JP7459531B2 - Lead-acid battery charging method, control device, and computer program - Google Patents

Description

The present invention relates to a lead-acid battery charging method, a control device, and a computer program.

Lead-acid batteries are used for various purposes, including automotive and industrial use. For example, automotive lead-acid batteries are mounted on moving objects such as automobiles, motorcycles, forklifts, and golf cars, and are used as a power supply source for starter motors when starting an engine, and as a power supply source for various electrical devices such as lights. For example, industrial lead-acid batteries are used as a power supply source for emergency power sources and UPS.
Lead-acid batteries are also used as power sources for electric vehicles such as forklifts, golf cars, aerial work vehicles, construction machinery, transport vehicles, and low-lift vehicles, as well as small EV cars.

As a charging method for a lead-acid battery (hereinafter referred to as a battery), there is a multi-stage (N-stage) constant current charging method as shown in Patent Document 1. In this charging method, when the battery voltage rises to a switching value (target value), the charging proceeds to the next step (stage), and this is repeated up to the Nth stage. The charging current is reduced step by step.
If a battery cell shorts out during use, the voltage will not rise to the switching value and charging will continue, which can lead to overcharging and an unsafe situation. To prevent this, an upper limit time is set for each stage, and if the voltage does not rise to the switching value even after the upper limit time is reached, charging will be stopped.

Patent No. 4747549

All of the lead sulfate generated during discharging is not reduced to lead during charging, and a portion remains as lead sulfate. When charging and discharging are repeated, the crystal size of the remaining lead sulfate gradually increases, and so-called sulfation occurs, in which the crystal size of the remaining lead sulfate is unable to return to lead even after charging. Sulfation occurs due to dark current discharge (several mA to several tens of mA) from the vehicle, and due to insufficient charging due to a decrease in charging efficiency during low temperatures in winter.
If the battery is sulfated and the reaction resistance is increased, the current is high at the initial stage of charging and the voltage immediately rises to the switching value. When the current becomes smaller, that is, when the efficiency improves, the charging reaction is promoted, but because the current is small, it takes time for the voltage to reach the switching value, and even though no short circuit has occurred, the charging reaction reaches the upper limit. There is a problem in that when the charging time is reached, it is determined that there is an abnormality and charging is stopped.

The present invention aims to provide a charging method, control device, and computer program for a lead-acid battery that determines whether to continue charging based on a change in voltage.

A method for charging a lead-acid battery according to one aspect of the present invention includes N stages of constant current charging steps, and when the voltage reaches a target value, the process moves to the next step, and the N-1 step is performed. Alternatively, if the voltage does not reach the target value at the first time point in the N-2nd step, it is determined whether or not to continue charging based on the change in voltage.

A method for charging a lead-acid battery according to one aspect of the present invention includes N stages of constant current charging steps, and when the voltage reaches a target value, the process moves to the next step, and the N-1 step is performed. , the current value in the N-2nd stage, or in the steps after the Nth stage is set to 0.01 CA or more and 0.03 CA or less.

A control device according to one aspect of the present invention has N constant current charging steps, and when the voltage reaches a target value, the control device controls charging of a lead-acid battery to move to the next step. The device includes a determination unit that determines whether or not to continue charging based on a change in voltage when the voltage does not reach the target value at the first time point in the N-1st or N-2nd step. Be prepared.

A computer program according to one aspect of the present invention has N stages of constant current charging, and when the voltage reaches a target value, the computer is caused to execute a process of determining whether the voltage has reached the target value at a first point in time in the N-1th or N-2th stage of charging, which transitions to the next stage, and, when it is determined that the voltage has not reached the target value at the first point in time, determining whether to continue charging based on the change in voltage over a predetermined time.

According to the present invention, it is possible to determine whether to continue charging based on the change in voltage, rather than the passage of time, and continue charging a lead-acid battery that is not abnormal.

It is a graph showing the relationship between time and current, and time and voltage in the case of charging by five stages of constant current charging. It is a graph showing the relationship between time and current, and time and voltage when sulfation occurs in a battery. 1 is a block diagram showing the configuration of a charging/discharging system, a charger, and a server according to Embodiment 1. FIG. 10 is a flowchart showing a procedure of a fourth stage of charging processing by the control unit. The fourth row is a graph showing the relationship between time and voltage. It is a graph showing the relationship between time and voltage in the fourth row. It is a graph showing the relationship between time and voltage in the fourth row. 1 is a graph showing a charge/discharge cycle. 13 is a flowchart showing a procedure of a fourth stage process by the control unit. FIG. 7 is an explanatory diagram regarding learning model generation processing according to the second embodiment. It is a flowchart which shows the procedure of the process of deriving a charging curve by a control part. 13 is a graph showing the relationship between time and current, and between time and voltage when charging by constant current charging according to the third embodiment.

