CN110850316A

CN110850316A - Direct current resistance tester and method for all single batteries in battery pack

Info

Publication number: CN110850316A
Application number: CN201810884656.2A
Authority: CN
Inventors: 郑小鹿; 严晓
Original assignee: Jiaxing Mason Energy Storage Equipment Co Ltd; Yingkou Tianwei Semiconductor Manufacturing Co Ltd
Current assignee: Jiaxing Meikesheng Energy Storage Equipment Co ltd
Priority date: 2018-07-27
Filing date: 2018-07-27
Publication date: 2020-02-28
Anticipated expiration: 2038-07-27
Also published as: CN110850316B

Abstract

The invention discloses a tester of a battery, in particular to a direct current resistance tester and a direct current resistance testing method for all single batteries in a battery pack. The tester includes a dc load, a current detector, a Battery Management System (BMS), a bus controller and transceiver in communication with the BMS, a microprocessor, and the like. The direct current resistance (direct current internal resistance) of all the single batteries is detected at one time by setting and switching on and off the current of the direct current constant current load, and the ohmic internal resistance value is extracted. The BMS contained in the power battery pack can be directly utilized, and the method is suitable for detecting the echelon utilization of the retired power battery.

Description

Direct current resistance tester and method for all single batteries in battery pack

The technical field is as follows:

the invention relates to a battery tester, in particular to a test of direct current resistance of all single batteries in a battery pack, which is suitable for testing the echelon utilization of a power battery. The invention also relates to a method for testing the direct current resistance of all single batteries in a battery pack by using the tester.

Background art:

the invention relates to testing of battery packs, in particular to testing of all single batteries in a battery pack formed by connecting a plurality of single batteries in series. Such battery packs are increasingly used in communication base stations, data centers, energy storage, electric vehicles and other industries. Failure or premature degradation of any individual cell in the battery pack can have serious consequences. Therefore, the regular or online test of all the single batteries in the battery pack is the guarantee of safe operation. On the other hand, a large number of retired electric vehicle power battery packs (groups) will enter the market of echelon utilization, and the main trend is to adopt the original integral battery pack as much as possible and replace individual failed or degraded single batteries on the premise of not performing integral disassembly. Therefore, all the single batteries in the battery pack need to be tested quickly, and the connection between the original battery management system and the single batteries utilized by the testing method can avoid a large amount of wiring and disassembling work.

The invention relates to a battery testing technology, in particular to a direct current resistance testing technology (DC Load). Compared with other testing technologies, such as alternating current conductivity (AC conductivity) and Electrochemical Impedance Spectroscopy (EIS), the direct current resistance testing technology adopts working current close to actual working current, and can reflect the actual running condition of the battery; the rapid current switching is adopted, so that two parts (ohmic internal resistance and polarization resistance) included in a direct current resistance (direct current internal resistance) are easy to separate, and the numerical value of the ohmic internal resistance can more simply and directly represent the fault and the degradation of the battery; the transient response of the ohmic internal resistance is utilized to shorten the detection time to a time of several seconds or less. If the direct current load is combined with the load in the actual working condition, the direct current resistance testing technology is also suitable for online detection.

The invention relates to a Battery Management System (BMS) which can test the voltages of all single batteries in a circulating way and transmit the voltage values to a testing upper computer in a wired or wireless communication way according to a certain sequence and a certain protocol. The current power battery pack is equipped with a battery management system (also divided into a master machine and a slave machine) which transmits the voltage value of the single battery according to the communication protocol of the CAN, and the repetition period is not less than 250 milliseconds. The invention intercepts and captures the communication messages and analyzes the communication messages to obtain the voltage values of all the single batteries. The battery pack of the non-power battery at present is not necessarily provided with a battery management system meeting the requirements, and the implementation of the invention needs to be additionally provided with a corresponding battery management system.

