ANALYZER AND METHOD FOR DETERMINING BATTERY SELF-DISCHARGE - Patent application

Abstract

A differential battery analyzer (DBA) for testing batteries includes a control circuit configured to apply a controllable current to a normal battery as a standard battery in the DBA, and includes two terminals (IOH) and (IOL) for connecting a battery under test between them. The current through the standard battery is controlled to be equal to its self-discharge current, whereby the voltage of the standard battery is kept constant at its open circuit voltage. The terminal (IOH) is connected to one end of a branch in which the standard battery is located, and the voltage between the terminals (IOH) and (IOL) is kept at a constant value approximately equal to the voltage of the standard battery within a desired accuracy range, and the terminal (IOL) is connected to the other end of the branch.

Description

[Technical field]

[0001] This patent application relates to the formation, testing, and classification of batteries, and in particular to high accuracy, high speed, and low cost battery testing techniques and analyzers that use a conventional rechargeable battery as a standard battery for differential voltage measurements, and more specifically to measuring battery self-discharge, open circuit voltage, and DC internal resistance. [Background technology]

[0002] One of the important characteristics of a battery is its leakage or self-discharge current. The leakage current is affected by the quality of the battery, the state of charge and the temperature. One way to measure the leakage current is to hold the battery at a constant voltage and measure the charging current when the current stabilizes to a constant value. The self-discharge analyzer from Keysight Technologies is believed to use this method. This method requires very expensive equipment and can still take a long time to measure, e.g., several hours. The voltage sourcing stability of 3 μV peak can cause disturbances in the battery's electrochemical system, making it difficult to obtain the actual leakage current. Furthermore, the Keysight self-discharge analyzer is believed to require one channel per battery.

[0003] The indirect method is to measure the voltage drop of the battery at open circuit over a period of time. This method can take a very long time to perform (days or weeks) and still does not provide a leakage current value, but it is popular among battery manufacturers because it does not require expensive equipment. This method assumes that the capacitance of all cells is the same within an acceptable accuracy. Summary of the Invention [Problem to be solved by the invention]

[0004] It is desirable to have a method that can measure battery self-discharge (SD), open circuit voltage (OCV) and direct current internal resistance (DCIR) quickly, accurately and at a reasonable cost for battery manufacturers and battery research. [Means for solving the problem]

[0005] In one aspect, the present disclosure relates to a differential battery analyzer (DBA) for testing a battery. The DBA includes a control circuit configured to apply a controllable current to a normal battery (SB) in the DBA, the current (I) through the SB being a standard battery. sb a control circuit, in which the voltage of SB is controlled to be equal to its self-discharge current, whereby the voltage of SB is held constant at its open circuit voltage (OCV), and two terminals (IOH) and (IOL) for connecting the battery under test between them, the terminal (IOH) being connected to one end of a branch in which the SB is located, the voltage between the terminals (IOH) and (IOL) being held at a constant value approximately equal to the voltage of SB within a desired accuracy, and the terminal IOL being connected to the other end of that branch.

[0006] In one exemplary embodiment, the DBA further includes a first current sensor connected in series with the SB to measure the current through the SB and provide feedback for controlling the output current (It) from the control circuit, and / or a second current sensor to measure the output current from the control circuit and provide feedback for controlling the output current. Alternatively, when a battery is connected to the DBA via terminals (IOH) and (IOL), a current (I O ) follows to maintain the potential of the terminal (IOH), and I t =I O +I sb It is. In an exemplary embodiment, the DBA further includes two other terminals (VH) and (VL), and a voltage measurement circuit block (VM) connected to the DBA via the terminals (VH) and (VL) for measuring a differential voltage between a reference voltage and the voltage of the battery under test, the reference voltage being determined based on the voltage of the SB. Alternatively, the reference voltage is selected as one of a plurality of reference voltages within a range equal to or less than the value of the voltage of the SB. Alternatively, the DBA further includes a plurality of resistors connected in series with each other and in parallel with the branch in which the SB is located, each resistor having its own reference voltage output terminal selected via a multiplexer connected to the VM, and the voltage of the SB is divided into a plurality of reference voltages by this selection.

[0007] In one embodiment, the normal battery includes a secondary rechargeable battery. In another embodiment, the normal battery has the same type as the battery under test. The DBA preferably further includes two other terminals (IH) and (IL) connected to a circuit block (IM) for current measurement.

[0008] In another aspect, the present disclosure relates to a method for measuring a differential voltage, the method including using the above DBA to measure a differential voltage representing a difference between a reference voltage and a voltage at a terminal (VH) by a VM, the battery under test being connected to the terminals (VH) and (VL). Alternatively, the battery under test includes a group of batteries connected in parallel.

[0009] In yet another aspect, the present disclosure provides a method for determining the self-discharge current (I sd This method involves the constant current method for measuring the charge of the battery under test by applying a small current I 1 and I 2 and I 1 At (dV / dt) 1 I 2 At (dV / dt) 2 and two equations: (dV / dt) 1 *DNC=I 1 +I sd and (dV / dt)2 *DNC=I 2 +I sd By solving sd and calculating the dynamic capacitance (DNC).

[0010] In one embodiment, a galvanostatic method can be implemented using the DBA described above. In another embodiment, a galvanostatic method can be used to measure the self-discharge current (I) of a battery or battery group using the DBA described above. sd ) can be measured.

[0011] In yet another aspect, the present disclosure provides a method for determining the self-discharge current (I sd This method involves another method for measuring the current I through SB using a control circuit in DBA. sd A step of controlling the voltage of SB to be constant by controlling the voltage of SB to be equal to sd is determined using the constant current method described above, allowing sufficient time for the batteries to reach equilibrium, and measuring the current through each battery, thereby determining the self-discharge current I sd is determined to be equal to the value of the current passing through the battery.

[0012] In another aspect, the present disclosure provides a method for determining the self-discharge current (I sd This method involves the steps of allowing the batteries being tested sufficient time to reach equilibrium and measuring the current through each battery, the batteries being connected in parallel with each other but not connected to any power source to keep the batteries in an open circuit, and measuring the self-discharge current (I sd and calculating the DNC of all the batteries in the group from the following equation: The difference in DNC of all the batteries in the group can be ignored in the calculation of the self-discharge current, and the AIsd Assuming that is known, I sd #=AI sd -I b #And AI sd represents the average self-discharge current of the battery pack, and I b # represents the current through the corresponding battery #.

[0013] In one exemplary embodiment, the average self-discharge current of a group of batteries is determined as the ratio of the total self-discharge current of the group of batteries to the number of batteries in the group being tested, where the group of batteries is considered an equivalent battery in the calculation of the total self-discharge current, and the total self-discharge current is determined using the constant current method described above.

[0014] In yet another aspect, the present disclosure relates to a method for evaluating the self-discharge of a battery. The method includes the steps of: using the above-mentioned DBA to measure a first differential OCV (DOCV1) and a second differential OCV (DOCV2) for a standard battery (SB), which represent the difference between a reference voltage and the voltage of a terminal (VH) at two different times T1 and T2, the battery being tested is connected to the terminals (VH) and (VL), the DBA further includes a first current sensor connected in series with the SB to measure the current through the SB and provide feedback to control the output current from the control circuit, and the current through the SB is controlled to be equal to the self-discharge current of the SB, thereby keeping the voltage of the SB constant at its open circuit voltage (OCV); calculating the differential DOCV (ΔDOCV) between the two differential OCVs for a period (Δt) from T1 to T2; and evaluating the self-discharge state of the battery being tested based on the ratio of ΔDOCV to Δt.

[0015] In one exemplary embodiment, the battery being tested includes a group of batteries connected in parallel, and the method further includes classifying the group of batteries according to a self-discharge state. Alternatively, the method includes classifying the self-discharge current (I) of one or more batteries in the group based on known dynamic capacitance (DNC) values ​​of one or more batteries in the group or an average DNC value of the group of batteries.sd Alternatively, the average DNC value for a group of batteries is determined as a ratio of the total DNC (TDNC) for that group of batteries to the number of batteries in the group being tested, the group of batteries being considered as an equivalent battery in the TDNC calculation, and the DNC value of one or more batteries in the group or the TDNC of the group of batteries is determined using the constant current method described above.

[0016] In yet another aspect, the present disclosure relates to a method for measuring a direct current internal resistance (DCIR) of a battery. The method includes the steps of applying a first current and a second current to a battery under test at two different times T1 and T2, the battery under test being connected to said DBA via terminals (VH) and (VL), the DBA further including two terminals (IH) and (IL) connected to a circuit block (IM) for current measurement, the sensor being connected between the terminals (IH) and (IL) and being connected in series with the battery to measure the current through the battery; measuring a differential current (ΔI) by IM representing the difference between a first measured current and a second measured current of the battery during a period from T1 to T2; measuring a first differential voltage and a second differential voltage by VM representing the difference between a reference voltage and the voltage at the terminal (VH) while applying the first current and the second current, respectively; calculating a change in the differential voltage (ΔV) of the battery representing the difference between the first differential voltage and the second differential voltage during a period from T1 to T2; and calculating a DCIR of the battery under test as equal to ΔV / ΔI.

