JP4252024B2 - Rechargeable battery charging method - Google Patents

Description

  The present invention relates to a method for charging a secondary battery.

Conventional charging methods for secondary batteries are disclosed in the following patent documents. In this publication, it is determined whether or not the temperature rise gradient is steeper than the set gradient, in other words, whether or not the battery temperature rise value at a predetermined time is equal to or higher than the set temperature rise value. Detected.
No. 7-33564

  For example, a portable device such as a notebook personal computer having a built-in rechargeable secondary battery pack is charged as follows. When using a portable device while AC commercial power is being supplied from an outlet, if the battery capacity is a predetermined capacity (for example, 95% of the full charge capacity) or less, the battery can be used while continuing to use the portable device. Is charged with a small current.

  Even when the power switch of the portable device is off (= power off), if AC commercial power is supplied from the outlet, a control circuit incorporating a microcomputer is operating so that predetermined control can be performed. For this reason, charging is started when the battery capacity is equal to or less than a predetermined capacity (for example, 95% of the full charge capacity) while the power is off. Such charging when the power is off is performed with a large current. Since there is a limit to the total power supply capacity (actually, the power supply capacity of the AC / DC conversion adapter) that can be used in the mobile device, the charging current used by the mobile device is set to a small current.

  Here, the present applicant has tested the detection of full charge due to the temperature rise gradient, which is the above-described conventional example, in such a portable device, and found the following problems.

  When charging with a large current when the power is off, a full charge can be detected by comparing the temperature rise gradient with the set gradient, but in charging with a small current while using the portable device, It was discovered that full charge could not be detected because of such a small temperature rise gradient.

  The present invention has been made to solve such problems, and an object thereof is to appropriately control charging by comparing a temperature rise gradient with a set gradient.

  A charging method for a secondary battery according to the present invention is a charging method for controlling charging by determining whether a temperature rise value of the battery at a predetermined time is equal to or higher than a set temperature rise value, and according to a charging current. Then, the set temperature rise value is changed.

  Further, the secondary battery charging method of the present invention is a first temperature comparison for determining whether or not the temperature rise value of the battery at a predetermined time is equal to or higher than a first set temperature rise value when charging the secondary battery. A current comparison step of detecting a charging current and comparing it with a predetermined current value if the step is less than the first set temperature rise value, and the charging current detected in the step is the predetermined current value The second temperature comparison step for determining whether the temperature rise value of the battery at a predetermined time is equal to or higher than a second set temperature rise value, and the first set temperature rise per unit time The value is larger than the second set temperature rise value per unit time. If the battery temperature rise value is equal to or higher than the first set temperature rise value in the first temperature comparison step, the charging is controlled, The temperature rise value of the battery in the two temperature comparison step is the second set temperature. For more Noborichi, and controlling the charging. Furthermore, the predetermined time in the first temperature comparison step is shorter than the predetermined time in the second temperature comparison step.

  Furthermore, the charging method of the secondary battery of the present invention is a charging method for controlling charging by determining whether the temperature rise gradient of the secondary battery is steeper than the set gradient, and depending on the charging current, The setting gradient is changed.

  In the present invention, a charging method for controlling charging by determining whether or not a temperature rise value of the battery at a predetermined time is equal to or higher than a set temperature rise value, wherein the set temperature rise value is determined according to a charging current. To change. When the charge current value is small, the battery temperature rise value is compared with a small set temperature rise value, so the large set temperature rise value adopted when the charge current value is large cannot be detected with a small battery set temperature rise value. Therefore, charging can be controlled appropriately.

  In the present invention, it is a charging method for controlling charging by determining whether or not the temperature rise gradient of the secondary battery is steeper than the set gradient, and the set gradient is changed according to the charging current. When the charging current value is small, the temperature rise gradient of the battery is compared with a small setting gradient. Therefore, it is possible to detect a temperature gradient of a small battery that cannot be detected with a large setting gradient adopted when the charging current value is large. Therefore, charging can be controlled appropriately.

  Embodiments of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, the present embodiment includes a battery pack A and a portable device PC including a power source for charging the battery pack A. The portable device PC is a portable personal computer such as a notebook computer. The battery pack A usually has a structure that is detachably attached to the portable device PC. The portable device PC is supplied with DC power output from an adapter (not shown) that converts AC commercial power from an outlet into DC power, and a power circuit S that includes a microcomputer for controlling and supplying this power is provided. I have. Moreover, the control element 7 which consists of a switching transistor etc. which on / off-control the charging / discharging electric current of the battery pack A is provided.

  In the battery pack A, a secondary battery 1 such as a nickel metal hydride battery, a current detection unit 2 comprising a resistor or the like for detecting current during charging / discharging of the battery 1, and a microprocessor for monitoring and controlling charging / discharging of the battery 1 Unit (hereinafter referred to as MPU). Further, in the battery pack A, a temperature detection unit 3 including a thermistor disposed in close contact with the battery 1 (10 series connection of nickel-metal hydride batteries, capacity 3.6 AH) is provided.