U.S. Pat. No. 4322685 issued in 1982, entitled Automatic battery and charging apparatus for determining presence of single cell, uses a load of fixed resistance to discharge a lead-acid battery containing 6 cells through a mechanical switch of a relay while taking a lumped voltage value. Whether there is a bad cell is judged from the change of the total voltage at the time of opening and in the discharge. This method does not take out the voltage value of each cell. When the number of the units is not large, the positioning can be judged but can not be carried out; when the number of cells increases, it is difficult to make a reliable judgment only by a slight change in the value of the total voltage.

U.S. patent publication No. US7212006 issued in 2007 uses a fixed value resistive load to discharge a battery through an electronic switch of a power transistor, while collecting voltage values across the battery and across the fixed resistive load. The loop current value calculated by combining the latter can obtain the total direct current resistance of the battery. However, this method cannot obtain the direct current resistance of the unit cell.

In the chinese patent publication No. CN101339230 entitled in 2009, "device and method for measuring internal resistance of battery" and the chinese patent publication No. CN101359035, "method and device for measuring internal resistance of battery" adopt resistors with different fixed resistance values as loads to be connected to a battery to be measured, respectively, so as to obtain a difference value of a certain direct current internal resistance. However, these methods cannot obtain the direct current resistance of the unit cells of the battery pack.

U.S. Pat. No. US7782061, issued in 2010 as Battery ohmic resistance calculation system and method, proposes to use a control sampling box having an estimation function to sequentially collect the on-line voltage and current values of a certain cell in a series circuit Battery pack twice, obtain the change value of the dc resistance from the change of the two values of the voltage and current values, and correct the initial estimation value of the dc resistance, but from these change values, even the accumulated change value, the absolute dc resistance value cannot be obtained.

United states patent System and method for measuring battery internal resistance granted in 2011 as US8063643 adopts a resistance box with variable combination of a plurality of resistors with fixed resistance values and a switch containing a power transistor as a load, and adopts a multiplexer to select a certain cell in a battery pack, a certain string of a plurality of adjacent cells in series or a battery pack string of the whole cell, and the selected string is connected to a voltage test module for testing. Only one of which can be selected per test. When all the single batteries of the battery pack are tested once, the required time is long, and the initial state of each battery is changed due to the test discharge for a plurality of times.

Chinese patent publication No. CN102116847A issued in 2011, "system for acquiring performance parameters of battery cells" proposes a battery management system specially manufactured for acquiring parameters of battery cells, which claims higher accuracy and higher speed than a general BMS supporting a power battery. But the detection of the power battery pack which is utilized in a echelon mode has more advantages by utilizing the original BMS in the battery pack as a data source of the single battery. .

U.S. patent No. US8159228 granted in 2012 for Method for determining battery internal resistance proposes that in online operation of a battery pack, a battery management system is adopted to collect voltage and current values of a single battery, and the values of time before and after the voltage and current values are combined to obtain a change value of direct current resistance. However, from these change values, even the integrated change values, absolute dc resistance values cannot be obtained.

In 2015, granted as chinese patent "a lithium ion battery dc internal resistance estimation method" with publication number CN104330636A, it is proposed to test a series of dc resistance and ac impedance of a sample battery and find out the correlation function therein; the direct current resistance of the battery to be tested can be calculated by only testing the alternating current impedance once, so that the actual discharge test is avoided. For a battery pack with multiple single batteries, the access of an alternating current impedance spectrometer introduces larger errors. In the test of the echelon utilization of the power battery, it is difficult to prepare a corresponding sample battery and a control correlation function of a series of aging tests.

A method for testing the direct current internal resistance of a power battery cell by using a battery management system is provided in the chinese patent publication No. CN104880605B entitled in 2018, "battery management system and method for measuring the direct current internal resistance of a battery cell". The system is different from a common battery management system in that a priority level 'internal resistance testing mode' is added, a BMS special for testing is constructed, and the tests of the single batteries, the voltage and the current can be executed after an instruction of calling the mode is received by an upper computer every time. The method is to calculate the difference value of the direct current resistance of the time interval from the test of two adjacent times, and the difference value is not the absolute value of the direct current internal resistance required by the test. On the other hand, from the perspective of convenient detection, especially for the power battery pack used in the echelon, the original BMS in the battery pack is used instead of a test-dedicated BMS for another wiring exchange. However, the general BMS function meeting the national standard GB/T27930-2015 is qualified for the requirement of automatically testing sampling and sending values, and an internal resistance measuring mode does not exist or is needed.

