JPH11339857A - Discharge control device for secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately determine a battery residual quantity at the time of an electric discharge without being conscious of the fully charged state by providing a means storing an absolute residual quantity when a battery is fully charged and a means changing the discharging efficiency at the time of the electric discharge according to the absolute residual quantity to determine the battery residual quantity. SOLUTION: This discharge control device 3 is provided with an absolute residual quantity detection section 3b detecting a battery capacity (absolute residual quantity) in the fully charged state of a fully charged secondary battery BAT and storing the absolute residual quantity in a memory 3a, for example. The absolute residual quantity detection section 3b determines charging efficiency according to the absolute residual quantity and stores the charging efficiency in the memory 3a. The discharge control device 3 is provided with a discharging efficiency set section 3c setting discharging efficiency according to the absolute residual quantity (or charging efficiency) stored in the memory 3a at the time an electric discharge. A residual quantity display section 3d calculates the discharging current quantity at the time of the electric discharge at the set discharging efficiency and the residual capacity according to the battery temperature and reports them or displays a residual quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge management device for a secondary battery, which can accurately determine the remaining amount of a secondary battery that has been fully charged in a high-temperature environment when discharging.

[0002]

[Related Background Art] In a secondary battery such as a lithium-ion battery or a nickel-metal hydride battery, charge control is performed in accordance with the environmental temperature at the time of the full charge process, so that the battery capacity to be fully charged (absolute remaining amount) Changes. For example, in a high-temperature environment, when the charging of about 80% of the battery capacity originally possessed by the secondary battery itself is completed, this is regarded as a full charge, the charging process is stopped, and further charging ( Charge control is performed to prevent deterioration of battery characteristics due to overcharging.

[0003]

By the way, the discharge management of this type of secondary battery is based on the battery capacity (relative remaining amount) in a fully charged state.
Is set to 100%, the remaining battery level is calculated in accordance with the discharge current under a certain discharge efficiency, and processing such as prompting recharging by displaying the remaining level is performed. However, when the secondary battery is charged after being charged in a high-temperature environment as described above, the actual remaining battery capacity is zero (in spite of the fact that the calculated remaining battery capacity is about 20%). 0). When this happens,
For example, a personal computer driven by the secondary battery may suddenly stop operating, causing an accident that data may be lost, and the reliability of the secondary battery may be significantly impaired.

The present invention has been made in view of such circumstances, and an object of the present invention is to accurately determine a remaining battery amount at the time of discharging a secondary battery without being concerned with a fully charged state of the secondary battery. An object of the present invention is to provide a discharge management device for a secondary battery.

[0005]

In order to achieve the above-mentioned object, a secondary battery discharge management device according to the present invention comprises means for storing an absolute remaining amount when a secondary battery is fully charged. Means for changing the discharge efficiency at the time of discharging the next battery in accordance with the absolute remaining amount to obtain the remaining battery amount.

In other words, when the discharge efficiency is changed in accordance with the absolute remaining amount of a secondary battery that has been fully charged, the relative remaining amount in a fully charged state is managed as 100% to manage the remaining amount during discharging. However, the present invention is characterized in that the remaining battery level can be accurately grasped.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a discharge management device for a secondary battery according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic configuration of a charge / discharge circuit of a secondary battery provided with a discharge management device. BAT is a secondary battery such as a lithium ion battery or a nickel hydride battery, and 1 is a constant current-constant. A charging power supply having a voltage characteristic and used for charging the secondary battery BAT, and 2 is a load, for example, a personal computer or a mobile phone, which operates using the secondary battery BAT as a power supply. The secondary battery BAT may be provided as a single battery cell (unit cell), but may be configured by combining a plurality of battery cells in series and in parallel.

Thus, the discharge management device 3 is realized, for example, as a part of a function of a fuel gauge (FG) circuit 4 which is integrated into a secondary battery BAT and constitutes a battery pack. The fuel gauge circuit 4 performs a remaining amount display function, a charge / discharge control function, a protection function, and the like for the secondary battery BAT, and is basically a current detection for detecting a charge / discharge current of the secondary battery BAT. Part 4a, the secondary battery BA
A voltage detector 4b for detecting the charging voltage of T, a temperature detector 4c for detecting the battery temperature, and the like are provided. Under the charge control by the fuel gauge circuit 4, the charging power source 1
(Full charge processing) of the secondary battery BAT is performed.

The discharge management device 3 detects the battery capacity (absolute remaining amount) of the fully charged secondary battery BAT in a fully charged state, and for example, stores the absolute remaining amount in the memory 3a. A portion 3b is provided. Note that the absolute remaining amount detection unit 3b may calculate the charging efficiency according to the absolute remaining amount and store the charging efficiency in the memory 3a. Further, the discharge management device 3 includes a secondary battery BAT.
A discharge efficiency setting unit 3c for setting the discharge efficiency according to the absolute remaining amount (or charging efficiency) stored in the memory 3b at the time of discharging. The remaining amount display unit 3d displays the secondary battery BA in accordance with the discharge current amount and the battery temperature when discharging the secondary battery BAT under the discharge efficiency set as described above.
The remaining amount of T (remaining capacity) is calculated, and this is
And the remaining amount is displayed to the battery pack user.

