JP2000131404A - Cell deterioration degree determining apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cell deterioration degree determining apparatus superior in handling. SOLUTION: The present capacity being the dischargeable power from the fully charged state to a specified discharge voltage is computed, based on a discharge voltage V and a discharge current A (S32), and the cell deterioration degree, i.e., the ratio of the present capacity to the initial capacity of a dischargeable power from the initial fully charged state of a cell to the specified discharge voltage is computed (S34). Thus, the cell deterioration degree can be determined at a high accuracy even at other stages than the discharge end stage with a low internal resistance change ratio. For a hybrid car's cell, e.g. being normally charged by an engine with a frequently varying discharge current, a practical cell deterioration degree determining apparatus can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for determining the degree of deterioration of a battery mounted on an electric vehicle, for example.

[0002]

2. Description of the Related Art For example, a secondary battery used in an electric vehicle is repeatedly charged and discharged, so that the dischargeable capacity is gradually reduced due to deterioration. It is desired to know the degree. For this reason, JP-A-8-254573 discloses
A method for determining the internal resistance of a battery based on the discharge voltage V and the discharge current I of the battery and determining the degree of deterioration of the battery based on the gradient of the internal resistance of the battery (a method of determining the degree of deterioration of the battery based on the rate of change in internal resistance). Has been proposed.

[0003]

However, in the above-described battery deterioration degree judging method based on the internal resistance change rate, since the internal resistance change rate is small except at the end of discharge where the internal resistance change rate is large, the error is large and the battery deterioration is highly accurate. It is difficult to determine the degree of deterioration of the battery, so do not use it in applications where the battery is regularly deeply discharged. Was difficult.

It is most convenient to determine the degree of deterioration of the battery in terms of the rate of reduction in the amount of dischargeable power that can be extracted from the battery in use. However, in the above-described method of determining the degree of deterioration of the battery based on the internal resistance change rate, However, it is difficult to accurately determine the rate of decrease in the dischargeable power, and the usability is poor. Further, in the above-described method of determining the degree of deterioration of the battery based on the rate of change in internal resistance, in a battery for a hybrid vehicle that is used outdoors and the battery temperature fluctuates greatly, the error in determining the degree of deterioration of the battery is further increased due to the change in internal resistance due to the battery temperature. There was a problem of becoming.

[0005] The present invention has been made in view of the above problems, and has as its object to provide a battery deterioration degree judging apparatus which is excellent in usability.

[0006]

According to a first aspect of the present invention, there is provided a battery deterioration determining apparatus for solving the above-mentioned problems.
A current capacity, which is a dischargeable electric energy from a full charge state to a predetermined discharge voltage value, is calculated based on the discharge voltage V and the discharge amount Ah, and the current capacity and the predetermined capacity from the initial full charge state of the battery are calculated. The battery deterioration degree is calculated as a ratio with the initial capacity which is the dischargeable electric energy up to the discharge voltage value.

In this way, the degree of deterioration of the battery can be determined with high accuracy even at times other than the end of discharge where the rate of change in internal resistance is small. For example, the battery is constantly charged by the engine and the discharge current changes frequently. A practical battery deterioration degree determination device for a hybrid vehicle battery can be realized. In addition, the battery deterioration degree determination device of this configuration has:
Since the degree of battery deterioration is determined based on the rate of decrease in the amount of dischargeable power that can be taken out of the battery, the degree of battery deterioration can be determined based on the rate of decrease in the amount of usable power, which is excellent in usability.

According to a second aspect of the present invention, in the battery deterioration degree judging device according to the first aspect, the battery discharge voltage V
Discharge characteristics indicating the relationship between the discharge amount Ah and the discharge amount Ah
And at least the remaining dischargeable electric energy in the current capacity is calculated using the discharge characteristics obtained based on the discharge voltage V. Therefore, the residual dischargeable electric energy can be calculated by the area integration operation of the discharge characteristics, and thus, it is simple. In addition, the remaining dischargeable power amount can be accurately obtained.

