CN102088122B - Charging method and charging device for secondary lithium battery pack - Google Patents

Abstract

The invention relates to a method for charging a lithium secondary battery pack, comprising the following steps: judging whether the lithium secondary battery pack needs to be charged, if so, performing the following steps, otherwise, exiting; disconnecting each cell from the battery pack The connection of other cells in the battery makes the battery group into a plurality of individual cells; the individual cells are charged with adjustable constant current; after all the cells are charged, the reading indicates that the cell composition A configuration file of the connection relationship of the battery pack, according to which the single cells are connected to form a battery pack. The invention also relates to a lithium secondary battery charging device. The charging method and charging device of the lithium secondary battery pack of the present invention have the following beneficial effects: the connection mode between the cells inside the battery pack can be adjusted online, and each cell can be charged individually during charging.

Description

Charging method and charging device for lithium secondary battery pack

technical field

The invention relates to battery charging, more specifically, to a charging method and charging device for a lithium secondary battery pack.

Background technique

With the development of electronic technology, more and more portable electronic products, such as medical equipment, notebooks, game consoles, PDAs, cameras, etc., use lithium secondary batteries for power supply. The specifications of the single cell of the lithium secondary battery pack are relatively standard, such as: the capacity of the 18650 cylindrical cell is 2200mAh, the nominal voltage is 3.7V, and the maximum charging voltage is 4.25V. However, the existing single-cell terminal voltage and capacity are limited, and it is difficult to meet the requirements in many applications. Usually, a series-parallel battery pack with multiple rechargeable cells is used to meet many applications. However, this method is different due to different application requirements. For example, sometimes the output voltage of the battery pack is required to be 7.4V, while other applications may require the output voltage to be 14.8V. Different output voltages and different capacities have different internal connection modes of the lithium secondary battery pack. For example: the lithium secondary battery pack requires a capacity of 2200mAh, 29.6V, and will connect 8 single cells in series; requires a capacity of 4400mAh, and 14.8V, will connect 8 single cells in 4 series and 2 parallels; requires a capacity of 8800mAh, 7.4V, will Connect 8 single cells in 2 series and 4 in parallel. The required capacity is 17600mAh, 3.7V, and 8 single cells will be connected in parallel. Although among the above four requirements, the basic unit is common, all of which are 8 cells. However, manufacturers of lithium secondary battery packs often produce 4 types of battery packs to meet user needs. Greatly reduce production efficiency and increase follow-up maintenance costs. In addition, there are large differences in capacity, internal resistance, attenuation characteristics, self-discharge and other performances between the single cells of lithium secondary battery packs. In the prior art, when the lithium secondary battery pack is charged in series as a whole, the single lithium battery cell with the smallest capacity in the battery pack will be fully charged first, and at this time, the other cells are not yet fully charged. If you continue to charge in series, the fully charged Li-ion cells may be overcharged. An explosion may occur, affecting the safety of the lithium secondary battery pack. If charging is stopped, other lithium-ion single cells cannot be fully charged, resulting in insufficient capacity of the entire lithium secondary battery pack.

Contents of the invention

The technical problem to be solved by the present invention is to provide a factory-delivered battery for the defects of the prior art that the connection mode between the battery cells inside the battery pack cannot be adjusted, and each battery cell cannot be charged separately during charging. A charging method and device for a lithium secondary battery pack in which the connection mode between the cells inside the pack can be adjusted, and each cell can be charged individually during charging.

The technical solution adopted by the present invention to solve the technical problem is to construct a charging method for a lithium secondary battery pack, wherein the lithium secondary battery pack is composed of a plurality of lithium battery cells connected in series or in parallel, comprising the following steps:

A) Determine whether the lithium secondary battery pack needs to be charged, if so, perform the following steps, otherwise, exit;

B) Disconnecting each cell from the other cells in the battery pack so that the battery pack is a plurality of individual cells;

C) Carry out adjustable constant current charging to the individual batteries respectively;

D) After all the cells are charged, read the configuration file indicating the connection relationship of the cells forming the battery pack, and connect the single cells to form a battery pack according to the configuration file.

In the lithium secondary battery charging method of the present invention, each cell in the battery pack is connected to other cells in the battery pack through at least one controllable switch, and the control switch is controlled by a microcontroller Its on and off.

