JP4861007B2 - Battery state management device - Google Patents

Description

  The present invention relates to a battery state management device that manages the state of a battery (in this specification, a lead battery) mounted on a vehicle.

  Conventionally, there is a technique for detecting the state of a battery (for example, the degree of deterioration or the remaining charge amount) based on the voltage drop characteristic of the battery at the time of discharging such as when the engine is started (for example, Patent Document 1 below).

JP 2004-190604 A

  A battery mounted on a vehicle uses dilute sulfuric acid as a battery solution. Then, the sulfuric acid concentration of the battery liquid may be intentionally set to a different value depending on the vehicle type on which the battery is mounted and the region (export destination, etc.) where the battery is used. Further, the sulfuric acid concentration of the battery liquid also varies due to the decrease of the battery liquid and the influence of sulfation.

  When the sulfuric acid concentration is different, the specific gravity of the battery liquid also changes. However, the technique disclosed in Patent Document 1 has a problem that the change in the specific gravity of the battery liquid is not considered in the battery state management.

  The present invention has been made to solve such a problem. Even when the specific gravity of the battery liquid changes due to a change in the sulfuric acid concentration, the battery state management corresponding to the change in the specific gravity is performed. An object is to obtain a battery state management device that can be realized.

The battery state management device according to the present invention is a battery state management device that is mounted on a vehicle and manages the state of the battery, and changes in the internal resistance of the battery with respect to changes in the open-circuit voltage of the battery according to the remaining charge amount Storage means for storing information relating to characteristics; the information; an open-circuit voltage that is measured with respect to the battery in a fully charged state; that is, an output voltage of the battery that is not discharged; and the battery at the start of the engine of the vehicle based of the respective measured value of the lower limit voltage and a minimum voltage, and processing means for deriving a reference discharge characteristic indicating the relationship between the open voltage and the minimum voltage in the battery, the processing means, Mitsuru If the measured value of the open circuit voltage at the battery state of charge is changed, the open-circuit voltage and the front of the battery after the change and the information Based on the measured value of the lower limit voltage, characterized by deriving a new reference discharge characteristic.

According to the battery state management device of the present invention, when the open voltage in the fully charged state (the output voltage of the battery that has not been discharged) changes, the processing means changes the information stored in the storage means and Based on the measured values of the open circuit voltage and the lower limit voltage, a new reference discharge characteristic indicating the relationship between the open circuit voltage and the lower limit voltage is derived. Therefore, for batteries with a specific gravity different from the battery used to derive the reference discharge characteristics, or for batteries whose specific gravity has changed since the reference discharge characteristics were derived, a new reference discharge characteristic is used to manage the state of the battery. Therefore, it is possible to realize battery state management appropriately corresponding to a change in specific gravity.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the element which attached | subjected the same code | symbol in different drawing shall show the same or corresponding element.

<Principle explanation>
First, the evaluation principle of the battery state in the battery state management device according to the present embodiment will be described.

  FIG. 1 shows an open-circuit voltage (output voltage when the battery is not substantially discharged) and a lower limit voltage at engine start (battery output voltage due to discharge at engine start) for batteries with different deterioration conditions and remaining charge levels. Is a minimum voltage when the voltage drops, and corresponds to the voltage at the time of discharge according to the present invention). The horizontal axis corresponds to the open circuit voltage value of the battery before the start of discharge at engine start in each discharge test, and the vertical axis corresponds to the lower limit voltage value of the battery during discharge at engine start in each discharge test. Further, a curve G1 in FIG. 1 is drawn based on a measurement result of a new battery (substantially a new one (hereinafter the same)), and the curves G2 to G4 are used and deteriorated to some extent. It is drawn based on the measurement result about the battery, and the use period of the battery becomes longer in the order of the curves G2, G3, G4, and the deterioration progresses. It should be noted that by using the open-circuit voltage value after a certain time has elapsed from the end of charging (when the engine is stopped), the accuracy of obtaining the discharge characteristics and evaluating the state of the battery 1 is further improved.

  From the graph of FIG. 1, it can be seen that the corresponding curves G1 to G4 are shifted in the right direction (or the lower right direction) of the graph as the deterioration of the battery proceeds. In particular, in a region where the lower limit voltage value is a predetermined reference level (for example, 9 V) or less, the shift amount in the right direction of the curves G2 to G4 with respect to the curve G1 increases as the deterioration of the corresponding battery progresses. It turns out that there is a tendency. From this, if the discharge characteristic at the time of engine start of the new battery corresponding to the curve G1 (the lower limit voltage value during discharge at the start of the engine with respect to each discharge voltage value corresponding to each remaining charge amount) is derived, this is used as a reference. As a result, the battery state can be evaluated.

  However, the state of the load connected to the battery when the engine is started varies greatly depending on the vehicle type. For this reason, applying the conventional method to obtain the engine start-up discharge characteristic of the battery corresponding to the curve G1, for example, the engine start-up discharge of the battery corresponding to the curve G1 under a certain reference condition. The characteristic is detected by a test, and the discharge characteristic is finely adjusted using an adjustment parameter set for each vehicle type.

