JP7086651B2 - Storage battery system and control method of storage battery system - Google Patents

Description

Embodiments of the present invention relate to a storage battery system and a control method for the storage battery system.

The storage pack included in the storage battery system is composed of a plurality of battery cells connected in series in order to obtain the required output voltage. When any one of the plurality of battery cells is in an overcharged state or an overdischarged state, the risk of smoke and ignition increases. In order to prevent this, a storage battery system has been developed for monitoring the charge state of each battery cell and preventing the battery cell from becoming an overcharged state or an overdischarged state.

Japanese Unexamined Patent Publication No. 2008-125297

The conventional storage battery system stops charging when the output voltage of any of the plurality of battery cells reaches a voltage indicating an overcharged state. Further, when the output voltage of any of the plurality of battery cells reaches a voltage indicating an over-discharged state, the load device is disconnected from the storage battery system and the discharge is stopped.

There are individual differences in the discharge depth characteristics of a plurality of battery cells. The discharge depth characteristic is a characteristic that represents the relationship between the electric energy stored in the battery cell and the output voltage. If the discharge depth characteristic is different for each battery cell, the voltage in the overcharged state and the voltage in the overdischarged state will also be different for each battery cell.

When the same amount of electric energy is charged to each of a plurality of battery cells having different discharge depth characteristics, the voltage of the battery cells increases greatly as the capacity is smaller. Further, when the same amount of electric energy is discharged, the voltage of the battery cell decreases greatly as the capacity becomes smaller. In a conventional storage battery system, charging is stopped when one battery cell in a plurality of battery cells is in an overcharged state, and discharge is stopped when one battery cell in a plurality of battery cells is in an overdischarged state. do. Therefore, the execution capacity of the battery pack included in the storage battery system is determined by the capacity of the battery cell having the smallest capacity. Therefore, the running capacity of the battery pack is smaller than the average capacity of the plurality of battery cells.

The present invention has been made under the above-mentioned circumstances, and an object of the present invention is to increase the execution capacity of a battery pack.

In order to solve the above problems, the storage battery system according to the present embodiment controls a battery pack including a plurality of battery cells connected in series, a charger for individually charging each of the plurality of battery cells, and a charger. It is provided with a control unit for charging each of a plurality of battery cells. The control unit includes a function creation unit that creates a function representing the discharge depth characteristics of each of the plurality of battery cells, and an operating range setting unit that sets the charge start voltage and charge end voltage of each battery cell based on the function. Be prepared. The operating range setting unit is a device type selection unit that selects a device type classified according to the relationship between the rated voltage range of the battery pack and the operating voltage range of the load device that receives electrical energy from the battery pack, and the device type. And the charge start voltage setting unit that sets the charge start voltage that starts charging the battery cell based on the function, and the charge end voltage that sets the charge end voltage that ends the charge of the battery cell based on the device type and function. It is equipped with a setting unit.

It is a block diagram of the power storage system which concerns on embodiment. It is a figure for demonstrating the discharge depth characteristic of a battery pack. It is a figure for demonstrating the discharge depth characteristic of a battery cell. It is a block diagram of the charger which concerns on embodiment. It is a block diagram of the overcharge detection part which concerns on embodiment. It is a block diagram of the over discharge detection part which concerns on embodiment. It is a block diagram of the voltage adjustment part which concerns on embodiment. It is a block diagram of the control part which concerns on embodiment. It is a figure for demonstrating the function creation part which concerns on embodiment. It is a figure for demonstrating the threshold value setting part which concerns on embodiment. It is a block diagram of the operation range setting part which concerns on embodiment. It is a figure for demonstrating the apparatus type selection part which concerns on embodiment. It is a figure for demonstrating the operation range setting part which concerns on embodiment. It is a figure for demonstrating the operation range setting part which concerns on embodiment. It is a figure for demonstrating the operation range setting part which concerns on embodiment. It is a figure for demonstrating the operation range setting part which concerns on embodiment. It is a figure for demonstrating the operation range setting part which concerns on embodiment. It is a figure for demonstrating the operation range setting part which concerns on embodiment. It is a figure for demonstrating the operation range setting part which concerns on embodiment. It is a figure for demonstrating the operation range setting part which concerns on embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The storage battery system according to this embodiment is used for vehicles, ships, aircraft, home appliances and the like. FIG. 1 is a configuration diagram of a storage battery system 100 according to an embodiment. The storage battery system 100 supplies electric energy to the load device 200 from the built-in battery pack 10. The load device 200 is an electric device that consumes electric energy, such as a motor, an air conditioner, a lighting device, and a mobile terminal.

As shown in FIG. 1, the storage battery system 100 includes a battery pack 10, a charger 20, an overcharge detection unit 30, an overdischarge detection unit 40, a voltage adjustment unit 50, a current sensor 60, a circuit breaker 70, and a control unit 80. ..