In the lithium secondary battery pack charging method described in the present invention, the step C) further includes the following steps:

C1) Determine whether the cell voltage is greater than 2 volts, if less than, use 0.01C constant current charging; if not, use 1C constant current charging;

C2) Judging whether the cell voltage is less than 4.1V, if less, return to step C1); otherwise, use the gradually decreasing constant current charging with the monotonous descending edge of the quadratic curve or Gaussian curve as the control method.

In the lithium secondary battery pack charging method described in the present invention, the step C) further includes the following steps:

C3) Measure the capacity of the single battery cell respectively to determine whether it is fully charged, if so, execute the next step, otherwise, return to step C1);

C4) Determine whether all cells in the lithium secondary battery pack are fully charged, if yes, perform step D); otherwise, return to step C1).

In the lithium secondary battery pack charging method described in the present invention, the step D) further includes the following steps:

D1) Read the configuration file stored in the memory or transmitted by the microcontroller communication bus;

D2) The microcontroller outputs control signals at different output terminals according to the content of the configuration file, so that the controllable switches between the corresponding connected cells are turned on or off.

The present invention also relates to a lithium battery charging device. The lithium secondary battery pack is composed of a plurality of lithium battery cells connected in series or in parallel. The device includes:

Battery capacity detection and judgment module: used to judge whether the lithium secondary battery pack needs to be charged;

Cell splitting module: used to disconnect each cell from other cells in the battery pack, so that the battery pack can be divided into multiple separate cells;

Adjustable constant current charging module: perform adjustable constant current charging on the individual batteries;

Cell combination module: After all the cells are charged, read the configuration file indicating the connection relationship of the cells forming the battery pack, and connect the single cells to form a battery pack according to the configuration file. the

In the lithium secondary battery charging device of the present invention, the adjustable constant current charging module further includes:

Cell voltage judging unit: used to judge whether the cell voltage is greater than 2 volts;

Battery charging state judging unit: used to judge whether the battery voltage is less than 4.1 volts;

Constant current charging unit: it is used to judge the output of the unit based on the cell voltage and the charging state of the cell, respectively adopting 0.01C constant current charging or 1C constant current charging or taking the quadratic curve or Gaussian curve as the control mode. The gradually decreasing constant current charging mode charges the batteries.

In the lithium secondary battery pack charging device according to the present invention, the battery cell assembly module further includes:

Configuration file obtaining unit: used to read the configuration file stored in the memory or transmitted by the microcontroller communication bus;

Configuration unit: It is used to output control signals at different microcontroller output terminals according to the content of the configuration file, so that the controllable switches between the corresponding connected cells are turned on or off.

In the lithium secondary battery pack charging device of the present invention, the battery capacity detection and judgment module further includes:

Battery pack current measurement unit: used to measure the voltage or current of the battery pack respectively, obtain the remaining capacity of the battery pack, and judge whether the battery pack needs to be charged. the

Implementing the charging method and charging device of the lithium secondary battery pack of the present invention has the following beneficial effects: due to disconnecting the connection between a plurality of battery cores that make up the battery pack when the battery pack needs to be charged, each battery pack can be charged separately. Carry out constant current charging suitable for its state. After all the batteries are charged, connect them according to the description of the configuration file (at this time, it can be the same as before charging, or it can be different). Therefore, after leaving the factory, the connection mode between the cells inside the battery pack can be adjusted, and each cell can be charged separately when charging.

Description of drawings

Fig. 1 is a method flow chart in the charging method and device embodiment of a lithium secondary battery pack of the present invention;

Fig. 2 is the flow chart of charging the adjustable constant current of the cell separately in the described embodiment;

Fig. 3 is the structural representation of device in described embodiment;

Fig. 4 is a schematic diagram of the battery adjustable constant current charging circuit in the embodiment;

Fig. 5 is a schematic structural view of the cell unit in the lithium secondary battery pack in the embodiment;

Fig. 6 is an electrical schematic diagram of the lithium secondary battery pack in the embodiment.

Detailed ways

Embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

As shown in Figure 1, in a charging method and device embodiment of a lithium secondary battery pack of the present invention, the charging method includes the following steps:

Step S101 Start: In this step, charge management of the lithium secondary battery pack is started.

Step S102 Microcontroller receives user instructions: In this step, the microcontroller as the control device receives user instructions, and starts outputting control signals according to user instructions or the default mode set to control the discharge of the battery pack. The communication protocol between the microcontroller and the user includes the protocol bits for selecting and setting the voltage output mode (that is, the combination mode of multiple batteries). 8 sections in parallel. Through the combination of communication protocol bits, the above-mentioned voltage combination output modes are distinguished. 00 means 8 cells in series, 01 means 4 strings and 2 parallels, 10 means 4 parallels and 2 strings, 11 means 8 cells in parallel.

Step S103 Store the configuration file set by the user: In this step, the microcontroller receives the above instructions, the main content of which is the voltage output mode (that is, the configuration file), and stores the configuration file in the memory. These configuration files will be used in subsequent steps.

，电流的确定可以在回路中串联一个高精度的电流检测电阻Rsense，（一般为10mΩ~20mΩ）。通过采集电阻Rsense两端的电压Usense，可计算电池输出的电荷

。 Step S105 Battery capacity detection: In this step, the microcontroller detects the battery capacity according to the Coulomb method, specifically, the remaining capacity of the lithium secondary battery pack = the current full capacity Q _of the lithium secondary battery pack - the output charge of the battery Q; while the charge output by the battery

, The current can be determined by connecting a high-precision current detection resistor Rsense in series in the loop (generally 10mΩ~20mΩ). By collecting the voltage Usense across the resistor Rsense, the battery output charge can be calculated

.

，其中

为电池的总容量，SOC为电池的充电状态。通过统计恒流源充电的时间，修正SOC能细化锂二次电池组当前充满的电池容量，将电池容量测量精度提高了2～5％。 The current full capacity Q of the lithium secondary battery pack _is :

,in

is the total capacity of the battery, and SOC is the state of charge of the battery. By counting the charging time of the constant current source, correcting the SOC can refine the current full battery capacity of the lithium secondary battery pack, and improve the measurement accuracy of the battery capacity by 2-5%.

Step S106 Whether the capacity is sufficient: In this step, the microcontroller judges the capacity of the battery pack. If the power of the battery pack is sufficient, continue to supply power, that is, execute step S108; if it is found that the power of the cells is insufficient, disconnect the connection between the cells to exit the power supply mode, and automatically enter the adjustable constant current charging mode, that is, execute step S107.

Step S107 Disconnect the connection between the batteries and enter the adjustable constant current charging mode: In this step, the batteries in the battery pack are disconnected from each other to become separate batteries, and these separate batteries are charged Adjustable constant current charging is carried out respectively, and the specific steps are described later. After this step is performed, step S108 is performed.

Step S108 Serial-parallel combination output according to the predetermined mode: first set the output mode, and then output the voltage according to the predetermined mode after the battery is fully charged, which will increase the safety of the battery pack and reduce user misoperation. In this step, since it has been judged that the capacity of the battery pack is normal or the capacity of the battery pack is normal through the adjustable constant current charging of a single battery cell, the cells in the battery pack are combined here again, and the output will be combined according to the predetermined mode. . For example, 8 cells can be composed: 8 cells in series, 4 cells in 2 parallels, 4 cells in parallel with 2 cells, and 8 cells in parallel. The factory setting mode is the default mode. If no software command is received, the output voltage will be set according to the factory setting. Combination mode, select the specific series-parallel combination mode by turning off and on the field effect transistors, photoelectric control devices or relays connected between the cells and controlled by the output of the microcontroller, see Figure 4.

Step S109 Output voltage: In this step, the battery pack starts to supply power to the load it carries.

Step S110 Voltage and current detection: In this step, while the battery pack supplies power to its load, the microcontroller monitors the state of the lithium battery cells.

Step S111 Whether the voltage and current exceed the limit? In this step, the microcontroller judges whether the voltage and current supplied by the battery pack exceed normal limits according to the detected voltage and current values, if yes, execute step S112, otherwise, execute step S114.

Step S112 Single-cell protection: In this step, when the terminal voltage and output current of the battery exceed the normal limit, the single-cell protection module will be activated to complete the protection of the lithium battery cells.

Step S113 Fault alarm and processing: generate relevant alarm prompts to the user, and wait for the user to handle. After the fault ends, step S114 is executed.