The invention content is as follows:

the invention aims to overcome the defects or shortcomings of the prior art, and provides a direct current resistance tester for all single batteries in a battery pack, which can utilize a battery management system originally configured in the battery pack as much as possible without or reducing complicated reconnection, or adopt a general battery management system conforming to the national standard of GB/T27930-2015 to complete the test of all the single batteries at one time; the method adopts the constant current technology of power electronics and the technology of a large current switch, does not relate to estimation values, hypothesis and conjecture in the testing principle, and the results of the test and calculation are directly the absolute value of the ohmic internal resistance.

Another object of the present invention is to provide a method for testing the dc resistance of all the unit cells in a battery pack by using the above dc resistance tester.

In order to achieve the purpose, the invention adopts the following technical scheme:

a DC resistance tester for all single batteries in a battery pack comprises a DC load, a current detector, a battery management system (originally configured in the battery pack, if not, the battery management system needs to be added), a bus control and transceiver communicated with the battery management system, a microprocessor, an electromagnetic valve and the like. Connecting the electrode of the battery pack to be tested to a circuit breaker, an electromagnetic valve, a current detector and a direct current load through a cable; connecting a communication interface of a battery management system matched with the battery pack to a bus control and transceiver and a microprocessor in a wired or wireless mode; setting a sequence combination of a given current value for the direct current load, and setting a sequence combination of corresponding actions of off-on-off and the like for an electronic switch of the direct current load, wherein the closing time of the electronic switch is 0.25 to 60 seconds; meanwhile, the bus control and transceiver and the microprocessor receive and process communication messages of the battery management system, and the microprocessor analyzes the related messages to obtain voltage values of all the single batteries; and the microprocessor calculates the direct current resistance values of all the single batteries according to the change of the current set value and the change of the voltage value.

According to the scheme, the battery management system is configured for the primary battery pack or added, the voltage values of all the single batteries in the battery pack can be detected in a wired or wireless mode, the range of the detected voltage values is within 0 volt to 4-15 volts (depending on the types of the batteries), and the response time is within 50 milliseconds; the voltage values of all the single batteries in the battery pack obtained by detection can be output in a certain communication mode through a wired or wireless communication mode, and the repetition period is within 250 milliseconds.

According to the scheme, the direct current load is a constant current load capable of receiving a current set value, and the output of electric energy can be of a resistance heat dissipation type, an energy conversion type, a feed type or an energy storage type; the direct current load comprises a non-mechanical solid-state electronic switch, switching between two or more set current values is allowed, the current value ranges from 0 ampere to 300 amperes, the switching time is shorter than 10 milliseconds, and the switching life is longer than 5 ten thousand times.

According to the scheme, the current detector is composed of a Hall sensor, a magneto-resistive sensor or a voltage dividing or shunting element connected in series with a loop, the range of the measured current value is 0 ampere to 300 amperes, and the response time is within 10 milliseconds.

According to the scheme, the bus control and transceiver for communication with the battery management system is an independent chip or a part of a microprocessor; the microprocessor is provided with an interface matched with the bus control and transceiver, an input interface matched with the current detector, an output interface matched with the current setting of the direct current load, a trigger interface matched with the electronic switch of the direct current load and a trigger interface matched with the electromagnetic valve.