The battery pack 10 is configured by connecting a plurality of battery cells C1 to Cn in series. The battery cells C1 to Cn are composed of a lithium ion battery, a lead storage battery, and the like.

FIG. 2 shows a graph showing the discharge depth characteristics of the battery pack 10. The vertical axis is the output voltage of the battery pack 10. The horizontal axis is the discharge depth. The output voltage of the battery pack 10 when the discharge depth is 0 Ah is defined as the full charge voltage. For example, when 15 Ah of electrical energy is discharged from a fully charged state, the discharge depth becomes 15 Ah. In the example shown in FIG. 2, the output voltage of the battery pack 10 at a discharge depth of 15 Ah is about 27.4 V.

FIG. 3 shows a graph showing the discharge depth characteristics of the battery cells C1 to Cn constituting the battery pack 10. The discharge depth characteristics of the battery cells C1 to Cn are generally different due to variations in manufacturing, deterioration over time, and the like. As shown in FIG. 3, the battery pack 10 is configured by connecting a plurality of battery cells having different discharge depth characteristics in series.

The charger 20 individually charges each of the plurality of battery cells C1 to Cn. FIG. 4 is a block diagram of the charger 20. The charger 20 includes the same number of constant current sources 21, current sensors 22, and voltage sensors 23 as the number of battery cells. The current sensor 22 is a DC ammeter and measures the charging current supplied from the constant current source 21. The current sensor 22 supplies the measured data to the control unit 80. The voltage sensor 23 is a DC voltmeter and measures the voltage of the battery cell. The voltage sensor 23 supplies the measured data to the control unit 80.

FIG. 5 shows the configuration of the overcharge detection unit 30. When the overcharge detection unit 30 detects that any one of the plurality of battery cells C1 to Cn is in the overcharge state, the overcharge detection unit 30 controls the charger 20 to stop charging the battery cells C1 to Cn. The overcharge detection unit 30 includes a number of overcharge detection circuits 31 corresponding to the number of battery cells C1 to Cn and one charge stop control circuit 33. The overcharge detection circuit 31 is provided for each battery cell C1 to Cn. Different charge stop voltages V11 to V1n are set in each of the overcharge detection circuits 31 according to the discharge depth characteristics of the battery cell. The charge stop voltage of the battery cell C1 is V11, the charge stop voltage of the battery cell C2 is V12, and similarly, the charge stop voltage of the battery cell Cn is V1n. The overcharge detection circuit 31 outputs a low-level signal when the voltage of the battery cells C1 to Cn becomes the charge stop voltage V11 to V1n or more. When any of the overcharge detection circuits 31 outputs a low-level signal, the charge stop control circuit 33 outputs a low-level signal and controls the charger 20 to stop charging the battery cells C1 to Cn. ..

FIG. 6 shows the configuration of the over-discharge detection unit 40. When the over-discharge detecting unit 40 detects that any of the plurality of battery cells C1 to Cn is in the over-discharged state, the circuit breaker 70 is shut off to stop the discharge to the load device 200. The over-discharge detection unit 40 includes a number of over-discharge detection circuits 41 corresponding to the number of battery cells C1 to Cn and one discharge stop control circuit 43. The over-discharge detection circuit 41 is provided for each battery cell C1 to Cn. In each of the over-discharge detection circuits 41, different discharge stop voltages V21 to V2n are set for each of the battery cells C1 to Cn according to the discharge depth characteristics of the battery cells C1 to Cn. The discharge stop voltage of the battery cell C1 is V21, the discharge stop voltage of the battery cell C2 is V22, and so on, the discharge stop voltage of the battery cell Cn is V2n. The over-discharge detection circuit 41 outputs a low-level signal when the voltage of the battery cells C1 to Cn becomes the discharge stop voltage V21 to V2n or less. When any of the over-discharge detection circuits 41 outputs a low-level signal, the discharge stop control circuit 43 outputs a low-level signal, shuts off the circuit breaker 70, and disconnects the storage battery system 100 and the load device 200.

FIG. 7 shows a configuration diagram of the voltage adjusting unit 50. The voltage adjusting unit 50 is connected in parallel to each of the plurality of battery cells C1 to Cn, and discharges each of the battery cells C1 to Cn individually. The voltage adjusting unit 50 connected in parallel to the battery cell C1 will be described. The voltage adjusting unit 50 includes a switch SW1, a resistance Rcb1, and a control IC1. The switch SW1 and the resistance Rcb1 connected in series are connected in parallel to the battery cell C1. Both ends of the battery cell C1 are connected to the input terminals VC1 and VC2 of the control IC1 via the resistors R _VC1 and R _VC2 . A capacitor C _VC1 is connected between the input terminals VC1 and VC2 of the control IC1. The switch SW1 is composed of a semiconductor such as a FET. The control IC 1 has a voltage comparison function.

