Single-string battery cell quantitative discharging device

Abstract

The utility model discloses a single-string battery cell quantitative discharging device, which relates to the field of battery management and comprises an electric quantity metering unit and a discharging unit. The first input end of the electric quantity metering unit is connected to an external control device; the second output end of the electric quantity metering unit is connected to the input end of the discharging unit; after the first input end of the electric quantity metering unit obtains a metering starting signal, the second output end of the electric quantity metering unit outputs a discharging starting signal to the discharging unit and starts to meter the discharging electric quantity, and after the discharging electric quantity reaches a preset value delta Q, the output end of the electric quantity metering unit sends a discharging stopping signal to the discharging unit; the discharging unit starts discharging after receiving the discharging starting signal and stops discharging after receiving the discharging stopping signal. The discharge management method is not influenced by voltage fluctuation of the batteries, and more accurate equalization management of the batteries can be realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of battery management, and more particularly to a single string battery cell quantitative discharging device. BACKGROUND

[0002] New energy lithium battery has become an indispensable element in people's life, however, all series battery packs must face a problem, that is, the battery balancing problem, and the balancing problem greatly reduces the capacity and service life of the series battery pack.

[0003] The closest single string lithium battery balancing scheme is to start the balancing discharge of a fixed duration when the battery string voltage reaches the balancing start threshold. One problem of this balancing method is that the balancing amount is easily affected by the battery string voltage after the balancing is started. The battery string has a 40% voltage fluctuation from full to empty, and the balancing amount also has a deviation of about 40%, resulting in a large difference in balancing effect under different conditions. In addition, the common battery cell discharging method is the method of consuming electric energy by resistance heating, which has low efficiency. SUMMARY

[0004] In view of the deficiencies of the existing balancing scheme, the single string battery cell quantitative discharging device can improve the balancing accuracy and efficiency.

[0005] The embodiments of the present application disclose the following technical solutions:

[0006] A single string battery cell quantitative discharging device, the quantitative discharging device includes an electric quantity metering unit and a discharging unit; the first input end of the electric quantity metering unit is connected to an external control device, and the second output end of the electric quantity metering unit is connected to the input end of the discharging unit; after the first input end of the electric quantity metering unit obtains a metering start signal, the second output end outputs a discharging start signal to the discharging unit, and starts to meter the discharging electric quantity; after the discharging electric quantity reaches a predetermined value ΔQ, the output end of the electric quantity metering unit sends a discharging stop signal to the discharging unit; the discharging unit starts discharging after receiving the discharging start signal, and stops discharging after receiving the discharging stop signal.

[0007] Further, the electric quantity metering unit includes a coulomb meter.

[0008] Further, the electric quantity metering unit includes a current detection circuit and a timing accumulation circuit or a timing subtraction circuit, the current detection circuit is connected to the timing accumulation circuit or the timing subtraction circuit, and the discharging electric quantity is metered by timing accumulation or timing subtraction of the discharging current value.

[0009] Further, the electric quantity metering unit includes a voltage detection circuit and a timing accumulation circuit or a timing subtraction circuit, the voltage detection circuit is connected to the timing accumulation circuit or the timing subtraction circuit, and the discharging electric quantity is metered by timing accumulation or timing subtraction of the voltage value representing the discharging current.

[0010] Further, the electric quantity metering unit further comprises a delay circuit, and the electric quantity metering unit outputs the discharging start signal after delaying for a preset time length Δt after receiving the metering start signal, and starts metering the discharging electric quantity.

[0011] Further, the discharging unit comprises a circuit structure in which a switching circuit and a discharging resistor are connected in series.

[0012] Further, the discharging unit comprises a transformer driving circuit and an isolation transformer, and the isolation transformer isolates and outputs the battery string electric energy.

[0013] Further, the quantitative discharging device further comprises a temperature detection unit, and the temperature detection unit outputs a first discharging prohibition signal when detecting that the temperature is higher than a threshold temperature VT.

[0014] Further, the quantitative discharging device further comprises a voltage detection unit, an input end of the voltage detection unit is connected to an external battery string voltage signal, and an output end of the voltage detection unit is connected to a first input end of the electric quantity metering unit, and the voltage detection unit outputs the metering start signal when the external battery string voltage is higher than a set threshold V1.

