JP4802414B2 - Battery remaining capacity meter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for detecting the remaining capacity of a battery.
[0002]
[Prior art]
An apparatus for detecting the remaining capacity of a battery is known (see, for example, Japanese Patent Laid-Open No. 06-174808). Since the capacity of the battery depends on the temperature of the battery, this apparatus detects the temperature of the battery and corrects the remaining capacity.
[0003]
[Problems to be solved by the invention]
However, in the above-described conventional battery remaining capacity meter, the remaining capacity is corrected by detecting the battery temperature. Therefore, when the battery temperature rises due to discharge, the remaining capacity is corrected and increased more than necessary. There is a problem that the remaining capacity cannot be detected.
[0004]
An object of the present invention is to accurately detect the remaining capacity of a battery.
[0005]
[Means for Solving the Problems]
(1) The invention of claim 1 is applied to a battery remaining capacity meter that repeatedly calculates the remaining capacity of the battery, corrects the remaining capacity by detecting the temperature of the battery, and calculates the discharge capacity of the battery. And a temperature rise rate calculating means for calculating a rate of increase of the battery temperature with respect to the battery discharge capacity, and determining whether the battery temperature rise is a temperature rise due to the discharge based on the temperature rise rate with respect to the battery discharge capacity. If the battery temperature increase is determined to be a temperature increase due to discharge, the lesser of the previous calculated value and the current calculated value of the remaining capacity is displayed as the calculated calculated remaining capacity value. Control means.
(2) The invention of claim 2 is applied to a battery remaining capacity meter that repeatedly calculates the remaining capacity of the battery, detects the temperature of the battery, and corrects the remaining capacity, and based on the voltage and current of the battery, Dischargeable output calculation means that repeatedly calculates the maximum dischargeable output, and if the current calculated value of the battery's maximum dischargeable output is not lower than the previous calculated value, the previous remaining capacity calculated value is the current remaining capacity Control means for displaying as a calculated value.
(3) The invention of claim 3 is applied to a battery remaining capacity meter that repeatedly calculates the remaining capacity of the battery, detects the temperature of the battery and corrects the remaining capacity, and based on the voltage and current of the battery, Internal resistance calculation means for calculating internal resistance, and control that displays the previous remaining capacity calculation value as the current remaining capacity calculation value when the current calculation value of the battery internal resistance is lower than the previous calculation value Means.
[0006]
【The invention's effect】
(1) According to the invention of claim 1, even if the temperature of the battery rises due to discharge, the remaining capacity is not unnecessarily corrected and increased, and the remaining capacity can be detected accurately.
(2) According to the invention of claim 2 and claim 3, in addition to the effect of claim 1, it is possible to detect the temperature rise inside the battery earlier than the temperature detector detects the temperature outside the battery. The remaining capacity can be accurately detected from a state where the remaining capacity is large. Furthermore, the calculation accuracy of the remaining capacity at a low temperature is improved as compared with the conventional apparatus.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
<< First Embodiment of the Invention >>
FIG. 1 shows the configuration of the first embodiment. In the assembled battery 1, for example, a plurality of single cells (cells) of lithium ion batteries are connected in series, and DC power is supplied to the load 2. In addition, the kind of single battery which comprises the assembled battery 1 is not limited to a lithium ion battery. For example, in the case of an electric vehicle, the motor corresponds to the load 2. The voltage detection circuit 3 detects the voltage V across the assembled battery 1, and the current detection circuit 4 detects the current A flowing from the assembled battery 1 to the load 2. The temperature detection circuit 5 detects the temperature θ of the assembled battery 1.
[0008]
The arithmetic circuit 6 includes a microcomputer and peripheral components such as a memory and an AD converter, calculates a remaining capacity based on the voltage V, current A, and temperature θ of the assembled battery 1 and displays it on the display 7.
[0009]
FIG. 2 is a flowchart showing the remaining capacity detection program. The operation of the first embodiment will be described with reference to this flowchart. The arithmetic circuit 6 executes this remaining capacity detection program every predetermined time.
[0010]
In step 1, the voltage detection circuit 3, the current detection circuit 4, and the temperature detection circuit 5 detect the voltage V across the assembled battery 1, the current A flowing to the load 2, and the temperature θ of the assembled battery 1. In the subsequent step 2, the discharge capacity discharged so far is calculated by integrating the load current A. Further, in step 3, the dischargeable capacity with respect to the detected temperature θ of the assembled battery 1 is calculated from a map of the dischargeable capacity with respect to the temperature θ of the assembled battery 1 measured in advance.