When the voltage between the terminals VC1 and VC2 rises to the charge stop voltage V11, the control IC1 outputs a high-level signal from the CB1 output. When the CB1 output of the control IC1 outputs a high-level signal, the switch SW1 is turned on. When the switch SW1 is turned on, the electric energy stored in the battery cell C1 is discharged via the resistor Rcb1. Due to this discharge, the output voltage of the battery cell C1 is lowered.

Even after charging is stopped, the voltage of the battery cell C1 rises due to an internal chemical reaction, and the battery cell C1 may fall into an overcharged state. The voltage adjusting unit 50 suppresses the battery cell C1 from being overcharged by discharging the electric energy stored in the battery cell C1 when the voltage of the battery cell C1 rises above the charging stop voltage V11. ..

Further, the voltage adjusting unit 50 discharges a part of the electric energy of the battery cell having a small capacity when charging the battery cell having a small capacity based on the control of the control unit 80. That is, the voltage adjusting unit 50 has a function of adjusting the charging speed of the battery cell. Details will be described later.

Returning to FIG. 1, the current sensor 60 measures the load current supplied to the load device 200. The current sensor 60 is composed of a DC ammeter. The current sensor 60 supplies the measured data to the control unit 80.

The circuit breaker 70 cuts off the storage battery system 100 and the load device 200. The breaker 70 is composed of a semiconductor switch such as a MOS-FET (Metal Oxide Semiconductor-Field effect transistor) or an IGBT (Insulated gate bipolar transistor), and a relay.

The control unit 80 controls the charger 20 to charge each of the plurality of battery cells C1 to Cn. Further, the control unit 80 controls the voltage adjustment unit 50 to discharge each of the plurality of battery cells C1 to Cn. FIG. 8 shows the configuration of the control unit. The control unit 80 includes a function creation unit 81, a threshold value setting unit 83, and a drive unit 85.

The function creation unit 81 creates a function representing the discharge depth characteristics of each of the plurality of battery cells C1 to Cn. A method of creating a function representing the discharge depth characteristic will be described with reference to FIG. The battery cells C1 to Cn approach a fully charged state as electric energy is supplied from the charger 20, and the voltage increases. Further, the voltage of the battery cells C1 to Cn decreases as the load device 200 is discharged. The function creation unit 81 acquires the charging current supplied from the charger 20 from the current sensor 22 and the discharge current supplied to the load device 200 from the current sensor 60. Further, the function creation unit 81 acquires the output voltage of the battery cell at the time of charging / discharging from the voltage sensor 23. The function creation unit 81 plots the change in the discharge depth and the change in the output voltage with reference to the voltage of the battery cell having a discharge depth of 0 Ah at the time of manufacture as shown in FIG. The function creation unit 81 obtains a function representing the discharge depth of the battery cells C1 to Cn by the least squares method or the like. The discharge depth characteristics change due to aging deterioration and environmental temperature. The function creation unit 81 updates the function representing the discharge depth characteristic, for example, weekly or monthly.

As shown in FIG. 8, the threshold value setting unit 83 includes a discharge stop voltage setting unit 831, a charge stop voltage setting unit 832, and an operation range setting unit 90.

The discharge stop voltage setting unit 831 sets the discharge stop voltages V21 to V2n for detecting that the state of the battery cell is in the over-discharge state in the over-discharge detection unit 40. FIG. 10 shows the discharge stop voltages V21, V22, and V2n of the battery cells C1, C2, and Cn. The voltage of the battery cell in the over-discharged state is a substantially constant voltage regardless of the capacity of the battery cell.

The charge stop voltage setting unit 832 sets the charge stop voltage V11 to V1n for detecting that the state of the battery cell is the overcharge state in the overcharge detection unit 30. For example, the charge stop voltage setting unit 832 sets the full charge voltage as the charge stop voltage. FIG. 10 shows the charge stop voltages V11, V12, and V1n of the battery cells C1, C2, and Cn. The full charge voltage tends to vary depending on the capacity of the battery cell. The charging stop voltage V11 to V1n may be set to, for example, 95% or 90% of the full charge voltage.

The operating range setting unit 90 sets the charging start voltage and the charging end voltage of the battery cells C1 to Cn based on the relationship between the rated voltage range of the battery pack 10 and the operating voltage range of the load device 200. FIG. 11 shows the configuration of the operating range setting unit 90. The operation range setting unit 90 includes a device type selection unit 91, a charge start voltage setting unit 92, a charge end voltage setting unit 93, and an adjustment unit 94.