  Therefore, the inventor of the present application pays attention to the problems of the conventional method, and automatically calculates the discharge characteristics at the time of engine start of the battery reflecting the load condition at the time of engine start specific to the car body without using the adjustment parameters peculiar to the car body. Measures were taken so that it could be acquired in an efficient manner. The principle is as follows.

FIG. 2 is a graph for explaining the discharge characteristics of the battery when the engine is started. A curve G1 in the graph of FIG. 2 corresponds to the curve G1 of FIG. As shown in FIG. 3, the resistance value of the engine start load L _S (which is a load other than the internal resistance of the battery and includes a starter, other resistance elements, etc.) connected to the battery 1 at the time of engine start is expressed as R _S. and then, the internal resistance of the battery 1 and R _B, the open circuit voltage value of the battery 1 and V _O, at a minimum value of the output voltage at the time of to perform the discharge by connecting a load L _S when starting the engine in the battery 1 When a certain lower limit voltage value is V _L , the following relationship is established among these parameters R _S , R _B , V _O , and V _L.

Solving this equation (1) for V _L gives the following.

In the formula (2), the internal resistance value R _B is open voltage value V _O (i.e., the remaining charge of the battery 1) Assuming no change, the resistance value R _S when the load L _S engine start open voltage value because it is constant regardless of the value of V _O, the formula corresponding to the straight line G5 through the origin of the coordinate system of the graph of FIG. 2 (equation representing the proportionality relationship between the values V _O, V _L) is obtained.

Actually, since the internal resistance value R _B in the equation (2) increases with a decrease in the open circuit voltage value V _O (remaining charge of the battery 1), the lowering rate of the lower limit voltage value V _L is represented by the curve G1. In this way, it increases as the open circuit voltage value V _O decreases. That is, the internal accompanying gradually become large, a decrease in open circuit voltage value V _O divergence of the longitudinal axis minus direction with decreasing open circuit voltage value V _O from the straight line G5 of the curve G1 in the graph of FIG. 2 it can be said to be due to increase in the resistance R _B.

Therefore, the present inventor has increased the proportion of open-circuit voltage value V _O internal resistance of the battery 1 with decreasing (remaining charge of the battery 1) R _B is approximately for any battery 1 if battery 1 of new Focusing on the common characteristics, and effectively using the characteristics, it is possible to easily detect the vehicle-specific discharge characteristics with respect to the engine start load L _S of the new battery 1. It came.

In other words, may be stored in the system previously acquired by the information about the rate of increase of the open circuit voltage value V _O internal resistance value R _B with decreasing of the battery 1 is new, when the vehicle completely assembled at the factory, the factory, vehicle When the battery 1 is delivered to the end user, or when the battery 1 is in a new state, such as within a certain period after the end user is delivered, the discharge characteristics using the engine start load L _S for the battery 1 (remaining charge remaining as a reference) 2 is obtained by measuring the open-circuit voltage value V _O of the new battery 1 and the lower limit voltage value V _L when the engine start load L _S is connected) in the graph of FIG. , based on the information about the rate of increase of pre-stored internal resistance value R _B and the measurement points, acquires the vehicle-specific discharge characteristics for when starting the engine of the new battery 1 load L _S It was found that the kill. In addition, about the measurement point peculiar to the vehicle, a result obtained by performing numerical processing such as averaging (including weighted average) on the measurement result obtained by performing the measurement a plurality of times may be used. Depending on the value of the open-circuit voltage (remaining charge) of the battery 1 at the time of measurement, methods such as preferential use of the measurement point with the maximum open-circuit voltage or increasing the contribution of the weighted average can be considered.

More specifically, first, the open-circuit voltage value V _OIF and the internal resistance value R when the remaining charge of the new battery 1 is in a fully charged state (substantially fully charged state (the same applies hereinafter)). _{The BIF} and the rate of change (R _BI / R _BIF ) of the internal resistance value R _BI with respect to R _BIF at each open-circuit voltage value V _OI when the remaining charge amount is reduced are measured by tests. The function changing rate of the internal resistance value R _BI and (R _BI / R _BIF), where the open-circuit voltage value V _OI and variable with respect to a change in open-circuit voltage value V _OI of new battery 1 (e.g., Formula (3) Information about the function is previously stored in the system. Alternatively, as a modified example, the open circuit voltage value V _OI and the corresponding change rate (R _BI / R _BIF ) of the internal resistance value R _BI are stored in the system in advance as a data table. May be. A specific method for measuring the rate of change (R _BI / R _BIF ) of the internal resistance value R _BI at each open circuit voltage value V _OI will be described later.