[0011]
FIG. 3 shows the relationship of the dischargeable capacity [%] with respect to the temperature θ [° C.] of the assembled battery 1. Generally, the dischargeable capacity of a battery decreases as the temperature of the battery decreases. In the example shown in FIG. 3, the dischargeable capacity shows a value close to 100% when the battery temperature is 25 ° C., but the dischargeable capacity decreases to 50% when the battery temperature is lowered to −25 ° C.
[0012]
In step 4, the remaining capacity of the battery pack 1 is calculated by subtracting the discharge capacity calculated in step 2 from the dischargeable capacity calculated in step 3. For example, when the dischargeable capacity of the battery pack 1 is 60 Ah and the discharge capacity discharged so far is 30 Ah, the remaining capacity is 30 Ah, that is, 50%.
[0013]
In step 5, the battery temperature increase rate [° C./Ah] with respect to the discharge capacity discharged this time is calculated. In subsequent step 6, it is determined whether or not the battery temperature increase rate calculated in step 5 is greater than or equal to a predetermined determination reference value. Here, the determination reference value varies depending on the battery, but is, for example, a value of about 0.4 ° C. per 1% of the discharge capacity. If the battery temperature increase rate is less than the determination reference value in step 7, the remaining capacity calculated in step 4 is set as the current remaining capacity detection value.
[0014]
On the other hand, in Step 8, when the battery temperature increase rate is equal to or higher than the determination reference value, the remaining capacity displayed on the display unit 7 is compared with the remaining capacity calculated in Step 4 above. In step 9, the smaller of the compared remaining capacities is set as the current remaining capacity detection value. In step 10, the current remaining capacity value [%] determined in step 7 or 9 is displayed on the display 7.
[0015]
FIG. 4 shows the detection result of the remaining capacity of the first embodiment in comparison with the detection result of the conventional remaining capacity. The horizontal axis of the figure is the discharge capacity [%] of the battery, where 0 is not discharged at all. The vertical axis represents the remaining capacity [%] of the battery. When the discharge capacity is 0, the remaining capacity is 100%. When the battery temperature does not rise, the remaining capacity decreases linearly as the discharge capacity increases. When the discharge capacity is large, the temperature rise of the battery is large, so that the dischargeable capacity of the battery increases. For this reason, as shown in the conventional example in the figure, a phenomenon occurs in which the remaining capacity increases even though the battery is discharged. On the other hand, according to the first embodiment, as shown in the present invention in the figure, a phenomenon unlike the conventional apparatus does not occur.
[0016]
According to the first embodiment, based on the rate of battery temperature increase with respect to the discharge capacity (° C./Ah, ° C./Wh, ° C./%), it is determined whether or not the battery temperature increase is a temperature increase due to discharge. When it is determined that the temperature rises due to discharge, the lesser of the previous calculated value of the remaining capacity and the current calculated value is displayed as the calculated value of the remaining capacity. Even if the battery temperature rises, the remaining capacity is not unnecessarily corrected and increased, and the remaining capacity can be detected accurately.
[0017]
In order to prevent the phenomenon that the remaining capacity increases when the battery is discharged, a method of making the remaining capacity constant when the remaining capacity increases during discharging can be considered. However, since the calculation of the remaining capacity is less accurate than the calculation of the battery temperature, the present invention prevents the remaining capacity from being unnecessarily corrected as the temperature rises due to discharge from the state where the remaining capacity is higher. it can.
[0018]
In the first embodiment described above, current integration is used to calculate the remaining capacity. However, the present invention is not limited to current integration, and a method of calculating remaining capacity by integrating energy (electric power) or a dischargeable output is calculated. Thus, the present invention can be applied to all remaining capacity calculation methods such as a method for obtaining the remaining capacity.
[0019]
When calculating the remaining capacity by integrating the energy, the voltage V and the current A are detected every time the remaining capacity detection program is executed, the output (energy) is obtained from the product of the voltage V and the current A, and the discharge has been performed so far. Accumulate the output to determine the remaining capacity. On the other hand, when the dischargeable output is calculated to determine the remaining capacity, the voltage V and current A are sampled for a certain period, and they are linearly regressed. The point at which the regression line intersects the minimum battery voltage is the maximum dischargeable output. And Then, the remaining capacity of the battery is obtained by subtracting the output discharged so far from the maximum dischargeable output.