Step S114 Output voltage: In this step, the output voltage of the battery pack drives the load, and maintains the set time, and then enters step S102 again, and repeats.

In this embodiment, as shown in FIG. 2, the adjustable constant current charging for a disconnected single cell includes the following steps:

Step S201 Cut off the connection between the batteries and enter the constant current charging mode for individual batteries: In this step, the batteries in the battery pack are disconnected from each other to become individual batteries, and these individual batteries are charged The so-called adjustable constant current charging mode includes three stages: 0.01C current constant current, 1C current constant current, and gradually decreasing constant current charging.

Step S202 Battery over-discharge? It is judged whether there is over-discharge of the battery cell, if yes, execute step S203, otherwise, execute step S205. For long-term lithium secondary battery packs, there is a risk of over-discharge of the cells. In this embodiment, when the cell voltage is lower than 2V, it is judged that it is in an over-discharge state. At this time, a current charging of 0.01C should be adopted to gradually activate the performance of the lithium battery cell.

Step S203 0.01C constant current charging: In this step, 0.01C constant current charging is provided for the cells judged to be in an over-discharge state, and lasts for a certain period of time.

Step S204 0.01C constant current charging to activate battery performance? It is judged in step S203 whether to activate the battery performance after a period of time, that is, whether to increase the voltage of the cell to above 2V, if yes, execute step S205; otherwise, execute step S210.

Step S205 1C constant current charging: When the cell voltage is greater than 2V, it indicates that the cell is in an active state, and 1C constant current charging is adopted. After some batteries have been used for a period of time, the internal resistance increases to varying degrees, and it is difficult to accurately guarantee 1C constant current charging one by one. The constant-current charging end of each cell in the present invention is independently controlled by a microcontroller, and is combined with an operational amplifier to form a negative feedback sub-device, which can fully guarantee the accuracy of charging the cell. See Figure 4. The independent 1C constant current charging of the battery continues until the battery reaches state 1, and the constant current charging enters the next stage. For a cylindrical lithium secondary battery pack, state 1 means that the voltage of a single cell is 4.1V.

Step S206 The voltage of the cell reaches 4.1V: In this step, determine whether the voltage of the cell reaches 4.1V, if yes, execute step S207; otherwise, return to step S205.

或 高斯曲线

的单调下降边。渐小恒流充电可以保证电芯的安全性，直到电芯充满结束。 Step S207 Decreasing constant current charging: when the cell voltage reaches the state of 4.1V, gradually decreasing constant current charging will be adopted. The microcontroller will gradually reduce the charging current I(t), and the control method is: quadratic curve

or Gaussian curve

The monotonous descending edge of . Gradual constant current charging can ensure the safety of the battery until the battery is fully charged.

Step S208 Are all batteries fully charged? In this step, it is judged whether all the cells in the battery pack are fully charged, if yes, step S209 is performed; otherwise, step S207 is performed to continue charging the cells.

Step S209 Obtain the configuration file, and output according to the predetermined serial-parallel combination: when all the batteries are fully charged, in this step, obtain the above-mentioned configuration file or protocol bit, and control the connection between the batteries under the action of the microcontroller. The controllable switch is turned on or off to obtain a predetermined series-parallel combination output.

Step S210 Cut off the charging power supply and generate an alarm: In this step, for the lithium secondary battery pack that cannot be effectively activated by 0.01C current charging, when the charging power supply is cut off, a relevant alarm prompt will be generated to the user. Waiting for user processing.

In this embodiment, it also relates to a charging device for a lithium secondary battery pack. The lithium secondary battery pack is composed of a plurality of lithium battery cells connected in series or in parallel. As shown in FIG. 3 , the device includes a battery capacity detection and judgment module 1 , a cell disassembly module 2 , an adjustable constant current charging module 3 and a cell assembly module 4 . Among them, the battery capacity detection and judgment module 1 is used to judge whether the above-mentioned lithium secondary battery pack needs to be charged; the cell separation module 2 is used to disconnect each cell from other cells in the battery pack, so that the above-mentioned battery pack It is a plurality of individual batteries; the adjustable constant current charging module 3 is used to carry out adjustable constant current charging on the above-mentioned individual batteries respectively; the battery combination module 4 is used to read the said The configuration file of the connection relationship of the cells forming the battery pack, and the single cells are connected to form the battery pack according to the configuration file. the