Next, when the battery 1 at the time of vehicle assembly completion at the factory is in a new state and the battery 1 is fully charged, the open-circuit voltage value (initial reference discharge voltage value) V _OIF and the battery 1 The lower limit voltage value (initial reference lower limit voltage value) V _LIF of the battery 1 when the engine starting load L _S is connected is measured. Whether or not the battery 1 is in a fully charged state is determined by, for example, measuring the open-circuit voltage value of the battery 1 and determining whether or not the value is equal to or higher than a predetermined reference level corresponding to the fully charged state. Is done. As described above, the initial reference discharge voltage value V _OIF and the initial reference lower limit voltage value V _LIF may be measured a plurality of times and averaged.

By using the measurement result of the initial reference discharge voltage value V _OIF and the initial reference lower limit voltage value V _LIF and the function of the above equation (3) (or a data table equivalent thereto), a new battery mounted on the vehicle A relational expression indicating a change in the lower limit voltage value V _LI accompanying a change in the open circuit voltage value V _OI with respect to the engine starting load L _S is given by the following expression.

Here, the parameter V _LK in the above equation (4) is a lower limit voltage value when the open-circuit voltage value on the straight line G5 in the graph of FIG. 2 is V _OI , and is given by the following equation (5).

The relational expression of the expression (4) is derived, for example, as follows. That is, when considering that the relationship of the above equation (1) is applied to the coordinate point P _F in the graph of FIG. 2, the internal resistance value R _B when the open-circuit voltage value is V _OIF (at full charge) is expressed as R _BIF . Then, the following relational expression (6) is obtained.

Also, when considering the fitting the relationship of the above equation (1) coordinate point P _I in the graph of FIG. 2, internal resistance value R _B is above equation when the open circuit voltage value V _OI (3) from R _B = F (V _OI ) · R _BIF is obtained, the following relational expression (7) is obtained.

Therefore, when the parameter V _LI is solved by substituting the right side of the relational expression (6) for the parameter (R _S / R _BIF ) on the left side of the relational expression (7), the relational expression (4) is obtained.

From another point of view, the relational expression of the above formula (6) is based on the straight line G5 in the graph of FIG. 2, and the open circuit voltage at that point given by the relation of the above formula (3) by shifted in the vertical axis minus direction by a shift amount corresponding to the variant of the change rate of the internal resistance of the battery 1 in accordance with the value V _OI, the lower limit voltage value at each remaining charge (each open-circuit voltage value V _OI) V _LI is derived.

The information regarding the relationship between the open circuit voltage value V _OI and the lower limit voltage value V _LI derived in this way reflects the resistance value R _S of the engine starting load L _S inherent to the vehicle. Thus, the state evaluation of the battery 1 reflecting the vehicle-specific load environment and the like can be performed.

Here, the values V _OIE and V _{LIE in} the graph of FIG. 2 are the open-circuit voltage values when the new battery 1 has a remaining charge level of zero (the remaining charge level should be substantially zero (the same applies hereinafter)). And the lower limit voltage value. Specific examples of the values V _OIF and V _OIE are 12.86V and 11.9V, for example.

Next, a method for acquiring information related to the increase rate of the internal resistance value R _B accompanying the decrease of the open circuit voltage value V _O in the new battery 1 will be described. First, in the present embodiment, a capacity test is performed on a new battery 1 in accordance with the JIS standard related to the battery capacity test. Here, the capacity test of the JIS standard means that the battery 1 in a fully charged state is discharged at a constant current value (for example, 0.2 A), and the output voltage of the battery 1 is zero after the discharge starts. In this test, the time required to reach a corresponding voltage value (for example, 11.9 V) is measured, and the product of the required time and the discharge current value (for example, 0.2 A) is used as the battery capacity. As a modification, discharge characteristics other than the conditions (current value, temperature, etc.) of the JIS-compliant discharge test may be used instead.

In other words, in the present embodiment, a new battery 1 in a fully charged state is discharged with a constant current value (for example, 0.2 A) conforming to the JIS standard, and the transition of the output voltage of the battery 1 at that time is measured. . The curve G7 in the graph of FIG. 4 shows the result of measuring the transition of the output voltage of the battery 1 at that time, and the value V _AF in the graph is the output voltage of the fully charged battery 1 before the start of discharging. Value (open-circuit voltage value), which corresponds to the aforementioned value V _OIF . The value V _AE is an open-circuit voltage value at the end of discharging corresponding to zero remaining charge of the battery 1, and corresponds to the aforementioned value V _OIE described above. The value V _BF is the output voltage value of the battery 1 immediately after the start of discharging, the value V _BE is the output voltage value at the end of discharging corresponding to the remaining charge amount of the battery 1, and the value _TE is the remaining charge amount. The time at the end of discharge corresponding to zero is shown. A straight line G8 approximates the transition of the measured value of the open-circuit voltage of the battery 1 that changes with a decrease in the remaining charge amount due to discharge by a straight line. Further, the hatched region in the graph is the impact portion reflecting the increase in the internal resistance R _B of the battery 1 with decreasing remaining charge, the graph of FIG. 5 to FIG. 2 and described below Corresponds to the hatched area.