  In the MPU, the battery voltage (measurement point d), the output from the current detection unit 2, and the analog voltage output from the temperature detection unit 3 are input, converted into digital values, and the actual voltage [mV] or actual current value [mA] An A / D conversion unit 4 is provided for converting to. Then, the output from the A / D conversion unit 5 is input to the charge control unit 5, where calculation, comparison, determination, and the like are performed, and a control element in the portable device PC is obtained by a signal from the charge control unit 5. 7 is turned on and off. Using the well-known technique, the charge control unit 5 calculates the remaining capacity by integrating the charge / discharge current. It is also possible to detect full charge of the battery 1 with this calculated remaining capacity.

  The power supply circuit S of the portable device PC operates as follows. When using the portable device PC while DC power is supplied from the adapter, if the capacity of the battery 1 is less than a predetermined capacity (for example, 95% of the full charge capacity), the use of the portable device is continued. The battery 1 is charged with a constant current of a small current (for example, 1A, about 0.3C).

  When the power switch of the portable device is off (= power off) and the DC power is supplied from the adapter, the power supply circuit S is operating so that predetermined control can be performed. For this reason, when the battery capacity is less than a predetermined capacity (for example, 95% with respect to the full charge capacity) while the power is turned off, charging is started. When the power is turned off, the battery is charged with a constant current of a large current (for example, 2A, about 0.6C).

  The charge control unit 5 detects the full charge by performing the following control. It is determined whether or not the temperature rise value of the battery 1 in the first predetermined time (= 1 minute, 30 seconds to 2 minutes is possible) is equal to or higher than the first set temperature rise value (for example, 1 ° C./1 minute), If this value is exceeded, charging is controlled as full charge. If it is less than this value, the charging current is detected and compared with a predetermined current value (for example, 1.5 A). When the current value is lower than the predetermined current value, the temperature increase value of the battery 1 in the second predetermined time (= 10 minutes, even 5 minutes to 20 minutes is possible) becomes the second set temperature increase value (for example, 5 ° C./10 minutes). ) Whether or not is greater than or equal to this value. If greater than or equal to this value, charge is controlled as full charge. Here, the first set temperature rise value per unit time is 1 ° C./1 minute, the second set temperature rise value per unit time is 0.5 ° C./1 minute, and the first set temperature rise value per unit time is 1 The set temperature rise value is larger.

  FIG. 2 shows changes in current, battery temperature, and voltage with respect to time when the battery 1 is charged in this embodiment. With respect to the current (Current), the battery temperature (Temperature), and the voltage (Voltage), the line A shows the charging characteristics at a large current when the power is off. The unit of time on the horizontal axis is hour: minute: second. For example, a scale of 1:20:00 represents 1 hour, 20 minutes, and 0 seconds. The battery of the line A shows a case where the battery 1 in an almost empty state is charged. The first time at the battery temperature at the first predetermined time (= 1 minute) is about 1 hour and 40 minutes after the start of charging. A temperature rise value equal to or higher than a set temperature rise value (1 ° C./1 minute) is detected, full charge is detected, and charging is controlled.

  A line B indicates a case where the battery 1 is charged with a constant current of a small current (for example, 1 A) while continuing to use the portable device PC, and the battery 1 is charged by the charge control unit 5 of the battery pack A. Is less than a predetermined capacity (for example, 95% of the full charge capacity), charging is started. After confirming that the small current has continued for 20 minutes or more from the start of charging, the temperature rise value over the second set temperature rise value (5 ° C / 10 minutes) at the second predetermined time (= 10 minutes) It detects and detects full charge and controls charging.

  Here, in this embodiment, the full charge is detected by detecting the temperature rise of the line B based on the second set temperature rise value per unit time smaller than the first set temperature rise value per unit time. Yes. Here, if only the first set temperature rise value is detected, the temperature rise of the line B cannot be detected, and the battery 1 is overcharged. In line A, since the current is 1.5 A or more as described in the next flow, full charge is not detected at the second set temperature.

  The second predetermined time is 10 minutes and the first predetermined time is 1 minute. The temperature increase due to instability within a short time can be deleted and the total temperature increase after 10 minutes can be detected. This is because charging with a small current requires a long time because the temperature rise value is small.

  In addition, about the control after full charge detection, you may stop charge, you may perform trickle charge by a constant current, and supplementary charge by a pulse.

  Next, the charging method of the present embodiment will be described for each step using the flowchart of FIG. First, the charging control unit 5 detects that the battery capacity is less than 95% and starts charging. In step 1 (step is denoted as S in the figure), the current detection unit 2 reads the charging current. With respect to this charging current value, as described above, the battery 1 is charged with a constant current of a small current (for example, 1 A) when the portable device PC is used under the control of the power supply circuit S of the portable device PC. When the portable device PC is turned off, it is charged with a constant current of a large current (for example, 2 A). Such control of the power supply circuit S of the portable device PC is general control, and for the portable device PC adopting such control, the charging current value is obtained by using the MPU of this embodiment. Therefore, the MPU and battery pack A of this embodiment are highly versatile.