The remaining dischargeable power may be the remaining dischargeable power from the current time to the end of a predetermined discharge, and the remaining dischargeable power from a fully charged state or a predetermined discharge state and the current discharge from the state. The difference from the accumulated discharge power up to may be used. According to a third aspect of the present invention, in the battery deterioration degree judging device according to the second aspect, the initial capacity and the remaining dischargeable power amount are further calculated or stored as a dischargeable power amount by discharging at a predetermined reference discharge power value. Therefore, it is possible to obtain the degree of battery deterioration when discharging at the reference discharge power value, which is practical. In addition, the degree of battery deterioration can be accurately obtained regardless of a change in discharge power.

According to a fourth aspect of the present invention, in the battery deterioration degree judging apparatus according to the second aspect, the integrated discharge power amount W
The current capacity is calculated as the sum of h and the remaining dischargeable power. By doing so, the discharge amount up to the present can be a measured value instead of an estimated value, so that the current capacity can be accurately calculated. According to a fifth aspect of the present invention, in the battery deterioration degree judging apparatus according to any one of the second to fourth aspects, the initial discharge characteristics are further compressed in the decreasing direction of the discharge amount Ah to obtain the current discharge characteristics. If you do this,
The remaining dischargeable electric energy can be easily estimated.

For example, a change amount ΔAh of the discharge amount Ah from the point of the predetermined discharge amount Ah ′ to the current discharge voltage V and the point of the discharge amount Ah is obtained, and the initial discharge characteristic is calculated from the point of the predetermined discharge amount Ah ′. At the initial discharge amount Ahin corresponding to the discharge voltage V
A change amount ΔAhini of the initial discharge amount Ahini up to i is obtained, a ratio K (= ΔAh / Ahini) of the both change amounts is obtained, and the remaining dischargeable power amount is multiplied by the ratio of the initial discharge amount Ahini of the initial discharge characteristic to discharge. The discharge characteristic with the amount Ah is determined, and the discharge area of the discharge characteristic is integrated to determine the remaining dischargeable power amount. This makes it possible to easily and accurately determine the change in the current capacity due to the battery deterioration.

This operation has been performed by the applicant of the present invention that the ratio K (= ΔAh / Ahini) is substantially equal at each discharge voltage V in both the initial discharge characteristics and the discharge characteristics in which the battery has deteriorated in the same battery. Based on experimental results and findings based on their analysis. For the experimental results and the analysis thereof, refer to Japanese Patent Publication No. Hei 10-246760 filed by the present applicant.

According to a sixth aspect of the present invention, in the battery deterioration degree judging device according to any one of the first to fifth aspects, the battery deterioration degree for the current capacity in which the influence of the memory effect of the battery is canceled is output. In this way, the current capacity decrease due to the memory effect eliminated by the complete discharge is not erroneously determined to be permanent current capacity decrease due to battery deterioration.

According to a seventh aspect of the present invention, in the battery deterioration degree judging device according to the sixth aspect, when a predetermined amount of power is charged while a predetermined amount of dischargeable power remains in the battery. The battery deterioration degree is not output until all the charged electric energy is discharged. By doing so, the battery deterioration degree can be always displayed or output accurately without displaying the error of the battery deterioration degree due to the influence of the charge polarization remaining in the battery after the charging.

According to an eighth aspect of the present invention, in the battery deterioration degree judging apparatus according to the seventh aspect, when the battery is charged in a state where the battery has a predetermined remaining dischargeable electric energy, the battery is charged. After all the charges increased by the charging after the end are discharged, a memory effect voltage drop amount ΔVm, which is a difference between the detected discharge voltage Vmafter and the discharge voltage Vmbefore before charging, is calculated.
The memory effect cancel discharge voltage V obtained by adding the memory effect voltage decrease amount ΔVm to the memory effect voltage ΔVm is regarded as the future discharge voltage V.