(Summary of embodiment)
The method for charging a lead-acid battery according to the embodiment has N constant current charging steps, and when the voltage reaches a target value, moves to the next step and performs the N-1st step or N-th step. If the voltage does not reach the target value at the first time point in the second step, it is determined whether or not to continue charging based on the change in voltage.
Here, the change in voltage may be a change in voltage over a predetermined period of time, or may be a change in voltage over time.

FIG. 1 is a graph showing the relationship between time and current, and time and voltage when charging is performed using five stages of constant current charging. In FIG. 1, the horizontal axis is time (seconds), the right vertical axis is current (A), and the left vertical axis is voltage (V). For example, the charging currents for the first stage, second stage, third stage, fourth stage, and fifth stage are 0.2 CA, 0.1 CA, 0.05 CA, and 0.025 CA, respectively. The switching voltage V is calculated, for example, by the following equation.
V=14.4+0.03(25-T)
Here, T: battery temperature

Conventionally, in order to prevent the occurrence of unsafe events as described above, an upper limit time is set for each stage, and if the voltage does not rise to the switching value when the upper limit time is reached, charging is stopped.
If sulfation occurs in the battery and the reaction resistance increases, the charging current decreases in the latter stage, and the charging reaction is promoted as the charging efficiency improves, but because the current is small, it takes time for the voltage to reach the switching value, and when the upper limit time is reached, charging is stopped as an abnormality. If sulfation occurs at low temperatures, the lead sulfate accumulated in the negative electrode is accelerated in the reaction of returning to lead during charging as the environmental temperature rises, making it difficult to reach the switching voltage.
When sulfation occurs in the battery, as shown in Figure 2, the first to third stages reach the switching voltage in a shorter time than in Figure 1, but the fourth stage does not reach the switching voltage. For example, if the upper limit time is set to 180 minutes after the start of the fourth stage, when 180 minutes has elapsed, a notification that the upper limit time has elapsed is issued and charging is stopped.

According to the charging method of the embodiment, if the voltage change is negative, it is assumed that a short circuit has occurred and it is possible to determine that charging should be stopped without waiting for the upper limit time to elapse, thereby preventing the occurrence of an unsafe event. If the voltage change is not negative, it is assumed that a short circuit has not occurred and charging can be continued. As it is determined whether or not to continue charging based on the voltage change, not the passage of time, it is possible to continue charging a battery that is not abnormal.

In the above-described charging method, charging may be continued if it is determined that the voltage change is a positive value and the voltage will reach the target value within a second time point.

According to the above configuration, if it is determined that the change in voltage is a positive value, no short circuit has occurred, and the voltage will reach the target value within the second time point, charging is continued, so that an unsafe event occurs. It is possible to secure the required amount of charging electricity without causing a problem.

In the charging method described above, after it is determined at the first time point that charging should be continued, a change in voltage is derived, and if it is determined at the second time point that the voltage has not reached the target value, charging may be stopped at the time point of determination.

According to the above configuration, if it is determined that the switching voltage is unlikely to be reached at the second time point based on the change in voltage after the first time point has passed, charging is stopped, thereby preventing unnecessary continuation of charging. If a short circuit occurs after the first time point has passed, this will be detected, and the occurrence of an unsafe event can be prevented.

In the above-described charging method, charging may be stopped when it is determined that the voltage change is a negative value at the first time point or that the voltage does not reach the target value at the second time point.

According to the above configuration, if the change in voltage is negative and a short circuit has occurred, charging can be stopped to prevent an unsafe event from occurring. Further, if it is determined that there is no possibility of reaching the switching voltage at the second time point, charging is stopped, so that unnecessary continuation of charging can be prevented.

In the above-mentioned charging method, if the voltage does not reach the target value at the second time point during periodic refresh charging or refresh charging when incomplete charging continues for a predetermined number of times, the charging method is terminated from the second time point. Push-in charging without providing a voltage may also be performed.