[0017] In another aspect, the present disclosure relates to an automated analyzer for evaluating a battery, the automated analyzer for evaluating a battery including a power source, one or more processors, and one or more storage media storing instructions executable by the one or more processors, which when executed cause the automated analyzer to operate according to any one of the methods described above.

[0018] This Summary is provided to introduce a selection of concepts in a simplified form that are further described herein in the Detailed Description. This Summary is not intended to identify key elements or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. These and other features and advantages of the present invention will be described in, or will become apparent to those skilled in the art upon consideration of, the following Detailed Description of exemplary embodiments of the invention.

[0019] These and other features of the present disclosure will now be described with reference to the drawings summarized below. The drawings and the associated description are provided to illustrate exemplary embodiments of the present disclosure and are not intended to limit the scope of the disclosure. [Brief description of the drawings]

[0020] [Figure 1] Diagram of a simple equivalent circuit of a battery versus self-discharge current (Isd). The OCV drop rate dV / dt for a small voltage range is proportional to Isd. [Diagram 2] 1 is a block diagram of an exemplary differential battery analyzer (DBA) in accordance with the present disclosure. [Diagram 3] 4 is a block diagram of another example DBA according to the present disclosure. [Figure 4] 4 is a block diagram of yet another example DBA in accordance with the present disclosure. [Diagram 5] FIG. 1 is a block diagram of an exemplary universal differential battery analyzer (UDBA) in accordance with the present disclosure. [Figure 6] FIG. 2 is a block diagram of another exemplary universal differential battery analyzer (UDBA) in accordance with the present disclosure. [Figure 7] 4 is a block diagram of yet another example DBA according to the present disclosure. [Figure 8] 1 illustrates an exemplary circuit for measuring differential voltage using a DBA in accordance with the present disclosure. [Figure 9]An example circuit for measuring Isd by applying a constant voltage equal to the battery's OCV, called the potentiostatic method. This method is believed to be used by Keysight's self-discharge analyzers. [Figure 10] 1 is an exemplary circuit for measuring Isd by applying a constant current to a battery in accordance with the present disclosure. [Figure 11] FIG. 2 is an illustrative block flow diagram of an example process for measuring Isd by applying a constant current to a battery according to the present disclosure, referred to as the constant current method. [Figure 12] FIG. 1 shows an exemplary circuit for measuring Isd by applying a constant current to a battery using a DBA in accordance with the present disclosure. [Figure 13] FIG. 1 shows an exemplary circuit for measuring the Isd of a group of batteries connected in parallel by applying a constant current to the batteries using a DBA, in accordance with the present disclosure. [Figure 14] FIG. 13 is another illustrative block flow diagram of a process for measuring Isd by applying a constant current to a battery in accordance with the present disclosure. [Figure 15] FIG. 2 is another illustrative circuit for measuring Isd by applying a constant current to a battery using a DBA in accordance with the present disclosure. [Figure 16] FIG. 2 is an illustrative block flow diagram of an example process for measuring Isd without applying any current to the battery, according to the present disclosure, referred to as the passive method. [Figure 17] FIG. 1 is an illustrative block flow diagram of an example process for assessing battery self-discharge using DBA in accordance with the present disclosure. [Figure 18] FIG. 2 is an illustrative block flow diagram of an example process for measuring the DC internal resistance of a battery using DBA in accordance with the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The terms used herein include the following: OCV: Battery open circuit voltage ·R:Resistor ·SDR: Self-discharge resistance ·SB: A standard battery that can maintain a constant voltage for a very long time to serve as a reference voltage. ·IM: Circuit block for current measurement. ·VM: Circuit block for voltage measurement. I t , I O , I sb , I b #, IH, IL, IOH, IOL: I represents current. ·V sb , VH, VL: V represents voltage. ·V rf : Reference voltage I sd :Self-discharge current AI sd : Average self-discharge current of the batteries DBA: Differential Battery Analyzer ·UDBA: Universal Differential Battery Analyzer GST: Galvanostat that provides a controlled current output PST: A potentiostat that provides a controlled voltage output SW#: Switch Mux: Multiplexer FIG. 1 illustrates a self-discharge current (I sd As shown in Figure 1, the OCV drop rate dV / dt for a small voltage range is I sd is proportional to I sd is usually a negative value.

[0022] FIG. 2 is a block diagram illustrating an exemplary differential battery analyzer (DBA) according to the present disclosure. The DBA provides a reference voltage using a normal battery as a standard battery (SB). In the DBA, a control circuit configured to apply a controllable current is connected to the normal battery. The battery under test may be connected between terminals (IOH) and (IOL) of the DBA. In the DBA, terminal (IOH) is connected to one end of the branch where SB is located, and terminal (IOL) is connected to the other end of the branch. The current (I sd ) is I sd Let SB's self-discharge current (I sd When the voltage on SB (V sb (denoted by ) is held constant at its open circuit voltage (OCV), so that the voltage between terminals (IOH) and (IOL) is kept constant to within the desired accuracy of the voltage V sb It is noted that the use of the constant current or galvanostatic method described herein to maintain the voltage of the standard battery and the voltage of the battery under test is different from the potentiostatic (i.e., constant voltage) method of the prior art. The constant current method has the advantages of lower noise, smaller ripple, less sensitivity to temperature changes, and less change in the battery's SOC (state of charge) and OCV.

[0023] In some examples, the control circuit configured to apply the controllable current may include a GST. In such examples, the output current from the GST is controlled via a control unit therein based on feedback from current sensors (e.g., R1, R2). In some examples, such a battery under test may include a battery group connected in parallel. The DBA described herein can maintain a standard battery voltage by making the controllable current through the SB equal to the absolute value of the self-discharge current of the SB. Thus, constant voltage control of the battery under test and its self-discharge measurement can be performed.

[0024] 3 is a block diagram illustrating another example DBA according to the present disclosure. As shown in FIG. 3, the DBA may further include a first current sensor (shown as R1) outside the GST. In some examples, the current sensor R1 detects a current I sd is connected in series with SB to measure the controllable current (I t ) may be controlled by feedback from current sensor R1. In some examples, the DBA may further include a second current sensor (shown as R2) within the GST. In some examples, current sensor R2 is for directly measuring the current It, thereby determining whether the current I t can be controlled by feedback from current sensor R2. Note that the DBA may include only one of current sensors R1 and R2, or both.

[0025] In some examples, when the battery is connected to DBA through terminals (IOH) and (IOL), the equation I t =I O +I sb is satisfied, wherein I O represents the current flowing through the terminal (IOH). Therefore, the current I O can be followed to maintain the potential of the terminal (IOH).

[0026] In some examples, the normal battery may include a secondary rechargeable battery instead of a dedicated special primary (non-rechargeable) standard battery. In some examples, the normal battery may include a lithium ion battery. In some examples, the normal battery may have the same type as the battery under test. When using a battery of the same type as the battery under test as the standard battery, the effect of temperature on the battery can be offset or eliminated. The normal battery may include a secondary rechargeable battery. 4 is a block diagram of yet another exemplary DBA according to the present disclosure. As shown in FIG. 4, the DBA may further include another two terminals (VH) and (VL) and a circuit block (VM) for voltage measurement. Alternatively, the DBA may further include a first switch (shown as SW1) and a second switch (shown as SW2) as shown in FIG. 4. The switch SW1 may be connected in series with the current sensor R1, and the switch SW2 may be connected in series with the current sensor R2 to detect the current I O When the battery being tested is connected to DBA through terminals (VH) and (VL) and both SW1 and SW2 (if present) are kept on, VM detects the voltage of the battery under test and the voltage V sb The reference voltage (V rf The DBA measures the difference between the voltage V and the reference voltage V. Thus, the DBA described above can be used for high accuracy battery voltage measurement / comparison through differential voltage measurement, usually by applying a constant current to the battery to provide a constant voltage as a reference voltage. In some examples, the DBA may have multiple reference voltage ranges. The programmable reference voltage can be provided by a variety of methods. In some examples, the voltage V rf can be selected as one of the above multiple normal batteries having different OCVs.

[0027] 5 is a block diagram illustrating an exemplary universal differential battery analyzer (UDBA) according to the present disclosure. As shown in FIG. 5, the DBA may further include another switch (shown as S1) for selecting one from multiple normal batteries (SB1, SB2, SBn, etc.) having different OCVs based on the description in FIG. 4 above. Thus, the voltage V provided by the DBA may be rf can be changed with the battery selected.

[0028] In some instances, for a normal battery that is near equilibrium, a change in current through that battery will cause a voltage change of that battery within a very small voltage range, and such current through a normal battery is usually so small that it does not disturb the electrochemical equilibrium of the battery. In some instances, such current may be at the level of the leakage current of a normal battery. Under these circumstances, the voltage of a normal battery can change slowly with the current through it. Thus, the voltage V rf usually changes when the battery voltage changes slowly. This method uses the voltage V rf Although it takes a longer time to reach equilibrium for varying θ, the resulting reference voltage range has the lowest electrical signal noise.

[0029] In some cases, the voltage V rf is the voltage V sb SB may be selected as one of a number of reference voltages within a range of values ​​up to and including 4.2±0.2V. FIG. 6 is a block diagram illustrating another exemplary universal differential battery analyzer (UDBA) according to the present disclosure that provides a programmable reference voltage by dividing the voltage of a standard battery. As shown in FIG. 6, the UDBA may further include a number of resistors (R4, R5, R6, R7, R8, etc.) connected in series with each other and in parallel with the branch in which SB is located. Each resistor has its own reference voltage output terminal (V1, V2, V3, V4, VL, etc.) that is used to be selected via a multiplexer (shown as SW3) connected to the VM mentioned above. Thus, a UDBA with multiple voltage ranges is obtained. In one embodiment, the voltage ranges are 4.2±0.2V (V sb In another embodiment, the voltage ranges include 4.0±0.5V (corresponding to V1) / 3.0±0.5V (corresponding to V2) / 2.0±0.5V (corresponding to V3) / 1.0±0.5V (corresponding to V4) / 0.0±5.0V (VL range).

[0030] Alternatively, a switch (shown as SW4) can be placed in a branch where the divider resistors are connected in series with each other. SW4 is connected to V sb It can be turned off in the VL range or VL range, i.e., the branches of the divider resistor can be cut off to reduce the noise level. The role of DBA / UDBA in the VL range is the same as that of the general VM. It is worth noting that the V sb The range has the lowest noise, and when using voltage divider resistors the noise is V sb 2 to 3 times higher than that of the range.

[0031] Alternatively, a ground resistor (shown as R3) may be connected between SB and the terminal (IOL) to cancel or eliminate voltage fluctuations on GND (ground). Alternatively, one or more of the components R1, R2, SW1, and SW2 may be eliminated.

[0032] There are advantages to using the above-mentioned UDBA. The reference voltage value can be quickly switched to obtain different ranges of differential voltage measurements, which is very versatile and practical. The normal voltage range is to meet various scales of voltages of the object under test, such as ±100V / ±10V / ±1 / ±0.1V / . The reference voltage range in this disclosure is different and unique, meeting the requirements of different sections of the voltage scale, such as 0-5V. This is especially specific to be applied to the reference voltage from a standard battery. Examples include 4.0±0.5V / 3.0±0.5V / 2.0±0.5V / 1.0±0.5V / 0.0±0.5V on the voltage scale of 0-4.5V.

[0033] In some examples, the DBA may further include two other terminals (IH) and (VL) connected to the circuit block (IM) for current measurement based on the above DBA. In these circumstances, a DBA having a current reading terminal is provided.

[0034] 7 is a block diagram of yet another exemplary DBA according to the present disclosure. For the components of the DBA shown in FIG. 7, reference may be made to the above. FIG. 8 is an exemplary circuit for measuring a differential voltage using a DBA according to the present disclosure. As shown in FIG. 8, a battery under test may be connected to the DBA described above via terminals (VH) and (VL). A detailed description of the components of the DBA shown in FIG. 8 is provided above. In this manner, a voltage V rf A differential voltage representing the difference between the voltage at terminal (VH) and the voltage at terminal (VH) can be measured. In some examples, such batteries under test include batteries that are connected or not connected in parallel. Thus, the circuit can be used for differential voltage measurements of single or multiple batteries.

[0035] Figure 9 shows the I by applying a constant voltage equal to the OCV of the battery under test, known as the potentiostatic method. sb FIG. 1 is an example demonstrative circuit for measuring self-discharge. This method may be used in Keysight's self-discharge analyzers.

[0036] FIG. 10 shows the current I by applying a constant current to a battery under test according to the present disclosure. sd FIG. 10 is an exemplary circuit for measuring the self-discharge current of a battery. As shown in FIG. 10, a constant current method is used to measure the self-discharge current of a battery. This disclosure uses the concept of dynamic capacitance to model a battery and preferably illustrates a mechanism for using this modeling during self-discharge current measurement. Using the above model, a galvanostat to provide a controlled current output is driven by a small current I 1 and I 2 may be applied to the battery under test. 1 (dV / dt) at 1 and I 2 (dV / dt) at 2 By measuring each of these, two equations are obtained: (dV / dt) 1 *DNC=I 1 +I sd and (dV / dt) 2 *DNC=I 2+I sd By solving sd and the dynamic capacitance (DNC) can be calculated.

[0037] FIG. 11 illustrates a method for measuring I by applying a constant current to a battery under test, referred to as a constant current method, in accordance with an example of the present disclosure. sd 11 shows an example process 1100 for measuring. For example, some or all of the process 1100 may be performed by one or more components in the DBA shown in FIGS. 2-8 as described herein.

[0038] In operation 1110, the process includes applying a first constant current (I 1 ) and the second constant current (I 2 ) for a certain period (dt 1 ) and the same or different periods (dt 2 ) to the battery being tested. 1 and I 2 is low enough so as not to disturb the electrochemical equilibrium of the battery being tested, but preferably high enough to accelerate the test.

[0039] In some examples, the current I 1 and I 2 Each of the currents I 1 and I 2 Each of the currents I 1 and I 2 Each of may be in the mA range but greater than 100 μA depending on the dynamic capacity of the battery being tested. In some examples, such a battery being tested includes a group of batteries connected in parallel.

[0040] In operation 1120, the process 1 and dt 2 The first voltage change (dV 1) and the second voltage change (dV 2 In some examples, the two voltage changes may be measured by various means, such as a DBA with VM as described above. In some examples, the period dt 1 and dt2 are each less than 24 hours.

[0041] In operation 1130, the process comprises: 1 In the period dt 1 The first voltage change rate (dV 1 / dt 1 ) and current I 2 In the period dt 2 The second voltage change rate (dV 2 / dt 2 )

[0042] In operation 1140, the process solves two equations: (dV 1 / dt 1 )*DNC=I 1 +I sd and (dV 2 / dt 2 )*DNC=I 2 +I sd The I sd and dynamic capacitance (DNC). It is noted that using the current-controlled (galvanostatic) method described herein is different from the prior art voltage-controlled (potential-controlled) method for analyzing the self-discharge current of a battery. The galvanostatic method is particularly useful in battery formation and testing procedures.

[0043] FIG. 12 shows the I sd 12 is an exemplary circuit for measuring the first constant current I. As shown in FIG. 12, the battery under test is connected to the above DBA via terminals (IOH) and (IOL). DBA supplies a first constant current I 1 and the second constant current I 2 As mentioned above, the period dt 1 and dt2 The first and second voltage changes of the battery being tested can then be measured over a period of time. sd and the dynamic capacitance can be calculated by solving the above two equations.

[0044] In some examples, the DBA is connected to two other terminals (VH) and (VL) and a reference voltage (V rf ) and the voltage of the battery being tested. rf is the voltage V sb As shown in Figure 12, the battery under test may be further connected to DBA via terminals (VH) and (VL), so that two voltage changes can be measured by VM.

[0045] FIG. 13 shows the I of a group of parallel connected batteries by applying a constant current to the batteries using DBA in accordance with the present disclosure. sd FIG. 13 is an exemplary circuit for measuring the current through each battery in the battery group. As shown in FIG. 13, a group of batteries connected in parallel can be connected to a DBA via terminals (IOH) and (IOL). The group of batteries is further connected to an IM in the DBA via terminals (IH) and (IL). In such an example, each of the IM and VM has multiple channels for measuring multiple batteries simultaneously. That is, the current through each battery in the group of batteries and the voltage change due to the current can be measured by the IM and VM, respectively.

[0046] Referring to Figure 13, the self-discharge current (I sd A constant current method for measuring the small current I from a GST is provided as follows. 1 and I 2can be applied to the battery when SW2 is on. For one battery among the multiple batteries connected in parallel, the current through it and its voltage change can be measured by IM and VM, respectively. Then, the I sd The dynamic capacitance (DNC) can be calculated by solving the two equations provided above. Therefore, the I sd And a constant current method for obtaining DNC is provided.

[0047] FIG. 14 illustrates a graph showing the I sd 14 shows another example process 1400 for measuring. For example, some or all of the process 1400 may be performed by one or more components in the DBA shown in FIGS. 2-8 as described herein.