In this embodiment, the adjustable constant current charging module 3 further includes: a cell voltage judging unit 31 for judging whether the cell voltage is greater than 2 volts; a cell charging state judging unit for judging whether the cell state is less than 1 32; used for judging the output of unit 32 based on the cell voltage and the charge state of the cell, respectively adopting 0.01C constant current charging or 1C constant current charging or gradually decreasing with the monotonous descending edge of the quadratic curve or Gaussian curve as the control method The constant current charging mode is the constant current charging unit 33 for charging the batteries. The cell combination module 4 further includes a configuration file obtaining unit 41 for reading configuration files previously stored in the memory or transmitted by the micro-control communication bus and used for different micro-controllers according to the content of the configuration file. The configuration unit 42 that outputs a control signal at the output terminal of the device, so that the controllable switch between the corresponding connected cells is turned on or off. The battery capacity detection and judgment module 1 further includes a battery current measurement unit 11 for measuring the voltage or current of the battery pack, obtaining the remaining capacity of the battery pack, and judging whether the battery pack needs to be charged.

In this embodiment, Fig. 4 and Fig. 5 respectively show the schematic electrical schematic diagrams of the connection of a single cell and the microcontroller and the connection of multiple cells combined. Figure 4 actually shows the constant current charging module for a single cell, which includes: microcontroller U1, operational amplifier U2, MOS tube U3, cell B1, resistor R1, and resistor R2. The I/O pin of the microcontroller U1 outputs an analog signal, which is connected to the non-inverting terminal of the op amp U2. The negative terminal of the operational amplifier U2 is connected to the source terminal of the MOS transistor U3, and then to the ground through the resistor R2. The battery cell B1 is connected between the drain terminal of the MOS transistor U3 and the charging power source. The output terminal of the operational amplifier U2 is connected to the gate terminal of the MOS transistor U3 through the resistor R1, so that the resistor R1 and the MOS transistor U3 form a negative feedback loop of the operational amplifier. Since the operational amplifier follows the principle of "virtual short and virtual break", the output voltage of the microcontroller U1 connected to the positive phase terminal of the operational amplifier U2 is equal to the R2 connected to the negative phase terminal of the operational amplifier U2. That is to say: the voltage value output by the I/O pin of the microcontroller U1 is equal to the voltage applied to the resistor R2. Resistor R2 is a linear element, and the current flowing through it will change proportionally with the voltage. Changing the adjustable voltage will change the drain-source current of the MOS tube U3, which can control the charging current of the battery B1.

Take resistance R2 = 0.5 ohms; 18650 cylindrical cell with a capacity of 2200mAh, a nominal voltage of 3.7V, a maximum charging voltage of 4.25V, a discharge termination voltage of 2.75V, and an over-discharge protection voltage of 2.3V as an example. When the battery is not used for a long time and the cell voltage is lower than 2V, it is in an over-discharge state. In the constant current charging mode, the output voltage of the I/O pin of the microcontroller U1 is 11mV, and the voltage added to R2 is 11mV. The current flowing through the linear resistor R2 is 11mV/0.5 ohm=22mA, and 22mA is the charging current of the battery B1. For a 18650 cylindrical cell with a capacity of 2200mAh, if the battery is not permanently damaged, a 0.01C current of 22mA is an effective activation current. For lithium secondary battery packs that cannot be effectively activated by 0.01C current charging, relevant alarms will be generated when the charging power is cut off.

The battery voltage is higher than 2.75V, and the battery is in a normal state. In the constant current charging mode, the I/O pin of the microcontroller U1 outputs a voltage of 1.1V, and the voltage added to R2 is 1.1V. The current flowing through the linear resistor R2 is 1.1V/0.5 ohm = 2.2A, and 2.2A is the charging current of the battery B1. For the 18650 cylindrical cell with a capacity of 2200mAh, 1C current of 2.2A is an optimal charging current, which not only ensures the safety of the battery, but also fully charges the cell in the shortest time.