According to the above configuration, when sulfation occurs and the voltage does not reach the target value at the second time point, by performing forced charging, it is possible to secure the required amount of charging electricity. It is also possible to reduce the amount of sulfation.

In the above-described charging method, when the voltage is input in time series, the voltage is input in time series to a recurrent neural network that outputs the time series transition of the future voltage, and the time series of the future voltage of the lead-acid battery is input. The transition may be estimated and it may be determined whether the voltage reaches the target value at the second time point.

The above configuration makes it possible to easily and accurately estimate the future time series change in voltage and determine whether the voltage will reach the target value at the second point in time.

In the above-mentioned charging method, if the voltage does not reach the target value at the first point during normal charging or equalized charging, it may be determined whether to continue charging based on the change in voltage.

According to the above configuration, when the battery life is extended by performing equal charging after normal charging a predetermined number of times, if the voltage does not reach the target value at the first point of each charging, the voltage It is determined whether or not to continue charging based on the change in . If the change in voltage is negative, it is assumed that a short circuit has occurred, and it can be determined that charging should be stopped, thereby preventing an unsafe event from occurring. If the change in voltage is not negative, it can be assumed that no short circuit has occurred, and charging can be continued.

The charging method for a lead-acid battery according to the embodiment has N stages of constant current charging, and when the voltage reaches a target value, the charging proceeds to the next stage, and the current value in the N-1st stage, N-2nd stage, or a step after the Nth stage is set to 0.01 CA or more and 0.03 CA or less.

The above configuration can suppress the accumulation of lead sulfate. When the current value is between 0.01 CA and 0.03 CA, the temperature does not rise, side reactions are unlikely to occur, and the charging time is not long, so battery deterioration is suppressed.

In the above charging method, the current value may be set to 0.01 CA or more and 0.0125 CA or less.

According to the above configuration, accumulation of lead sulfate can be further suppressed.

A control device according to an embodiment is a control device for controlling charging of a lead-acid battery, which has N constant current charging steps and moves to the next step when the voltage reaches a target value. A determination unit is provided that determines whether or not to continue charging based on a change in voltage when the voltage does not reach the target value at the first time point in the N-1st or N-2nd step.

According to the above configuration, when the change in voltage is negative, it is estimated that a short circuit has occurred, and it can be determined that charging should be stopped, thereby making it possible to prevent unsafe events from occurring. If the change in voltage is not negative, it can be assumed that no short circuit has occurred, and charging can be continued. It is possible to continue charging a battery with no abnormality by determining whether to continue charging based on changes in voltage rather than the passage of time.

The computer program according to the embodiment has N stages of constant current charging, and when the voltage reaches a target value, the computer executes a process to determine whether the voltage has reached the target value at a first point in time in the N-1th or N-2th stage of charging, which transitions to the next stage, and, when it is determined that the voltage has not reached the target value at the first point in time, to determine whether to continue charging based on the change in voltage over a predetermined period of time.

According to the above configuration, it is possible to determine whether or not to continue charging based on a change in voltage rather than the passage of time, and to continue charging a battery that has no abnormality.

(Embodiment 1)
FIG. 3 is a block diagram showing the configurations of the charge/discharge system 1, the charger 8, and the server 9 according to the first embodiment.
The charge/discharge system 1 includes a lead-acid battery (hereinafter referred to as battery) 3, a control device 4, a voltage sensor 5, a current sensor 6, and a temperature sensor 7. The battery 3 is used in electric vehicles such as electric forklifts, golf cars, and small EVs.

The battery 3 is a valve-regulated lead-acid battery (sealed lead-acid battery). Valve-regulated lead-acid batteries have a high degree of freedom in their installation position because they do not have an electrolyte that flows inside. The battery 3 includes a housing, a positive terminal, a negative terminal, and a number of cells 2. The cells 2 include a positive plate, a negative plate, and a separator. The separator is impregnated with an electrolyte (e.g., dilute sulfuric acid).

The control device 4 includes a control unit 41 , a memory unit 42 , a timer unit 44 , an input unit 45 , a communication unit 46 , and a display unit 47 .
The server 9 includes a control unit 91 and a communication unit 92 .
The control unit 41 of the control device 4 is connected to the control unit 91 via the communication unit 46 , the network 10 , and the communication unit 92 .
The battery 3 is connected to a charger 8 via terminals 11 and 12 .