The invention has the advantages that: 1. the testing of the direct current resistance of all the single batteries of the battery pack is quickly finished at one time within a few seconds; 2. the battery management system contained in the power battery pack is directly utilized, complex connection is not required to be reconnected, the preparation time between two tests is shortened, and the method is particularly suitable for detection before a large number of retired power batteries enter echelon utilization; 3. if the battery pack does not include a battery management system, a general battery management system without additional requirements can be added for testing; 4. the constant current value of the electronic load can be continuously set between 0 ampere and the maximum value without switching the external load (such as replacing a resistor); 5. the direct current load is combined with the load in the actual working condition, and the method is suitable for online detection; 6. the calculation of the absolute value of the ohmic internal resistance does not involve assumptions and guesses; 6. constant current discharge is adopted, and the absolute value of the obtained ohmic internal resistance is linearly proportional to the measured voltage difference value.

Description of the drawings:

fig. 1 is a schematic diagram of a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a DC load according to a first embodiment of the present invention

Fig. 3 shows the measured voltage of three typical single batteries according to the first embodiment of the present invention, which varies with the current switch, and the obtained data of the other 21 single batteries in the same battery pack are not shown.

Fig. 4 is a schematic diagram of a second embodiment of the present invention.

Fig. 5 is a second schematic diagram of a second embodiment of the invention.

The specific implementation mode is as follows:

the first embodiment is as follows:

a schematic diagram of an inventive example of a dc resistance tester for all cells in a battery pack is shown in fig. 1. The battery pack 90 to be tested comprises a battery string 91 formed by serially connecting a plurality of single batteries and a matched battery management system 92. Under the condition that a battery management system of a primary battery pack is absent, 92 needs to be added in advance, and the test can be carried out after complete configuration; if the voltage of the single battery is lower than 5V, a general battery management system for the power battery pack which conforms to the national standard GB/T27930-2015 can be directly adopted, and for models of different manufacturers, corresponding changes only need to be made in software analysis codes of a communication protocol; if the voltage of the single battery is higher than 5V, after a multi-way voltage converter is added between the battery string 91 and the battery management system 92, a general battery management system for the power battery pack meeting the national standard of GB/T27930-2015 can be adopted,

the dc resistance tester 100 in the present example includes, among other things, a dc constant current load 101, a current limiting breaker 105, a solenoid valve 106, a current detector 107, a bus control and transceiver 102 in communication with the battery management system 92, and a microprocessor 103. In fig. 1, power channels are indicated by thick lines, and communication or control channels are indicated by thin lines. In practice, the positive terminal of the battery string 91 to be detected is connected to the breaker 105, the solenoid valve 106, the current detector 107 and the direct current constant current load 101 through the power line, and then returns to the negative terminal of the battery string 91 from the other end of the load 101; then, a given current value is set for the direct current load 101, and corresponding off-on-off operation is carried out on the electronic switch in the direct current load 101; communication messages of the battery management system 92 obtained from the bus control and transceiver 102 at the same time; the microprocessor 103 analyzes the related messages to obtain the voltage values of all the single batteries 90 in the battery string 91; and the microprocessor calculates the direct current resistance values of all the single batteries according to the change of the current value and the voltage value.

The message sending and receiving device 102 in the embodiment of the present invention employs a CAN bus controller chip such as MCP2515 or SJA1000 and a transceiver chip such as TJA1050 or SN65HVD230, and communicates with the microprocessor 103 through a communication bus. The message transmitter and receiver 102 may also be comprised in the microprocessor LPC11Cxx of the CAN controller/transceiver physical layer included.

The current detector 107 in the present embodiment uses a Hall type ACS770LCB-50 sensor with a sensitivity of 80mV/1A, or may use a magnetoresistive sensor, a magneto-impedance sensor, or a sensor formed by a voltage dividing or shunting element connected in series with the circuit.

In the embodiment of the present invention, a given current value is set for the dc load 101, or a sequence combination of current values may be set, and a corresponding sequence combination of off-on-off actions is set for the switch, so that the difference of the dc resistance value under different current settings can be detected.