Subsequently, the magnitude of the difference along the vertical axis of the graph between the point at point a straight line G8 in the upper curve G7 in the graph of FIG. 4 is proportional to the internal resistance value R _B of the battery 1 at that point in time The ratio (D3 / D3) of the difference D2 between the value V _AF and the value V _BF at the start of discharge (at the time of full charge) and the difference D3 between each point on the straight line G8 and each point on the curve G7 By D2), the rate of change (R _B / R _BF ) of the internal resistance value R _B at each open circuit voltage value V _O can be derived. A curve G9 in the graph of FIG. 5 shows the rate of change (R _B / R _BF ) of the internal resistance value R _{B with} respect to the change of the open-circuit voltage value V _O derived as described above. (3) is determined.

Next, referring to FIG. 6, the relational expressions (4) and (5) above (or the data table in which the open circuit voltage value V _OI and the lower limit voltage value V _LI equivalent to the relational expressions are associated) are shown. An evaluation principle of the state (deterioration degree and remaining charge amount) of the used battery 1 will be described.

First, the evaluation principle of the degree of deterioration will be described. The curve G1 in the graph of FIG. 6 indicates the relational expressions (4) and (5) previously stored in the system as described above (or the open-circuit voltage value V _OI and the lower limit voltage value equivalent to the relational expressions). (Data table in which V _LI is associated) and the above-described initial reference open circuit voltage value V _OIF and initial reference lower limit voltage value V _LIF . Information on the curve G1 and the values V _OIF and V _{LIF in} FIG. 6 is stored in the system and used for evaluating the state of the battery 1.

When the use of the battery 1 is started, when the degree of deterioration of the battery 1 is evaluated, the engine start load L _S at the start of the engine is an open voltage before being connected to the battery 1. A post-opening voltage value V _OR and a post-use lower limit voltage value V _LR that is a lower limit voltage when the engine starting load L _S is connected to the battery 1 are measured. At this time, the remaining charge of the battery 1 does not have to be fully charged.

Subsequently, the open-circuit voltage value when the lower-limit voltage value on the curve G1 in the graph of FIG. 6 is equal to the post-use lower-limit voltage value V _LR is derived as the corresponding reference open-circuit voltage value V _{OS and} stored in advance. A first difference value D11 that is the difference between the reference open circuit voltage value V _OIF and its corresponding reference open circuit voltage value V _OS, and a second that is the difference between the initial reference open circuit voltage value V _OIF and the used open circuit voltage value V _OR . The degree of deterioration of the battery 1 at that time is detected by comparing the difference value D12.

This detection principle has a characteristic that the measurement point (V _O , V _L ) on the graph shifts substantially to the left so as to approach the curve G1 as the deterioration degree of the battery 1 described with reference to FIG. 1 is smaller. It is used. That is, as the degree of deterioration of the battery 1 is smaller, the measurement point P11 (V _OR , V _LR ) on the graph of FIG. 6 is closer to the coordinate point P12 on the corresponding curve G1. The degree of deterioration of the battery 1 is evaluated based on the degree of approach to the coordinate point P12 of P11.

Next, the evaluation principle of the remaining charge will be described. Similar to the evaluation of the degree of deterioration, the evaluation of the remaining charge amount is performed using the relationship between the discharge voltage and the lower limit voltage when the battery 1 represented by the curve G1 in the graph of FIG. In the evaluation, the post-use open-circuit voltage value V _OR and the post-use lower limit voltage value V _LR are measured. The storage unit 17 stores a minimum reference open circuit voltage value V _OIE that is an open circuit voltage when the remaining amount of charge of the new battery 1 acquired with the acquisition of the internal resistance change rate of the above equation (3) is zero. It is stored in advance as an initial setting.

Similarly to the evaluation of the degree of deterioration, the open-circuit voltage value when the lower-limit voltage value on the curve G1 of the graph of FIG. 6 is equal to the post-use lower-limit voltage value V _LR is used as the corresponding reference open-circuit voltage value V _OS. Derived as Then, a minimum post-use open-circuit voltage value V _ORE that is an open-circuit voltage when it is assumed that the remaining charge of the battery 1 at the time when the use is started is zero is derived as follows. That is, a ratio of a value D14 obtained by subtracting the minimum post-use open-circuit voltage value V _ORE from the initial reference open-circuit voltage value V _OIF to a value D13 obtained by subtracting the minimum standard open-circuit voltage value V _OIE from the initial reference open-circuit voltage value V _OIF acquired in advance. but to be equal to the ratio of the initial reference open circuit voltage value V corresponding reference from the _OIF open voltage value V _OS initial reference to the value D11 obtained by subtracting the open circuit voltage value V value obtained by subtracting the open circuit voltage value V _OR after use _OIF D12 The minimum post-use open-circuit voltage value V _ORE is derived.

The difference between the initial reference open-circuit voltage value V _OIF and the minimum post-use open-circuit voltage value V _ORE, and the difference between the post-use open-circuit voltage value V _OR and the minimum post-use open-circuit voltage value V _OS. Is compared with the fourth difference value D22, so that the remaining charge of the battery 1 at that time is detected.