The control units 41 and 91 are configured with, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), and control the operation of the control device 4 and the server 9 .
The storage unit 42 stores various programs and data.
The communication units 46 and 92 have a function of communicating with other devices via a network, and can transmit and receive required information.

The memory unit 42 of the control device 4 stores a charging control program 421, a history DB 422, and a curve DB 423. The program 421 is provided in a state stored on a computer-readable recording medium 43, such as a CD-ROM, DVD-ROM, or USB memory, and is stored in the memory unit 42 by installing it in the control device 4. The program 421 may also be obtained from an external computer (not shown) connected to a communication network and stored in the memory unit 42.

The history DB 422 stores the history of charging and discharging.
The charge and discharge history is the operating history of the battery 3, and includes information indicating the period (usage period) during which the battery 3 was charged or discharged, and information regarding the charging or discharging performed by the battery 3 during the usage period. The information indicating the usage period of the battery 3 includes information indicating the start and end points of charging or discharging, and the accumulated usage period during which the battery 3 was used. The information regarding the charging or discharging performed by the battery 3 is information indicating the voltage, rate, etc. during charging or discharging performed by the battery 3.
The curve DB 423 stores a charging curve that indicates a time series transition of voltage, which is derived as described below.

The input unit 45 receives input of the detection results from the voltage sensor 5 , the current sensor 6 , and the temperature sensor 7 .
The display unit 47 can be configured with a liquid crystal panel, an organic EL (Electro Luminescence) display panel, or the like. The control unit 41 performs control to display required information on the display unit 47. When it is determined in a charging control process described later that charging should be stopped, this is displayed. Instead of displaying on the display panel, the stop of charging may be notified by sound.

In the first embodiment, the control device 4 functions as the estimation device of the present invention. The server 9 may function as an estimation device. When the server 9 does not function as an estimation device, the charging/discharging system 1 does not need to be connected to the server 9.

The voltage sensor 5 is connected in parallel to the battery 3 , and outputs a detection result corresponding to the overall battery 3 voltage.
The current sensor 6 is connected in series to the battery 3 and outputs a detection result according to the current of the battery 3. Note that the current sensor 6 may also be one that is not electrically connected to the battery 3, such as a clamp-type current sensor.
The temperature sensor 7 is disposed in the vicinity of the battery 3 and outputs a detection result corresponding to the battery 3 temperature.

The charging method of the embodiment 1 will be described below. A case will be described in which the charging method has five constant current charging steps, and in the fourth step, it is determined whether or not to continue charging based on a change in voltage.
In the first to third stages, when the voltage reaches the switching value, the charging proceeds to the next stage. An upper limit time is set in each step, and when the upper limit time is reached, charging is stopped if the voltage has not reached the switching value. In the first to third stages, even if sulfation occurs, it does not take long for the voltage to reach the switching value, so there is a low possibility of a time error occurring.

FIG. 4 is a flowchart showing the procedure of the fourth stage charging process performed by the control unit 41 when the voltage has reached the switching value in the third stage.
The control unit 41 determines whether the voltage has reached the switching value at time _t1 (S1). An example of the time point _t1 is, for example, 90 minutes after the start of the fourth stage. If the voltage has reached the switching value at time t ₁ (S1: YES), the control unit 41 ends the fourth stage processing and moves to the fifth stage.

If the voltage has not reached the switching value at time t ₁ (S1: NO), the control unit 41 derives the difference ΔV between the voltage at time t ₁ and the voltage a predetermined time before time t ₁ (S2 ). If the time point t ₁ is, for example, 90 minutes, the difference ΔV between the voltage at the 75th minute and the voltage at the 90th minute is derived.

The control unit 41 determines whether ΔV>0 (S3). If ΔV>0 is not satisfied (S3: NO), the control unit 41 stops charging (S4) and ends the process. The control unit 41 displays the stoppage of charging on the display unit 47.
FIG. 5 is a graph showing the relationship between time and voltage in the fourth stage. In FIG. 5, the horizontal axis is time (minutes) and the vertical axis is voltage (V). In FIG. 5, 90 minutes corresponds to time _t1 , and 180 minutes corresponds to time _t2 , which is the upper limit time. As shown in FIG. 5, ΔV is negative. The control unit 41 extrapolates based on the voltage transition up to 90 minutes to derive a charging curve up to 180 minutes, and stops charging if it is determined that the voltage does not reach the switching value in 180 minutes. The control unit 41 derives a charging curve based on the V at time t ₁ and a plurality of Vs acquired in the past, using a method such as curve approximation, for example. If ΔV is negative, it is considered that there is a short circuit, and the occurrence of unsafe events can be prevented.

