Method and device for regularly monitoring the state of a rechargeable electric energy store, and uninterruptible power supply

Abstract

The invention relates to, inter alia, a method and a device for regularly monitoring the state of a rechargeable electric energy store (500) which can be connected to an electric resistor network (420) via at least two switching elements (410, 411) which are controllable by means of a control device (450). During a monitoring process, current of a first current intensity is drawn from the energy store (500) for a predetermined first time period and an associated first terminal voltage is measured, and subsequently current of a second current intensity is drawn for a predetermined second time period and an associated second terminal voltage is measured. The internal impedance of the electric energy store (500) is determined on the basis of the measured first terminal voltage and second terminal voltage. The state of the electric energy store (500) is then determined on the basis of the determined internal impedance and a provided reference value. The monitoring process is repeated regularly, wherein the electric energy store (500) is kept at a predetermined state of charge between two successive monitoring processes.

Description

[0001] Method and device for regularly monitoring the condition of a rechargeable electrical energy storage device and an uninterruptible power supply

[0002] Description

[0003] The invention relates to a method and a device for regularly monitoring the state of a rechargeable electrical energy storage device, in particular to detect a faulty state of the rechargeable electrical energy storage device. Furthermore, the invention relates to an uninterruptible power supply in which the device for regularly monitoring the state of a rechargeable electrical energy storage device is implemented.

[0004] In order to check the condition of a battery, in particular to determine a battery fault, the impedance, preferably the ohmic internal resistance of the battery, can be determined.

[0005] For example, WO 2021 / 213669 A1 discloses a method and device for testing the battery condition of at least one battery. According to the known method, a first impedance test is performed to determine the internal resistance of the battery. The battery is excited with an electrical current at a specific frequency, and a resulting voltage response of the battery is measured. The measurement result of the first impedance test is then recorded and stored. A high-current load test of the battery is then performed using a test pulse. A second impedance test is then performed, and the measurement result of the second impedance test is also recorded and stored.Finally, the first and second impedance tests are evaluated by relating the measurement results of the first and second impedance tests and / or the high-current load test to one another in such a way that the battery condition can be derived therefrom, in particular, it can be determined whether a faulty battery is present. The present invention is based on the technical object of providing a method and a device for regularly monitoring the condition of a rechargeable electrical energy storage device, as well as an uninterruptible power supply, which proposes an alternative solution approach for regularly monitoring the condition of a rechargeable electrical energy storage device, in which, in particular, no high-current load test is performed.

[0006] The above-mentioned technical problem is solved on the one hand by the method steps of claim 1, the features of claim 10 and by the features of claim 15.

[0007] Advantageous further developments and refinements are the subject of the subclaims.

[0008] According to a first aspect, a method is provided for regularly monitoring the state of a rechargeable electrical energy storage device that can be connected to an electrical resistance network via at least two switching elements that can be controlled by a control device. The method preferably comprises the following method steps: a) providing a reference value for the internal resistance of the rechargeable electrical energy storage device;b) carrying out a monitoring process for monitoring the state of the rechargeable electrical energy store by b1) switching the at least two switching elements into a first switching state for a predetermined first time period, so that the electrical energy store is connected to the electrical resistance network in such a way that the electrical energy store is discharged with a current of first current intensity during the predetermined first time period, and a first terminal voltage is measured between two connection terminals of the electrical energy store while the electrical energy store is discharged with the current of first current intensity;b2) subsequently, the at least two switching elements are switched to a second switching state for a predetermined second period of time, so that the electrical energy store is connected to the electrical resistance network in such a way that the electrical energy store is discharged with a current of second current intensity during the predetermined second period of time, and a second terminal voltage is measured between the two connection terminals of the electrical energy store while the electrical energy store is discharged with the current of second current intensity, wherein the first and second current intensity are different; b3) the internal resistance of the electrical energy store is determined as a function of the first terminal voltage measured in step b1) and the second terminal voltage measured in step b2);b4) the state of the rechargeable electrical energy storage device is determined as a function of the internal resistance determined in step b3) and the reference value provided in step a); and c) regularly repeating step b), wherein the electrical energy storage device is maintained at a predetermined charge state between two consecutive monitoring processes. This charge is also known as a maintenance charge, which is intended, in particular, to compensate for self-discharge of the electrical energy storage device.