[0048] In operation 1410, the process uses a control circuit in the DBA described above to control a current I sb Let SB current I sd By controlling the voltage V sb The battery group may include a battery charger connected in parallel to the DBA via terminals (IOH) and (IOL). In some examples, the means includes a GST. Alternatively, the GST may use feedback from the sensor R1 to determine the current I sb In this example, the current I sd Alternatively, the current I of the battery SB is sd can be determined using the constant current method described above with reference to FIG.

[0049] In operation 1420, the process may include allowing sufficient time for the batteries to reach an equilibrium condition. In such an example, the voltage of each battery under test reaches its OCV under its equilibrium condition and remains constant at its OCV.

[0050] In operation 1430, the process may include measuring a current through each battery, thereby determining a self-discharge current I of each battery. sd The value of is determined to be equal to the value of the current passed through the battery. In some embodiments, the current (I b #) is the self-discharge current (I sd #), so there is no need to measure the voltage and dV / dt of each battery.

[0051] FIG. 15 shows the current I by applying a constant current to a battery using a DBA in accordance with the present disclosure. sd 15 is another illustrative circuit for measuring the current IOH and IOL of a parallel battery. As shown in FIG. 15, a parallel battery group can be connected to the DBA described above via terminals (IOH) and (IOL).

[0052] In some examples, the DBA may further include an IM as described above. In such examples, the IM may measure the current through each battery by multiple channels. sd It can be seen that the value of is determined as being equal to the value of the current through its corresponding battery with reference to the method shown in FIG. 14 where both SW1 and SW2 are on.

[0053] FIG. 16 illustrates a method for calculating the I of a battery in a group connected in parallel, referred to as a passive method, according to an example of the present disclosure. sd 15 shows another example process 1600 for measuring . For example, FIG. 15 provides one example demonstrative circuit for performing a passive method, where the battery may be open circuited if SW2 remains off.

[0054] In operation 1610, the process may include allowing sufficient time for the batteries to reach equilibrium and measuring the current through each battery, where the batteries are connected in parallel with each other but are not connected to any power source to keep the batteries open circuit. In some examples, the current through one battery (Battery #) of the plurality of batteries is measured as I b # In some examples, equilibrium may be considered to have been reached when the current through the battery or the rate of change of the battery's voltage no longer changes or changes within a small predetermined range.

[0055] In operation 1620, the process calculates the self-discharge current (I sd #), sd #=AI sd -I b #.AI sd represents the average self-discharge current of all batteries in the group. I b # represents the current through the corresponding battery #. In calculating the self-discharge current, the difference in dynamic capacitance (DNC) of all batteries in the group can be ignored, and the AI sd Assuming that the DNC of the batteries is known, the self-discharge current of each battery can be calculated from the above equation. Therefore, assuming that the DNC of the batteries is known and the difference in DNC between batteries can be neglected, there is no need to measure the voltage and dV / dt of each battery. This method is particularly useful during the finishing procedure in battery manufacturing.

[0056] In some instances, such AI sd is the total self-discharge current (TI) of a battery group being tested versus the number of batteries in the group. sd) of the first constant current (I 1 ) and the second constant current (I 2 ) for a certain period (dt 1 ) and the same or different periods (dt 2 ) to a group of batteries connected in parallel, 1 and I 2 is sufficiently low so as not to disturb the electrochemical equilibrium of the group of batteries being tested, and 1 and dt 2 The first voltage change (dV 1 ) and the second voltage change (dV 2 ) and the current I 1 In the period dt 1 The first voltage change rate (dV 1 / dt 1 ) and current I 2 In the period dt 2 The second voltage change rate (dV 2 / dt 2 ) and two equations: (dV 1 / dt 1 )*TDNC=I 1 +TI sd and (dV 2 / dt 2 )*TDNC=I 2 +TI sd The total self-discharge current (TI sd ) and the total dynamic capacitance (TDNC). Thus, the AI ​​of the battery group can be calculated. sd A constant current method for obtaining

[0057] 17 illustrates an exemplary process 1700 for assessing battery self-discharge using a DBA with a VM, according to an example of the present disclosure. For example, some or all of the process 1700 may be performed by one or more components in the DBA illustrated in FIGS. 4-8, as described herein.

[0058] In operation 1710, the process may include measuring a first differential OCV (represented as DOCV1) and a second differential OCV (represented as DOCV2) for a standard battery (SB) that represent the difference between the above-mentioned reference voltage and the voltage at the terminal (VH) at two different times T1 and T2 using the above-mentioned DBA, where the battery being tested is connected to the DBA having the above-mentioned VM via the terminals (VH) and (VL). In some examples, the DBA further includes a first current sensor connected in series with the SB to measure the current through the SB and provide feedback for controlling the output current from the control circuit. In such an embodiment, the current through the SB is controlled to be equal to the self-discharge current of the SB, thereby keeping the voltage of the SB constant at its open circuit voltage (OCV). For example, an exemplary circuit for performing the method may refer to FIG. 8 where SW1 is on. In some examples, DOCV1=V1-V rf and DOCV2 = V2 - V rf where V1 and V2 represent the voltages at the terminals at times T1 and T2, respectively. In some examples, each of T1 and T2 is less than 24 hours.

[0059] In operation 1720, the process may include calculating a differential DOCV (ΔDOCV) between the two differential OCVs for a time period (Δt) from T1 to T2. In such an example, ΔDOCV=DOCV2-DOCV1 and Δt=T2-T1.

[0060] In operation 1730, the process may include evaluating a self-discharge state of the battery being tested based on the ratio of ΔDOCV to Δt. In some examples, a K value representing the ratio of ΔDOCV to Δt of the battery may be calculated to evaluate the self-discharge state of the battery under test. This method for measuring the differential OCV may be particularly useful in manufacturing batteries.

[0061] In some examples, the battery being tested includes a group of batteries. Each of the group of batteries can be connected or disconnected to the VM via a switch. In such examples, the process may further include classifying the group of batteries according to a self-discharge state. In such examples, the group of batteries can be classified according to values ​​of their self-discharge parameters. These parameters may include, but are not limited to, at least one of the following: OCV, SD represents the differential DOCV (ΔDOCV) between two differential OCVs over a period of time, and K values ​​are as described above. In some examples, these parameters include I sd and SDR. In this way, batteries with reasonably consistent values ​​for the parameters can be classified into one group. Compared with other methods for grading and classifying batteries, including modeling, algorithms and electrochemical analysis, the method provided in the present disclosure is much easier, thereby saving or reducing storage time and improving the battery manufacturing process.

[0062] In some examples, the process may determine a self-discharge current (I) of one or more batteries in the group based on a known dynamic capacitance (DNC) value of one or more batteries in the group or an average DNC value of the group of batteries. sd In such an example, the self-discharge current of each battery is calculated from the following equation: I sd #=ΔQ / Δt=DNC (or ADNC)*ΔDOCV / Δt, where I sd# represents the self-discharge current of subject battery #. ADNC represents the average DNC value of all batteries in the group.

[0063] In some examples, ADNC may be calculated from the historical DNC obtained. In some examples, the ADNC value of a battery group may be determined as the ratio of the total DNC (TDNC) of all batteries in the group to the number of batteries in the group being tested. Alternatively, TDNC can be calculated using two equations: (dV 1 / dt 1 )*TDNC=I 1 +TI sd and (dV 2 / dt 2 )*TDNC=I 2 +TI sd By solving: the equivalent battery can be determined with reference to the constant current method described above for the battery group.

[0064] 18 shows an example process 1800 for measuring the DC internal resistance of a battery using a DBA, according to an example of the present disclosure. For example, FIG. 13 provides an example demonstrative circuit for performing this method with both SW1 and SW2 turned on.

[0065] In operation 1810, the process may include applying a first current and a second current at two different times T1 and T2 to a battery being tested, the battery being tested being connected to the DBA mentioned above via terminals (VH) and (VL). The DBA further includes two terminals (IH) and (IL) connected to a circuit block (IM) for current measurement, and a sensor is connected between the terminals (IH) and (IL) and connected in series with the battery to measure the current through the battery. In some examples, the first current and the second current are low enough not to disturb the electrochemical system of the battery. In some examples, the IM can have multiple channels for measuring the current through each battery in the group connected to it.

[0066] In operation 1820, the process may include measuring, by the IM, a differential current (ΔI) representing a difference between a first measured current and a second measured current of the battery being tested during the time period from T1 to T2. In some examples, for one battery (denoted as Battery #) of the battery group, the differential current is calculated according to the equation ΔI b #=I b # 2 -I b # 1 It is determined by I b # 1 and I b # 2 represent the first measured current and the second measured current through battery # using IM, respectively.