  According to this detection principle, as the remaining charge of the battery 1 decreases from the fully charged state, the coordinate point P21 corresponding to the measurement point P11 on the virtual line L1 parallel to the horizontal axis of the graph of FIG. This utilizes the characteristic of approaching from the coordinate point P22 side corresponding to the amount to the coordinate point P23 side corresponding to the state of zero remaining charge.

<Device configuration>
FIG. 7 is a block diagram of a battery state management device according to an embodiment of the present invention. As shown in FIG. 7, the battery state management device includes a current sensor 11, a voltage sensor (voltage detection means) 13, a processing unit 15, a storage unit 17, and an output unit 19, and is mounted on a vehicle. The state of the battery 1 is managed.

  The current sensor 11 detects an input / output amount of current to the battery 1. The voltage sensor 13 detects the output voltage of the battery 1. The processing unit 15 includes a CPU and the like, and performs various information processing operations (including control operations) for managing the battery 1. The storage unit 17 includes a memory and the like, and stores information necessary for various information processing operations performed by the processing unit 15. The output unit 19 is for outputting a determination result of the state of the battery 1 and the like.

<Whole predetermined operation>
First, the overall processing operation of the battery state management apparatus will be described with reference to FIG. As the ignition switch (hereinafter referred to as “IG switch”) 21 is turned on in step S1, the processing unit 15 performs an initial charge remaining amount detection operation in step S2. In this detection operation, the open-circuit voltage of the battery 1 is measured via the voltage sensor 13, and the remaining charge (initial charge remaining) of the battery 1 before starting the engine is detected based on the measured value of the open-circuit voltage. At this time, it is also determined whether or not the battery 1 is fully charged. Note that the open-circuit voltage of the battery 1 measured here is used for engine start state determination in step S5 described later or reference discharge characteristic derivation processing in step S6.

  As the starter 23 is driven and the engine (not shown) is started in the subsequent step S3, the processing unit 15 determines whether or not the process for deriving the reference discharge characteristics of the battery 1 is necessary in step S4. That is, after the vehicle assembly is completed, if the reference discharge characteristic derivation process has not yet been performed, the process proceeds to step S6, where the reference discharge characteristic derivation process is performed. If the derivation process has already been performed, step S6 is performed. Proceeding to S5, engine starting state determination processing is performed. Whether or not the reference discharge characteristics have already been derived is determined, for example, by whether or not the relational expression (or equivalent data table) relating to the above expressions (4) and (5) is stored in the storage unit 17. It is done by judging. In addition, the derivation of the reference discharge characteristics does not need to be performed until the battery 1 is replaced if it is substantially performed once at the time of completion of vehicle assembly. When the reference discharge characteristic deriving process in step S6 or the starting state determination process in step S5 is performed, the process proceeds to step S7, and a post-startup deterioration determination process is performed. The specific contents of the reference discharge characteristic derivation process and the starting state determination process will be described later.

  Then, the processing unit 15 performs a deterioration determination operation after engine start in the subsequent step S7. In this deterioration determination operation after starting, a current inflow state to the battery 1 that has become fully charged (or a state close thereto) by charging after the engine is started is detected via the current sensor 11, and the battery is determined based on the current inflow state. A degradation degree of 1 is determined.

  Moreover, the process part 15 performs charge control (charge remaining amount management of the battery 1) with respect to the battery 1 by continuing step S8. In this charge control, by integrating the measured current value of the current sensor 11, the total amount of current discharged from the battery 1 from a predetermined reference time such as when the engine is started is sequentially detected, and the battery 1 is based on the detection result. The amount of charge to be performed is determined. As a result, the remaining charge of the battery 1 during traveling is maintained within a predetermined range. The charge amount is controlled, for example, by controlling the power generation amount (output voltage or the like) of an alternator (not shown).

  The deterioration determination operation and charge control after engine start in steps S7 and S8 are repeatedly continued until the engine is stopped.

<Standard discharge characteristics derivation process>
Here, the reference discharge characteristic deriving process performed in step S6 of FIG. 8 described above will be described. As a premise of the reference discharge characteristic deriving process, the storage unit 17 has an open circuit that approximately represents the rate of change (R _BI / R _BIF ) of the internal resistance value R _{BI with} respect to the change of the open circuit voltage value V _OI of the new battery 1. Information on the function such as the above expression (3) with the voltage value V _OI as a variable (or the equivalent open circuit voltage value V _OI and the rate of change of the internal resistance value R _BI at each open circuit voltage value V _OI (R _BI / R _BIF ) must be stored in advance.

  The processing unit 15 performs the reference discharge characteristic derivation process only when the battery 1 is in a fully charged state based on the detection in step S2. If the battery 1 is not in the fully charged state, For example, the process proceeds to step S7 without performing the derivation process. If the battery 1 is in a fully charged state at the next engine start, a reference discharge characteristic derivation process is performed at step S6.