The function and operation of the discharge management device 3 will be described in more detail. The full charge process for the secondary battery BAT is performed by, for example, monitoring the charge voltage and integrating the charge current according to the charge time while the charge capacity is integrated. It is done in search of. At this time, charging control is executed according to the environmental temperature of the secondary battery BAT to prevent overcharging. By such charge control, for example, at room temperature as shown in FIG. 2, the charge is performed up to the maximum charge capacity of the secondary battery BAT as shown by a broken line in the figure, but in a high temperature environment, When the battery is charged to about 80% of the maximum charging capacity, it is considered that the battery has reached the fully charged state,
The charging is stopped.

On the other hand, the discharge management of the secondary battery BAT is based on the fact that the secondary battery BAT is fully charged, and based on the fact that the remaining battery charge is 100%, the remaining battery charge is reduced. It is executed while asking. In general, the battery capacity consumed by the load 2 is obtained in accordance with a discharge current amount and a battery temperature when discharging the secondary battery BAT under a predetermined discharge efficiency, and a remaining capacity of the secondary battery BAT at that time is obtained. The discharge management is performed by calculating what percentage the amount (remaining capacity) is. Therefore, in this case, when the full charge process is performed in a high-temperature environment as described above, the absolute capacity itself is small, and therefore, for example, as shown by a broken line in the drawing, the remaining battery capacity is 20%
Despite being recognized as being on the order, the actual remaining battery level may be zero (0).

Therefore, in the discharge management device 3 according to the present invention, the absolute remaining amount (or charging efficiency) of the fully charged secondary battery BAT in the fully charged state is stored in the memory 3a, and the absolute remaining amount is stored. (Or charging efficiency), the discharging efficiency at the time of discharging is variably set. Specifically, as shown in FIG. 2, when the absolute remaining amount at the time of full charge is low, the discharge capacity is set to a high value to increase the consumption capacity required for the discharge current. It is exactly what you want. In other words, as shown by the area of the shaded region in FIG. 2, the discharge efficiency is set so that the capacity A charged by the full charge process and the capacity B consumed by the discharge become equal. It has become.

According to the discharge management apparatus thus configured, regardless of the temperature environment in which the full charge process is performed on the secondary battery BAT, the absolute remaining battery capacity in the full charge state Since the discharge efficiency is set in accordance with the following equation, even when the discharge of the secondary battery BAT is managed under the relative remaining amount where the fully charged state is 100%, it is necessary to accurately grasp the remaining amount. Can be. Therefore, it is possible to effectively avoid such a problem that the actual battery capacity is zero (0) even though it is determined that the relative remaining amount is about 20%.

In particular, even when the charging process of the secondary battery BAT is performed in a high-temperature environment, when the secondary battery BAT is used (during discharge), there is usually no way to know its charging status. However, since the recharge time of the secondary battery BAT can only be managed based on the relative remaining amount indicated by the remaining amount, the present apparatus in which the remaining amount of the battery is obtained under the variably set discharge efficiency as described above. According to this, the use of the secondary battery BAT can be effectively managed, and the reliability of the secondary battery BAT can be sufficiently improved.

The present invention is not limited to the above embodiment. For example, the secondary battery BAT is provided only with a memory function for storing the absolute remaining amount at the time of the full charge process, and in the discharge management device provided on the load 2 side to which the secondary battery BAT is attached, May be read and the discharge efficiency is variably set to manage the remaining battery level. In addition, the present invention can be variously modified and implemented without departing from the gist thereof.

[0017]

As described above, according to the present invention, the absolute remaining amount when the secondary battery is fully charged is stored,
Since the discharge efficiency at the time of discharging the secondary battery is changed in accordance with the absolute remaining amount to obtain the remaining amount of the battery, the remaining amount of the battery can be accurately determined regardless of the temperature environment at the time of charging the secondary battery. And accurate discharge management is possible. In particular, even when the relative remaining amount in the fully charged state is set to 100% and the remaining amount at the time of discharging is centrally managed, the remaining amount of the battery can be accurately grasped, and the reliability of the secondary battery is sufficiently improved. The effect of being able to secure it is exhibited.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of a charge / discharge circuit including a discharge management device for a secondary battery according to an embodiment of the present invention.

FIG. 2 is a diagram conceptually showing functions and operations of a discharge management device according to the present invention.

[Explanation of symbols]

 BAT Secondary battery 1 Charging device 2 Load 3 Discharge management device 3a Memory 3b Absolute remaining amount detection unit 3c Discharge efficiency setting unit 3d Remaining amount display unit 4 Fuel gauge circuit

Claims (1)

[Claims] 1. A means for storing an absolute remaining amount when a secondary battery is fully charged, and changing a discharge efficiency at the time of discharging the secondary battery in accordance with the absolute remaining amount to change the battery remaining amount. A discharge management device for a secondary battery, comprising: