TW201528653A - Method of searching for full charge capacity of stacked recargeable battery cells in recargeable battery pack and battery management system made of the same - Google Patents

Abstract

A method of searching for full charge capacity of stacked battery cells in a rechargeable battery pack and a battery management system based on the method are disclosed. The method includes the steps of: predefining an end-of-discharge condition as a ratio of change of open-circuit cell voltage to change of state of charge; providing a full charge capacity for a rechargeable battery pack assembled of several stacked battery cells; charging the rechargeable battery pack until it is fully; discharging the rechargeable battery pack; measuring current values and open-circuit cell voltages periodically; processing coulomb counting based on the measured current values; estimating state of charge during discharging periodically; calculating a running ratio; and updating the full charge capacity by a sum of the coulomb counting when the running ratio is equal to or greater than the end-of-discharge condition.

Description

Method for searching for full charge of stacked rechargeable battery cells in rechargeable battery pack and battery management system using the same

The present invention relates to a method and battery management system for exploring full charge. In particular, it relates to a method and battery management system for charging a rechargeable battery cell in a rechargeable battery pack during operation (discharge).

Rechargeable batteries are widely used in many products, such as notebook computers, tablets, mobile phones, and even large electric vehicles and robots. Because the durability of these products depends on rechargeable batteries, it is important to use appropriate rechargeable batteries and carefully maintain them within the time limits of these products.

Recently, among all rechargeable batteries, nickel-cadmium batteries, nickel-hydrogen batteries, nickel-zinc batteries, and lithium batteries have become more and more popular because of their stable physical properties and small volume suitable for stacking. They can also be charged and discharged without Or have a small memory effect. In addition, these rechargeable batteries have a very small self-discharge rate and a high energy density. However, because they often use sub-batteries (or cells) that are connected in series and in parallel with each other, the imbalance of the power between the sub-batteries during charging or discharging may drag down the performance of the overall battery. In order to avoid battery imbalance and to take advantage of the best performance of these rechargeable batteries, battery management systems often perform monitoring of rechargeable battery power. Full charge is an indicator of electricity. The full charge of a rechargeable battery is set to a certain value when the rechargeable battery is produced at the factory. However, as the rechargeable battery is repeatedly charged and discharged, the full charge is gradually reduced. Thus, the full charge of each rechargeable battery needs to be constantly updated to check the state of charge.

A prior art for confirming the full charge of a rechargeable battery is disclosed in U.S. Patent Application Serial No. 20130057290. Please refer to FIG. 1, which is a flow chart of the aforementioned application. A battery performs charging and discharging operations (S1) in accordance with control of a battery protection circuit. When a charger is electrically connected to a battery pack, the charging operation begins. When an electrical device is connected to the battery pack, the discharge operation begins. A monitoring unit monitors each battery cell in series during battery charging and discharging operations to measure at least one of voltage, current and temperature (S2). A control unit receives the monitoring result from the monitoring unit and determines whether the monitoring result satisfies the battery full charge update condition (S3). For example, the control unit determines whether the voltage, current, and temperature measurements of the battery conform to corresponding values in a preset table. If it is determined in the job that the update condition is not satisfied (S3), the workflow returns to step S1. In addition, the battery is repeatedly charged The electricity and discharge, the monitoring unit continues to perform monitoring substantially. On the other hand, if it is determined that the update condition is satisfied in the job (S3), during the voltage increase period of the battery, it is determined whether or not the time point at which the condition is satisfied is included (S4). For example, it is determined whether or not the discharge operation of the battery has been discontinuous. When it is determined in S4 that the voltage of the battery is rising, the operation flow returns to step S1. On the other hand, when it is determined in S4 whether or not the voltage of the battery is rising, the full charge of the battery is updated and the updated full charge is stored in a recording unit (S5).

Although the previous case does not indicate that a particular method can be used to calculate the full charge, it indicates the update conditions so that the calculated full charge of each cell in the battery is acceptable under this condition. At the same time, since many rechargeable battery cells are assembled in series in the battery, the full charge of the battery is set to the minimum full charge of all the rechargeable battery cells. When a slight imbalance occurs in the measurement between the rechargeable cells, the full charge should reflect the real condition so that people can know if the battery needs repair. After the repair, some of the rechargeable battery cells are replaced, and the aforementioned update conditions need to be reviewed again. The operation is really troublesome.

Therefore, in the rechargeable battery operation, a simpler and more effective method for exploring the charge of the stacked rechargeable battery cells is still to be developed.