In this way, it is possible to simply and accurately cancel a virtual decrease in the remaining dischargeable power due to the memory effect. In addition, this operation is performed in the same battery at the point in time after the charge that has been increased by the charge after the end of the charge is completely discharged (the re-detection discharge voltage V after the charge), if the battery deterioration due to the charge and the subsequent discharge is ignored. , The value Vmb of the discharge voltage V at a predetermined discharge amount Ah immediately before charging
efore and the value Vmafte of the redetected discharge voltage after charging
This is based on the results of an experiment conducted by the present applicant that the difference from r can be regarded as a decrease in the electromotive force of the battery due to the memory effect, and knowledge based on its analysis. That is, according to the experimental results of the present application and the knowledge based on the analysis thereof, the capacity decrease due to the battery deterioration is caused by the increase in the internal resistance of the battery, and the capacity decrease due to the memory effect is caused by the decrease in the electromotive force of the battery. You can think. For the experimental results and the analysis thereof, refer to Japanese Patent Publication No. Hei 10-246760 filed by the present applicant.

According to a ninth aspect of the present invention, in the battery deterioration degree judging device according to any one of the first to eighth aspects,
The current capacity at a predetermined reference temperature is calculated based on the discharge voltage V, the discharge current A, and the battery temperature. Further, the initial capacity is also assumed to be the dischargeable electric energy by the discharge at the reference temperature. This makes it possible to obtain the degree of battery deterioration at a predetermined reference temperature, which is practical. In addition, the degree of battery deterioration can be accurately obtained regardless of a change in battery temperature.

According to a tenth aspect of the invention, in the battery deterioration degree judging device according to any one of the first to ninth aspects, the calculated battery deterioration degree is updated and displayed at predetermined time intervals. In this way, even if the degree of battery deterioration suddenly increases for some reason, it is possible to cope with the sudden increase in the degree of battery deterioration and to know the current degree of deterioration of the battery.

According to the eleventh aspect of the present invention, in the battery deterioration degree judging device according to the ninth and tenth aspects, the value before the deviation is output when the battery temperature deviates from a predetermined range. When the temperature deviates from the normal use range to a high temperature or a low tone and the battery deterioration degree in the normal temperature range cannot be accurately calculated, extremely erroneous information is not output and the usability is good.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a battery deterioration degree judging device according to the present invention will be described below with reference to the drawings.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Apparatus Configuration) FIG. 1 is a block diagram showing an example of a battery deterioration degree judging apparatus for a hybrid vehicle according to the present invention. Reference numeral 1 denotes a battery, and 2 denotes power transmission means including a rotating electric machine of a hybrid vehicle. The power transmission means is connected to an engine and a drive shaft of the vehicle and exchanges energy between them and the battery in the form of electric power. Reference numeral 3 denotes a bidirectional power converter that converts between DC power input / output to / from the battery 1 and AC power input / output to / from the power transmission means 2. Since the configurations of the power transmission means 2 and the bidirectional power converter 3 are well known and are not the gist of the present invention, further detailed description will be omitted.

The battery 1 is composed of an assembled battery in which a number of Ni-MH batteries are connected in series. A current sensor 5 detects the charging / discharging current, a temperature sensor 6 detects the temperature, and the current, temperature, Is input to a controller 4 having a microcomputer configuration for calculating and displaying the battery deterioration degree together with the output voltage of the battery 1. Hereinafter, the battery deterioration degree calculation process of this embodiment will be described with reference to the flowcharts shown in FIGS. First, the discharge voltage V, the charge / discharge current A, and the battery temperature T are detected (S10), and the charge / discharge current A is integrated to calculate the charge / discharge amount from the previous full charge (S12). Investigation (S14), the charge / discharge amount (hereinafter referred to as
Ah is simply set to 0 (S1) (S1).
6). Note that there are various methods for determining the full charge, but here, the change amount dV / change amount of the discharge voltage V with respect to the discharge amount Ah is described.
A method of determining that the battery is fully charged when a peak value of dAh is detected is employed.