In this derivation process, as described above, the lower limit voltage value when the engine starting load L _S is connected to the battery 1 is measured via the voltage sensor 13 as the initial reference lower limit voltage value V _LIF , and this initial reference lower limit voltage is set. Using the value V _LIF , the initial reference open circuit voltage value V _OIF that is the open circuit voltage measured in the immediately preceding step S 2, and the above equation (3) (or a data table equivalent to the above equation (3)) The reference discharge characteristic of the new battery 1 with respect to the engine starting load L _S is derived. That is, the reference discharge characteristic of the new battery 1 is derived as a relational expression of the above expression (4) indicating the change in the lower limit voltage value V _LI accompanying the change in the open circuit voltage value V _OI . However, the parameter R _LK in the equation (4) is given by the above equation (5).

In the present embodiment, the relationship between the change in the open circuit voltage value V _{OI and} the change in the lower limit voltage value V _LI in the new battery 1 derived in this way is expressed in the form of relational expressions (4) and (5) in the storage unit 17. However, a data table substantially equivalent to the relational expressions (4) and (5) (a curve G1 on a two-dimensional coordinate with the open-circuit voltage and the lower limit voltage taken on the vertical axis and the horizontal axis is shown. The coordinate information may be stored in the storage unit 17 in the form of coordinate information.

In this reference discharge characteristic derivation process, the initial reference open circuit voltage value V _OIF and the initial reference lower limit voltage value V _LIF used for the derivation process are stored in the storage unit 17.

<Start-up state determination process>
Next, the starting state determination process performed in step S5 of FIG. 8 described above will be described. This start-up state determination process is executed regardless of the remaining charge of the battery 1, but it is a precondition that the reference discharge characteristic deriving process in step S6 has been completed.

In this starting state determination process, as described above, the lower limit voltage value when the engine starting load L _S is connected to the battery 1 is measured via the voltage sensor 13 as the lower limit voltage value V _LR after use. Post-lower limit voltage value V _LR , post-use open-circuit voltage value V _OR which is the open-circuit voltage measured in the immediately preceding step S2, and information acquired by the reference discharge characteristic derivation process in step S6 and stored in the storage unit 17 Based on the above, the degree of deterioration and the remaining charge of the battery 1 at that time are determined.

First, the case processing for the degree of deterioration will be described. First, when the lower limit voltage value on the curve G1 of the graph of FIG. 6 represented by the relational expressions (4) and (5) stored in the storage unit 17 is equal to the lower limit voltage value V _LR after use. The open circuit voltage value is derived as the corresponding reference open circuit voltage value V _OS . Alternatively, the value of the variable V _OI when the post-use lower limit voltage value V _LR is substituted for the variable V _LI in the equations (4) and (5) is derived as the corresponding reference open circuit voltage value V _OS .

Subsequently, a first difference value D11 that is a difference between the initial reference open circuit voltage value V _OIF stored in the storage unit 17 and the corresponding reference open circuit voltage value V _OS , the initial reference open circuit voltage value V _OIF, and the open circuit after use. By comparing the second difference value D12, which is the difference from the voltage value _VOR , the degree of deterioration of the battery 1 at that time is detected. For example, the degree of deterioration of the battery 1 is detected based on the ratio of the second difference value D12 to the first difference value D11 (corresponding to the hatched portion C1 in FIG. 6).

Next, the remaining charge determination process will be described. In this determination process, the process is performed using the post-use lower limit voltage value V _LR and the corresponding reference open circuit voltage value V _OS acquired by the deterioration degree determination process.

Subsequently, a minimum post-use open-circuit voltage value V _ORE that is an open-circuit voltage when assuming that the remaining charge of the battery 1 at that time is zero is derived as follows. In other words, the initial reference open circuit voltage value V _OIF acquired in advance is subtracted from the initial reference open circuit voltage value V _OIF for the value D13 obtained by subtracting the minimum standard open circuit voltage value V _OIE stored in the storage unit 17 by the initial setting. The ratio of the value D14 obtained by subtracting the voltage value V _ORE is the initial reference open voltage value V _OIF to the post-use open circuit voltage value V _OR for the value D11 obtained by subtracting the corresponding reference open voltage value V _OS from the initial reference open circuit voltage value V _OIF. The minimum post-use open-circuit voltage value V _ORE is derived so as to be equal to the ratio of the subtracted value D12.

The difference between the initial reference open-circuit voltage value V _OIF and the minimum post-use open-circuit voltage value V _ORE, and the difference between the post-use open-circuit voltage value V _OR and the minimum post-use open-circuit voltage value V _OS. Is compared with the fourth difference value D22, so that the remaining charge of the battery 1 at that time is detected. For example, the remaining charge of the battery 1 is detected based on the ratio of the second difference value D22 to the third difference value D21 (corresponding to the hatched portion C2 in FIG. 6).

<Reference Discharge Characteristic Correction Processing>
Although the process for deriving the reference discharge characteristic has been described above, the process for correcting the derived reference discharge characteristic will be described below.

