Battery charging method and apparatus with thermal mass equalization

• US 5,548,201 A
• Filed: 09/13/1994
• Issued: 08/20/1996
• Est. Priority Date: 09/13/1994
• Status: Expired due to Term

• Current Assignee: Unova Incorporated (Honeywell International Inc.)
• Original Assignee: Norand Corporation (Baker Hughes Company)
• Inventors: Grabon, Robert J.
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): TOATLEY, GREGORY J
• Application Number:
  US08/304,989
• Time in Patent Office: 707 Days
• Field of Search: 320/35, 320/48, 320/43
• US Class Current: 320/150
• CPC Class Codes: N/A

Abstract

A battery charging method in an environment of variable temperatures provides for a temperature correction to determine an onset of an overcharge phase which is detected by a discernible thermal energy output of a charging battery. The method comprises a precursory operation of determining time period required for effecting a temperature change in the battery in response to a temperature change of an ambient space about the battery. The temperature of the battery is then monitored throughout the charging process by measuring the temperature of the battery at timed, predetermined intervals. Over the same timed intervals the temperature of the ambience is measured. A measured difference in the temperature of the ambience with respect to a prior temperature of the ambience is applied to a measured temperature of the battery as modified by a predetermined time delay factor. The temperature is thereby corrected to reflect a change which would have occurred as a result of a temperature change of the ambient space about the battery. The corrected temperature, consequently, represents a temperature of the battery which is the result of the charging process. An apparatus for determining the onset of an overcharge phase of a battery charging cycle includes a control temperature sensor, a battery temperature sensor and a provision for determining when the battery temperature deviates from an anticipated temperature in response to a temperature change of the environment of the battery.

Claims

1. A method of charging a battery including detection of an onset of an overcharge phase of a battery charging cycle, the method comprising:

prior to charging the battery, periodically measuring the temperature of the battery with a first temperature sensor and measuring the change in temperature of the battery'"'"'s environment to determine a characteristic delay in temperature change at the battery in response to a temperature change of the environment of the battery;

as the battery is being charged, monitoring the temperature of the environment of the battery having an external temperature effect on the battery to determine temperature changes occurring in the monitored temperature of the environment;

determining an anticipated temperature change at the battery in response to the monitored temperature changes of the environment of the battery by adjusting the temperature changes determined by the temperature monitoring step for the characteristic delay in temperature at the battery;

measuring the actual temperature change at the battery with a temperature sensor;

comparing the anticipated temperature change at the battery with the actual temperature change at the battery during said monitoring intervals to determine whether the actual temperature measured at the battery is increased over the anticipated temperature change at the battery indicating an onset of an overcharge phase of the battery charging cycle; and

discontinuing charging of the battery.

2. The method according to claim 1, wherein the characteristic delay in temperature change is determined by applying a known temperature change to the environment of the battery and obtaining a sequence of periodic temperature measurements which define the characteristic delay in temperature change at the battery during an adjustment time interval.

3. The method according to claim 1, wherein the characteristic delay in temperature change is determined by applying a known temperature change to the environment of the battery and obtaining a sequence of periodic temperature measurements during an adjustment interval at a control temperature sensor and at a battery temperature sensor to determine the characteristic delay in temperature change as measured at the control temperature sensor and at the battery temperature sensor.

4. The method according to claim 1, wherein comparing the anticipated temperature change at the battery with the actual temperature change at the battery during said monitoring intervals comprises comparing the anticipated temperature at the battery with a measured s change of the temperature at the battery and wherein an onset of an overcharge phase of the battery charging method is determined to have occurred and charging of the battery is discontinued when the measured change of the temperature at the battery exceeds the anticipated temperature at the battery by a predetermined number of degrees.

5. Apparatus for determining an onset of an overcharge phase of a battery charging cycle comprising:

a control temperature sensor;

a battery temperature sensor; and

control means communicatively coupled to the control temperature sensor and to the battery temperature sensor and including means for determining a deviation of a battery temperature from an anticipated battery temperature in response to a temperature change of the environment of the battery wherein the anticipated battery temperature is determined from a pre-charging time/temperature relationship between changes in the temperature of the battery in response to changes in the temperature of the environment of the battery.

6. The apparatus according to claim 5, wherein the control means comprises a microprocessor circuit including a microprocessor device and the control temperature sensor and the battery temperature sensor are communicatively coupled through respective first and second analog to digital signal converters and through a data bus of the microprocessor circuit to communicate with the microprocessor in order to apply the time/temperature relationship to determine the deviation of the battery temperature from the anticipated battery temperature.

7. The apparatus according to claim 5, wherein the battery is embedded within a portable device powered by the battery, and the apparatus comprises part of the portable device, the control temperature sensor is disposed within and adjacent to a casing of the portable device, and the battery temperature sensor for determining the deviation of the battery temperature from the anticipated battery temperature determined from the time/temperature relationship is disposed between cells of the battery.

8. A method of charging a battery, comprising the steps of:

prior to charging the battery, using a first temperature sensor to measure the temperature of the environment of the battery and a second temperature sensor to measure the temperature of the battery to determine a time/temperature relationship between the battery'"'"'s temperature in reponse to a change in the temperature of the battery'"'"'s environment;

using said first temperature sensor to operatively obtain measurements of the temperature of the battery'"'"'s environment as the battery is being charged;

as the battery is being charged, using said second temperature sensor to operatively obtain a measurement of the battery'"'"'s temperature and determining a corresponding anticipated temperature of the battery resulting from said measurements of the temperature of the battery'"'"'s environment in combination with said time/temperature relationship; and

automatically discontinuing charging of the battery when said measurement of the battery'"'"'s temperature exceeds said corresponding anticipated temperature of the battery by a predetermined number of degrees.