Next, it is determined whether or not the battery temperature T is within an appropriate range, and the battery temperature T is determined to be within the operating temperature range (here, 10 to 40).
C), the error is large and the process returns to the main routine without calculating the subsequent battery deterioration degree (S18). If the battery temperature T is within the operating temperature range, it is checked whether or not charging has been performed since the previous calculation of the battery deterioration degree (S20), and if so, an initial discharge characteristic corresponding to the battery temperature T is selected. (S22). Here, the initial discharge characteristic is a characteristic indicating a relationship between a discharge amount Ah and a discharge voltage V of a new battery that has been subjected to initial activation charge / discharge a predetermined number of times at first. What corresponds to the current battery temperature T may be selected from the plurality of initial discharge characteristics stored as. However, this initial discharge characteristic is a predetermined reference discharge power (here, 2 kW).
Is an initial discharge characteristic in the case where is discharged.

However, the detected discharge voltage V is not necessarily a discharge voltage obtained by discharging the reference discharge power, and is higher if the discharge power is smaller than the reference discharge power.
If it is larger, it is detected smaller, so that the error of the discharge voltage V due to this discharge power is corrected, and the corrected discharge voltage V is used from this step onward. The correction of the discharge voltage V can be performed as follows. First, the internal resistance r and open circuit voltage of the battery are determined. The internal resistance r can be determined, for example, as ΔV / ΔA in the VI characteristic on the characteristics of the discharge voltage V and the discharge current A. next,
The open circuit voltage is obtained by multiplying the detected discharge current A by the internal resistance r and multiplying by the internal resistance r of the battery to obtain the voltage drop.
The battery voltage when the model battery thus obtained discharges the reference discharge power is calculated.

Next, V− determined by the initial discharge characteristics
The area on the Ah plane is obtained by integrating a predetermined reference discharge power (here, 2 kW) from a fully charged state within a dischargeable range, and is determined as an initial capacity (S24). Note that a numerical value corresponding to the initial capacity may be stored in advance. Next, the detected discharge amount Ah is substituted for the selected initial discharge characteristic to obtain an initial discharge voltage Vo which is a discharge voltage on the initial discharge characteristic (S26).

Next, the current memory effect cancel discharge voltage V 'is added to the current detected discharge voltage V by adding all of the memory effect voltage drop ΔVm, which will be described later, occurring in the discharge amount up to the discharge amount Ah. It is determined (S28). Next, a change amount ΔAh of the discharge amount Ah from the point of the predetermined discharge amount Ah ′ to the current discharge voltage V and the point of the discharge amount Ah is obtained,
A change amount ΔAhini of the initial discharge amount Ahini from the point of the predetermined discharge amount Ah ′ to the initial discharge amount Ahini corresponding to the discharge voltage V on the initial discharge characteristics is obtained, and a ratio K (= ΔAh / ΔAhini) of both the change amounts is obtained. Is calculated by multiplying the initial discharge amount Ahini of the initial discharge characteristic by the above ratio and the current discharge amount Ahini.
Then, the discharge characteristic is set as h (S30).

The point of the predetermined discharge amount Ah 'is the point of the discharge amount Ah at which the previous charging was started. That is, when the previous charge is started with the discharge amount Ah ', and after the end of the charge, the discharge is advanced to this point again, the subsequent discharge characteristics are estimated based on the predetermined discharge amount Ah'. For this reason, when discharging is performed after the previous charging is completed, it is assumed that there is no battery deterioration even if a memory effect occurs between the previous charging and the current charging, and the next discharging is performed based on the previous discharging characteristics. Estimate the degree of battery deterioration. However, when the previous charge has reached the full charge, the predetermined discharge amount Ah ′ is set to 0, and the ratio K (= ΔAh / Ahini) of the two change amounts can be obtained.

