JP2023047092A - Charging method for battery - Google Patents

Abstract

To execute charging properly even when an estimated battery capacity has a large error.SOLUTION: A charging method for a battery includes steps of: estimating a capacity deterioration coefficient that shows a degree of capacity deterioration of the battery; calculating a time degradation coefficient that shows a degree of time degradation of the battery; and calculating a limit current value on the basis of the smaller one of the capacity deterioration coefficient and the time degradation coefficient and charging the battery with the calculated limit current value.SELECTED DRAWING: Figure 8

Description

The present invention relates to a battery charging method.

Patent Literature 1 discloses calculating the maximum charging current value during charging based on the state of the battery (usage history, deterioration state).

JP 2017-108604 A

In the configuration described in Patent Document 1, although the current value during charging is calculated in consideration of the state of deterioration of the battery, it is difficult to accurately grasp the state of deterioration of the battery. Therefore, if the battery capacity estimation error is large and the capacity deterioration state estimation accuracy is low, the charging current value will exceed the allowable current value, or the allowable current value will be limited in advance more than necessary. , there is a possibility that appropriate charging cannot be performed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a battery charging method capable of appropriately charging a battery even when the battery capacity estimation error is large.

The present invention is a battery charging method, comprising the steps of estimating a capacity deterioration coefficient indicating the degree of deterioration of the capacity of the battery; calculating the aging deterioration coefficient indicating the degree of deterioration of the battery over time; calculating a limited current value based on the smaller one of the deterioration coefficient and the temporal deterioration coefficient, and charging the battery with the calculated limited current value.

In the present invention, since the charging current value is set using the smaller one of the capacity deterioration coefficient and the deterioration coefficient over time, appropriate charging can be performed even when the battery capacity estimation error is large. If the battery capacity estimation error is large and the capacity deterioration coefficient is estimated to be larger than the actual deterioration state, the smaller coefficient, the aging deterioration coefficient, is used to calculate the limiting current value. Appropriate charging according to the state of deterioration can be performed.

FIG. 1 is a diagram schematically showing a charging system according to an embodiment. FIG. 2 is a map diagram showing an allowable current value map when the battery temperature is 25.degree. FIG. 3 is a diagram showing the relationship between the capacity retention rate and the capacity deterioration coefficient when there is no estimation error. FIG. 4 is a diagram showing the relationship between the capacity retention rate and the capacity deterioration coefficient when the estimation error is X %. FIG. 5 is a diagram showing the relationship between the capacity retention rate and the capacity deterioration coefficient when the estimation error is 10%. FIG. 6 is a map diagram showing the relationship between the capacity maintenance rate reflecting the estimation error of capacity estimation and the capacity deterioration coefficient. FIG. 7 is a map diagram showing a temporal deterioration coefficient map. FIG. 8 is a flow chart showing a battery charging method. FIG. 9 is a map diagram showing a case where the capacity deterioration coefficient and the aging deterioration coefficient are used together.

Hereinafter, a battery charging method according to an embodiment of the present invention will be specifically described with reference to the drawings. In addition, this invention is not limited to embodiment described below.

FIG. 1 is a diagram schematically showing a charging system according to an embodiment. When the charging system 1 charges the battery 2, the battery 2 and the charger 3 are electrically connected. This charging system 1 includes a charging control device 10, and the charging control device 10 controls a charging current value during charging.

The battery 2 is a secondary battery, and is composed of, for example, a lithium ion battery. The battery 2 is an assembled battery composed of a plurality of battery cells. During discharging, the electric power stored in the battery 2 is supplied to a motor or the like. During charging, in charging system 1 , power supplied from an external power supply via charger 3 is stored in battery 2 .

Charger 3 is a device capable of supplying power from an external power source to battery 2 . When charging the battery 2 , the battery 2 is electrically connected to an external power supply via the charger 3 by attaching the charger 3 to the device on which the battery 2 is mounted. When the battery 2 is not to be charged, the charger 3 can be removed from the device in which the battery 2 is mounted.