A schematic diagram of a dc load 101 in an example of the invention is shown in fig. 2. Power channels are represented by thick lines and communication or control channels are represented by thin lines. The current controller 201 is a current or voltage modulation type PWM chip or DSP chip as a core, receives a constant current setting value from the microprocessor 103, compares the constant current setting value with a feedback signal rectified from the transformer 205, and adjusts a pulse width of a PWM waveform outputted therefrom. The PWM control signal is amplified by the power driver 202 and drives the full bridge inverter 203 formed by IGBT or power MOS transistors, thereby realizing the adjustability of the power current. The modulated high frequency current is transformed and rectified, and the energy is finally dissipated in the fixed resistor 206. The current controller 201 receives the control signal of the other electronic switch from the microprocessor 103 to control the on/off of the PWM chip, so as to open or close the power current.

The direct current load 101 in the embodiment of the present invention adopts a high frequency switch electronic technology, and the full bridge converter 203 in fig. 2 can also be replaced by a half bridge converter, a forward converter or a flyback converter; in the embodiment, the direct current load 101 adopts DC output, and can also be power frequency output after inversion; the DC load 101 may be a linear constant current circuit using a DC output.

The resistance and power of resistor 206 in the present example are selected based on the measured voltage, capacity of the battery pack and the maximum current to be discharged. In this example, a retired power battery pack is used, which contains 24 single batteries, and has a total of 80V and a nominal capacity of 50Ah, and if the maximum discharge test current is 1C and the transformation ratio of the high-frequency transformer is 1: 3, the resistance value of the resistor 206 is 80V/50A × 3 — 4.8 ohm. R may be chosen to be slightly smaller in consideration of the loss of the full-bridge converter 203, the off-time of the anti-cross conduction and the loss of the transformer 204. The resistance power can be chosen to be smaller than the full power because the discharge time in the test is only in the range of seconds to tens of seconds and generally does not follow the continuous discharge test within tens of seconds. In this example, the full power is 4000W, and a nominal power of 2000W is actually selected.

The resistor 206 may be replaced by other energy transfer devices such as resistive heat dissipation type (e.g., PTC ceramic heater), optical energy conversion type, mechanical energy conversion type, power feeding type, or energy storage type.

FIG. 3 is representative measured data for an example of the present invention. The power battery pack containing 24 single batteries which is out of service is tested at the same time. A discharge current of 26.3 amps is set for a duration of 10 seconds, with the current settings before and after being 0. Illustrated is data of actual voltage versus current switching for three typical cells. The dc resistance can be seen to vary from r ═ 3291-. The curve with a smaller direct current resistance value responds more slowly with time, and the polarization impedance is the main factor; the curve with a large dc resistance value responds relatively fast with time, which is seen to be dominated by the ohmic internal resistance.

Example two:

a schematic diagram of an inventive example of a dc resistance tester for all cells in a battery pack is shown in fig. 4 and 5. The battery pack 90 to be tested comprises 4 battery strings 91-1, 91-2, 91-3 and 91-4 which are formed by connecting a plurality of single batteries in series, and slave machines 92-1, 92-2, 92-3 and 92-4 and a master machine 92-0 which are correspondingly matched with a battery management system. Fig. 4 and 5 differ in that: in fig. 4, bus control and transceiver 302 receives messages from BMS host 92-0; in fig. 5, bus control and transceiver 302 intercepts messages from BMS slaves 92-1, 92-2, 92-3, 92-4. In many cases, the BMS host does not send the cell message, and the example shown in fig. 5 takes advantage of the feature that the BMS slave must send the cell information online. In fig. 5, four slaves share a physical communication channel. If four slaves are individually connected to and communicate with four ports of the master, 4 bus control and transceiver devices 302 are required to receive messages from the four slaves.