If ΔV>0 (S3: YES), the control unit 41 determines whether the switching value is reached at time _t2 (S5). As shown in FIG. 6, the control unit 41 derives a charging curve up to 180 minutes after the start by extrapolating based on the voltage transition up to 90 minutes, and determines whether the switching value is reached in 180 minutes. Determine whether

When the control unit 41 determines that the switching value has not been reached at the time _t2 (S5: NO), the control unit 41 advances the process to S4.
When the control unit 41 determines that the switching value is reached at time _t2 (S5: YES), the control unit 41 acquires the voltage at a predetermined interval (S6). The control unit 41 acquires the voltage at intervals of, for example, 10 or 15 minutes.
The control unit 41 derives a charging curve up to the time _t2 by extrapolating based on the transition of the voltage up to the time of determination, and stores the charging curve in the curve DB 423 (S7).
The control unit 41 determines whether or not the voltage reaches the switching value at time _t2 based on the charging curve (S8). The control unit 41 determines whether or not the voltage reaches the switching value when, for example, 180 minutes have elapsed.

When the control unit 41 determines that the switching value has not been reached at time t ₂ (S8: NO), the control unit 41 advances the process to S4.
If the control unit 41 determines that the switching value is reached at time t ₂ (S8: YES), it determines whether or not time t ₂ has been reached (S9).
If the time point t ₂ has not yet been reached (S9: NO), the control unit 41 returns the process to S6.
If the time point t ₂ has been reached (S9: YES), the control unit 41 ends the process.

As shown in FIG. 7, if the voltage difference ΔV between 105 minutes and 120 minutes becomes negative and the voltage is unlikely to reach the switching value after 180 minutes, charging is stopped at the point 120 minutes after it is determined that the voltage will not reach the switching value.

According to the charging method described above, if the voltage change is negative, it is assumed that a short circuit has occurred, and it is possible to determine that charging should be stopped without waiting for time _t2 to be reached, thereby preventing the occurrence of an unsafe event. If the voltage change is not negative, it is assumed that a short circuit has not occurred, and charging can be continued. Since it is determined whether or not to continue charging based on the voltage change, not the passage of time, it is possible to continue charging a battery that is not abnormal.
Although the above-mentioned charging process is described as being performed in the fourth stage (N-1 stage), the present invention is not limited to this, and may be performed in the third stage (N-2 stage).

FIG. 8 is a graph showing charging/discharging cycles. In FIG. 8, the horizontal axis is time (days) and the vertical axis is SOC (%). Each time, it supplies power to the load by discharging and then charging.
Among the 5 cycles, normal charging for 4 consecutive cycles has a small amount of overcharge electricity (e.g. 105%), and equal charging for the 5th cycle has a larger amount of overcharge electricity for the 5th step (e.g. 110%). %). By performing equal charging once every 5 times, compared to charging with the overcharged electricity amount (110%) at the 5th cycle every time, the decrease in capacity is prevented, the lifespan is extended, and the battery life is longer. Has stable cycle life characteristics.
In both normal charging and equal charging, the above-described charging process is performed in the fourth stage.

When performing regular refresh charging or refresh charging after a predetermined number of consecutive incomplete charges, the control unit 41 performs the following charging process.
FIG. 9 is a flowchart showing the procedure of the fourth stage process by the control unit 41.
The control unit 41 determines whether or not the voltage has reached the switching value at time _t1 (S11). If the voltage has reached the switching value at time _t1 (S11: YES), the control unit 41 ends the processing in the fourth stage and proceeds to the fifth stage.

When the voltage has not reached the switching value at time _t1 (S11: NO), the control unit 41 derives the voltage difference ΔV for a predetermined time before time _t1 is reached (S12).
The control unit 41 determines whether or not ΔV>0 (S13). If ΔV>0 is not true (S13: NO), the control unit 41 stops charging (S14) and ends the process.

If ΔV>0 (S13: YES), the control unit 41 acquires the voltage at predetermined intervals (S15).
The control unit 41 derives the difference ΔV between the voltage at the time of determination and the voltage at the immediately preceding time, and determines whether ΔV>0 (S16). If ΔV>0 is not satisfied (S16: NO), the control unit 41 advances the process to S14.

