Cranking system performance indicator

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;
• 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;
• 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;
• and a predetermined maximum elapsed time interval for cranking the engine at the end of 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 sets of minimum battery voltage values as a function of battery temperature and engine temperature values, the stored set of voltage values at each combination of engine and battery temperature values representing the minimum capacity of the battery required at predetermined sample times during the elapsed time interval to achieve the minimum cranking speed at the end of the elapsed time interval at the 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 at each of the predetermined sample times;
• e. comparing the measured voltage of the battery at each of the sample times with the corresponding voltage value from the set of minimum voltage values 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.

A performance indicator for 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 an input terminal on the cranking motor through a conducting cable and a switch, the current required by the cranking motor to crank the engine increasing with decreasing temperature of the engine, the cranking system 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, comprising:

• means for storing a schedule of minimum input terminal 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 input terminal voltage produced in a cranking system capable of providing the minimum power required by the cranking motor to achieve the minimum cranking speed at the predetermined low limit operating condition;
• means for measuring the temperature of the engine;
• means for measuring the temperature of the battery;
• means for measuring the voltage at the input terminal of the cranking motor during cranking of the engine;
• means for comparing the measured voltage at the input terminal with the stored minimum input terminal voltage value corresponding to the measured engine temperature and the measured battery temperature to determine whether the measured voltage is less than the minimum input terminal voltage value;
• and
• means, responsive to the means for comparing, for indicating the condition of the cranking system, whereby the engine cranking system is tested during engine cranking to predict whether the cranking system will perform at the predetermined low limit operating condition and at temperatures greater than those corresponding to the predetermined low limit operating condition.

A performance indicator for 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;
• 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;
• 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;
• and a predetermined maximum elapsed time interval for cranking the engine at the end of which it is desired that the cranking system be capable of achieving the minimum cranking speed, comprising:
• means for storing a schedule of sets of minimum battery voltage values as a function of battery temperature and engine temperature values, the stored set of voltage values at each combination of engine and battery temperature values representing the minimum capacity of the battery required at predetermined sample times during the elapsed time interval to achieve the minimum cranking speed at the end of the elapsed time interval at the low limit operating condition;
• means for measuring the temperature of the engine;
• means for measuring the temperature of the battery;
• means for measuring the voltage of the battery during cranking of the engine at each of the predetermined sample times;
• means for comparing the measured voltage of the battery at each of the sample times with the corresponding voltage value from the set of minimum voltage values in the stored schedule corresponding to the measured battery and engine temperatures to determine whether at least one of the measured voltages is less than the corresponding minimum voltage value;
• and
• means, responsive to the means for comparing, for indicating the condition of the cranking system, 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.

In a motor vehicle cranking system having a storage battery for providing power to an input terminal of an electric cranking motor to crank an internal combustion engine during starting, in which the battery capacity decreases with decreasing battery temperature and increasing battery current, the battery current required to crank the engine increases with decreasing engine temperatures, and the engine requires a minimum cranking speed for starting, a cranking system performance indicator for testing during engine cranking whether the cranking system can achieve the minimum cranking speed at a predetermined minimum operating condition corresponding to a minimum battery temperature and engine temperature, comprising:

• means for storing a schedule of minimum input terminal 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 input terminal voltage achieved experimentally by using a battery having a capacity no greater than is necessary to achieve the minimum cranking speed at the minimum operating condition;
• means for measuring the engine temperature;
• means for measuring the battery temperature;
• means for measuring the input terminal voltage during cranking of the engine;
• means for comparing the measured voltage of the battery with the voltage value in the stored schedule corresponding to the measured engine and battery temperatures and indicating that the measured voltage is less than the stored voltage value, whereby the driver of the motor vehicle is warned that the capacity of the vehicle battery is less than the capacity necessary to achieve the minimum cranking speed at the minimum operating condition.