[0020]
<< Second Embodiment of the Invention >>
A second embodiment for calculating the remaining capacity of the battery will be described. The configuration of the second embodiment is the same as that of the first embodiment shown in FIG. 1, and illustration and description thereof are omitted.
[0021]
FIG. 5 is a flowchart showing the remaining capacity detection program. The operation of the second embodiment will be described with reference to this flowchart. The arithmetic circuit 6 executes this remaining capacity detection program every predetermined time.
[0022]
In step 11, the voltage detection circuit 3, the current detection circuit 4, and the temperature detection circuit 5 detect the voltage V across the assembled battery 1, the current A flowing to the load 2, and the temperature θ of the assembled battery 1. In the following step 12, a dischargeable output is calculated based on the voltage V and the current A. The battery maximum dischargeable output is calculated by sampling current and voltage for a certain period and performing linear regression on them.
[0023]
FIG. 6 shows the relationship between current and voltage in a certain state of the assembled battery 1. The point at which the regression line in the figure intersects the lowest voltage of the assembled battery 1 is the maximum dischargeable output of the assembled battery 1.
[0024]
In step 13, the maximum dischargeable output calculated in step 12 is compared with the previously calculated dischargeable output. When the maximum dischargeable output calculated this time is not lower than the previously calculated maximum dischargeable output, the remaining capacity calculated last time in step 14 is used.
[0025]
On the other hand, when the maximum dischargeable output calculated this time is smaller than the previously calculated maximum dischargeable output, in step 15, the set is determined based on the relationship between the discharge capacity at the temperature θ of the assembled battery 1 and the maximum dischargeable output. The remaining capacity of the battery 1 is calculated. FIG. 7 shows the relationship between the discharge capacity [%] of the assembled battery 1 at a certain temperature θ and the maximum dischargeable output. In step 16, the remaining capacity value [%] obtained in step 14 or step 15 is displayed on the display 7.
[0026]
FIG. 8 shows the calculation result of the remaining capacity of the second embodiment in comparison with the conventional calculation result of the remaining capacity. The horizontal axis of the figure is the discharge capacity [%] of the battery, where 0 is not discharged at all. The vertical axis represents the remaining capacity [%] of the battery. When the discharge capacity is 0, the remaining capacity is 100%. When the battery temperature does not rise, the remaining capacity decreases linearly as the discharge capacity increases. When the discharge current is large, the temperature rise of the battery is large, so that the dischargeable capacity of the battery increases. For this reason, as shown in the conventional example in the figure, a phenomenon occurs in which the remaining capacity increases even though the battery is discharged. On the other hand, according to the second embodiment, the phenomenon as in the conventional apparatus does not occur as shown in the present invention in the figure.
[0027]
According to the second embodiment, when the current calculated value of the maximum dischargeable battery output is not lower than the previous calculated value, the previous remaining capacity calculated value is displayed as the current remaining capacity calculated value. Thus, even if the battery temperature rises due to discharge, the remaining capacity is not unnecessarily corrected and increased, and the remaining capacity can be accurately detected.
[0028]
Compared with the method of making the value of the remaining capacity constant by the rate of temperature increase with respect to the discharge capacity described in the first embodiment, the second embodiment uses the method of judging by the dischargeable output, so the temperature detector Therefore, the temperature inside the battery can be detected more quickly than when the temperature outside the battery is detected, and the remaining capacity is higher than in the first embodiment. The capacity can be prevented from being corrected, and the remaining capacity can be accurately detected from a state where the remaining capacity is large. The calculation accuracy of the remaining capacity at a low temperature is improved as compared with the conventional apparatus.
[0029]
<< Third Embodiment of the Invention >>
A third embodiment for calculating the remaining capacity using the internal resistance of the battery will be described. The configuration of the third embodiment is the same as that of the first embodiment shown in FIG. 1, and illustration and description thereof are omitted.
[0030]
FIG. 9 is a flowchart showing the remaining capacity detection program. The operation of the third embodiment will be described with reference to this flowchart. In addition, the same code | symbol is attached | subjected to the step which performs the process similar to the process of 1st Embodiment shown in FIG. 2, and it demonstrates centering on difference. The arithmetic circuit 6 executes this remaining capacity detection program every predetermined time.