In the charging system 1 , as shown in FIG. 1 , a second connection portion 31 provided in the charger 3 is connected to a first connection portion 21 provided in a device in which the battery 2 is mounted. The first connection portion 21 is a connection portion on the battery 2 side and includes a positive electrode side connection portion 21 a connected to the positive electrode of the battery 2 and a negative electrode side connection portion 21 b connected to the negative electrode of the battery 2 . The second connection portion 31 is a connection portion on the charger 3 side, and includes a positive electrode side connection portion 31 a connected to the positive electrode side connection portion 21 a of the first connection portion 21 and a negative electrode side connection portion of the first connection portion 21 . 21b, and a negative electrode side connection portion 31b connected to 21b. Then, the positive electrode side connection portion 21a on the battery 2 side and the positive electrode side connection portion 31a on the charger 3 side are connected, and the negative electrode side connection portion 21b on the battery 2 side and the negative electrode side connection portion 31b on the charger 3 side are connected. The connection forms an electrical circuit during charging.

For example, if the device equipped with the battery 2 is a vehicle, the battery 2 is a vehicle-mounted battery, and the charger 3 is charging equipment such as a charging station. In this case, the electric power stored in the battery 2 can be supplied to the driving motor during discharging. At the time of charging, a charging cable provided in the charger 3 is connected to a charging port provided in the vehicle, whereby the battery 2 and the external power source are electrically connected and ready for charging. Thereby, the battery 2 can be charged with the power supplied from the external power source.

The charging control device 10 is an electronic control device that controls the charging current value based on the state of the battery 2 . This electronic control unit includes a microcomputer having a CPU, a RAM, a ROM, and an input/output interface. Therefore, the charging control device 10 performs signal processing according to a program pre-stored in the ROM. For example, the charging control device 10 is provided in a device on which the battery 2 is mounted.

Signals from various sensors are input to the charging control device 10 . For example, signals from a voltage/temperature detection device 4 that detects the voltage and temperature of the battery 2 and a current detection device 5 that detects a current value during charging are input to the charging control device 10 . When the battery 2 is composed of a plurality of cells, the voltage/temperature detector 4 detects the voltage and temperature of each cell. Current detection device 5 detects the value of the current flowing through the electric circuit in which battery 2 and charger 3 are electrically connected. This current detection device 5 is arranged on the negative electrode side of the battery 2 as shown in FIG. 1, and detects the value of the current flowing into the battery 2 from the charger 3 side.

Then, charging control device 10 executes charging control based on signals input from voltage/temperature detecting device 4 and current detecting device 5 . That is, the charging control device 10 executes charging control according to the current state of the battery 2 . The charging control is a control for charging within a range in which the charging current value does not exceed the allowable current value Idc of the battery 2 . The charging control device 10 controls the charging current value to a desired current value according to the current state of the battery 2 during charging. At that time, charging control device 10 outputs a control signal to charger 3 in order to control the charging current value.

As shown in FIG. 1 , the charging control device 10 includes a computing section 11 .

The calculation unit 11 calculates the state of charge (SOC) of the battery 2 based on the voltage and temperature of the battery 2 detected by the voltage/temperature detection device 4 . Since the voltage and temperature of the battery 2 being charged can be detected by the voltage/temperature detection device 4, the calculation unit 11 can calculate the current SOC based on the voltage and temperature of the battery 2 being charged.

Further, the calculation unit 11 estimates the deterioration amount (deterioration state) of the battery 2 based on the usage history such as the capacity retention rate of the battery 2 . That is, the calculation unit 11 estimates the capacity deterioration coefficient Dcap, which is a coefficient indicating the degree of capacity deterioration of the battery 2 .

Further, the calculation unit 11 calculates a deterioration coefficient due to the passage of time after the battery 2 is started to be used. That is, the calculation unit 11 calculates the aging deterioration coefficient Dtime, which is a coefficient indicating the degree of deterioration of the battery 2 over time.

Then, when the charge control device 10 executes charge control, the calculation unit 11 calculates the allowable current value Idc based on the current battery state (temperature, SOC). Furthermore, the calculation unit 11 calculates the smaller one of the capacity deterioration coefficient Dcap corresponding to the current estimated capacity value and the aging deterioration coefficient Dtime corresponding to the elapsed time from the start of use of the battery 2 as the allowable current value Idc. is multiplied by to calculate the limit current value Ilim. Then, the charge control device 10 charges the battery 2 at the limit current value Ilim. That is, during charging, the charging control device 10 controls the charging current value to the limit current value Ilim.