的单调下降边，直到都充满后关闭MOS管U3，对电芯B1充电完成。 When the voltage of the cell is higher than 4.1V, that is, the cell in the flow chart 3 reaches state 1, and the constant current charge is gradually reduced. The output voltage of the I/O pin of the microcontroller U1 starts from 1.1V and decreases gradually. The way the voltage decreases is a quadratic curve or Gaussian curve

The monotonous falling edge of the battery will turn off the MOS tube U3 until it is fully charged, and the charging of the battery cell B1 is completed.

In this embodiment, the lithium secondary battery pack is composed of a plurality of battery cells, and the transformation of the connection relationship between these battery cells makes the final output voltage and current of the lithium secondary battery pack different. However, no matter how the connection relationship between these battery cell units is changed, the battery cells in these battery cell units are all charged separately when charging.

As shown in Figure 5, in this embodiment, a lithium secondary battery pack includes a plurality of battery cells, which can be connected by connecting wires or connection switches (see Figure 6), and a The structure of the battery cell unit roughly includes the battery cell E, two SPDT switches K1, K2, and charging switch K3. VCC falls to the ground through terminal 1 of switch K1, positive pole of battery E, negative pole of battery E, terminal 1 of switch K2, and charging switch K3 to form a charging circuit 51; When the switch terminal marked as 2 is shown, the positive and negative poles of the battery E are connected to the external circuit or other battery units through the two terminals of the switch K1 and the switch K2 respectively, forming a discharge circuit 52 .

In this embodiment, the aforementioned single pole double throw switch, connection switch or charging switch are all controlled switches, which are composed of field effect transistors or transistors respectively. Meanwhile, in the present embodiment, the above-mentioned lithium secondary battery pack also includes a microcontroller, and the SPDT switch, the connection switch or the charging switch are respectively provided with control terminals, and the control terminals are respectively different from those of the microcontroller. The output terminal (that is, the I/O terminal of the microcontroller) is connected and controlled by the control signal output by the microcontroller.

In this embodiment, each battery cell is charged with the above-mentioned constant current, and the charging terminal is independently controlled by the microcontroller, which can completely guarantee the accuracy of charging the battery cell. After all the batteries are fully charged, they will be combined and output according to the last received mode. The discharge principle of the lithium secondary battery pack is the same as that of the current technology, and no specific explanation is given. This embodiment provides a serial-parallel combination output module applying the above method. In order to express clearly, some circuits are selected to take automatic switching of 4 series 2 parallel and 4 parallel 2 series as an example, as shown in FIG. 6 .

The circuit schematic diagram of the series-parallel combination output of the lithium secondary battery pack includes: fuse Fuse, capacitor y1, capacitor y2, independent batteries B1, B2, B3, B4, B5, B6, B7, B8, operational amplifiers U1, U2, Switching MOS tubes Q1, Q2, Q3, Q4, Q5, Q6, Q7, Q8, resistors R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15, R16, R17, R18, R19. SPDT switching tubes K11, K12, K21, K22, K31, K32, K41, K42, K51, K52, K61, K62, K71, k72, K81, k82, K9, K10.

Capacitor y1 and capacitor y2 are connected in series between the positive pole and the negative pole to filter out noise. Ck1, Ck2, and Ck3 are connected to the digital I/O pins of the microcontroller, and connected in series to the single-pole double-throw switch tubes K11, K12, K21, K22, K31, K32, K41, K42, Control terminals of K51, K52, K61, K62, K71, k72, K81, k82, K9, K10. Operational amplifiers U1, U2, switching MOS tubes Q1, Q2, Q3, Q4, Q5, Q6, Q7, Q8, resistors R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15, R16 form an adjustable constant current charging unit of 8 independent batteries B1, B2, B3, B4, B5, B6, B7, B8.

The microcontroller outputs a high level through the digital I/O pin control signal Ck1, and the single-pole double-throw switch tubes K11, K12, K21, K22, K31, K32, K41, K42, K51, K52, K61, K62, K71, k72, K81, k82 are respectively turned on at nodes C11, C12, C21, C22, C31, C32, C41, C42, C51, C52, C61, C62, C71, C72, C81, Cf82, and the battery pack is in a charging state. Each battery cell is in an adjustable constant current charging state, and the specific principle is detailed in the above description.

The microcontroller outputs a low level through the digital I/O pin control signal Ck1, and the single-pole double-throw switch tubes K11, K12, K21, K22, K31, K32, K41, K42, K51, K52, K61, K62, K71, k72, K81, k82, K9, and K10 are respectively turned on at nodes f11, f12, f21, f22, f31, f32, f41, f42, f51, f52, f61, f62, f71, f72, f81, and f82, and the battery pack is in discharge state.