[0067] In operation 1830, the process may include measuring a first differential voltage and a second differential voltage representing a difference between a reference voltage and a voltage at the terminal (VH) while applying the first current and the second current, respectively, by the VM. In some examples, for one battery (denoted as Battery #) of the plurality of batteries, the first differential voltage is determined according to the equation V b # 1 =V# 1 -V rf Determined by: V# 1 represents the voltage at the terminals (VH) of battery # during application of the first current. And the second differential voltage is given by the equation V b # 2 =V# 2 -V rf Determined by: V# 2 represents the voltage at the terminals (VH) of battery # during application of the second current. In operation 1840, the process may include calculating a change in the differential voltage (ΔV) of the battery representing the difference between the first differential voltage and the second differential voltage for the time period from T1 to T2. In some examples, for one battery (denoted as Battery #) of the plurality of batteries, the change in the differential voltage (ΔV) of the battery being tested over the time period from T1 to T2 may be calculated according to the equation ΔV#=V b #2 -V b # 1 is determined by. In operation 1850, the process may include calculating the DCIR of the battery being tested as equal to ΔV / ΔI. In some examples, for one battery (denoted as battery #) of the battery group, the DCIR of the battery being tested is determined by the equation DCIR#=ΔV# / ΔI#. Similarly, the equivalent resistance of the battery group under test can be calculated with reference to the above method, regarding the battery group as an equivalent battery. This method can be applied to battery testing in general, and battery formation in particular.

[0068] An automated analyzer for evaluating a battery is provided in the present disclosure. In some embodiments, the automated analyzer for evaluating a battery may include a power source, one or more processors, and one or more storage media storing instructions executable by the one or more processors, which when executed cause the automated analyzer to operate according to any one of the following: a method for measuring a differential voltage, a constant current method for measuring a self-discharge current of a battery, a constant current method for measuring a self-discharge current of a battery using the aforementioned differential analyzer, a passive method for measuring the self-discharge current of a battery in a group connected in parallel, a method for evaluating the self-discharge of a battery, and a method for measuring a direct current internal resistance of a battery. A detailed description of these methods is provided above with reference to Figures 8 to 18.

[0069] In some examples, the processor(s) may be any suitable processor capable of processing data and executing instructions to perform the operations described herein. By way of example and not limitation, the processor(s) may include one or more central processing units (CPUs), graphics processing units (GPUs), or any other device or part of a device that processes electronic data and converts it into registers and / or other electronic data that may be stored in memory. In some examples, the processor(s) may include circuit assemblies such as integrated circuits (e.g., ASICs, etc.), gate arrays (e.g., FPGAs, etc.), and other hardware devices, so long as they are configured to implement the coded instructions.

[0070] In some examples, the storage medium may include a non-transitory computer-readable medium such as a memory. In such examples, the memory may store an operating system and one or more software applications, instructions, programs, and / or data to implement the functions attributable to the methods and various systems described herein. In various implementations, the memory may be implemented using any suitable memory technology, such as static random access memory (SRAM), synchronous dynamic RAM (SDRAM), non-volatile / flash type memory, or any other type of memory capable of storing information.

[0071] In some cases, the memory may include at least a working memory and a storage memory. For example, the working memory may be a limited capacity high-speed memory (e.g., cache memory) used to store data to be operated on by the processor(s). In some examples, the memory may include a storage memory, which may be a relatively large capacity slow memory used for long-term storage of data. In some cases, the processor(s) may not operate directly on data stored in the storage memory, and as described herein, the data may need to be loaded into the working memory to perform operations on the data.

[0072] In some examples, the automated analyzer may be integrated into the DBA described above, in which case the DBA with the automated analyzer can automatically test various parameters of the battery.

[0073] It should be understood that the architectures, systems, and individual elements described herein may include many other logical, programmatic, and physical components, of which those shown in the accompanying drawings are merely examples relevant to the description herein. Further embodiments of the present invention For a perfectly balanced battery, a very small current, at the level of the battery's leakage current, will cause a linear voltage change with time within a very small voltage range, such as tens of microvolts to a few millivolts. In this invention, a perfectly balanced battery is considered to behave like a supercapacitor at very small currents and within a small voltage range. A supercapacitor behaves according to (dV / dt)*C=I+LC, where LC is the leakage current, C is the capacitance, and I is the current applied to the capacitor. For a supercapacitor, C is a constant value and does not change with SOC (state of charge), but the leakage current LC changes with the SOC of the supercapacitor. If the voltage change rate dV / dt is measured with a constant current I, then LC can be calculated with the known C value as LC=(dV / dt)*CI. When a supercapacitor is used to model a battery, the battery will have a dynamic LC and a dynamic C at a certain SOC, according to (dV / dt)*C=I+LC, where both LC and C change with different SOCs. If two different currents I 1 and I 2 If I1 and I2 are applied at the same SOC and correspondingly measure (dV / dt)1 and (dV / dt)2, assuming that both LC and C are the same for the two currents, the LC and C values ​​of the battery can be obtained by solving the two equations (dV / dt)1*C=I1+LC and (dV / dt)2*C=I2+LC. If the battery is fully balanced and this SOC and currents I1 and I2 do not significantly disturb the electrochemical balance of the battery, the dynamic LC calculated accordingly can be regarded as the leakage current at this SOC. When I1 and I2 are several times larger than LC, the dV / dt is larger and requires less time to measure and / or less voltage accuracy from the voltmeter. Only a few hours are sufficient to measure the LC of a battery at 95%-100% SOC.

[0074] Because current control is much easier than voltage control at very low current levels, and batteries are very sensitive to even very small voltage noise / ripples, this method requires a much simpler and lower-cost test system and takes much less time to obtain reliable results compared to the method using voltage control. Instead of using special equipment that is very expensive and may not be accurate enough, normal battery test systems and battery formation systems with sufficiently high measurement accuracy / precision can be used for this method. If the dynamic capacitance (DNC) of the battery is known within some accuracy, then the dynamic LC (DNLC) can be calculated directly from (dV / dt)*C=I+LC, where dV / dt, C, and I are known or measured. When multiple (N) batteries with very similar characteristics are connected in parallel, the parallel group of batteries can be assumed to have a certain average dynamic capacitance ADNC=sum(DNC(1):DNC(N)) / N and a certain average dynamic leakage current ADNLC=sum(DNLC(1):DNLC(N)) / N. When the parallel battery group reaches electrochemical equilibrium, DNLC(n) should be equal to ADNLC-I(n)+Ig / N, where I(n) is the current into battery n and Ig is the total current into the parallel battery group. If batteries with the same chemical and mechanical construction and specifications can be assumed to have fairly constant ADNC and ADNLC (which may be the case in large-scale battery testing and formation processes where battery cells are connected in parallel), the leakage current of each battery can be measured directly by measuring the current flow into each battery while the battery group is in equilibrium and there is zero or very small external current Ig through the parallel group by DNLC(n)=ADNLC-I(n)+Ig / N. This process involves only current measurement under open circuit or very small current to the battery bank and can be done instantly when the battery bank reaches equilibrium without requiring long periods of time for voltage control / variation and measurement. The present invention significantly reduces the time and equipment required for battery manufacturing. Even if one does not have the exact values ​​of ADNLC and DNLC(n), once the parallel battery group is in balance, one can compare the DNLC of each battery in the group by the value of I(n). The effect of comparing I(n), i.e., ALC(n)=LC(n)-ALC, instantaneously is similar to comparing the voltage drop AV(n) over a long period of time. Further embodiments of the present invention include a mechanism to model the battery during leakage current measurement using a dynamic supercapacitor with dynamic capacitance and dynamic leakage current, and using said model to apply two different currents, low enough not to disturb the electrochemical equilibrium of the battery, but high enough to accelerate the test, to obtain two equations (dV / dt)1*C=I1+LC and (dV / dt)2*C=I2+LC. The LC and C values ​​of the battery can be solved from these two equations, and using current control instead of voltage control on the battery for leakage current measurement, connecting several batteries in parallel without applying any current to the group (open circuit), measuring the current through each battery, and obtaining the difference of leakage current from the average leakage current ALC(n)=LC(n)-ALC. LC(n)=ALC(n)-Ib(n);Assume ADNC=sum(LC1:LCn) / n and ADNC=sum(C1:LCn) / n by solving two equations (dVg / dt)1*ADNC=ADNLC and (dVg / dt)2*ADNC=Ig+ADNLC to get ADNC and ADNLC.By applying Ig=-N*ALC to a group of parallel batteries and checking if dVg / dt is close to 0 (μV level), we can check if ALC is the correct value and calculate the actual ALC,Measure the leakage current of multiple cells simultaneously using only one current source or without any current source.