If ΔV>0 (S16: YES), the control unit 41 derives the charging curve up to time t ₂ by extrapolating based on the voltage transition up to the determination time, and stores it in the curve DB 423 ( S17).
The control unit 41 determines whether the switching value is reached at time t ₂ based on the charging curve (S18). The control unit 41 determines whether or not the switching value is reached after, for example, 180 minutes.
If the control unit 41 determines that the switching value has not been reached at time t ₂ (S18: NO), it determines whether or not time t ₂ has been reached (S19). If the time point t ₂ has not been reached (S19: NO), the control unit 41 advances the process to S15.
If the time point t ₂ has been reached (S19: YES), the control unit 41 performs push-in charging for a predetermined time (S20), and ends the process.

When the control unit 41 determines that the switching value is reached at time t ₂ (S18: YES), it determines whether or not time t ₂ has been reached (S21).
If the control unit 41 has not reached the time t ₂ (S21: NO), the control unit 41 returns the process to S15.
If the time point t ₂ has been reached (S21: YES), the control unit 41 ends the process.

According to the above-described charging process, when sulfation occurs and the voltage does not reach the switching value at time t ₂ , by performing forced charging from time t ₂ , it is possible to secure the required amount of charging electricity. It is also possible to reduce the amount of sulfation.

(Embodiment 2)
The control device 4 according to the second embodiment stores in the memory unit 42 a learning model 424 that estimates a future voltage in order to generate a charging curve.
10 is an explanatory diagram regarding the generation process of the learning model 424 according to the embodiment 2. The control device 4 learns based on teacher data in which multiple voltages in a time series are used as question data and voltages at multiple time points in the future are used as answer data, thereby constructing (generating) a neural network in which multiple voltages in a time series are used as input and voltages at multiple time points in the future are used as output.

Multiple voltages over time refer to multiple voltages over time for the same battery 3 from the past to the determination time point. Voltages at multiple points in the future refer to voltages at multiple points in the future, such as the point after the determination time point and the point after that.

The input layer has one or more neurons that accept a plurality of voltages in time series, and passes each of the input voltages to the intermediate layer. The intermediate layer includes an autoregressive layer that includes multiple neurons. The autoregressive layer is implemented, for example, as a LSTM (Long Short Term Memory) model, and a neural network including such an autoregressive layer is called an RNN (recurrent neural network). The intermediate layer outputs the amount of change caused by each of the plurality of voltages input sequentially in time series. The output layer has one or more neurons, and outputs voltages at multiple points in the future based on the amount of change due to each of the multiple voltages output from the intermediate layer. Such learning for the RNN is performed using, for example, a BPTT (Backpropagation Through Time) algorithm.

The teacher data may be stored in an array format. When the training data is in an array format, for example, the value of each element from array number 0 to 4 (t-4 to t) is used as problem data, and the value of each element from array number 5 to 7 (t+1 to t+3) is used as problem data. The answer data may be the value of . The time series problem data (t-2, t-1, t) input from the input layer is sequentially passed to the LSTM (autoregressive layer), and the LSTM (autoregressive layer) transfers the output value to the output layer and , it is possible to process sequence information including temporal changes and order by outputting it to its own layer.

FIG. 11 is a flowchart illustrating the process of deriving a charging curve by the control unit 41. The control unit 41 derives the charging curve in S7 of FIG. 4 or S17 of FIG. 9 as follows.
The control unit 41 reads the history DB 422 and obtains a plurality of voltages up to the time of determination (S31).
The control unit 41 inputs a plurality of voltages to the learning model 424 and obtains a plurality of future voltages (S32).
The control unit 41 derives a time-series voltage transition (charging curve) based on a plurality of voltages in the past, present, and future, stores it in the curve DB 423 (S33), and ends the process.
Thereafter, the processes from S8 in FIG. 4 or S18 in FIG. 9 are performed.

According to this embodiment, it is possible to easily and accurately estimate the future time series transition of the voltage and to determine whether or not the voltage will reach the target value at time _t2 .

(Embodiment 3)
The control unit 41 according to the third embodiment performs charging with the current value in the fourth and fifth steps set to 0.01 CA or more and 0.03 CA or less. The current value is preferably 0.01 CA or more and 0.0125 CA or less.

