cranking speed for starting, a storage battery having a capacity that decreases with decreasing battery temperature and increasing current load on the battery, and an electric cranking motor drivingly engaged with the engine when current is supplied from the battery to the cranking motor, the current required by the cranking motor to crank the engine increasing with decreasing temperature of the engine, and further including a predetermined low limit operating condition corresponding to a minimum battery and engine temperature at which it is desired that the cranking system be capable of achieving the minimum cranking speed, a method of testing the cranking system during engine cranking, comprising the steps of:

  • a. storing a schedule of minimum battery voltage values as a function of battery temperature and engine temperature values, the stored value at each combination of engine and battery temperature values representing the minimum capacity of the battery required to achieve the minimum cranking speed at the predetermined low limit operating condition;

    b. measuring the temperature of the engine;

    c. measuring the temperature of the battery;

    d. measuring the voltage of the battery during cranking of the engine;

    e. comparing the measured voltage of the battery with the voltage value in the stored schedule corresponding to the measured battery and engine temperatures; and

    f. indicating the condition of the cranking system based upon the comparing step, whereby the indication represents a forewarning of an impending failure of the cranking system to achieve the minimum cranking speed at the predetermined low limit operating condition.

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