Here, with reference to FIGS. 2 to 7, the allowable current value map, capacity deterioration coefficient Dcap, and aging deterioration coefficient Dtime will be described in more detail.

First, referring to FIG. 2, the allowable current value map will be described.

The allowable current value map is a map preset for each temperature and SOC of the battery 2 . In the charging method according to the embodiment, when calculating the allowable current value Idc according to the current state (temperature, SOC) of the battery 2, a preset allowable current value map is referred to. That is, charging control device 10 uses the allowable current value map when calculating allowable current value Idc.

For example, when the temperature of the battery 2 is 25° C., the charge rate is set for each SOC. The charge rate represents the speed of charging and relatively represents the magnitude of the current value. In the case of constant current charging/discharging measurement, 1C is defined as the magnitude of the current value that fully charges the theoretical capacity of the battery 2 within the maintenance time. 1C during charging is the current value when the fully discharged state changes to the fully charged state in one hour. As shown in FIG. 2, when the battery temperature is 25, the charging rate is 1C when the SOC is less than about 30%, and the charging rate is less than 1C when the SOC is greater than about 30%. In this example, there are cases where the charge rate becomes 1C and cases where the charge rate becomes less than 1C at the border of about 30% SOC. In the range where the SOC is greater than about 30%, the charging rate gradually decreases as the SOC increases.

To explain the method of creating the allowable current value map, the allowable current value Idc at which lithium deposition does not occur is determined by experiment for each temperature and SOC of the battery 2 that is not degraded. Then, the permissible current value Idc obtained by experiment is mapped for each temperature and SOC of the battery 2 . Thereby, the charging control device 10 can preset an allowable current value map for each temperature and SOC of the battery 2 .

Next, the capacity deterioration coefficient Dcap will be described with reference to FIGS. 3 to 6. FIG. FIG. 3 is a diagram showing the relationship between the capacity retention rate and the capacity deterioration coefficient when there is no estimation error. FIG. 4 is a diagram showing the relationship between the capacity retention rate and the capacity deterioration coefficient when the estimation error is X %. FIG. 5 is a diagram showing the relationship between the capacity retention rate and the capacity deterioration coefficient when the estimation error is 10%. FIG. 6 is a map diagram showing the relationship between the capacity maintenance rate reflecting the estimation error of capacity estimation and the capacity deterioration coefficient.

The capacity deterioration coefficient map is a map showing the relationship between the capacity retention rate obtained based on the estimated value of the battery capacity calculated from the usage history or the like and the capacity deterioration coefficient Dcap, which is the deterioration coefficient thereof. The capacity retention rate of the battery 2 is set to a value that reflects the estimation error of capacity estimation.

For example, when there is no estimation error in capacity estimation, the capacity deterioration coefficient Dcap is set to "1.00" when the capacity maintenance rate is "100"%, as shown in FIG. When , the capacity deterioration coefficient Dcap is set to "0.5".

When the estimated error of capacity estimation is "X%", as shown in FIG. can be represented. Then, when the capacity retention rate is "50+X", the capacity deterioration coefficient Dcap is set to "0.50", and when the capacity retention rate is "60+X", the capacity deterioration coefficient Dcap is set to "0.60". be done.

Therefore, when the estimation error of capacity estimation is "10%", as shown in FIG. 5, when the capacity maintenance rate is "60"% reflecting the estimation error of 10%, the capacity deterioration coefficient Dcap is "0. 50”, and the capacity retention rate is set to “70”% reflecting an estimated error of 10%, the capacity deterioration coefficient Dcap is set to “0.60”. However, in this state, the maximum capacity deterioration coefficient Dcap becomes "0.9" from the initial state.

Then, as shown in FIG. 6, the map of the capacity deterioration coefficient Dcap is a map that can determine the capacity deterioration coefficient Dcap based on the capacity maintenance rate that reflects the estimation error of the battery capacity.