The device type selection unit 91 selects the device type of the load device 200 based on the relationship between the rated voltage range of the battery pack 10 and the operating voltage range of the load device 200. This will be described with reference to FIG. The rated voltage of the battery pack 10 is a range of the output voltage of the battery pack 10 in which none of the plurality of battery cells C1 to Cn included in the battery pack 10 is in an overcharged state or an overdischarged state during the operation guarantee period. The device operating voltage range is a voltage range in which the load device 200 can normally operate.

The device type selection unit 91 classifies the load device 200 into the four types shown in FIG. 12 based on the relationship between the rated voltage range of the battery pack 10 and the operating voltage range of the load device 200. The device type selection unit 91 classifies the load device 200 in which the upper limit of the operating voltage range is lower than the upper limit of the rated voltage range of the battery pack 10 into type 1. When the battery cells C1 to Cn are charged to a fully charged state, the output voltage of the battery pack 10 becomes higher than the operating voltage range of the load device 200. Therefore, when supplying electric energy to the load device 200 classified as type 1, the battery cells C1 to Cn are not charged to the fully charged state. Therefore, the battery cells C1 to Cn are repeatedly charged and discharged with a large margin until the battery cells are overcharged.

The device type selection unit 91 classifies the load device 200 having a lower limit of the operating voltage range higher than the lower limit of the rated voltage range of the battery pack 10 into type 2. When the battery cells C1 to Cn are discharged to the discharge stop voltage V21 to V2n, the output voltage of the battery pack 10 becomes lower than the operating voltage range of the load device 200. Therefore, when the electric energy is supplied to the load device 200 classified into the type 2, the battery cells C1 to Cn are not discharged until the over-discharged state is reached. Therefore, the battery cells C1 to Cn are repeatedly charged and discharged with a large margin until the over-discharged state is reached.

The device type selection unit 91 classifies the load device 200 having the same operating voltage range and the rated voltage range of the battery pack 10 into type 3. When supplying electric energy to the load device 200 classified into type 3, the battery cells C1 to Cn are repeatedly charged and discharged without a margin until the overcharge state and a margin until the overdischarge state is reached. become.

The device type selection unit 91 sets the load device 200 in which the upper limit of the operating voltage range is lower than the upper limit of the rated voltage range of the battery pack 10 and the lower limit of the operating voltage range is higher than the lower limit of the rated voltage range of the battery pack 10. Classify into type 4. When supplying electric energy to the load device 200 classified into the type 4, the battery cells C1 to Cn are repeatedly charged and discharged with a large margin until the overcharge state and a margin until the overdischarge state is reached. become.

Returning to FIG. 11, the charging start voltage setting unit 92 sets the charging start voltages V41 to V4n of the battery cells C1 to Cn according to the device type in the drive unit 85. The charge end voltage setting unit 93 sets the charge end voltages V31 to V3n of each of the battery cells C1 to Cn according to the device type in the drive unit 85.

When the device type selection unit 91 classifies the load device 200 into type 1, the adjustment unit 94 controls the charger 20 via the drive unit 85 to charge a battery cell having a small capacity. When the device type selection unit 91 classifies the load device 200 into type 2, the adjustment unit 94 controls the voltage adjustment unit 50 via the drive unit 85 to discharge a battery cell having a small capacity. In the adjusting unit 94, when the device type selection unit 91 classifies the load device 200 into type 3, when the remaining amount of the battery cell having a small capacity becomes 50% or less at the time of discharging, the charger 20 via the drive unit 85. When the battery cell with a small capacity is charged by controlling and the remaining amount of the battery cell with a small capacity becomes 50% or more at the time of charging, the voltage adjusting unit 50 is controlled via the drive unit 85 to control the battery with a small capacity. Discharge the cell. Details will be described later.

The drive unit 85 controls the charger 20 to charge the battery cells C1 to Cn whose charging start voltage has dropped to V41 to V4n. Further, the drive unit 85 controls the charger 20 to stop charging the battery cells C1 to Cn whose charging end voltage has risen to V31 to V3n. Further, the drive unit 85 controls the charger 20 based on the instruction of the adjustment unit 94 to charge the designated battery cells C1 to Cn. Further, the drive unit 85 controls the voltage adjustment unit 50 based on the instruction of the adjustment unit 94 to discharge the designated battery cells C1 to Cn.

Next, the control method of the storage battery system 100 will be described for each device type. The storage battery system 100 has an operable time of the load device 200 by a battery cell (second battery cell) having a capacity smaller than that of a battery cell (first battery cell) having a reference capacity, and a reference capacity. The charge / discharge control of the battery cells C1 to Cn is performed so that the operable time of the load device 200 by the battery cells is the same. Here, a case where a battery cell having an average capacity is used as a reference will be described.

