JP3729532B2 - Secondary battery charging control method - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a charge control method for a secondary battery, and more particularly, to a charge control method capable of preventing insufficient charging due to malfunction when a low temperature secondary battery is charged at room temperature by temperature differential control.
[0002]
[Prior art]
Secondary batteries, such as nickel-hydrogen secondary batteries or nickel-cadmium secondary batteries, have been widely put into practical use as operating power sources for various equipment systems such as mobile phones and portable imaging devices. Yes. That is, since the secondary battery can repeatedly operate driving (discharging) the load by securing or storing power by charging operation and using the secured or stored power as a power source, various power sources can be used repeatedly. It is incorporated into the equipment system and used.
[0003]
By the way, charging and discharging are the main functions of the secondary battery in any case. Also, from the viewpoint of safety, the charging start voltage and the discharging start voltage are set as limits, and charging and discharging are performed at voltages within the limit range.
[0004]
Furthermore, in order to charge the secondary battery in a short time, the quick charging method using a constant current is performed in order to complete (end) the charging. The end of the charging is, for example, a temperature differential control method in which a temperature change (temperature differential value) per unit time of the battery to be charged is detected and determined / determined based on whether or not the temperature change has reached a predetermined value. Has been done. For example, when a secondary battery and a charger are used at the same temperature as in a desk cordless telephone used indoors, the temperature of the secondary battery is at least equal to the ambient temperature. The temperature rise caused by the heat generated by the secondary battery itself can be accurately detected, and thus temperature differential control can be sufficiently performed.
[0005]
[Problems to be solved by the invention]
However, when used outdoors such as a portable telephone, a secondary battery that has been cooled by use in a cold place outdoors may be brought into a warm room and charged immediately. In this case, the recharged secondary battery is warmed by the room temperature in addition to the temperature rise due to heat due to charging, temperature differential control is activated before the completion of constant current charging, and it is charged before full charge (uncharged) There is a problem that the work ends. That is, the secondary battery is often used as a power source without sufficiently maintaining a predetermined charging capacity. The use in the state of insufficient charging means that, for example, when used as a driving power source for a portable telephone, the driving time may be shortened, or the function as a portable telephone may be reduced or the function may be lost. It will raise a serious problem.
[0006]
The present invention has been made in response to the above circumstances, and even when the temperature of the secondary battery as the charged object is lower than the temperature of the charger and the room / place to be charged, the battery can always be fully charged. It aims at providing the charge control method of a secondary battery.
[0007]
[Means for Solving the Problems]
In the first aspect of the present invention, the secondary battery is rapidly charged with a constant current, a full charge is detected by a temperature change (temperature differential value) per unit time of the battery temperature as the charging progresses, and charging is stopped or charging is terminated. Charge control method for a secondary battery, and the temperature change per unit time (temperature differential value) of the battery temperature during preliminary charging with a current lower than the constant current / rapid charge current is a preset temperature differential The charging control method is characterized by shifting to constant current / rapid charging when the value becomes smaller than the value.
[0008]
According to a second aspect of the present invention, in the charge control method according to the first aspect, when the temperature of the battery to be charged is lower than the ambient temperature of the charger to be charged at the start of the preliminary charging, a predetermined time is passed after shifting to constant current / rapid charging. Inside, the temperature change per unit time (temperature differential value) value of the battery temperature for detecting full charge is set as a third temperature differential value that is larger than the preset second temperature differential value, After the certain time, the temperature change (temperature differential value) value per unit time of the battery temperature for detecting the full charge is set as the second temperature differential value, and the battery temperature to be charged is charged at the start of precharging. When the temperature is the same as the ambient temperature of the charger, the temperature change (temperature differential value) value per unit time of the battery temperature for detecting the full charge is determined after the transition to the constant current / rapid charge. As temperature differential value, You and detecting the charge.
[0011]
[Action]
In the charging control method according to the present invention, when the temperature of the battery to be charged is lower than the ambient temperature of the charger, the preliminary charging is performed at a current lower than the rapid charging current, and the influence of the ambient temperature is avoided at the initial stage of charging. Control malfunction is easily prevented. That is, in the preliminary charging, when the temperature change per unit time of the battery to be charged becomes smaller than a certain value, a method of shifting to rapid charging with a constant current is adopted. More specifically, within a certain period of time at the beginning of charging, the charged secondary battery is warmed to the ambient temperature at which the charging operation is performed by preliminary charging, and the temperature differential value at the end of charging greatly changes due to the influence of the ambient temperature. It avoids and prevents the malfunction that the charging ends when the full charge is not achieved. On the other hand, after a certain period of time, the secondary battery temperature to be charged is almost equal to the temperature around the charger (ambient), so at this point in time, a full charge can be detected using the temperature differential value. Optimal charge control is easily performed.