Batteries B1 and B2 are connected in series to one circuit, batteries B3 and B4 are connected in series to one circuit, and these two branches are connected in parallel; batteries B5 and B6 are connected in series to one circuit, batteries B7 and B8 are connected in series to one circuit, and these two branches are connected in parallel; The 2 branches connected in parallel can be connected in parallel to form 4 parallel 2 series, and the 2 branches connected in parallel can also be connected in series to form 2 parallel 4 series.

The communication protocol between the lithium secondary battery pack and the user includes the protocol bits for selecting and setting the voltage output mode. For example, 8 cells can be composed of: 8 cells in series, 4 in series and 2 in parallel, 4 in parallel and 2 in series, and 8 cells in parallel. Through the combination of communication protocol bits, the above-mentioned voltage combination output modes are distinguished. 00 means 8 cells in series, 01 means 4 strings and 2 parallels, 10 means 4 parallels and 2 strings, 11 means 8 cells in parallel. After receiving the user's software command, the combination can be implemented so that the battery has 4 optional voltage outputs. The factory setting mode is the default mode, no software command is received, and the output voltage is set according to the factory setting.

When the protocol bit of the output mode received last time is: 01, it represents 4 strings and 2 parallels. The microcontroller outputs high level through the digital I/O pin control signal Ck2, Ck3, and Ck1 outputs low level, then the single-pole double-throw switch tubes K11, K12, K21, K22, K31, K32, K41, K42, K51, K52, K61, K62, K71, k72, K81, k82, K9, K10, respectively at nodes f11, f12, f21, f22, f31, f32, f41, f42, f51, f52, f61, f62, f71, f72, f81 , f82, K92, K101 conduction. Realize the voltage output mode of single cell 4 series and 2 parallel.

When the protocol bit of the output mode received last time is: 10, it represents 2 strings and 4 parallels. The microcontroller outputs low level through the digital I/O pin control signal Ck2, Ck3, and Ck1 outputs low level, then the single-pole double-throw switch tubes K11, K12, K21, K22, K31, K32, K41, K42, K51, K52, K61, K62, K71, k72, K81, k82, K9, K10, respectively at nodes f11, f12, f21, f22, f31, f32, f41, f42, f51, f52, f61, f62, f71, f72, f81 , f82, K91, K102 conduction. Realize the voltage output mode of single cell 2 series and 4 parallel.

K11, K12, K21, K22, K31, K32, K41, K42, K51, K52, K61, K62, K71, k72, K81, k82, K9, K10 in Figure 6 are single-pole double-throw switch tubes, replaced by photoelectric control Devices, field effect transistors, relays and other switching devices can also achieve the above functions. The closing and opening of the single-pole double-throw switch tube are completely controlled by the microcontroller, and the specific series-parallel combination mode is selected.

In this implementation, 8 cells are taken as an example, but in other embodiments, the lithium secondary battery pack is not limited to 8 cells. In other embodiments, the number of cells in the lithium secondary battery pack can be arbitrary. For lithium secondary battery packs with more cells, the implementation is the same, except that the communication protocol includes the protocol bits for selecting and setting the voltage output mode, and the combination number of switch tubes are respectively expanded. At present, in the application of lithium secondary battery packs, it is more commonly used from 4 cells to 24 cells. For example, 24 batteries can be composed: 12 series in 2 parallel, 8 series in 3 parallel, 6 series in 4 parallel, 4 series in 6 parallel, 3 series in 8 parallel, 2 series in 12 parallel. Through the expansion of the communication protocol bits, the above-mentioned voltage combination output modes are distinguished, such as: 000 represents 12 series and 2 parallels, 001 represents 8 series and 3 parallels, 010 represents 6 series and 4 parallels, 011 represents 4 series and 6 parallels, 100 represents 3 series 8 parallels and 101 represent 2 strings and 12 parallels. After receiving the user's software command, the microcontroller can implement the combination so that the battery has 6 optional voltage outputs. The factory setting mode is the default mode, no software command is received, and the output voltage is set according to the factory setting.