In FIGS. 13A, 13B, 15A, 15B, 17A, and 17B, the change in voltage during charging / discharging of a battery cell having an average capacity is shown by a broken line, and the voltage during charging / discharging of a battery cell having a small capacity is shown by a broken line. The change in is shown by a solid line. In FIGS. 14 and 16, the discharge depth characteristic of the battery cell C2 shown by the broken line is the discharge depth characteristic of the battery cell having an average capacity, and the discharge depth characteristic of the battery cell Cn shown by the solid line is the discharge depth of the battery cell having a small capacity. It is assumed that the characteristics and the discharge depth characteristic of the battery cell C1 shown by the alternate long and short dash line are the discharge depth characteristics of the battery cell having a large capacity.

(Type 1)
The case of type 1 will be described. As shown in FIG. 12, in the case of type 1, the device operating voltage range is 20 to 25 V. As shown in FIG. 13A, the time of the battery cell Cn from the start of discharging to the time when the discharge stop voltage V2 is lowered is shorter than that of the battery cell C2. The over-discharge detection unit 40 detects an over-discharge state when the voltage of the battery cell Cn is lower than the discharge stop voltage V2. Therefore, the operable time t1 of the battery cell Cn having a small capacity is shorter than the operating time t2 of the battery cell C2 having an average capacity.

This will be described with reference to FIG. It is assumed that the battery cells C1, C2, and Cn are discharged from the fully charged state by 15 Ah. At this time, the remaining amount of the battery cell C1 is 10Ah, the remaining amount of the battery cell C2 is 7Ah, and the remaining amount of the battery cell Cn is 4Ah. If the discharge is continued in this state, when the battery cell Cn is discharged for 4 Ah, the battery cell Cn becomes an over-discharged state, the circuit breaker 70 is cut off, and the discharge to the load device 200 is stopped. The discharge to the load device 200 is stopped even though the battery cell C2 still has a remaining amount of 3 Ah. As described above, when the charge state of the battery cell Cn is not controlled, the execution capacity of the battery pack 10 is determined by the capacity of the battery cell Cn having a small capacity.

In FIG. 14, if the remaining amount of the battery cell Cn is increased by 3 Ah, the remaining amount of the battery cell Cn and the battery cell C2 can be made the same. That is, the execution capacity of the battery pack 10 can be increased to the capacity of the battery cell C2 having an average capacity.

The adjusting unit 94 drives the charger 20 via the driving unit 85 and controls the battery cell Cn to be charged for 3 Ah. Specifically, the adjusting unit 94 has a discharge depth (22Ah) in V22 of the battery cell C2 and a discharge depth in V2n of the battery cell Cn based on the function representing the discharge depth characteristics of the battery cells C2 and Cn shown in FIG. The difference (3Ah) from (19Ah) is calculated. Next, the adjusting unit 94 obtains what V the voltage of the battery cell Cn becomes when the battery cell Cn is charged for 3 Ah in a state where the voltage is 2.3 V from a function representing the discharge depth characteristic of the battery cell Cn. .. In the example shown in FIG. 14, the voltage is about 2.36V. The adjusting unit 94 controls the charger 20 to charge the battery cell Cn so that the voltage becomes the obtained voltage. As a result, as shown in FIG. 14, the voltage of the battery cell Cn increases by ΔV (about 0.06V).

As shown in FIG. 13B, in the case of type 1, the charge end voltage V3 of the battery cells C1, C2, and Cn is set lower than the charge stop voltage V1. Therefore, even if the charge end voltage V3 of the battery cell Cn rises by ΔV, the relationship of V1> V3 + ΔV can be maintained, and the battery cell Cn does not become overcharged.

(Type 2)
The case of type 2 will be described. As shown in FIG. 12, in the case of type 2, the device operating voltage range is 25 to 30 V. As shown in FIG. 15A, the time of the battery cell Cn from the start of charging until the charge stop voltage V1 is exceeded is shorter than that of the battery cell C2. The overcharge detection unit 30 detects the overcharge state when the voltage of the battery cell Cn exceeds the charge stop voltage V1. Therefore, the operable time t1 of the battery cell Cn having a small capacity is shorter than the operating time t2 of the battery cell C2 having an average capacity.

This will be described with reference to FIG. It is assumed that the charging start voltage V4 is 2.5V. When charging is started when the voltage of the battery cells C1, C2, and Cn is 2.5V, the battery cell C1 is charged with 11Ah, the battery cell C2 is charged with 6Ah, and the battery cell Cn is charged with 2Ah by the time the charging is started. Is possible. When charging is continued in this state, when charging for 2 Ah, the battery cell Cn becomes an overcharged state, the overcharge detection unit 30 operates, and charging to the battery pack 10 is stopped. Charging to the battery cell C2 is stopped 4Ah before the fully charged state. That is, the execution capacity of the battery cell C2 is reduced by 4 Ah. As described above, when the charge state of the battery cell Cn is not controlled, the execution capacity of the battery pack 10 is determined by the capacity of the battery cell Cn having a small capacity.