[0012]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to FIGS.
[0013]
FIG. 1 is a circuit block diagram showing a configuration example of a charger used for carrying out a secondary battery charge control method according to the present invention. Here, reference numeral 1 denotes a charger, which has a configuration including an input power source 1a, a constant current control circuit 1b, a charge voltage measurement means and a charge control circuit 1c incorporating a computing unit (CPU), and a constant voltage application means 1d. Yes. Reference numeral 2 denotes a secondary battery pack, a secondary battery for charging (for example, a nickel-hydrogen secondary battery) 2a to which the output of the constant current control circuit 1b of the charger 1 is applied, and the secondary battery pack. A structure is provided that includes a temperature detection sensor 2b that is disposed in the vicinity of the secondary battery 2a, detects the temperature at the time of charging the secondary battery 2a, and inputs the detected temperature information to the charge control circuit 1c of the charger 1. ing.
[0014]
The temperature detection sensor 2b of the secondary battery pack 2 is inputted to the charge control circuit 1c as a divided voltage value with respect to the constant current applying means 1d of the charger 1. The charge control circuit 1c controls the output of the constant current control circuit 1b based on the battery temperature signal from the temperature detection sensor 2b. The charge control circuit 1c outputs a command to switch from preliminary charge to quick charge and to end quick charge. To do.
[0015]
In other words, the above configuration has a charger main body portion that rapidly charges the secondary battery 2a with a constant current, and a temperature change (temperature differential value) per unit time for the battery 2a to be charged as charging progresses by the charger main body portion. A temperature detection unit 2b to measure and calculate, a charge detector (built in the charge control circuit unit 1c) that detects full charge based on a temperature change measured and calculated by the temperature detection unit 2b, and determines whether to stop charging or end charging; The temperature of the battery 2a to be charged is measured and compared with the temperature around the charger main body, and the temperature of the battery to be charged is determined by the comparison / determination by the temperature comparator. A first charge switching device (built in the charge control circuit unit 1c) that performs preliminary charging at a current lower than the constant current / quick charging current when the temperature is lower than the ambient temperature of the charger body, and a battery to be charged in the preliminary charging Per unit time The charging device includes a second charge switching device (built in the charge control circuit unit 1c) that switches to and shifts to constant current / rapid charging when the temperature change of the two becomes smaller than a predetermined value.
[0016]
Next, an embodiment in which the charging control of the secondary battery is performed by the charger having the circuit configuration shown in FIG. 1 will be described with reference to the flowchart shown in FIG. 2 and the charging temperature-charging time shown in FIGS. 3 (a) and 3 (b). This will be described with reference to the relationship diagram.
[0017]
First, a secondary battery pack 2 is attached and connected to the charger 1 as a battery to be charged, and a predetermined low constant current is supplied to the secondary battery 2a to be charged via the constant current control circuit 1b for precharging. Start.
[0018]
As shown in FIG. 2, when the preliminary charging is started, the charger 1 first checks the voltage of the battery to be charged 2a, and if the voltage of the battery to be charged 2a is outside the allowable range, treats it as an abnormal battery. On the other hand, if the temperature of the rechargeable battery 2a is within the permissible range, the temperature of the rechargeable battery 2a is checked. If the temperature of the rechargeable battery 2a is outside the permissible range, the temperature is treated as abnormal. After the measurement, the first temperature differential value is measured.
[0019]
When the temperature differential value at the first time satisfies dT / dt <δs−α, tg = 0 is set, and when not satisfied, the voltage check of the charged battery 2a is returned. Here, when tg = 0 is set, the battery pack 2 and the charger 1 are used in an environment having the same ambient temperature. On the other hand, when returning to the voltage check of the charged battery 2a, the temperature of the battery pack 2 is lower than the ambient temperature. In the measurement of the temperature differential value, the time tg for changing the temperature differential value after the start of the rapid charge is set to 0, and the rapid charge start is started. Further, when returning to the voltage check of the battery 2a to be charged, the voltage check, the temperature check of the battery 2a to be charged, and the measurement of the count n = 1 are passed again, but 2 in the measurement of the count n = 1. Since this is the second time, the second temperature differential value is shifted to measurement. In this second temperature differential value measurement, whether or not the temperature differential value satisfies dT / dt <δs−α is checked. If not, the temperature check of the charged battery 2a is performed again and the same operation is repeated. However, if satisfied, the time tg for changing the temperature differential value after the start of the rapid charge is set to ta, and the rapid charge start is started. Here, the start of rapid charging starts when the temperature of the battery 2a to be charged is lower than the ambient temperature.Therefore, the temperature differential value dT / dt is detected early in the early stage of rapid charging so that no malfunction occurs. The time tg = ta is set by increasing the setting of the differential value dT / dt, and the rapid charging starts.