[0075] Embodiments of the present invention include the following. 1. A battery testing apparatus comprising: A normal battery that operates as a standard battery (SB) A controllable current equal to its self-discharge current is applied to a normal battery (I) so that the voltage of the normal battery is held constant at its open circuit voltage (OCV).sb a constant current source configured to apply a a positive terminal (IOH) and a negative terminal (IOL) configured to connect a battery under test between them, such that the voltage between the terminals (IOH) and (IOL) is maintained at a constant value approximately equal to the voltage of SB within a desired accuracy; 2. A battery testing apparatus comprising: 2. The battery testing apparatus of embodiment 1, further comprising a first current sensor configured to measure a current through SB and provide feedback for controlling an output current (It) from the constant current source.

[0076] 3. The battery testing apparatus of embodiment 1, wherein the normal battery includes a secondary rechargeable battery. 4. The battery testing apparatus of embodiment 1, wherein the normal battery has the same type as the battery under test.

[0077] 5. A battery testing device comprising: two other terminals (VH) and (VL) configured to connect a battery under test between them, the terminal (VL) being connected to the negative terminal of SB; and A circuit block (VM) for voltage measurement configured to measure a differential voltage between a reference voltage and a voltage of a battery under test, VM has a first lead connected to a terminal (VH) and a second lead connected to a positive terminal of SB, and a reference voltage is determined based on the voltage of SB. Circuit block for voltage measurement (VM) and 2. The battery testing apparatus of embodiment 1, further comprising: 6. A battery testing device comprising: two other terminals (VH) and (VL) configured to connect a battery under test between them, the terminal (VL) being connected to the negative terminal of SB; and a plurality of resistors configured to divide the voltage of SB into a plurality of reference voltages within a range less than or equal to the value of the voltage of SB; a circuit block (VM) for voltage measurement having a first lead connected to a terminal (VH) and a second lead connected to a multiplexer configured to select one of a plurality of reference voltages, the circuit block being configured to measure a differential voltage between a programmable reference voltage and a voltage of a battery under test; 2. The battery testing apparatus of embodiment 1, further comprising: 7. A battery analyzer for testing a battery, comprising: A normal battery that operates as a standard battery (SB) A controllable current equal to its self-discharge current is applied to a normal battery (I) so that the voltage of the normal battery is held constant at its open circuit voltage (OCV). sb a control circuit configured to apply a The current through SB is measured and the output current from the galvanostat (I t a first current sensor configured to provide feedback to control a positive terminal (IOH) and a negative terminal (IOL) configured to connect a battery under test between them, such that the voltage between the terminals (IOH) and (IOL) is maintained at a constant value approximately equal to the voltage of SB within a desired accuracy; current I sb a first switch for connecting or disconnecting the positive terminal; and a second switch for connecting or disconnecting the current flowing through the positive terminal. a battery analyzer for testing a battery, 8. A battery analyzer for testing a battery, comprising: A secondary rechargeable battery acting as a standard battery (SB) A controllable current equal to its self-discharge current is applied to a normal battery (I) so that the voltage of the normal battery is held constant at its open circuit voltage (OCV). sb ) a galvanostat configured to apply a The current through SB is measured and the output current from the galvanostat (I ta first current sensor configured to provide feedback for controlling a current I t A first current sensor configured to measure a positive terminal (IOH) and a negative terminal (IOL) configured to connect a battery under test between them, such that the voltage between the terminals (IOH) and (IOL) is maintained at a constant value approximately equal to the voltage of SB within a desired accuracy; current I sb a first switch for connecting or disconnecting the positive terminal; and a second switch for connecting or disconnecting the current flowing through the positive terminal. 2. A battery analyzer for testing a battery including: 9. A differential battery analyzer (DBA) for testing a battery, comprising: A secondary rechargeable battery acting as a standard battery (SB) A controllable current equal to its self-discharge current is applied to a normal battery (I) so that the voltage of the normal battery is held constant at its open circuit voltage (OCV). sb ) a galvanostat configured to apply a The current through SB is measured and the output current from the galvanostat (I t a first current sensor configured to provide feedback for controlling a current I t A first current sensor configured to measure a positive terminal (IOH) and a negative terminal (IOL) configured to connect a battery under test between them, such that the voltage between the terminals (IOH) and (IOL) is maintained at a constant value approximately equal to the voltage of SB within a desired accuracy; current I sb a first switch for connecting or disconnecting the positive terminal; and a second switch for connecting or disconnecting the current flowing through the positive terminal. two other terminals (VH) and (VL) configured to connect a battery under test between them, the terminal (VL) being connected to the negative terminal of SB; and a circuit block (VM) for voltage measurement configured to measure a differential voltage between a reference voltage and a voltage of a battery under test, the circuit block having a first lead connected to a terminal (VH) and a second lead connected to a positive or negative terminal of a battery under test via a third switch, whereby the reference voltage is determined as the voltage of the battery under test or zero; A Differential Battery Analyzer (DBA) for testing batteries including: 10. A differential battery analyzer (DBA) for testing a battery, comprising: A secondary rechargeable battery acting as a standard battery (SB) A controllable current equal to its self-discharge current is applied to a normal battery (I) so that the voltage of the normal battery is held constant at its open circuit voltage (OCV). sb ) a galvanostat configured to apply a The current through SB is measured and the output current from the galvanostat (I t a first current sensor configured to provide feedback for controlling a current I t A first current sensor configured to measure a positive terminal (IOH) and a negative terminal (IOL) configured to connect a battery under test between them, such that the voltage between the terminals (IOH) and (IOL) is maintained at a constant value approximately equal to the voltage of SB within a desired accuracy; current I sb a first switch for connecting or disconnecting the positive terminal; and a second switch for connecting or disconnecting the current flowing through the positive terminal. two other terminals (VH) and (VL) configured to connect a battery under test between them, the terminal (VL) being connected to the negative terminal of SB; and a circuit block (VM) for voltage measurement configured to measure a differential voltage between a reference voltage and a voltage of a battery under test, the circuit block having a first lead connected to a terminal (VH) and a second lead connected to a positive or negative terminal of a battery under test via a third switch, whereby the reference voltage is determined as the voltage of the battery under test or zero; a current measuring circuit block (IM) configured to measure the current of the battery under test via two other terminals (IH) and (IL); Power supply and Includes a Differential Battery Analyzer (DBA). The embodiments described herein are merely examples for clarity and are not intended to limit the scope of the present invention. Other variations or modifications may be made by those skilled in the art of the above-mentioned technical fields. It is not necessary, and there is no way, to describe all possible implementations of the principles of the differential measurement technology described herein. Obvious modifications or variations resulting therefrom are still within the scope of the present invention.

Claims

1. A differential battery analyzer (DBA) for testing a battery, A control circuit configured to apply a controllable current to a normal battery as a standard battery (SB) in the DBA, The current passing through the SB (I ｓｂ ) is controlled to be equal to its self-discharge current, thereby keeping the voltage of the SB constant at its open circuit voltage (OCV); two terminals (IOH) and (IOL) for connecting a battery under test between them, said terminal (IOH) being connected to one end of a branch in which said SB is located, the voltage between said terminals (IOH) and (IOL) being kept at a constant value approximately equal to said voltage of said SB within a desired accuracy, and said terminal (IOL) being connected to the other end of said branch, The control circuit A differential battery analyzer (DBA).

2. The current through the SB is measured, and the output current (I ｔ 2. The DBA of claim 1, further comprising a first current sensor connected in series with the SB to provide feedback for controlling a current source.

3. The DBA of claim 1 , further comprising a second current sensor for measuring an output current from the control circuit and providing feedback for controlling the output current.

4. When a battery is connected to the DBA via the terminals (IOH) and (IOL), a current (I Ｏ ) follows to maintain the potential of the terminal (IOH), and I ｔ = I Ｏ +I ｓｂ The DBA according to claim 2,

5. The DBA of claim 1 , wherein the conventional battery comprises a secondary rechargeable battery.

6. The DBA of claim 1 , wherein the normal battery has the same type as the battery under test.

7. The DBA of claim 1, further comprising two other terminals (VH) and (VL), and a voltage measurement circuit block (VM) connected to the DBA via the terminals (VH) and (VL) for measuring a differential voltage between a reference voltage and a voltage of the battery under test, wherein the reference voltage is determined based on the voltage of the SB.

8. The DBA of claim 7 , wherein the reference voltage is selected as one of a plurality of reference voltages within a range less than or equal to the value of the voltage of the SB.

9. 9. The DBA of claim 8, further comprising a plurality of resistors connected in series with each other and in parallel with the branch in which the SB is located, each resistor having its own reference voltage output terminal selected via a multiplexer connected to the VM, the selection dividing the voltage of the SB into a plurality of reference voltages.

10. 2. The DBA of claim 1, further comprising two other terminals (IH) and (IL) connected to the circuit block (IM) for current measurement.