In FIG. 16, if the electric energy of the battery cell Cn is discharged by 4 Ah at the start of charging, the overcharged state is not detected until the battery cell C2 is fully charged. That is, the execution capacity of the battery pack 10 can be increased to the capacity of the battery cell C2 having an average capacity.

The adjusting unit 94 drives the voltage adjusting unit 50 via the driving unit 85, and discharges the electric energy of the battery cell Cn by 4 Ah. Specifically, the adjusting unit 94 sets the discharge depth (6Ah) before the start of charging of the battery cell C2 and the start of charging of the battery cell Cn based on the function representing the discharge depth characteristics of the battery cells C2 and Cn shown in FIG. Obtain the previous discharge depth (2Ah). Next, the adjusting unit 94 obtains the voltage of the battery cell Cn at which the rechargeable capacity of the battery cell Cn is 6 Ah from a function representing the discharge depth characteristic of the battery cell Cn. In the example shown in FIG. 16, the voltage is about 2.44V. The adjusting unit 94 sets the control IC1 so as to output a high-level signal from the CB1 output when the voltage between the terminals VC1 and VC2 shown in FIG. 7 rises to 2.44V. When a high-level signal is output from the CB1 output, the switch SW1 is turned on, and the voltage of the battery cell Cn drops due to discharge. When the voltage of the storage battery Cn drops to 2.44V, the signal level output from CB1 becomes low level, and the switch SW1 is turned off. By the above control, the voltage of the storage battery Cn is discharged to 2.44V. As a result, as shown in FIG. 16, the voltage of the battery cell Cn drops by ΔV (about 0.06V) due to the discharge.

As shown in FIG. 15B, in the case of type 2, the charge start voltage V4 of the battery cells C1, C2, and Cn is set higher than the discharge stop voltage V2. Therefore, even if the charging start voltage V4 of the battery cell Cn drops by ΔV, the relationship of V2 <V4-ΔV can be maintained, and the battery cell Cn does not become over-discharged.

(Type 3)
The case of type 3 will be described. As shown in FIG. 12, in the case of type 3, the device operating voltage range is 20 to 30 V. In the case of type 3, since the charge stop voltage V1 and the charge end voltage V3 are the same, there is no margin on the overcharge side. Further, since the discharge stop voltage V2 and the charge start voltage V4 are the same, there is no margin on the overdischarge side. As shown in FIG. 17A, the voltage of the battery cell Cn drops faster than the voltage of the battery cell C2 when discharged. Also, when charging, it rises quickly. The overcharge detection unit 30 detects an overcharge state when the voltage of the battery cell exceeds the charge stop voltage V1. Further, the over-discharge detection unit 40 detects an over-discharge state when the voltage of the battery cell falls below the discharge stop voltage V2. Therefore, the operable time t1 of the battery cell Cn having a small capacity is shorter than the operating time t2 of the battery cell C2 having an average capacity. When the charge state of the battery cell Cn is not controlled, the execution capacity of the battery pack 10 is determined by the capacity of the battery cell Cn having a small capacity.

As shown in FIG. 17B, when the remaining amount of the battery cell Cn becomes 50% or less at the time of discharging, the adjusting unit 94 charges the battery cell Cn so that the battery cell Cn and the battery cell C2 are discharged at the same time. It is controlled to be V2. That is, the same control as in type 1 is performed. Specifically, the adjusting unit 94 drives the charger 20 via the driving unit 85, and charges the battery cell Cn so that the remaining capacity of the battery cell Cn and the remaining capacity of the battery cell C2 are about the same. As a result, as shown in FIG. 17B, the voltage of the battery cell Cn increases by ΔV.

Further, as shown in FIG. 17B, when the remaining amount of the battery cell Cn becomes 50% or more during charging, the adjusting unit 94 discharges the electric energy of the battery cell Cn to cause the battery cell Cn and the battery cell C2. Is controlled to be the charge stop voltage V1 at the same time. That is, the same control as in type 2 is performed. Specifically, the adjusting unit 94 drives the voltage adjusting unit 50 via the driving unit 85, and discharges the battery cell Cn so that the rechargeable electric energies of the battery cell Cn and the battery cell C2 are about the same. .. As a result, as shown in FIG. 17B, the voltage of the battery cell Cn drops by ΔV. By the above control, the execution capacity of the battery pack 10 can be increased to the capacity of the battery cell C2 having an average capacity.

(Type 4)
The case of type 4 will be described. As shown in FIG. 12, in the case of type 4, the device operating voltage range is 23 to 27 V. In the case of type 4, the charge stop voltage V1 is higher than the charge end voltage V3. Further, the discharge stop voltage V2 is lower than the charge start voltage V4. Therefore, there is a margin on both the overcharge side and the overdischarge side. The adjusting unit 94 does not control charging or discharging the battery cell Cn having a small capacity.