It is known that the method of confirming that the rechargeable battery is fully charged cannot be used to monitor each of the batteries, and the update condition cannot be adjusted with the physical characteristics of the battery.

Therefore, there is a need to develop a simpler and more efficient method for exploring the charge of a stacked rechargeable battery cell, which can be applied to various rechargeable batteries (groups) composed of a plurality of stacked rechargeable battery cells.

In accordance with an aspect of the present invention, a method for exploring the charge level of a rechargeable battery cell in a rechargeable battery pack includes the steps of: predefining a terminating discharge condition that is a ratio of an open circuit voltage change to a state change Providing a fully charged battery pack, the rechargeable battery pack being composed of a plurality of stacked rechargeable battery cells connected in series and/or in parallel; charging the rechargeable battery pack until being fully charged; discharging the rechargeable battery pack Periodically measuring the current value and the open circuit voltage of the rechargeable battery pack; performing a Coulomb count based on the measured current value; periodically estimating the state of charge of the rechargeable battery pack during the discharge; calculating a running ratio within a time range, The running ratio is a change in the estimated state of charge of the measured open circuit voltage change; and when the operating ratio is equal to or greater than the terminating discharge condition, the fully charged amount is updated with a sum of coulomb counts.

In accordance with the teachings of the present invention, the time range is equal to or greater than a time interval between two continuous current values or open circuit voltage measurements.

In accordance with the teachings of the present invention, the time range is an integer multiple of the time interval between the two continuous current values or the open circuit voltage measurements.

In accordance with the teachings of the present invention, updating the full charge is not performed when the estimated state of charge is above a predetermined level.

According to another aspect of the present invention, one can explore a charge A fully charged battery management system for stacking rechargeable battery cells in a battery pack includes: a voltage detecting unit electrically connected to a rechargeable battery pack, the rechargeable battery pack being composed of a plurality of stacked rechargeable battery cells connected in series and/or in parallel And configured to periodically measure an open circuit voltage of the rechargeable battery pack; a current measuring unit electrically connected to the rechargeable battery pack for periodically measuring a current value via the rechargeable battery pack, and based on the measured current The value is used for coulomb counting; a memory unit for storing and updating the full charge of the rechargeable battery pack; a switch unit for switching a circuit for controlling charging and discharging of the rechargeable battery pack; and a control unit connected to the voltage The detecting unit, the current measuring unit, the memory unit and the switching unit are configured to periodically estimate the state of charge of the rechargeable battery pack when the rechargeable battery pack is discharged, and calculate the measured open circuit voltage variation within a time range. The running ratio of the state change of the state of charge, when the running ratio is equal to or greater than a terminating discharge condition, the record is updated with a sum of coulomb counts Recall the full charge in the unit and control the switch unit for charging or discharging. The termination discharge condition is a ratio of an open circuit voltage change to a state change of the state of charge. A preset full charge has been stored in the memory unit before the rechargeable battery pack begins to charge. The switch unit switch causes the rechargeable battery pack to be charged until it is fully charged and then discharges the rechargeable battery pack.

In accordance with the teachings of the present invention, the time range is equal to or greater than a time interval between two continuous current values or open circuit voltage measurements.

In accordance with the teachings of the present invention, the time range is an integer multiple of the time interval between the two continuous current values or the open circuit voltage measurements.

According to the concept of the present invention, the control unit does not update the full charge when the estimated state of charge is above a predetermined level.

The method of the present invention can obtain the full charge of the rechargeable battery pack by measuring the open circuit voltage and the estimated state of charge under normal operation of the rechargeable battery pack. Provides additional evaluation performance for battery management systems by updating the full charge. The full charge provided by the present invention can be corrected according to the degree of deterioration of the physical properties of the rechargeable battery core, and it is not necessary to provide correction or comparison parameters, and the operation is very simple.

10‧‧‧Battery Management System

101‧‧‧Voltage detection unit

102‧‧‧current measuring unit

103‧‧‧ memory unit

104‧‧‧Control unit

105‧‧‧Control unit

20‧‧‧Rechargeable battery pack

201‧‧‧Charged battery core

Figure 1 is a flow chart of the previous case of determining the method of confirming the battery full charge.

Figure 2 is a block diagram of a battery management system in accordance with the present invention.

Figure 3 is a flow chart for exploring the full charge of a rechargeable battery pack in accordance with the present invention.

Figure 4 shows the relationship between voltage and state of charge when the rechargeable battery pack is discharged.

The invention will be more specifically described by reference to the following examples.