  The battery 1 uses dilute sulfuric acid as a battery solution. Then, the sulfuric acid concentration of the battery liquid may be intentionally set to a different value depending on the vehicle type on which the battery 1 is mounted and the region (export destination, etc.) where the battery 1 is used. Further, the sulfuric acid concentration of the battery liquid also varies due to the decrease of the battery liquid and the influence of sulfation.

FIG. 9 is a graph showing the relationship between sulfuric acid concentration, specific gravity, and open circuit voltage. The specific gravity of the battery liquid increases in proportion to the sulfuric acid concentration. Moreover, the open circuit voltage increases in proportion to the specific gravity of the battery fluid. That is, it can be seen that the open circuit voltage of the battery 1 increases as the sulfuric acid concentration of the battery liquid increases. The reference discharge characteristic (curve G1) shown in FIG. 6 is obtained for the battery 1 having a specific gravity of the battery liquid of 1.28. In this case, the open-circuit voltage (initial reference open-circuit voltage value V _OIF ) when the new battery 1 is fully charged is 12.86 V from the graph of FIG.

  Here, a situation is considered in which the battery 1 mounted on the vehicle is replaced with another battery having different specific gravity (hereinafter referred to as “battery 1 ′”). When the battery 1 is replaced with the battery 1 ′, a reference discharge characteristic derivation process for the battery 1 ′ after replacement is performed. This process is basically the same as the process for deriving the reference discharge characteristics for the battery 1 described above.

FIG. 10 is a graph showing the process of deriving the reference discharge characteristics related to the battery 1 ′. By measuring the open-circuit voltage value and the lower limit voltage value for a new and fully charged battery 1 ′, an initial reference open-circuit voltage value V _OIF ′ and an initial reference lower-limit voltage value V _LIF ′ for the battery 1 ′ are obtained. Thereby, the coordinate point P _F ′ relating to the battery 1 ′ is defined. FIG. 10 shows an example in which the initial reference open circuit voltage value V _OIF ′ is 13.06V.

Then, under the assumption that the internal resistance value R _B is not changed by the open-circuit voltage value V _O In the above formula (2), starting from the coordinate point P _F, a straight line passing through the origin of the coordinate axes (hereinafter "linear G5 '"). Next, with respect to the straight line G5 ′, a point on the straight line G5 ′ is defined as a rate of change of the internal resistance value of the battery 1 according to the open circuit voltage value V _OI at that point given by the relationship of the above equation (3). The vertical axis is shifted in the minus direction by a shift amount corresponding to the change mode. As a result, the lower limit voltage value V _LI for each remaining charge (each open circuit voltage value V _OI ) is derived. As a result, a curve G1 ′ starting from the coordinate point P _F ′ is obtained.

  The obtained curve G1 'is used for managing the state of the battery 1' as a reference discharge characteristic for the battery 1 '. As a state management method (degradation degree and remaining charge evaluation method), the same method as the battery 1 described above can be used.

In the example shown in FIG. 10, the minimum reference open circuit voltage value V _OIE for the battery 1 is 11.9V (the lower limit voltage value at that time is V _LIE ), and the minimum reference open circuit voltage value V _OIE 'for the battery 1 ′ is 12.1 V (the lower limit voltage value at that time is V _LIE ').

<Summary>
As described above, according to the present embodiment, while the discharge of the current value at a predetermined level conforming to the JIS standard for the battery capacity test is performed, the transition of the output voltage of the battery 1 over time is measured, Since the state management of the battery 1 is performed based on the discharge characteristic data of the battery 1 obtained by averaging the measurement results, there are individual differences even if the types of the batteries 1 are different in capacity, grade, etc. With respect to the battery 1, it is possible to uniformly handle changes in the internal resistance value with respect to changes in the output voltage. As a result, it is not necessary to perform characteristic evaluation or condition setting of the internal resistance for each type of the battery 1.

The processing unit 15 derives a new reference discharge characteristic when the fully charged open circuit voltage value (initial reference open circuit voltage value V _OIF ) is changed due to the change in the specific gravity of the battery fluid. Therefore, a new reference discharge characteristic (curve G1 ′) is used for the battery 1 ′ having a specific gravity different from that of the battery 1 used for deriving the reference discharge characteristic and for the battery 1 whose specific gravity has changed since the reference discharge characteristic was derived. Thus, by managing the battery state, it is possible to realize the battery state management appropriately corresponding to the change in specific gravity.

Further, since the rate of change of the internal resistance of the battery 1 with respect to the change of the open-circuit voltage according to the change of the remaining charge of the new battery 1 is almost the same regardless of the grade of the battery 1, the change in the internal resistance Rate and the voltage drop characteristic at the time of full charge of the battery 1 with respect to the engine starting load L _S unique to the vehicle at the time of vehicle assembly completion or the like. Discharge characteristics can be acquired automatically without setting parameters specific to each vehicle type, reducing human and equipment costs for parameter settings, as well as variations due to individual vehicle differences within the same vehicle type. Can be easily accommodated.