Fig. 12 is a graph showing the relationship between time and current, and time and voltage when charging by constant current charging according to embodiment 3. In Fig. 12, the horizontal axis is time (h), the right vertical axis is current (A), and the left vertical axis is voltage (V). In Fig. 12, _t0 , _ta , _tb , _tc , and _td represent the start of charging, the start of the fourth stage, the start of the fifth stage, the end of the conventional fifth stage, and the end of the fifth stage according to embodiment 3.
For example, the current values of the first, second and third stages are 0.2 CA, 0.1 CA and 0.05 CA, respectively.

The conventional current value in the fourth and fifth stages was 0.025 CA. The end time t _c is determined by calculating the charging electricity amount A based on the charging electricity amount based on the depth of discharge before charging and the charging electricity amount up to the third stage, and calculating the charging time based on the current value. is preferable.

In the third embodiment, the current values of the fourth and fifth stages are set to 0.0125 CA. The charging time calculated based on the charged amount of electricity A and the current value is twice as long as the conventional charging time, and the end time _td is set based on the charging time.

The current values in the fourth and fifth stages are determined by taking into consideration the end time of operation of the EV vehicle such as a forklift to which electric power is supplied, that is, the end time of discharge, and the start time of operation of the EV, that is, the start time of discharge. is preferable.

According to this embodiment, the accumulation of lead sulfate can be suppressed. When the current value is 0.01 CA or more and 0.03 CA or less, the temperature does not rise, side reactions are unlikely to occur, and the charging time is not long, so battery deterioration is suppressed.

The charging process of the third embodiment may be performed when it is determined that the switching value is not reached at the time t ₂ at the time t ₁ of the charging process of FIG. 4 of the first embodiment. That is, after time _t1 , charging is performed with the current value set to 0.01 CA or more and 0.03 CA or less.

In Embodiment 3, the case where the current value of the fourth stage and the fifth stage is set to 0.0125 CA is explained, but the current value is not limited to this, and the current value of the third stage (N-2nd stage) and thereafter is explained. The value may be set to 0.0125CA.

Hereinafter, an example of Embodiment 3 will be specifically described, but Embodiment 3 is not limited to this example.
[Example]
Normal charging in Figure 8 is performed with an overcharged electricity amount of 109%, equal charging is performed with an overcharged electricity amount of 110%, and in each charge, the current value in the 4th and 5th stages is set to 0.0125 CA. Charged.

[Comparative example]
The normal charging in Figure 8 is performed with an overcharged electricity amount of 109%, and the equal charging is performed with an overcharged electricity amount of 110%.The charging electricity amount is the same as in the example, but the fourth and fifth stage push charging is performed. Instead, a dark current of 0.0008 CA is applied after the fifth stage is completed.

Regarding the batteries of Examples and Comparative Examples, the occurrence of time errors was investigated by changing the environmental temperature to 0° C., 5° C., 15° C., 20° C., 25° C., and 35° C. The results are shown in Table 1 below.

The evaluation in Table 1 is as follows.
○…No time error occurred △…occurred once ×…occurred 5 times

The occurrence rate in Table 1 is expressed as a ratio of the number of occurrences in the example when the total number of occurrences in the comparative example is taken as 100%.
From Table 1, it can be seen that the batteries of Examples can reduce the incidence of time errors.

The present invention is not limited to the contents of the embodiments described above, and various changes can be made within the scope of the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included within the technical scope of the present invention.
For example, the battery 3 is not limited to a valve-controlled lead acid battery. Further, the battery 3 is not limited to use in electric vehicles such as electric forklifts, golf cars, and small EVs.

1 Charging/discharging system 3 Battery 4 Control device 41 Control section (judgment section)
42 Storage unit 421 Program 422 History DB
423 Curve DB
424 Learning model 43 Recording medium 44 Timing section 45 Input section 46, 92 Communication section 8 Charger 9 Server 10 Network

Claims (13)