Please refer to Figures 2 to 4. Figure 2 is a block diagram of a battery management system in accordance with the present invention. Figure 3 is a diagram of the search for charging power in accordance with the present invention. A flowchart of the full charge of the pool group. Figure 4 shows the relationship between voltage and state of charge when the rechargeable battery pack is discharged.

The method provided by the present invention can be implemented by a battery management system installed in a rechargeable battery, and the method can also be applied to a separate device to determine a rechargeable battery pack connected in series and/or in parallel by stacked rechargeable battery cells. Fully charged. In order to make the description of the present invention easier to understand, the embodiments are only focused on describing a battery management system, and are not specifically described for the stand-alone device to which the method of the present invention is applied.

A battery management system 1 (0 (surrounded by a broken line) according to the present invention is shown in Fig. 2. The battery management system 10 is electrically connected to a rechargeable battery pack 20, and can be used to search for a rechargeable battery in the rechargeable battery pack 20. The full charge of the core 201 is composed of a voltage detecting unit 101, a current measuring unit 102, a memory unit 103 and a control unit 104. The function of each component will be described first, and then its operation will be described. step.

The voltage detecting unit 101 is electrically connected to both ends of the rechargeable battery pack 20 in parallel. The rechargeable battery pack 20 is composed of four rechargeable battery cells 201 connected in series. According to the present invention, the number of rechargeable battery cells 201 is not limited to four, and may be any number greater than one. The manner in which the rechargeable battery cells 201 are connected is not limited to series connection, and may be parallel, or a combination of series and parallel. The voltage detecting unit 101 is used to periodically measure the open circuit voltage of the rechargeable battery pack 20. Here, the time interval between the two consecutive open circuit voltage measurements may be any time according to the demand of the rechargeable battery using the rechargeable battery pack 20. For example, it can be 20 Microseconds or greater than 1 second.

The electric current measuring unit 102 is electrically connected to the rechargeable battery pack 20. It periodically measures the current value of the rechargeable battery pack 20. Similarly, the time interval between two consecutive current value measurements can be any time. The time interval can be the same or different than the time interval between two consecutive open circuit voltage measurements. In this embodiment, the above two time intervals are set to 0.1 seconds and are synchronized. The electric current measuring unit 102 can further perform the Coulomb counting based on the measured current value. The current measuring unit 102 acts as a coulomb counter, which multiplies each measured current value by the time interval between consecutive measurements, and continuously accumulates the result of the multiplication.

The memory unit 103 can store the full charge value of the rechargeable battery pack, and when it receives an updated full charge, it can also update the stored full charge. The stored full charge can be provided as a reference for rechargeable battery operation, such as calculating the remaining charge. The switch unit 104 can switch a circuit to which the rechargeable battery pack 20 is connected to operate to control charging and discharging of the rechargeable battery pack 20.

The control unit 105 is connected to the voltage detecting unit 101, the current measuring unit 102, the memory unit 103, and the switching unit 104. It periodically estimates the state of charge when the rechargeable battery pack 20 is discharged. It is also capable of calculating an operating ratio in a time range that is a measured change in the open state voltage versus an estimated state of charge state, and when the operating ratio is equal to or greater than a terminating discharge condition, a sum of coulomb counts The full charge in the memory unit 103 is updated. In addition, the control unit 105 can also control the switch unit 104 to perform the rechargeable battery pack 20 Charging or discharging.

Please refer to Figure 3. The manner in which the battery management system 10 operates is described by reference to the corresponding steps of the flow chart in FIG. First, a termination discharge condition is predefined as a ratio of an open circuit voltage change state change in the memory unit 103 (S01). In order to better understand the termination discharge conditions, please see Figure 4. When each stacked rechargeable battery cell 201 is fully charged, the open circuit voltage across the rechargeable battery pack 20 will reach a maximum. However, usually not every stacked rechargeable battery cell 201 needs to be fully charged when a predetermined full charge reaches.

From Fig. 4, it is apparent that during discharge, since the open circuit voltage of each stacked rechargeable battery cell 201 drops, the measured open circuit voltage drops. Although the voltage drop of each of the rechargeable battery cells 201 may vary to some extent, the measured open circuit voltage of the rechargeable battery pack 20 appears as the sum of the open circuit voltages of each of the rechargeable battery cells 201. The curve in the open circuit voltage and charge state diagrams drops significantly after the rechargeable battery pack 20 begins to discharge. After a period of discharge, the slope of the curve becomes gentler. When the battery pack 20 is charged for most of its charge, the curve begins to drop significantly again. The steeper slope in the curve means that most of the rechargeable battery cells 201 will use their stored power at this time. According to Fig. 4, the termination discharge condition is described by a triangle in which the angle of the curve at the right angle indicates the slope of the curve of the termination discharge condition. Once the ratio of an open circuit voltage to a state change of the state of charge becomes equal to or greater than the slope, it means that the discharge condition is terminated.