[0015] Further, the voltage detection unit comprises a low-voltage detection circuit, and the low-voltage detection circuit outputs a second discharging prohibition signal when detecting that the external battery string voltage is lower than a set threshold V2.

[0016] Technical effects and advantages of the utility model: in the series battery pack, through using the single string electric core quantitative discharging device to each battery string, the battery string of voltage bias high at the end of each charging will be discharged one fixed capacity of electric quantity, and the battery string of voltage bias low will not be discharged, in the long-term use process, the battery string of voltage bias low voltage will gradually promote, finally catch up with the battery string of voltage bias high, finally reach the balanced effect of whole series battery pack;Compared with the discharging mode of specified time length, this discharging method will not be affected by the battery voltage, so that the discharging consistency of each string is higher;And use the transformer discharging mode, can recover the discharged electric energy, and make the energy efficiency further improve. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is single string electric core quantitative discharging device schematic diagram;

[0018] Figure 2 It is timing accumulation circuit schematic diagram;

[0019] Figure 3 It is delay circuit structure schematic diagram;

[0020] Figure 4 It is transformer driving circuit and isolation transformer structure schematic diagram; DETAILED DESCRIPTION

[0021] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and design various embodiments with various modifications suitable for a particular purpose. Example

[0022] A single-cell quantitative discharge device, such as Figure 1 As shown, the external battery is a 100AH ​​lithium iron phosphate series battery pack. Each battery string is equipped with a single-string cell quantitative discharge device, which includes a voltage detection unit 104, a temperature detection unit 103, a capacity metering unit 101, and a discharge unit 102. The input terminal of the voltage detection unit 104 is connected to the positive and negative terminals of the external battery cell, and the output terminal is connected to the input terminal of the capacity metering unit 101. The output terminal of the capacity metering unit 101 is connected to the input terminal of the discharge unit 102, and the output terminal of the temperature detection unit 103 is connected to the other input terminal of the capacity metering unit 101. When the external battery voltage exceeds the preset voltage of 3.5V, the output terminal of the voltage detection unit 104 sends a metering start signal to the capacity metering unit 101. At the input terminal, the power metering unit 101 sends a discharge start signal to the discharge unit 102 through its output terminal. The discharge unit 102 starts discharging, and at the same time, the power metering unit 101 starts measuring the discharge amount. The temperature detection unit 103 detects the device temperature. When the temperature is greater than or equal to the high temperature protection temperature of 60 degrees, the temperature detection unit outputs a low level, the power metering unit 101 shuts off the discharge start signal, and the discharge unit 102 stops discharging. When the temperature is lower than the high temperature protection temperature of 60 degrees, the temperature detection unit outputs a high level, and the power metering unit 101 continues to send a discharge start signal to the discharge unit 102. When the discharge amount reaches 0.5AH, the output terminal of the power metering unit 101 shuts off the discharge start signal, and this equalization cycle ends.

[0023] Regarding energy measurement, the most common type is the coulomb meter. A coulomb meter, with a start-meter input, outputs a high level during measurement and a low level after the target is reached, thus cooperating with the subsequent discharge unit. Of course, a single energy meter can be used as... Figure 2The architecture design is shown. The input terminal 201 of the voltage detection circuit 202 is connected to both ends of the equalization resistor of the discharge circuit. The resistance value of the equalization discharge resistor is 33 ohms. The current through the equalization discharge resistor can be calculated by the detected voltage. This voltage value is input to one input terminal of the accumulator 203 as the addend. At the same time, the accumulator 203 stores the result of each accumulation in its internal memory and uses it as the accumulation result of the current cycle and the addend for the next cycle. The timing signal generator 204 outputs a low-frequency square wave with a period of 1 second. At the rising edge of the square wave, the accumulator 203 completes the summation of the addend and the addend, and compares the accumulation result with the preset value of ampere-hours. If the result is less than the preset value ΔQ = 0.5AH, the accumulator 203 outputs a high level to the discharge unit, and the discharge unit continues to discharge. If the result is greater than or equal to the preset value of 0.5AH, the accumulator 203 outputs a low level to the discharge unit, and the discharge unit stops discharging.