Next, V determined by this discharge characteristic
-The area on the Ah plane is obtained by integrating a predetermined reference discharge power (here, 2 kW) from the discharge amount Ah up to the present to the dischargeable limit, and the remaining dischargeable power amount by the discharge at the predetermined reference discharge power value Then, the accumulated discharge power amount Wh up to the present is added to the current capacity (S32). Next, the current capacity is divided by the initial capacity to determine the degree of deterioration (S3
4) The degree of deterioration is displayed (S36).

On the other hand, if it is determined in step S20 that charging has been performed since the previous calculation of the degree of battery deterioration (if the charge amount Ah is not 0), it is checked whether or not charging is currently being performed ( S38) If the battery is being charged, the process returns to the main routine; otherwise, this charging is performed in a state where the dischargeable power amount remains in the battery, and the charge (charge amount Ah) increased by charging is obtained. It is checked whether or not the battery has been completely discharged by the accumulation of the charge / discharge current (S40).

If the battery has not been discharged, after the completion of the charging,
It is checked whether or not the complete discharge has been performed (S42). If not, the process returns to the main routine. If the complete discharge has been performed, it is determined that the memory effect has disappeared, and all of the memory effect voltage drop ΔVm is set to 0. Reset and return to the main routine (S44). On the other hand, in S40, when it is determined that the discharge of the charge amount or more has been performed, it is determined that the influence of the residual charge polarization has disappeared,
The discharge voltage Vmbefore detected at the pre-charge discharge amount Ahx, which is the value of the discharge amount Ah immediately before the charge, and the discharge voltage Vm detected at the discharge amount Ahx after the current charge
After that, the difference between the after-charge amount Ahx and the memory effect voltage drop amount ΔVm is stored as a set (SS).
46). Thus, even if a large number of charges cause a decrease in the electromotive voltage due to a large number of memory effects, the decrease in the memory effect voltage ΔVm in relation to the amount of discharge Ah caused
Can be stored.

FIG. 5 shows a part of the discharge characteristics of the battery in which the battery voltage is reduced due to the memory effect. X is the initial discharge characteristic, Y is the discharge characteristic before charging, Z is the discharge characteristic after charging is completed, and the discharge voltage Vmbefor at the point A immediately before charging is set.
e1 has a voltage difference equal to the memory effect voltage drop amount ΔVm between the discharge voltage Vmafter after the end of the charge and after the discharge by the charge.

Therefore, in the determination of the battery deterioration degree,
In order to cancel the influence of the memory effect, the value of the discharge amount Ah which is affected by the memory effect is A
hx and the memory effect voltage drop amount ΔVm are stored,
When the discharge characteristics for calculating the residual dischargeable power amount after the discharge amount Ahx are obtained (S30), the memory effect voltage reduction amount Δ is added to the discharge voltage V detected as the discharge voltage.
It can be seen that this can be realized by obtaining the memory effect canceling voltage Vo to which Vm is added (S28), and sliding the initial discharge characteristics based on this memory effect canceling voltage Vo to obtain the current discharge characteristics (S30).

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a battery deterioration degree determination device of the present invention.

FIG. 2 is a flowchart illustrating a battery deterioration degree determination operation.

FIG. 3 is a flowchart illustrating a battery deterioration degree determination operation.

FIG. 4 is a flowchart showing a battery deterioration degree determination operation.

FIG. 5 is a characteristic diagram showing a part of discharge characteristics of a battery in which a battery voltage is reduced due to a memory effect.