Next, a full charge is supplied to the rechargeable battery pack 20 (S02). The full charge can be a rating given after the rechargeable battery pack 20 is produced, and it can also be an empirically based estimate. Full charge can be used for any battery management purpose before it is updated. It should be noted that the full charge does not have to be the amount of charge of all of the rechargeable battery cells 201 from being fully charged to being depleted. If so, some rechargeable battery cells 201 may be damaged by over-discharge conditions. Regardless of the battery imbalance condition, when one of the rechargeable battery cells 201 cannot output power, the rechargeable battery pack 20 should stop discharging.

Next, the rechargeable battery pack 20 is charged until it is full (S03). Then, the rechargeable battery pack 20 is discharged (S04). The current value and the open circuit voltage are measured periodically (S05). As described above, the time interval is 0.1 second.

After the rechargeable battery pack 20 starts discharging, the current measuring unit 102 performs Coulomb counting based on the measured current value (S06). The algorithm for coulomb counting is quite simple. Multiply the measured current value by 0.1 second and accumulate the result. When the discharge is stopped, the final accumulated result can be the full charge.

Next, the control unit 105 periodically estimates the state of charge during discharge (S07). It is emphasized that there are many methods for estimating the state of charge that can be used as long as a method is suitable for the design of the rechargeable battery pack 20. Next, the control unit 105 calculates a running ratio value which is a ratio of the measured open circuit voltage change to the estimated change in the state of the electric quantity over a time range (S08). Finally, when the running ratio is equal to or greater than the terminating discharge condition, the control unit 105 updates the full charge amount with the coulomb count sum (S09).

Please see figure 4. There is a point, point A, that meets the specification requirements for stopping the discharge and determining the full charge of the update. The discharge ends at point B. However, the rechargeable battery cell 201 is over-discharged and thus subject to damage, thereby reducing the performance of the rechargeable battery pack 20. It is emphasized that the termination discharge condition must be selected to prevent further discharge of the rechargeable battery pack 20, and it is very important to determine the starting point for terminating the discharge condition.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

S01~S09‧‧‧Steps

Claims (2)

A method for searching for a full charge of a rechargeable battery cell in a rechargeable battery pack, comprising the steps of: predefining a termination discharge condition, wherein the termination discharge condition is a ratio of an open circuit voltage change to a state change of the power state; providing a full charge at a charge a battery pack comprising: a plurality of stacked rechargeable battery cells connected in series and/or in parallel; charging the rechargeable battery pack until being fully charged; discharging the rechargeable battery pack; periodically measuring the rechargeable battery pack The current value and the open circuit voltage; performing a Coulomb count based on the measured current value; periodically estimating the state of charge of the rechargeable battery pack during discharge; calculating an operating ratio within a time range, the running ratio being an open circuit of the measured The voltage change changes the estimated state of charge; and when the run ratio is equal to or greater than the terminating discharge condition, the full charge is updated with a sum of coulomb counts. A battery management system capable of searching for a full charge of a rechargeable battery cell in a rechargeable battery pack, comprising: a voltage detecting unit electrically connected to a rechargeable battery pack, the rechargeable battery pack being connected in series and/or in parallel The connected stacked rechargeable battery core is configured to periodically measure the open circuit voltage of the rechargeable battery pack; a current measuring unit electrically connected to the rechargeable battery pack for periodically measuring a current value via the rechargeable battery pack, and performing a Coulomb counting based on the measured current value; a memory unit for storing and updating the charging a full charge of the battery pack; a switch unit for switching a circuit for controlling charging and discharging of the rechargeable battery pack; and a control unit connected to the voltage detecting unit, the current measuring unit, the memory unit and the switching unit, When the rechargeable battery pack is discharged, periodically estimating the state of charge of the rechargeable battery pack, calculating a running ratio of the measured open circuit voltage change to the estimated power state change within a time range, when the running ratio is equal or greater than Updating the full charge in the memory unit with a coulomb count sum when a discharge condition is terminated, and controlling the switch unit to perform charging or discharging; wherein the termination discharge condition is a ratio of an open circuit voltage change to a state change of the state of charge, Before the rechargeable battery pack starts charging, a preset full charge has been stored in the memory unit, and the switch unit is cut. The switch of the rechargeable battery pack is charged up to full charge and then make up the rechargeable battery pack is discharged.