[0020]
While the quick charge is started, a quick charge protection timer that determines the maximum time during which quick charge is possible is started to determine whether the timer is out or not. If the timer is out, the quick charge is completed and terminated. If the timer is not out, the voltage of the charged battery 2a is checked. If the voltage is abnormal, the battery abnormality process is performed. If the voltage is normal, the temperature of the charged battery 2a is checked. Here, if the temperature is abnormal, processing as a temperature abnormality is performed. If the temperature is normal, the preset quick charging time tg is checked. If tg = 0, the temperature differential value dT / dt ≧ δ s is checked. If tg = ta, the temperature differential value dT / dt ≧ δ s + β is checked. If the temperature differential value dT / dt ≧ δ s and the temperature differential value dT / dt ≧ δ s + β are checked, rapid charging is completed (terminated) if satisfied. Go back and repeat the same operation until you get a satisfactory result.
[0021]
FIG. 3 (a) shows the change in the temperature of the battery 2a and the change in the battery voltage when the battery pack 2 is rapidly charged when the temperature of the battery pack 2 is lower than the ambient temperature. is there. In this charging operation, the temperature differential value dT / dt <δs-α is detected at the point A in the figure, and the process proceeds to rapid charging. The temperature differential value is still affected by the ambient temperature within the time ta at the initial stage of rapid charging. Therefore, the temperature differential value is set to dT / dt <δ s + β to prevent malfunction. In addition, after the time ta, when the influence of the ambient temperature disappears, the temperature differential value is set to dT / dt <δ s , and switching to low current charging (transition) is performed at the point B in the figure. The quick charging is completed.
[0022]
FIG. 3 (b) shows the change in the temperature of the battery 2a and the change in the battery voltage when the battery pack 2 is rapidly charged when the temperature of the battery pack 2 is the same as the ambient temperature. is there. In the charging operation, to detect the temperature differential value dT / dt <δs -α from the beginning at the pre-charging, the quick charge because it is tg = 0, the temperature differential value dT / dt ≧ δ s detected by the point C The quick charge is completed.
[0023]
【The invention's effect】
As can be seen from the description of the embodiments, according to the charging control method and the charging device according to the present invention, when the charging control is performed using the temperature differential value in the temperature rise accompanying the charging of the charged battery, The required charging can be appropriately performed without being influenced by the temperature at the initial stage of charging. That is, when the temperature of the battery to be charged is lower than the environmental temperature at the time of charging, first, charging is performed at a low current until the temperature of the battery to be charged becomes equal to the environmental temperature. After that, it can be switched to regular quick charging, so it is easy to avoid the malfunction of completing the charging operation in the state before full charging, and the trouble of short talk time that becomes a problem with mobile phones etc. is completely eliminated Will be.
[Brief description of the drawings]
FIG. 1 is a circuit block diagram showing a configuration example of a main part of a charge control device for a secondary battery according to the present invention.
FIG. 2 is a flowchart for explaining an exemplary embodiment of a charging control method for a secondary battery according to the present invention.
FIG. 3 shows an example of the relationship between the charging time and the temperature, voltage, and ambient temperature of the battery to be charged in the secondary battery charging control method according to the present invention. (A) The battery temperature is lower than the ambient temperature. (B) is a characteristic diagram when the battery temperature is almost equal to the ambient temperature.
[Explanation of symbols]
1 ... Charger
1a ……… Input power
1b ……… Constant current control circuit
1c ……… Charge control circuit
1d ......... Low voltage application means 2 ......... Battery pack
2a ……… Secondary battery
2b ……… Temperature sensor

Claims (2)

Charge control of the secondary battery that quickly charges the secondary battery at a constant current, detects full charge based on the temperature change (temperature differential value) per unit time of the battery temperature, and stops charging or terminates charging. A method,
When the temperature change per unit time (temperature differential value) of the battery temperature during pre-charging at a current lower than the constant current / rapid charge current becomes smaller than the preset temperature differential value, the constant current / rapid Charge control method characterized by shifting to charge. The charge control method according to claim 1,
When the temperature of the battery to be charged is lower than the ambient temperature of the charger to be charged at the start of preliminary charging, the battery temperature per unit time for detecting the full charge is within a certain period of time after shifting to constant current / rapid charging. The temperature change (temperature differential value) value is a third temperature differential value larger than a preset second temperature differential value, and the unit of battery temperature for detecting the full charge after the predetermined time The temperature change (temperature differential value) value per time is the second temperature differential value,
When the temperature of the battery to be charged at the start of preliminary charging is the same as the ambient temperature of the charger to be charged, the temperature change per unit time of the battery temperature for detecting the full charge after the transition to the constant current / rapid charging ( A charge control method, wherein full charge is detected by using a temperature differential value) value as the second temperature differential value.

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