  Further, as described above, by evaluating the degree of deterioration and the remaining charge based on the reference discharge characteristics of the battery 1 and the discharge characteristics of the battery 1 due to the discharge at the time of engine start at each evaluation time point, Without taking special measures such as parameter setting for individual differences, it is possible to accurately detect the degree of deterioration of the battery 1 and the remaining charge amount by a simple calculation process.

  Further, the degree of deterioration of the battery 1 at each time point can be detected without depending on the remaining charge amount of the battery 1, and the remaining charge amount of the battery 1 at each time point can be detected without depending on the degree of deterioration of the battery 1. Can be detected.

  In this embodiment, since the lowest value of the output voltage of the battery 1 when the engine is discharged is used as the discharge voltage value of the battery 1, the discharge voltage that effectively represents the characteristics of the battery 1 is used. The value can be acquired easily and reliably, and it is not necessary to cause the battery 1 to perform a special discharge for evaluating the state of the battery 1, and the engine starting ability of the battery 1 can be accurately evaluated. As a modification of this point, the discharge characteristics of the battery 1 may be detected by using a discharge by another load instead of a discharge at the time of starting the engine of the battery 1. Moreover, although the minimum value of the output voltage of the battery 1 at the time of discharge was used as the voltage value at the time of discharge, for example, the output voltage value after a predetermined minute time has elapsed from the start of discharge may be used as the voltage value at the time of discharge. .

  Moreover, since the fully charged state is used as a reference for the remaining charge of the battery 1 when acquiring the discharge characteristics of the battery 1 in a new state, the remaining charge of the battery 1 can be easily and accurately set to the reference state. As a result, the discharge characteristics of the battery 1 can be detected easily and accurately. In this regard, the discharge characteristics of the new battery 1 may be acquired with reference to another remaining charge level.

<Modification>
In addition, since the method for evaluating the state of the battery 1 according to the above-described embodiment tends to decrease in reliability as the lower limit voltage value V _LR of the battery 1 at each evaluation increases, in order to ensure the reliability of the evaluation result, The determination of the degree of deterioration of the battery 1 and the remaining charge amount may be performed only when the lower limit voltage value V _LR is equal to or lower than a predetermined reference level.

  In addition, a temperature sensor that measures the temperature of the battery 1 may be added to the apparatus configuration of FIG. 7 according to the above-described embodiment, and the state evaluation in consideration of the temperature of the battery 1 may be performed. More specifically, for example, two-dimensional coordinate information representing the relationship between the open circuit voltage and the lower limit voltage of a new battery 1 at each temperature (in this case, it can also be referred to as three-dimensional coordinate information when considering the temperature). Deriving and evaluating the state at the current temperature based on it, and evaluating the state by correcting the temperature-dependent parameters (open voltage, lower limit voltage, etc.) to a temperature (for example, correcting to the standard temperature value) May be performed.

It is a graph which shows the measurement result which measured the open circuit voltage and the minimum voltage at the time of engine starting about the battery from which a deterioration condition and charge remaining amount differ. It is a graph for demonstrating the discharge characteristic at the time of engine starting of a battery. It is a circuit diagram which shows typically the relationship between the load connected to a battery at the time of engine starting, and the internal resistance of a battery. It is the graph of the data obtained by measuring transition of the output voltage at the time of discharge of a new battery using a JIS capacity test, and performing predetermined averaging processing etc. about the data. It is a graph which shows transition of the internal resistance change rate with respect to the change of the open circuit voltage accompanying discharge. It is a graph for demonstrating the principle which performs the state evaluation of a battery based on the discharge characteristic at the time of engine starting of the derived | led-out battery. It is a block diagram of the battery state management apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows the whole processing operation of the battery state management apparatus of FIG. It is a graph which shows the mutual relationship of sulfuric acid concentration, specific gravity, and an open circuit voltage. It is a graph which shows the correction | amendment process of a reference | standard discharge characteristic.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery 11 Current sensor 13 Voltage sensor 15 Processing part 17 Memory | storage part 19 Output part 21 IG switch 23 Starter

Claims (1)

A battery state management device that is mounted on a vehicle and manages the state of a battery,
Storage means for storing information relating to a change characteristic of the internal resistance of the battery with respect to a change in an open-circuit voltage of the battery according to a remaining charge;
Each of the information, the open voltage that is the output voltage of the battery that is not discharged, and the lower limit voltage that is the lowest voltage of the battery at the start of the engine of the vehicle , measured for the fully charged battery . Processing means for deriving a reference discharge characteristic indicating a relationship between the open circuit voltage and the lower limit voltage in the battery based on a measured value ;
When the measured value of the open-circuit voltage in the fully charged battery changes , the processing means performs a new operation based on the information and the measured values of the open-circuit voltage and the lower limit voltage of the battery after the change. A battery state management device for deriving the reference discharge characteristic.

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