11. The control circuit includes a galvanostat, and the DBA further includes a second current sensor, two terminals (VH) and (VL), two other terminals (IH) and (IL) connected to a circuit block (IM) for measuring current, a circuit block (VM) for measuring voltage, a first switch connected in series to the first sensor, a second switch arranged to connect or disconnect the current flowing in the terminal (IOH), a ground resistor connected between the SB and the terminal (IOL), and a number of resistors connected in series with each other and in parallel with the branch in which the SB is located, each resistor 5. The DBA of claim 4, wherein the resistor has a reference voltage output terminal for each resistor selected via a multiplexer connected to the VM, such that the voltage of the SB is divided into a plurality of reference voltages by this selection; the second sensor is configured to measure an output current from the galvanostat and provide feedback to control it; the VM is configured to measure a differential voltage between a reference voltage and the voltage of the battery under test connected to the DBA via the terminals (VH) and (VL), and the reference voltage is determined based on the voltage of the SB.

12. 10. A method for measuring a differential voltage, comprising the steps of: measuring, by the VM, a differential voltage representing a difference between the reference voltage and the voltage at the terminal (VH) using the DBA of claim 7, wherein a battery under test is connected to the terminals (VH) and (VL).

13. The method of claim 12 , wherein the battery under test comprises a group of batteries connected in parallel.

14. Battery self-discharge current (I ｓｄ A constant current method for measuring The first constant current (I １ ) and a second constant current (I ２ ) for a certain period (dt １ ) and the same or different periods (dt ２ ) to the battery being tested, said current I １ and I ２ is sufficiently low so as not to disturb the electrochemical equilibrium of the battery being tested; The period dt １ and dt ２ a first voltage change (dV １ ) and the second voltage change (dV ２ ) measuring the The current I １ The period dt １ The first voltage change rate (dV １ / dt １ ) and the current I ２ The period dt ２ The second voltage change rate (dV ２ / dt ２ ) and By solving equations (1) and (2), the I ｓｄ and calculating a dynamic capacitance (DNC). Equation (1) is (dV １ / dt １ ) * DNC = I １ +I ｓｄ and Equation (2) is (dV ２ / dt ２ ) * DNC = I ２ +I ｓｄ That is, Steps and The method includes:

15. The method of claim 14 , wherein the battery being tested comprises a group of batteries connected in parallel.

16. The DBA of claim 1 is used to measure the self-discharge current (I ｓｄ A constant current method for measuring Using the control circuit in the DBA, a first constant current (I １ ) and a second constant current (I ２ ) for a certain period (dt １ ) and the same or different periods (dt ２ ) to a battery under test, the battery under test being connected to the DBA via the terminals (IOH) and (IOL), and the current I １ and I ２ is sufficiently low so as not to disturb the electrochemical equilibrium of the battery being tested; The period dt １ and dt ２ a first voltage change (dV １ ) and the second voltage change (dV ２ ) measuring the The current I １ The period dt １ The first voltage change rate (dV １ / dt １ ) and the current I ２ The period dt ２ The second voltage change rate (dV ２ / dt ２ ) and By solving equations (1) and (2), the I ｓｄ and calculating a dynamic capacitance (DNC). Equation (1) is (dV １ / dt １ ) * DNC = I １ +I ｓｄ and Equation (2) is (dV ２ / dt ２ ) * DNC = I ２ +I ｓｄ That is, Steps and The method includes:

17. 17. The method of claim 16, wherein the DBA further includes two other terminals (VH) and (VL) and a voltage measurement circuit block (VM) for measuring a differential voltage between a reference voltage and the voltage of the battery being tested, the reference voltage being determined based on the voltage of the SB, and the battery being tested is further connected to the DBA via the terminals (VH) and (VL), whereby the first voltage change and the second voltage change are measured by the VM.

18. 18. The method of claim 17, wherein the battery being tested includes a group of batteries connected in parallel, the group of batteries being further connected to a circuit block (IM) for current measurement in the DBA via terminals (IH) and (IL), each of the IM and the VM having a plurality of channels, each of the channels being configured to measure a current or a voltage of a battery.

19. The DBA of claim 1 is used to calculate the self-discharge current (I ｓｄ A method for measuring The control circuit in the DBA of claim 1 is used to control the current through the SB to the current I ｓｄ to keep the voltage of the SB constant by controlling the voltage of the SB to be equal to the voltage of the battery group, the battery group being connected in parallel to the DBA via the terminals (IOH) and (IOL); allowing sufficient time for the batteries to reach equilibrium; measuring the current through each battery, thereby determining the self-discharge current I of each battery; ｓｄ determining a value of the current flowing through the battery as being equal to the value of the current flowing through the battery; The method includes:

20. The DBA of claim 1 is used to calculate the self-discharge current (I ｓｄ A method for measuring The control circuit in the DBA of claim 1 is used to control the current through the SB to the current I ｓｄ a parallel battery group is connected to the DBA via the terminals (IOH) and (IOL), and the current I of the battery SB is controlled to be equal to the ｓｄ is determined using the constant current method of claim 14; allowing sufficient time for the batteries to reach equilibrium; measuring the current through each battery, thereby determining the self-discharge current I of each battery; ｓｄ determining a value of the current flowing through the battery as being equal to the value of the current flowing through the battery; The method includes:

21. The current through each battery is measured by a circuit block for current measurement (IM) in the DBA, and the DBA two other terminals (IH) and (IL) connected to the IM, the IM having a plurality of channels, each of the channels configured to measure a current of a battery; 21. The method of claim 20, further comprising:

22. The self-discharge current (I ｓｄ A passive method for measuring allowing sufficient time for the batteries being tested to reach equilibrium and measuring the current through each battery, said batteries being connected in parallel with each other but not connected to any power source to keep said batteries open circuit; The difference in dynamic capacitance (DNC) of all the batteries in the group can be ignored in the calculation of the self-discharge current, and AI ｓｄ Assuming that the self-discharge current (I ｓｄ #) into Equation I ｓｄ # = AI ｓｄ -I ｂ #, wherein AI ｓｄ represents the average self-discharge current of the battery group, and I ｂ # represents the current through its corresponding battery #, step and The method includes:

23. The average self-discharge current of the group of batteries is determined as a ratio of a total self-discharge current of the group of batteries to a number of batteries in the group being tested, the group of batteries being considered as an equivalent battery in calculating the total self-discharge current, and the total self-discharge current is determined using a constant current method, the constant current method being The first constant current (I １ ) and a second constant current (I ２ ) for a certain period (dt １ ) and the same or different periods (dt ２ ) to the group of batteries connected in parallel, １ and I ２ is sufficiently low so as not to disturb the electrochemical equilibrium of the battery group, The period dt １ and dt ２ A first voltage change (dV １ ) and the second voltage change (dV ２ ) measuring the The current I １ The period dt １ The first voltage change rate (dV １ / dt １ ) and the current I ２ The period dt ２ The second voltage change rate (dV ２ / dt ２ ) and By solving equations (1) and (2), the total self-discharge current (TI ｓｄ ) and calculating the total dynamic capacitance (TDNC), Equation (1) is (dV １ / dt １ ) * TDNC = I １ + T.I. ｓｄ and Equation (2) is (dV ２ / dt ２ ) * TDNC = I ２ + T.I. ｓｄ is Steps and 23. The method of claim 22, comprising:

24. A method for assessing the self-discharge of a battery, measuring a first differential OCV (DOCV1) and a second differential OCV (DOCV2) for the standard battery (SB), representing a difference between the reference voltage and the voltage at the terminal (VH) at two different times T1 and T2, using the DBA of claim 7, the battery being tested being connected to the terminals (VH) and (VL), the DBA further comprising a first current sensor connected in series with the SB to measure the current through the SB and provide feedback for controlling an output current from the control circuit, the current through the SB being controlled to be equal to a self-discharge current of the SB, whereby the voltage of the SB is kept constant at its open circuit voltage (OCV); calculating a differential DOCV (ΔDOCV) between the two differential OCVs for a time period (Δt) from T1 to T2; assessing a self-discharge state of the battery being tested based on a ratio of ΔDOCV to Δt; The method includes:

25. 25. The method of claim 24, wherein the battery being tested comprises a group of batteries, the method further comprising: sorting the group of batteries according to the self-discharge state.