[0031]
In steps 1 to 4, as described above, the discharge capacity that has been discharged so far is calculated by current integration, and the dischargeable capacity is calculated from the relationship between the battery temperature and the dischargeable capacity. Then, the remaining capacity of the battery is calculated from the relationship between the discharge capacity and the dischargeable capacity.
[0032]
Next, in step 21, the internal resistance of the assembled battery 1 is calculated from the relationship between the voltage V and the current A of the assembled battery 1. In the subsequent step 22, the internal resistance calculated this time is compared with the internal resistance calculated last time. If the internal resistance calculated this time is not lower than the previously calculated internal resistance, the remaining capacity calculated in step 4 is used in step 23. On the other hand, if the internal resistance calculated this time is less than the internal resistance calculated last time, the remaining capacity calculated last time in step 24 is used. In step 25, the remaining capacity value [%] obtained in step 23 or 24 is displayed on the display 7.
[0033]
According to the third embodiment, when the current calculated value of the internal resistance of the battery is smaller than the previous calculated value, the previous remaining capacity calculated value is displayed as the current remaining capacity calculated value. Therefore, even if the battery temperature rises due to discharge, the remaining capacity is not unnecessarily corrected and increased, and the remaining capacity can be accurately detected. In addition, as in the second embodiment, the temperature rise inside the battery can be detected earlier than when the temperature detector detects the temperature outside the battery, and the remaining capacity can be accurately determined from the state where the remaining capacity is large. Can be detected. Furthermore, the calculation accuracy of the remaining capacity at a low temperature is improved as compared with the conventional apparatus.
[0034]
In the configuration of the above embodiment, the arithmetic circuit 6 constitutes a discharge capacity calculation means, a temperature increase rate calculation means, a determination means, a control means, a dischargeable output calculation means, and an internal resistance calculation means.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a first exemplary embodiment.
FIG. 2 is a flowchart showing a remaining capacity detection program according to the first embodiment.
FIG. 3 is a diagram showing a characteristic of dischargeable capacity with respect to an assembled battery temperature.
FIG. 4 is a diagram showing a calculation result of remaining capacity of the first embodiment and the conventional apparatus.
FIG. 5 is a flowchart showing a remaining capacity detection program according to the second embodiment;
FIG. 6 is a diagram showing a method for obtaining a maximum output from a battery voltage and current.
FIG. 7 is a diagram showing the relationship between the discharge capacity at a certain temperature of a battery pack and the maximum dischargeable output.
FIG. 8 is a diagram showing a calculation result of remaining capacity of the second embodiment and a conventional apparatus.
FIG. 9 is a flowchart showing a remaining capacity detection program according to the third embodiment.
1 assembled battery 2 load 3 voltage detection circuit 4 current detection circuit 5 temperature detection circuit 6 arithmetic circuit 7 indicator

Claims (3)

In the battery remaining capacity meter that repeatedly calculates the remaining capacity of the battery, detects the temperature of the battery and corrects the remaining capacity,
Discharge capacity calculating means for calculating the discharge capacity of the battery;
A temperature increase rate calculating means for calculating an increase rate of the battery temperature relative to the discharge capacity of the battery;
Based on the rate of temperature increase with respect to the discharge capacity of the battery, determination means for determining whether or not the temperature increase of the battery is a temperature increase accompanying discharge;
When it is determined that the temperature rise of the battery is a temperature rise due to discharging, a control means is provided for displaying the lesser of the previous calculated value of the remaining capacity and the current calculated value as the calculated value of the remaining capacity. A remaining capacity meter for a battery. In the battery remaining capacity meter that repeatedly calculates the remaining capacity of the battery, detects the temperature of the battery and corrects the remaining capacity,
Dischargeable output calculating means for repeatedly calculating the maximum dischargeable output of the battery based on the voltage and current of the battery;
And a control means for displaying the previous remaining capacity calculation value as the current remaining capacity calculation value when the current calculation value of the maximum dischargeable battery output is not reduced from the previous calculation value. Battery capacity meter. In the battery remaining capacity meter that repeatedly calculates the remaining capacity of the battery, detects the temperature of the battery and corrects the remaining capacity,
Internal resistance calculating means for calculating the internal resistance of the battery based on the voltage and current of the battery;
Control means for displaying the previous remaining capacity calculation value as the current remaining capacity calculation value when the current calculation value of the internal resistance of the battery is lower than the previous calculation value. Remaining capacity meter.

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