Next, the temporal deterioration coefficient Dtime will be described with reference to FIG. FIG. 7 is a map diagram showing a temporal deterioration coefficient map.

The temporal deterioration coefficient map is a map showing the relationship between the elapsed time from when the battery 2 is started to be used and the temporal deterioration coefficient Dtime, which is the deterioration coefficient thereof. Elapsed time can be obtained using elapsed time information.

As the elapsed time information, the number of days elapsed since the battery 2 was started to be used can be used. The number of days elapsed can be obtained by calculating the elapsed time from the start of use of the battery 2 by the charging control device 10 .

For example, using the number of days elapsed when the device equipped with the battery 2 was operated under the severest conditions and the deterioration coefficient calculated from the life of the battery 2, as shown in FIG. Create a time deterioration coefficient map according to the number of elapsed days. The aging coefficient map is immune to capacity estimation errors. Therefore, as shown in FIG. 7, when the number of elapsed days is "0", the temporal deterioration coefficient Dtime is set to "1.00". As the number of elapsed days increases, the temporal deterioration coefficient Dtime continues to decrease.

The charging control device 10 configured in this manner uses a preset allowable current value map, and a capacity deterioration coefficient Dcap and a deterioration coefficient Dtime set according to the current state of the battery 2 to determine the current during charging. is calculated. FIG. 8 shows an example of a charging method for charging the battery 2 based on this limit current value Ilim.

FIG. 8 is a flow chart showing a battery charging method. The control shown in FIG. 8 is performed by charging control device 10 .

Charging control device 10 calculates allowable current value Idc according to the temperature and SOC of battery 2 (step S1). In step S1, the SOC is calculated based on the voltage and temperature detected by the voltage/temperature detection device 4, and the allowable current value Idc is calculated by referring to the allowable current value map based on the SOC and battery temperature. be done. This allowable current value map is a preset map.

The charge control device 10 determines whether or not the capacity deterioration coefficient Dcap is larger than the deterioration coefficient Dtime over time (step S2). In step S2, the capacity deterioration coefficient Dcap is determined by referring to the capacity deterioration coefficient map based on the capacity retention rate reflecting the estimation error of the capacity estimation. Further, in step S2, a temporal deterioration coefficient map is referred to, and a temporal deterioration coefficient Dtime corresponding to the number of elapsed days is determined. In this manner, the capacity deterioration coefficient Dcap and the temporal deterioration coefficient Dtime are determined according to the current state of the battery 2, and the magnitudes of the deterioration coefficients are compared.

When it is determined that the capacity deterioration coefficient Dcap is larger than the aging coefficient Dtime (step S2: Yes), charging control device 10 uses the aging coefficient Dtime, which is a relatively smaller coefficient, to determine the aging coefficient. A limit current value Ilim is calculated by multiplying Dtime by the allowable current value Idc (step S3). In step S3, the time-dependent deterioration coefficient Dtime indicating the current degree of time-dependent deterioration of the battery 2 is multiplied by the allowable current value Idc calculated in step S1.

When it is determined that the capacity deterioration coefficient Dcap is equal to or less than the aging coefficient Dtime (step S2: No), the charge control device 10 uses the capacity deterioration coefficient Dcap, which is a relatively smaller coefficient, to determine the capacity deterioration coefficient A limit current value Ilim is calculated by multiplying Dcap by the allowable current value Idc (step S4). In step S4, the capacity deterioration coefficient Dcap indicating the current degree of capacity deterioration in the battery 2 is multiplied by the allowable current value Idc calculated in step S1.

When either step S3 or S4 is performed, the charging control device 10 performs charging with the limit current value Ilim (step S5). In step S5, the charging current value of the battery 2 is controlled to the limit current value Ilim, so that charging is performed within a range not exceeding the allowable current value Idc.