The dc tester 300 in the present embodiment comprises a dc constant current load 301, a current limiting breaker 305, a solenoid valve 306, a hall current detector 307, a bus control and transceiver 302, a microprocessor 303, and the like. In the figure, power channels are represented by thick lines and communication or control channels are represented by thin lines. In implementation, a power line on the positive terminal of the battery string 91-1 to be detected is connected to the direct current constant current load 301 through the breaker 305, the electromagnetic valve 306 and the current detector 307, and then returns to the negative terminal of the battery string 91-4 from the other end of the load 301; then, a given current value is set for the direct current load 301, and corresponding off-on-off operation is carried out on the electronic switch in the direct current load 301; communication messages of the battery management systems 92-1, 92-2, 92-3 and 92-4 are simultaneously obtained from the bus control and transceiver 302; analyzing the related messages to obtain the voltage values of all the single batteries in the battery strings 91-1, 91-2, 91-3 and 91-4; analyzing the related messages to obtain the voltage values of all the single batteries in the battery string; and calculating the direct current resistance values of all the single batteries according to the change of the current set value and the change of the voltage value.

The principle of the dc load 301 in the present example is the same as that of the dc load 101 shown in fig. 2. The working principle of the method is described in the first embodiment. In contrast, as the voltage of the battery pack is increased, the transformation ratio of the high frequency transformer is decreased, and the resistance value and the nominal power of the fixed resistor are also different. Assuming that the voltage of the battery pack 90 is increased to 320V, the transformation ratio of the high-frequency transformer is 1: 1, the maximum discharge test current is 1C, the resistance value of the fixed resistor 206 is 6.4 ohms, the full power is 16KW, and a nominal power of 8KW is actually selected.

Claims

1. A direct current resistance tester of all single batteries in a battery pack is characterized by comprising a direct current load, a current detector, a Battery Management System (BMS), a bus control and transceiver for communicating with the BMS, a microprocessor and the like.

2. The direct current resistance tester as claimed in claim 1, wherein said battery management system is included or excluded in a battery pack comprising a plurality of cells connected in series under test; if not, it needs to be added and connected to the battery pack before testing.

3. The battery management system according to claims 1 and 2, which is capable of detecting the voltage values of all the unit cells in the battery pack in a wired or wireless manner, the detected voltage values ranging from 0 volt to 15 volts, and the response time being within 50 milliseconds; the voltage values of all the single batteries in the battery pack obtained by detection can be output in a wired or wireless communication mode in a certain protocol code mode, and the repetition period is within 250 milliseconds.

4. The direct current resistance tester as claimed in claim 1, wherein said direct current load is a constant current load capable of receiving a set value of current, and the output of electric power is of a resistance heat dissipation type, an energy conversion type, a feeding type or an energy storage type; the direct current load comprises a non-mechanical solid-state electronic switch, switching between two or more set current values is allowed, the current value ranges from 0 ampere to 300 amperes, the switching time is shorter than 10 milliseconds, and the switching life is longer than 5 ten thousand times.

5. The dc resistance tester as claimed in claim 1, wherein said current detector is a hall sensor, a magneto-resistive sensor, or a voltage dividing or current dividing element connected in series to the circuit, and the measured current value ranges from 0a to 300 a, and the response time is within 10 ms.

6. The direct current resistance tester of claim 1 wherein said bus control and transceiver in communication with the battery management system is a separate chip or part of a microprocessor; the microprocessor is provided with an interface matched with the bus control and transceiver, an input interface matched with the current detector, an output interface matched with the current setting of the direct current load and a trigger output interface matched with the electronic switch of the direct current load.

7. A method for testing the direct current resistance of all the cells in a battery pack, characterized in that the electrodes of the battery pack to be tested are connected to the current detector and the direct current load as claimed in claims 1, 4 and 5 by means of cables; connecting the communication interface of the battery management system as described in claims 1, 2 and 3 to the bus control and transceiver and the microprocessor as described in claims 1 and 6 by wire or wirelessly; setting a sequence combination of a given current value for the direct current load, and setting a corresponding sequence combination of on-off actions for an electronic switch of the direct current load, wherein the closing time of the electronic switch is 0.25 to 60 seconds; meanwhile, the bus control and transceiver and the microprocessor receive and process the communication message of the battery management system; the microprocessor analyzes the related messages to obtain the voltage values of all the single batteries; and the microprocessor calculates the direct current resistance values of all the single batteries according to the change of the current set value and the change of the voltage value.