A method for charging a lead-acid battery, wherein a control device controls five stages of constant current charging of the lead-acid battery based on the voltage of the lead-acid battery, the method comprising:
In the steps from the first stage to the third stage, when the voltage reaches the target value, the step moves to the next stage,
In the fourth step, if the voltage does not reach the target value at the first time point, it is determined whether or not to continue charging based on the change in voltage,
In the determination, if it is determined that the change in the voltage is a positive value and the voltage reaches the target value within a second time point, it is determined that charging is to be continued.
How to charge a lead acid battery. A charging method for a lead-acid battery, in which a control device controls five-stage constant current charging steps for the lead-acid battery based on a voltage of the lead-acid battery,
In the first and second steps, when the voltage reaches a target value, the process proceeds to the next step;
In a third step, if the voltage does not reach the target value at the first time point, it is determined whether or not to continue charging based on a change in the voltage;
and determining that charging is to be continued when it is determined in the determination that the change in the voltage is a positive value and that the voltage will reach the target value within a second time point.
How to charge a lead acid battery. After determining to continue charging at the first time point, a change in voltage is derived, and if it is determined that the voltage does not reach a target value at the second time point, charging is stopped at the time point of the determination . Or the method for charging a lead-acid battery according to claim 2. According to claim 1 or 2, charging is stopped when it is determined that the change in the voltage is a negative value at the first time point or that the voltage does not reach a target value at the second time point. How to charge a lead acid battery. If the voltage does not reach the target value at the second time point during periodic refresh charging or refresh charging when incomplete charging continues for a predetermined number of times, push-in charging without a final voltage is applied from the second time point. The method for charging a lead-acid battery according to claim 1 or 2 , wherein the method comprises: When the voltage is input in time series, the voltage is input in time series to a recurrent neural network that outputs the time series transition in the future voltage, and the future time series transition in the voltage of the lead-acid battery is estimated. The method for charging a lead-acid battery according to any one of claims 1 to 5, wherein it is determined whether the voltage reaches a target value at a second time point. A method for charging a lead-acid battery according to any one of claims 1 to 4, in which, if the voltage does not reach a target value at the first time point during normal charging or equalized charging, a determination is made as to whether or not to continue charging based on a change in voltage. A charging method for a lead-acid battery, in which a control device controls five-stage constant current charging steps for the lead-acid battery based on a voltage of the lead-acid battery,
When the voltage reaches a target value in each step , the process proceeds to the next step;
A method for charging a lead-acid battery, comprising setting a current value in the third or subsequent step, the fourth or subsequent step, or the fifth step to 0.01 CA or more and 0.03 CA or less. The method for charging a lead-acid battery according to claim 8, wherein the current value is set to 0.01 CA or more and 0.0125 CA or less. A control device comprising a control unit that controls five stages of constant current charging steps for a lead-acid battery based on the voltage of the lead-acid battery, the control device comprising:
The control unit includes:
In the steps from the first stage to the third stage, when the voltage reaches the target value, the step moves to the next stage,
In the fourth step, if the voltage does not reach the target value at the first time point, it is determined whether or not to continue charging based on the change in voltage,
In the determination, if it is determined that the change in the voltage is a positive value and the voltage reaches the target value within a second time point, it is determined that charging is to be continued.
Control device. A control device comprising a control unit that controls five stages of constant current charging steps for a lead-acid battery based on the voltage of the lead-acid battery, the control device comprising:
The control unit includes:
In the first and second steps, when the voltage reaches the target value, proceed to the next step,
In the third step, if the voltage does not reach the target value at the first time point, it is determined whether or not to continue charging based on the change in voltage,
When it is determined in the determination that the change in the voltage is a positive value and that the voltage will reach the target value within a second time point, it is determined to continue charging.
Control device. A computer program that causes a computer to execute a process of controlling five stages of constant current charging of a lead-acid battery based on the voltage of the lead-acid battery, the computer program comprising:
In the steps from the first stage to the third stage, when the voltage reaches the target value, the step moves to the next stage,
In the fourth step, if the voltage does not reach the target value at the first time point, it is determined whether or not to continue charging based on the change in voltage,
In the determination, if it is determined that the change in the voltage is a positive value and the voltage reaches the target value within a second time point, it is determined that charging is to be continued.
computer program. A computer program for causing a computer to execute a process of controlling five-stage constant current charging steps for a lead-acid battery based on a voltage of the lead-acid battery,
In the first and second steps, when the voltage reaches a target value, the process proceeds to the next step;
In a third step, if the voltage does not reach the target value at the first time point, it is determined whether or not to continue charging based on a change in the voltage;
and determining that charging is to be continued when it is determined in the determination that the change in the voltage is a positive value and that the voltage will reach the target value within a second time point.
Computer program.

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