  In step 2, the battery temperature is read by the temperature detector 3, and in step 3, the battery temperature digitally converted by the A / D converter 4 is calculated in the charging controller 5 as a temperature rise value with respect to time.

  Next, in step 4, it is determined whether the temperature rise is 1 ° C./1 minute or more. In step 4, the determination is made regardless of the magnitude of the charging current. This is because even when charging with a small current, the temperature rise may be 1 ° C./1 minute or more during overcharging. If the temperature rise is 1 ° C./1 minute or more, it is determined in step 5 that the battery is fully charged, and the charge controller 5 turns off the control element 7 to stop charging or perform supplementary charging.

  If the temperature rise is less than 1 ° C./1 minute in step 4, the charge current value read in step 1 is less than 1.5 A (ie, small current) in step 6, and continues for 20 minutes or more continuously. Determine if you did. If NO at step 4, the process returns to step 1.

  Here, it is as follows whether it is determined whether it continued continuously for 20 minutes or more. If the portable device PC is used immediately after charging with a large current, it is charged with a small current under the control of the power supply circuit S of the portable device PC. In this case, since the battery was charged with a large current until immediately before, the temperature increase was large due to the influence, and even with a small current, the temperature increase was 5 ° C./10 minutes or more, and full charge may be erroneously detected. Therefore, in such a case, the small current state is set to less than 20 minutes in step 6, and the process returns to step 1 and full charge is determined in step 4.

  In step 7, it is determined whether or not the temperature rise value is 5 ° C./10 minutes or more. In this determination, although some batteries 1 can be fully charged when the temperature rise value is 1 ° C./1 min or more with small current charging, many batteries 1 have a small temperature rise value and a temperature rise value. In this step 7, a temperature increase value of 5 ° C./10 minutes or more is detected without detecting 1 ° C./1 minute or more. If the temperature rise value is 5 ° C./10 minutes or more, charging is stopped in step 5 or supplementary charging is performed. If the temperature rise value is less than 5 ° C./10 minutes, return to Step 1.

  In addition, it is determined whether the temperature rise value of the battery at a predetermined time is equal to or higher than the set temperature rise value. Instead, whether the temperature rise gradient of the secondary battery is steeper than the set gradient. You may determine whether.

  In this embodiment, it is determined whether or not the temperature rise value of the battery at a predetermined time is equal to or higher than the set temperature rise value. Instead, the time required for charging per unit temperature change is detected. Then, the detected time may be compared with the previous detection time to determine whether or not the temperature increase gradient is steeper than the set gradient.

It is a circuit block diagram of the battery pack of the present invention. It is a graph which shows the Example of this invention. It is a flowchart which shows the Example of this invention.

Explanation of symbols

A Battery pack MPU Microprocessor unit PC Mobile device 1 Battery

Claims (3)

When charging the secondary battery, a first temperature comparison step for determining whether the temperature rise value of the battery at a predetermined time is equal to or higher than a first set temperature rise value;
If the step is less than the first set temperature rise value, a current comparison step of detecting a charging current and comparing it with a predetermined current value;
When the case where the charging current detected in the step is lower than the predetermined current value continues, it is determined whether the temperature increase value of the battery at a predetermined time is equal to or higher than a second set temperature increase value. And a second temperature comparison step.
When the case where the charging current detected in the step is lower than the predetermined current value is not continued, the determination is performed in the first temperature comparison step,
The first set temperature rise value per unit time is larger than the second set temperature rise value per unit time,
If the temperature rise value of the battery in the first temperature comparison step is greater than or equal to the first set temperature rise value, control charging,
When the temperature rise value of the battery is equal to or higher than the second set temperature rise value in the second temperature comparison step, the charging is controlled ,
The method for charging a secondary battery, characterized in that the duration of time when the current is lower than the predetermined current value is longer than a set time .   When charging the secondary battery, a first temperature comparison step for determining whether the temperature rise value of the battery at a predetermined time is equal to or higher than a first set temperature rise value;
  If the step is less than the first set temperature rise value, a current comparison step of detecting a charging current and comparing it with a predetermined current value;
  When the case where the charging current detected in the step is lower than the predetermined current value continues, it is determined whether the temperature increase value of the battery at a predetermined time is equal to or higher than a second set temperature increase value. And a second temperature comparison step.
  When the case where the charging current detected in the step is lower than the predetermined current value is not continued, the determination is performed in the first temperature comparison step,
The first set temperature rise value per unit time is larger than the second set temperature rise value per unit time,
  If the temperature rise value of the battery in the first temperature comparison step is greater than or equal to the first set temperature rise value, control charging,
  When the temperature rise value of the battery is equal to or higher than the second set temperature rise value in the second temperature comparison step, the charging is controlled,
The duration of time when the current is lower than the predetermined current value is 20 minutes or more.
A method for charging a secondary battery. 3. The method of charging a secondary battery according to claim 1, wherein the predetermined time in the first temperature comparison step is shorter than the predetermined time in the second temperature comparison step.

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