As described above, the storage battery system 100 according to the embodiment includes a function creation unit 81 that creates a function representing the discharge depth characteristics of each of the plurality of battery cells C1 to Cn. Further, the storage battery system 100 sets the charge start voltage and the charge end voltage of each of the battery cells C1 to Cn based on the function representing the discharge depth characteristics of each of the plurality of battery cells C1 to Cn created by the function creation unit 81. It is equipped with an operating range setting unit. As a result, the storage battery system 100 can increase the execution capacity of the battery pack 10 even when the capacity of any of the plurality of battery cells C1 to Cn constituting the battery pack 10 is reduced.

Further, the storage battery system 100 according to the embodiment includes a device type selection unit 91 that selects a device type classified according to the relationship between the rated voltage range of the battery pack 10 and the operating voltage range of the load device 200. The storage battery system 100 sets the charging start voltage for starting charging of the battery cells C1 to Cn based on the device type and the function representing the discharge depth characteristics of the battery cells C1 to Cn created by the function creation unit 81. Further, the storage battery system 100 sets the charge end voltage for terminating the charging of the battery cells C1 to Cn based on the function representing the discharge depth characteristics of the battery cells C1 to Cn created by the device type and the function creation unit 81. .. As a result, the storage battery system 100 avoids the overcharged state and the overdischarged state, and executes the battery pack 10 even when the capacity of any of the plurality of battery cells C1 to Cn constituting the battery pack 10 is reduced. The capacity can be increased.

In the above, the charge / discharge control of the battery cell having a small capacity when the battery cell having an average capacity is used as a reference has been described, but the battery cell that performs the charge / discharge control is limited to the battery cell having the smallest capacity. Not done. The charge / discharge control described above may be performed according to the capacity of the battery cell.

Further, in the above, the case of controlling the charging / discharging of the battery cell having a small capacity with the battery cell having an average capacity as a reference has been described. However, it is not necessary to limit the reference battery cell to a battery cell having an average capacity. For example, a battery cell having a large capacity may be used as a reference.

Further, in the above description, the function for expressing the discharge depth characteristic is created by using the least squares method or the like, but it is not necessary to limit the method for creating the function for expressing the discharge depth characteristic to this. For example, a function may be created by connecting vectors indicating the amount of change (discharge depth, output voltage) with charge / discharge. Further, the shape of the discharge depth characteristic curve at the time of shipment may be taken into consideration. Further, the function creating unit 81 may not be provided, and a function representing the discharge depth characteristics of the battery cells C1 to Cn may be acquired from the outside.

Further, the function creation unit 81 may create a function representing the discharge depth characteristic for each ambient temperature. For example, a function expressing the discharge depth characteristic may be created based on the data measured for each specified temperature range such as 10 ° C to 15 ° C, 15 ° C to 20 ° C, and so on. Then, a function corresponding to the operating environment temperature of the storage battery system 100 may be selected to perform the above-mentioned control.

Further, in the above description, as described with reference to FIG. 4, a case where the constant current source 21 having the same number as the number of battery cells C1 to Cn is provided has been described, but the configuration of the charger 20 is not limited to this. .. For example, one constant current source, a diversion circuit, a bypass circuit, a control circuit for controlling the diversion circuit and the bypass circuit, and the like may be provided so that the battery cells C1 to Cn can be charged individually.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

10 ... Battery pack 20 ... Charger 21 ... Constant current source 22 ... Current sensor 23 ... Voltage sensor 30 ... Overcharge detection unit 31 ... Overcharge detection circuit 33 ... Charge stop control circuit 40 ... Overdischarge detection unit 41 ... Overdischarge detection Circuit 43 ... Discharge stop control circuit 50 ... Voltage adjustment unit 60 ... Current sensor 70 ... Breaker 80 ... Control unit 81 ... Function creation unit 83 ... Threshold setting unit 831 ... Discharge stop voltage setting unit 832 ... Charge stop voltage setting unit 90 ... Operating range setting unit 91 ... Device type selection unit 92 ... Charging start voltage setting unit 93 ... Charging end voltage setting unit 94 ... Adjustment unit 100 ... Storage battery system 200 ... Load device C1 to Cn ... Battery cell

Claims (11)