[0024] like Figure 2 The voltage detection unit 202 shown can be designed as a combination of a voltage comparator and a reference voltage source. The reference voltage source generates a reference voltage and outputs it to the negative input terminal of the voltage comparator. The positive input terminal of the voltage comparator is connected to the positive terminal of the battery. When the battery charging voltage rises and exceeds the reference voltage source, the voltage comparator output changes from low to high. By reversing the positive and negative inputs of the voltage comparator, it becomes a low-voltage detection circuit. The low-voltage detection is set to a voltage below 2.2V, outputting a second discharge prohibition signal. This second discharge prohibition signal is input to the power metering unit, which disables the discharge start signal, and the discharge unit stops discharging. Voltage detection circuits commonly use voltage comparators or ADCs; this embodiment uses a voltage comparator and a reference voltage source.

[0025] like Figure 2 The timing signal generator 204 shown can be composed of a clock signal generator and a frequency divider. The clock signal generator can use an RC oscillator or a ring oscillator. The frequency divider converts the high-frequency periodic oscillation signal generated by the clock signal generator into a low-frequency signal, which is then sent to the accumulator. This reduces the operating frequency, workload, and power consumption. The accumulator is based on an adder, and the subtractor is based on a subtractor.

[0026] The main function of the delay circuit is to postpone the equalization discharge. This has the advantage of preventing current and voltage drop on the equalization line when multiple single-cell quantitative discharge devices are used together and share an equalization line at the end of charging. This would affect the voltage detection accuracy of adjacent strings. The delay circuit uses a delay Δt = 4096 seconds, activating only after receiving the activation signal. By this time, charging is usually complete, the battery voltage has dropped, and equalization is activated, preventing adjacent strings from erroneously activating due to inaccurate voltage detection. The delay circuit is designed using a series of trigger chains, such as... Figure 3As shown, the FF0~FFx flip-flop chain composed of flip-flops 303 and the like, the output terminal of the previous stage flip-flop is connected to the clock input terminal of the next stage flip-flop, the input terminal 301 of the JK flip-flop takes value 1, each clock JK flip-flop flips once, the further the stage, the slower the flip speed, x takes 13, the clock input 305 frequency uses 1HZ, the output QX=4096 seconds delay of the output terminal 302 can be obtained, the output terminal is used to generate reset signal with the pulse generating circuit, and the reset input 304 is input, and the delay circuit is reset after the delay is completed. This frequency division circuit is a common circuit, and users can obtain more related information from the public network, which will not be described here.

[0027] The equalization discharge circuit uses the circuit structure of series connection of resistance circuit and switch tube. The resistance circuit has the advantages of small interference and the disadvantage of much heat. Of course, the user can also use the output of the isolation transformer. If 4 is shown: the on-off of the switch signal 402 controls the switch tube 403, the positive and negative poles of the battery are connected in series through the switch tube 403 and the primary coil of the transformer, and the diode 404 is reversely connected in the circuit of the primary coil, so as to realize the freewheeling effect when the switch tube is turned off; the secondary coil of the isolation transformer is output through a series connection of a low conduction voltage drop Schottky diode, wherein the output positive voltage is output from the output terminal 407, and the output negative voltage is output from the output terminal 408. When the drive signal 402 sends the on signal, the switch tube 403 is turned on, and under the drive of the battery 401 voltage, the current flows from the positive pole of the battery through the switch tube, flows through the primary coil of the isolation transformer and returns to the negative pole of the battery, at this time, the induced current of the secondary coil of the transformer flows along the clockwise direction through the diode 406. When the drive signal 402 sends the off signal, the switch tube 403 is turned off, and due to the characteristics of the transformer coil, the current cannot be turned off immediately, at this time, the current will be freewheeled by the diode 404, and at this time, the output 407 and 408 of the secondary coil have no output. Compared with the resistance discharge, this mode has higher efficiency, and the discharge energy can be transferred to the third party power platform. The disadvantage is that the interference is relatively large, and the user can select according to the actual situation. Of course, the transformer can also use a flyback transformer, and these can be easily obtained from the public data, which will not be described here.