The series-parallel combination of 24 batteries will increase the corresponding number of switch tubes. Similar to K11, K12, K21, K22, K31, K32, K41, K42, K51, K52, K61, K62, K71, k72, K81, k82, K9, K10 in Figure 5 are single-pole double-throw switch tubes, which are replaced by Photoelectric control devices, relays, field effect transistors and other switching devices can also achieve the above functions.

The above-mentioned embodiments only express several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but should not be construed as limiting the patent scope of the present invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims. the

Claims (9)

1. A lithium secondary battery pack charging method, said lithium secondary battery pack is composed of a plurality of lithium battery cells connected in series or in parallel, it is characterized in that, comprising the steps: A) Determine whether the lithium secondary battery pack needs to be charged, if so, perform the following steps, otherwise, exit; B) Disconnecting each cell from the other cells in the battery pack so that the battery pack is a plurality of individual cells; C) Carry out adjustable constant current charging to the individual batteries respectively; D) After all the batteries are charged, read the pre-stored configuration file indicating the connection relationship of the batteries, and connect the single batteries to form a battery pack according to the configuration file. 2. The lithium secondary battery pack charging method according to claim 1, wherein each cell in the battery pack is connected to other cells in the battery pack through at least one controllable switch, the controllable switch The on-off of the control switch is controlled by the microcontroller. 3. The lithium secondary battery pack charging method according to claim 2, characterized in that said step C) further comprises the following steps: C1) Determine whether the cell voltage is greater than 2 volts, if less than, use 0.01C constant current charging; if greater, use 1C constant current charging; C2) Judging whether the cell voltage is less than 4.1V, if less, return to step C1); otherwise, use the gradually decreasing constant current charging with the monotonous descending edge of the quadratic curve or Gaussian curve as the control method. 4. The lithium secondary battery pack charging method according to claim 3, characterized in that said step C) further comprises the following steps: C3) Measure the capacity of the single battery cell respectively to determine whether it is fully charged, if so, execute the next step, otherwise, return to step C1); C4) Determine whether all cells in the lithium secondary battery pack are fully charged, if yes, perform step D); otherwise, return to step C1). 5. The lithium secondary battery pack charging method according to claim 4, characterized in that the step D) further comprises the following steps: D1) Read the configuration file stored in the memory or transmitted by the microcontroller communication bus; D2) The microcontroller outputs control signals at different output terminals according to the content of the configuration file, so that the controllable switches between the corresponding connected cells are turned on or off. 6. A charging device for a lithium secondary battery pack, the lithium secondary battery pack is composed of a plurality of lithium battery cells connected in series or in parallel, it is characterized in that the device comprises: Battery capacity detection and judgment module: used to judge whether the lithium secondary battery pack needs to be charged; Cell splitting module: used to disconnect each cell from other cells in the battery pack, so that the battery pack can be divided into multiple separate cells; Adjustable constant current charging module: perform adjustable constant current charging on the individual batteries; Cell combination module: After all the cells are charged, read the configuration file indicating the connection relationship of the cells forming the battery pack, and connect the single cells to form a battery pack according to the configuration file. 7. The lithium secondary battery pack charging device according to claim 6, wherein the adjustable constant current charging module further comprises: Cell voltage judging unit: used to judge whether the cell voltage is greater than 2 volts; Battery charging state judging unit: used to judge whether the battery voltage is less than 4.1 volts; Constant current charging unit: it is used to judge the output of the unit based on the cell voltage and the charging state of the cell, respectively adopting 0.01C constant current charging or 1C constant current charging or taking the quadratic curve or Gaussian curve as the control mode. The gradually decreasing constant current charging mode charges the batteries. 8. The charging device for a lithium secondary battery pack according to claim 7, wherein the cell assembly module further comprises: Configuration file obtaining unit: used to read the configuration file stored in the memory or transmitted by the microcontroller communication bus; Configuration unit: It is used to output control signals at different microcontroller output terminals according to the content of the configuration file, so that the controllable switches between the corresponding connected cells are turned on or off. 9. The lithium secondary battery pack charging device according to claim 8, wherein the battery capacity detection and judgment module further comprises: Battery pack current measurement unit: used to measure the voltage or current of the battery pack respectively, obtain the remaining capacity of the battery pack, and judge whether the battery pack needs to be charged.

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