A battery pack with multiple battery cells connected in series,
A charger that individually charges each of the plurality of battery cells,
A control unit that controls the charger to charge each of the plurality of battery cells,
Equipped with
The control unit
A function creation unit that creates a function that represents the discharge depth characteristics of each of the plurality of battery cells,
An operating range setting unit that sets the charge start voltage and charge end voltage of each of the battery cells based on the function.
Equipped with
The operating range setting unit is
A device type selection unit that selects a device type classified according to the relationship between the range of the rated voltage of the battery pack and the range of the operating voltage of the load device to which the electric energy is supplied from the battery pack.
A charging start voltage setting unit that sets the charging start voltage for starting charging of the battery cell based on the device type and the function.
A charge end voltage setting unit that sets the charge end voltage that ends charging of the battery cell based on the device type and the function.
To prepare
Storage battery system. When the device type selection unit determines that the upper limit of the operating voltage range of the load device is lower than the upper limit of the rated voltage range of the battery pack, the control unit has a first battery having a reference capacity. The second battery cell is charged so that the remaining amount of the second battery cell having a capacity smaller than that of the cell and the remaining amount of the first battery cell are the same.
The storage battery system according to claim 1 . The control unit is connected in parallel to each of the plurality of battery cells, and includes a voltage adjusting unit that individually discharges each of the battery cells.
When the device type selection unit determines that the lower limit of the operating voltage range of the load device is higher than the lower limit of the rated voltage range of the battery pack, the control unit has a first battery having a reference capacity. The voltage adjusting unit is set so that the capacity until the second battery cell, which has a smaller capacity than the cell, is fully charged and the capacity until the first battery cell is fully charged are the same. Controlled to discharge the second battery cell,
The storage battery system according to claim 1 . The control unit is connected in parallel to each of the plurality of battery cells, and includes a voltage adjusting unit that individually discharges each of the battery cells.
When the control unit determines that the device type selection unit has the same operating voltage range of the load device and the rated voltage range of the battery pack, the control unit determines.
When the remaining amount of the second battery cell having a capacity smaller than that of the first battery cell having the reference capacity becomes 50% or less at the time of discharging, the remaining amount of the second battery cell and the first battery Charge the second battery cell so that the remaining amount of the cell is the same.
When the remaining amount of the second battery cell becomes 50% or more at the time of charging, the capacity until the second battery cell is fully charged and the capacity until the first battery cell is fully charged. The second battery cell is discharged by controlling the voltage adjusting unit so that the capacity is the same as that of the second battery cell.
The storage battery system according to claim 1 . It is provided with an overcharge detection unit that detects that any of the plurality of battery cells has become overcharged.
When the overcharge detection unit detects that any of the plurality of battery cells is in the overcharge state, the overcharge detection unit controls the charger to stop charging the battery cells.
The storage battery system according to any one of claims 1 to 4 . A circuit breaker that cuts off the battery pack and a load device that receives electrical energy from the battery pack.
It is provided with an over-discharge detection unit that detects that any of the plurality of battery cells has become over-discharged.
When the over-discharge detecting unit detects that any of the plurality of battery cells is in an over-discharged state, the over-discharge detecting unit controls the circuit breaker to cut off the battery pack and the load device.
The storage battery system according to any one of claims 1 to 5 . A function creation process that creates a function that represents the discharge depth characteristics of each of the multiple battery cells that make up the battery pack,
A device type selection process that selects device types classified according to the relationship between the rated voltage range of the battery pack and the operating voltage range of the load device, and
A setting process for setting the charge start voltage and charge end voltage of each of the battery cells based on the device type, and
A control step for controlling charging of the battery cell based on the set charging start voltage and charging end voltage, and
How to control the battery system, including. In the control step, charge / discharge control of each of the battery cells is performed according to the capacity of each of the plurality of battery cells constituting the battery pack.
The control method for a storage battery system according to claim 7 . When the upper limit of the operating voltage range of the load device is lower than the upper limit of the rated voltage range of the battery pack, the second battery cell having a smaller capacity than the first battery cell having the reference capacity in the control step. The second battery cell is charged so that the remaining amount of the first battery cell is the same as the remaining amount of the first battery cell.
The control method for a storage battery system according to claim 8 . When the lower limit of the operating voltage range of the load device is higher than the lower limit of the rated voltage range of the battery pack, the second battery cell having a smaller capacity than the first battery cell having the reference capacity in the control step. The second battery cell is discharged so that the capacity until the first battery cell is fully charged and the capacity until the first battery cell is fully charged are the same.
The control method for a storage battery system according to claim 8 . When the operating voltage range of the load device and the rated voltage range of the battery pack are the same,
In the control step,
When the remaining amount of the second battery cell having a capacity smaller than that of the first battery cell having the reference capacity becomes 50% or less at the time of discharging, the remaining amount of the second battery cell and the first battery Charge the second battery cell so that the remaining amount of the cell is the same.
When the remaining amount of the second battery cell becomes 50% or more at the time of charging, the capacity until the second battery cell is fully charged and the capacity until the first battery cell is fully charged. Discharge the second battery cell so that the capacity is the same as that of the second battery cell.
The control method for a storage battery system according to claim 8 .

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