[0028] The temperature detection circuit prevents the device from being burned out or the service life from being reduced due to overheating. There are many ways to protect the temperature, and here the voltage comparator is used to compare the voltage divided by two fixed resistors and the voltage divided by the NTC resistor and the fixed resistor. The two resistors are connected in series between the positive and negative poles of the battery, the two fixed resistors are connected to the positive input terminal of the voltage comparator, and the NTC and the fixed resistor are also connected in series between the positive and negative poles of the battery, and they are connected to the negative input terminal of the voltage comparator. With the increase of temperature, the resistance of the NTC decreases, the negative input of the voltage comparator becomes high, when the voltage is higher than the voltage of the positive input terminal of the comparator, the output of the comparator changes from high to low, and the over-temperature protection signal is output, which informs the electric quantity measurement unit to close the discharge start signal and close the discharge unit.

[0029] This embodiment balances a 4-string 100AH battery. The capacity of the series battery before balancing is 93AH. After normal use, the battery is charged once a day. The strings that meet the balancing conditions are discharged by 0.5AH. After 14 days, the battery capacity is restored to 99.2AH, showing good balancing effect.

[0030] The above embodiments are for lithium iron phosphate. The balancing parameter settings for ternary, lithium manganate, lithium titanate, lead-acid, etc. can be modified according to the characteristics of the battery. These parameters are common knowledge for users in the industry and are not difficult.

[0031] Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by ordinary skilled persons in the art and related fields without creative labor shall belong to the scope of protection of the present application.

Claims

1. A single string cell dosing discharge device, characterized by, The quantitative discharging device comprises an electric quantity metering unit and a discharging unit; the first input end of the electric quantity metering unit is connected to an external control device, and the second output end of the electric quantity metering unit is connected to the input end of the discharging unit; after the first input end of the electric quantity metering unit obtains a metering start signal, the second output end of the electric quantity metering unit outputs a discharging start signal to the discharging unit, and the discharging electric quantity is started to be metered; after the discharging electric quantity reaches a predetermined value ΔQ, the output end of the electric quantity metering unit sends a discharging stop signal to the discharging unit; after the discharging unit receives the discharging start signal, the discharging unit starts to discharge, and after the discharging unit receives the discharging stop signal, the discharging unit stops discharging.

2. The single string cell quantitative discharging device according to claim 1, characterized in that, The electric quantity metering unit comprises a coulomb meter.

3. The single string cell quantitative discharging device according to claim 1, characterized in that, The electric quantity metering unit comprises a current detection circuit and a timing accumulation circuit or a timing subtraction circuit, the current detection circuit is connected to the timing accumulation circuit or the timing subtraction circuit, and the discharging electric quantity is metered by timing accumulation or timing subtraction of the discharging current value.

4. The single string cell quantitative discharge device according to claim 1, characterized in that, The electric quantity metering unit comprises a voltage detection circuit and a timing accumulation circuit or a timing subtraction circuit, the voltage detection circuit is connected to the timing accumulation circuit or the timing subtraction circuit, and the discharging electric quantity is metered by timing accumulation or timing subtraction of the voltage value representing the discharging current.

5. The single string cell quantitative discharge device according to claim 1, characterized in that, The electric quantity metering unit further comprises a delay circuit, the electric quantity metering unit outputs the discharging start signal and starts to meter the discharging electric quantity after a preset time delay Δt after receiving the metering start signal.

6. The single string cell quantitative discharge device according to claim 1, characterized in that, The discharging unit comprises a circuit structure in which a switching circuit and a discharging resistor are connected in series.

7. The single string cell quantitative discharge device according to claim 1, characterized in that, The discharging unit comprises a transformer driving circuit and an isolation transformer, and the isolation transformer isolates and outputs the battery string electric energy.

8. The single string cell quantitative discharge device according to claim 1, characterized in that, The quantitative discharging device further comprises a temperature detection unit, when the temperature detection unit detects that the temperature is higher than a threshold temperature VT, the temperature detection unit outputs a first discharging prohibition signal.

9. The single string cell quantitative discharging device according to any one of claims 1 to 8, characterized in that, The single-string cell quantitative discharging device further comprises a voltage detection unit, the input end of the voltage detection unit is connected to an external battery string voltage signal, the output end of the voltage detection unit is connected to the first input end of the electric quantity metering unit, and when the external battery string voltage is higher than a set threshold V1, the voltage detection unit outputs a metering start signal.

10. The single string cell quantitative discharge device according to claim 9, characterized in that, The voltage detection unit comprises a low-voltage detection circuit, and after the low-voltage detection circuit detects that the external battery string voltage is lower than a set threshold V2, the low-voltage detection circuit outputs a second discharging prohibition signal.

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