[Explanation of symbols]

1 is a battery, 4 is a controller, 5 is a current sensor, 6 is a temperature sensor (temperature detecting means), S10 is a discharge parameter detecting means, S32 is a current capacity calculating means, S34 is a battery deterioration degree calculating means, S36 is an output means.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G016 CA03 CB06 CB11 CB13 CB22 CB23 CC04 CC07 CC23 CC27 CC28 CF06 5H030 AA08 AS08 FF22 FF42 FF44 5H115 PA14 PC06 PG04 PI14 PI16 PI24 PI29 PO06 PO10 PU08 PV07 PV09 SE07 TI09 TI09

Claims (11)

[Claims] 1. A discharge parameter detecting means for detecting a discharge voltage V and a discharge current A of a chargeable / dischargeable battery; a discharge amount calculating means for accumulating a discharge amount Ah based on the discharge current A; Current capacity calculating means for calculating a current capacity that is a dischargeable power amount from a fully charged state to a predetermined discharge end voltage value based on the discharge amount Ah; and the predetermined discharge end from a fully charged state at an initial time of the battery. Battery deterioration degree calculating means for calculating a battery deterioration degree as a ratio of the current capacity to an initial capacity which is a dischargeable power amount up to a voltage value, and output means for outputting information relating to the calculated battery deterioration degree. A battery deterioration degree determination device, comprising: 2. The battery deterioration degree judging device according to claim 1, wherein said current capacity calculating means is stored in a memory and has a discharge voltage V and a discharge amount Ah of said battery.
At least the remaining capacity in the current capacity is determined by using the discharge characteristics obtained based on the initial discharge characteristics indicating the initial relationship with the discharge amount Ah obtained by accumulating the discharge current and the discharge voltage V. A battery deterioration degree judging device for calculating an electric energy. 3. The battery deterioration degree judging device according to claim 2, wherein the initial capacity and the remaining dischargeable power amount are the dischargeable power amounts by discharging at a predetermined reference discharge power value. Battery deterioration degree determining device. 4. The battery deterioration degree judging device according to claim 2, wherein the current capacity calculating means calculates the current capacity as a sum of the integrated discharge power amount Wh and the remaining dischargeable power amount. Battery deterioration degree determination device. 5. The battery deterioration degree judging device according to claim 2, wherein the current capacity calculating means obtains a current discharge characteristic by compressing the initial discharge characteristic in a decreasing direction of the discharge amount Ah. Battery deterioration degree determining device. 6. The battery deterioration degree judging device according to claim 2, wherein said battery has a memory effect, and said output means comprises: said current capacity in which said memory effect of said battery is canceled. A battery deterioration degree judging device for outputting the battery deterioration degree with respect to. 7. The battery deterioration degree judging device according to claim 6, wherein the output means charges the battery when a predetermined amount of power is charged while a predetermined amount of dischargeable power remains in the battery. A battery deterioration degree judging device which does not output the battery deterioration degree until all the electric charges increased in the battery are discharged. 8. The battery deterioration degree judging device according to claim 7, wherein the current capacity calculating means is configured to: when a predetermined charge is charged in a state where the battery has the predetermined remaining dischargeable power amount, After all of the charge that has been increased by the charge after the end of the charge is discharged, a memory effect voltage decrease amount ΔVm that is a difference between the detected discharge voltage Vmafter and the discharge voltage Vmbefore before the charge is obtained. A battery deterioration degree judging device characterized in that a memory effect cancel discharge voltage V obtained by adding the memory effect voltage drop amount ΔVm to a discharge voltage V is regarded as the discharge voltage V. 9. The battery deterioration degree judging device according to claim 1, further comprising a temperature detecting means for detecting a temperature T of the battery, and wherein the current capacity calculating means is configured to detect the detected discharge voltage V. Calculating the current capacity at a predetermined reference temperature based on the discharge current A and the temperature T, wherein the battery deterioration degree calculating means calculates the battery deterioration degree as a ratio of the current capacity to the initial capacity at the reference temperature. A battery deterioration degree judging device characterized by performing. 10. The battery deterioration degree judging device according to claim 1, wherein the output means has a display means for updating and displaying the calculated battery deterioration degree at predetermined time intervals. Battery deterioration degree determination device. 11. The battery deterioration degree judging device according to claim 9, wherein the output means outputs a value before the deviation as the battery deterioration degree when the temperature of the battery deviates from a predetermined range. A battery deterioration degree judging device characterized by the above-mentioned.