26. A self-discharge current (I) of one or more batteries in the group is determined based on a known dynamic capacitance (DNC) value of one or more batteries in the group or an average DNC value of the group of batteries. ｓｄ 26. The method of claim 25, further comprising: calculating

27. The average DNC value of the group of batteries is determined as a ratio of a total DNC (TDNC) of the group of batteries to the number of batteries in the group being tested, the group of batteries being considered as an equivalent battery in calculating TDNC, and the DNC value of one or more batteries in the group or the TDNC of the group of batteries is determined using a constant current method, the constant current method being The first constant current (I １ ) and a second constant current (I ２ ) for a certain period (dt １ ) and the same or different periods (dt ２ ) to a battery or group of batteries in the group of batteries being tested, １ and I ２ is sufficiently low so as not to disturb the electrochemical equilibrium of the battery or the battery group; The period dt １ and dt ２ a first voltage change (dV １ ) and the second voltage change (dV ２ ) measuring the The current I １ The period dt １ The first voltage change rate (dV １ / dt １ ) and the current I ２ The period dt ２ The second voltage change rate (dV ２ / dt ２ ) and By solving equations (1) and (2), the I ｓｄ and calculating a dynamic capacitance (DNC). Equation (1) is (dV １ / dt １ ) * DNC = I １ +I ｓｄ and Equation (2) is (dV ２ / dt ２ ) * DNC = I ２ +I ｓｄ That is, Step or Alternatively, by solving equations (3) and (4), the total self-discharge current TI of the batteries being tested is calculated. ｓｄ and calculating the total dynamic capacitance (TDNC). Equation (3) is (dV １ / dt １ ) * TDNC = I １ + T.I. ｓｄ and Equation (4) is (dV ２ / dt ２ ) * TDNC = I ２ + T.I. ｓｄ That is, Steps and 27. The method of claim 26, comprising:

28. A method for measuring the direct current internal resistance (DCIR) of a battery, applying a first current and a second current at two different times T1 and T2 to a battery under test connected via terminals (VH) and (VL) to the DBA of claim 7, the DBA further comprising two terminals (IH) and (IL) connected to a circuit block (IM) for current measurement, a sensor being connected between the terminals (IH) and (IL) and connected in series with the battery to measure the current through the battery; measuring a differential current (ΔI) representing a difference between a first measured current and a second measured current of the battery during a time period from T1 to T2 using the IM; measuring a first differential voltage and a second differential voltage representative of a difference between the reference voltage and the voltage at the terminal (VH) while injecting the first current and the second current, respectively, by the VM; calculating a change in differential voltage (ΔV) of the battery representing the difference between the first differential voltage and the second differential voltage during a time period from T1 to T2; calculating the DCIR of the battery being tested as equal to ΔV / ΔI; The method includes:

29. An automated analyzer for evaluating batteries, Power supply and One or more processors one or more storage media storing instructions executable by said one or more processors, said instructions, when executed, causing said automated analyzer to perform the operations recited in any one of claims 12, 14, and 16-28; Includes an automatic analyzer.

30. A battery testing device A normal battery that operates as a standard battery (SB) A controllable current equal to its self-discharge current is applied to the normal battery (I) so that the voltage of the normal battery is kept constant at its open circuit voltage (OCV). ｓｂ a constant current source configured to apply a a positive terminal (IOH) and a negative terminal (IOL) configured to connect a battery under test between them, the voltage between the terminals (IOH) and (IOL) being maintained at a constant value approximately equal to the voltage of the SB within a desired accuracy; 2. A battery testing apparatus comprising:

31. The current through the SB is measured, and the output current (I ｔ 31. The battery testing apparatus of claim 30, further comprising a first current sensor configured to provide feedback to control a current limiting factor (LCL) of the battery.

32. 31. The battery testing apparatus of claim 30, wherein the conventional battery comprises a secondary rechargeable battery.

33. 31. The battery testing apparatus of claim 30, wherein the normal battery has the same type as the battery under test.

34. two other terminals (VH) and (VL) configured to connect a battery under test between them, said terminal (VL) being connected to the negative terminal of said SB; and a circuit block (VM) for voltage measurement configured to measure a differential voltage between a reference voltage and the voltage of the battery under test, the VM having a first lead connected to the terminal (VH) and a second lead connected to the positive terminal of the SB, the reference voltage being determined based on the voltage of the SB; 31. The battery testing apparatus of claim 30, further comprising:

35. two other terminals (VH) and (VL) configured to connect a battery under test between them, said terminal (VL) being connected to the negative terminal of said SB; and a plurality of resistors configured to divide the voltage of the SB into a plurality of reference voltages within a range less than or equal to the value of the voltage of the SB; a circuit block (VM) for voltage measurement having a first lead connected to said terminal (VH) and a second lead connected to a multiplexer configured to select one of said reference voltages, said VM being configured to measure a differential voltage between a programmable reference voltage and said voltage of said battery under test; 31. The battery testing apparatus of claim 30, further comprising:

36. A battery analyzer for testing a battery, A normal battery that operates as a standard battery (SB) A controllable current equal to its self-discharge current is applied to the normal battery (I) so that the voltage of the normal battery is kept constant at its open circuit voltage (OCV). ｓｂ a control circuit configured to apply a The current through the SB is measured, and the output current (I ｔ a first current sensor configured to provide feedback to control the a positive terminal (IOH) and a negative terminal (IOL) configured to connect a battery under test between them, the voltage between the terminals (IOH) and (IOL) being maintained at a constant value approximately equal to the voltage of the SB within a desired accuracy; The current I ｓｂ a first switch for connecting or disconnecting a current flowing through the positive terminal; and a second switch for connecting or disconnecting a current flowing through the positive terminal. Includes a battery analyzer.

37. A battery analyzer for testing a battery, a secondary rechargeable battery that acts as a standard battery (SB); A controllable current equal to its self-discharge current is applied to the normal battery (I) so that the voltage of the normal battery is kept constant at its open circuit voltage (OCV). ｓｂ ) a galvanostat configured to apply a The current through the SB is measured, and the output current from the galvanostat (I ｔ a first current sensor configured to provide feedback for controlling the current I ｔ A first current sensor configured to measure a positive terminal (IOH) and a negative terminal (IOL) configured to connect a battery under test between them, the voltage between the terminals (IOH) and (IOL) being maintained at a constant value approximately equal to the voltage of the SB within a desired accuracy; The current I ｓｂ a first switch for connecting or disconnecting a current flowing through the positive terminal; and a second switch for connecting or disconnecting a current flowing through the positive terminal. Includes a battery analyzer.

38. A differential battery analyzer (DBA) for testing a battery, a secondary rechargeable battery that acts as a standard battery (SB); A controllable current equal to its self-discharge current is applied to the normal battery (I) so that the voltage of the normal battery is kept constant at its open circuit voltage (OCV). ｓｂ ) a galvanostat configured to apply a The current through the SB is measured, and the output current from the galvanostat (I ｔ a first current sensor configured to provide feedback for controlling the current I ｔ A first current sensor configured to measure a positive terminal (IOH) and a negative terminal (IOL) configured to connect a battery under test between them, the voltage between the terminals (IOH) and (IOL) being maintained at a constant value approximately equal to the voltage of the SB within a desired accuracy; The current I ｓｂ a first switch for connecting or disconnecting a current flowing through the positive terminal; and a second switch for connecting or disconnecting a current flowing through the positive terminal. two other terminals (VH) and (VL) configured to connect a battery under test between them, said terminal (VL) being connected to the negative terminal of said SB; and a circuit block (VM) for voltage measurement configured to measure a differential voltage between a reference voltage and the voltage of the battery under test, the VM having a first lead connected to the terminal (VH) and a second lead connected to the positive or negative terminal of the SB via a third switch, whereby the reference voltage is determined as the voltage of the SB or zero; A Differential Battery Analyzer (DBA) including:

39. A differential battery analyzer (DBA) for testing a battery, a secondary rechargeable battery that acts as a standard battery (SB); A controllable current equal to its self-discharge current is applied to the normal battery (I) so that the voltage of the normal battery is kept constant at its open circuit voltage (OCV). ｓｂ ) a galvanostat configured to apply a The current through the SB is measured, and the output current from the galvanostat (I ｔ a first current sensor configured to provide feedback for controlling the current I ｔ A first current sensor configured to measure a positive terminal (IOH) and a negative terminal (IOL) configured to connect a battery under test between them, the voltage between the terminals (IOH) and (IOL) being maintained at a constant value approximately equal to the voltage of the SB within a desired accuracy; The current I ｓｂ a first switch for connecting or disconnecting a current flowing through the positive terminal; and a second switch for connecting or disconnecting a current flowing through the positive terminal. two other terminals (VH) and (VL) configured to connect a battery under test between them, said terminal (VL) being connected to the negative terminal of said SB; and a circuit block (VM) for voltage measurement configured to measure a differential voltage between a reference voltage and the voltage of the battery under test, the VM having a first lead connected to the terminal (VH) and a second lead connected to the positive or negative terminal of the SB via a third switch, whereby the reference voltage is determined as the voltage of the SB or zero; a current measuring circuit block (IM) for measuring the current of the battery under test via two other terminals (IH) and (IL); Power supply and A Differential Battery Analyzer (DBA) including:

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