Then, the charge control device 10 determines whether or not the charge amount of the battery 2 is equal to or greater than a predetermined value (step S6). In step S6, the current charge amount of the battery 2 is calculated, and it is determined whether or not the charge amount is equal to or greater than a predetermined value set in advance. For example, the charge control device 10 can calculate the charge amount of the battery 2 based on the current SOC. Alternatively, the charge control device 10 uses the detected value of the charging current input from the current detection device 5 and the detected values of voltage and temperature input from the voltage/temperature detection device 4 to determine the charge amount of the battery 2. can be calculated.

If it is determined that the charge amount of the battery 2 is equal to or greater than the predetermined value (step S6: Yes), this control routine ends. In this case, charging control device 10 terminates charging of battery 2 .

If it is determined that the charge amount of the battery 2 is not equal to or greater than the predetermined value (step S6: No), this control routine returns to step S1.

As described above, according to the embodiment, the smaller one of the capacity deterioration coefficient Dcap and the aging coefficient Dtime is used to set the charging current value. It can be performed.

That is, when the estimation error of the battery capacity is large and the capacity deterioration coefficient Dcap is estimated to be a larger value than the actual deterioration state, the smaller coefficient, the temporal deterioration coefficient Dtime, is used to calculate the limiting current value Ilim. Therefore, it is possible to perform appropriate charging according to the state of deterioration of the battery 2 . As a result, even a deteriorated battery 2 can be charged within a range not exceeding the allowable current value Idc of the battery 2, and the charging current value of the battery 2 is not restricted more than necessary, thereby shortening the charging time. can be done.

As a modification, it is possible to use a map that uses both the capacity deterioration coefficient Dcap and the aging deterioration coefficient Dtime. While the aging coefficient Dtime is a coefficient that does not include an estimation error, the capacity deterioration coefficient Dcap is a coefficient that reflects the battery capacity estimation error. Dcap is set to a value less than "1.00". Therefore, this combination map can be created as a modified example. An example of this combination map is shown in FIG.

FIG. 9 is a map diagram showing a case where the capacity deterioration coefficient and the aging deterioration coefficient are used together. If the capacity deterioration coefficient map is used as it is, when the estimation error is 10%, the capacity retention rate is determined to be "100"%, and the capacity deterioration coefficient Dcap is set to "0.90". In some cases, the ability of 2 cannot be fully used. Therefore, as shown in FIG. 9, a deterioration coefficient map to be used together with the capacity deterioration coefficient Dcap and the aging deterioration coefficient Dtime is created.

For example, when the estimation error of the capacity estimation is X%, if the capacity maintenance rate of the estimated capacity is "100-X"%, if the aging coefficient Dtime is held, the capacity maintenance rate of the estimated capacity is "100%". The estimation error of the capacity deterioration coefficient map can be ignored until -X''%. That is, by using the aging coefficient Dtime together with the capacity deterioration coefficient Dcap, there is no need to make the initial deterioration coefficient smaller than necessary. On the other hand, when only the capacity deterioration coefficient Dcap is used, the deterioration coefficient is restricted more than necessary from the initial state. Conversely, if the control is performed using only the temporal deterioration coefficient Dtime, the allowable current value Idc may be exceeded when the deterioration progresses more than expected. It should be noted that the map shown in FIG. 9 is created as a deterioration coefficient map when the battery 2 is operated under the severest conditions while the device equipped with the battery 2 is operated.

Also, an example in which the battery 2 is mounted in a vehicle has been described, but the vehicle may be an electric vehicle or a plug-in hybrid vehicle.

Moreover, the device in which the battery 2 is mounted is not limited to a vehicle, and may be a mobile object, a portable electric device, or the like.

REFERENCE SIGNS LIST 1 charging system 2 battery 3 charger 4 voltage/temperature detection device 5 current detection device 10 charge control device 11 calculation unit 21 first connection portion 21a positive electrode side connection portion 21b negative electrode side connection portion 31 second connection portion 31a positive electrode side connection portion 31b Negative electrode side connection

Claims (1)

A battery charging method comprising:
estimating a capacity deterioration coefficient indicating the degree of capacity deterioration of the battery;
calculating a deterioration coefficient over time that indicates the degree of deterioration over time of the battery;
calculating a limited current value based on the smaller one of the capacity deterioration coefficient and the aging coefficient, and charging the battery with the calculated limited current value. charging method.

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