[0009] It should be noted that the determined internal resistance of the rechargeable electrical energy storage device is preferably an ohmic resistance.

[0010] Advantageously, for example, the first current intensity may be smaller than the second current intensity and / or the predetermined first and predetermined second time periods may be the same or different.

[0011] It should be noted that the process of monitoring the state of the rechargeable electrical energy storage device in step c) is repeated regularly, ie at predetermined time intervals, in particular until a faulty state of the electrical energy storage device has been detected.

[0012] According to an advantageous embodiment, a threshold value is provided, which can preferably be stored in a memory device. Step b4) then comprises the following steps: - Forming the absolute value between the internal resistance determined in step b3) and the reference value provided in step a); and

[0013] - Comparing the amount formed in step b4) with the threshold value in order to determine the state of the electrical energy storage device.

[0014] If the amount formed is greater than or equal to the threshold value, a faulty state of the electrical energy storage device is determined in step b4).

[0015] In order to further promote an automated sequence of the method, according to an advantageous development, the reference value can be determined before the execution of step b) in which a1) the at least two switching elements are switched into a first switching state for a predetermined first time period, so that the electrical energy store is connected to the electrical resistance network in such a way that the electrical energy store is discharged with a current of first current intensity during the first predetermined time period, and a first terminal voltage between two connection terminals of the electrical energy store is measured while the electrical energy store is discharged with the current of first current intensity;a2) subsequently, the at least two switching elements are switched to a second switching state for a predetermined second period of time, so that the electrical energy store is connected to the electrical resistance network in such a way that the electrical energy store is discharged with a current of a second current intensity during the second predetermined period of time, and a second terminal voltage is measured between the two connection terminals of the electrical energy store while the electrical energy store is discharged with the current of a second current intensity; wherein the first and second current intensities are different;a3) the internal resistance of the electrical energy storage device is determined as a function of the first terminal voltage measured in step a1) and the second terminal voltage measured in step a2), wherein the determined internal resistance is stored in a storage device as a reference value for the internal resistance of the rechargeable electrical energy storage device. Advantageously, for example, the first current intensity can be smaller than the second current intensity and / or the predetermined first and predetermined second time periods can be the same or different.

[0016] Alternatively, the reference value can also be specified manually and stored in a memory device.

[0017] In order to be able to increase the accuracy in determining the internal resistance of the electrical energy storage device, steps b1) and b2) can preferably be repeated n times periodically, wherein in step b3) the internal resistance of the electrical energy storage device is determined as a function of at least some of the first terminal voltages measured n times and at least some of the second terminal voltages measured n times.

[0018] According to an advantageous embodiment, the current of the first current intensity in step a1) and the current of the second current intensity in step a2) are each a constant low current. Advantageously, the current of the first current intensity in step a1) and the current of the second current intensity in step a2) can form a rectangular current waveform.

[0019] Advantageously, the first current intensity can be smaller than the second current intensity. Advantageously, the predetermined first and predetermined second time periods can be the same or different. Advantageously, for example, steps a1) and a2) can be repeated periodically n times, wherein in step a3), the internal resistance of the electrical energy storage device is determined as a function of at least one of the first terminal voltages measured n times and at least some of the second terminal voltages measured n times.

[0020] Advantageously, the first current intensity of step b1) and the second current intensity of step b2) can each be a constant low-voltage current. Advantageously, the constant low-voltage current can be between 1 A and 15 A, and in particular between 4.5 A and 9 A, depending on the capacity and / or the nominal voltage of the electrical energy storage device. Advantageously, for example, the first current intensity of step b1) and the second current intensity of step b2) can form a rectangular current waveform. Advantageously, the rechargeable electrical energy storage device is a rechargeable battery.

[0021] Advantageously, the nominal voltage of the rechargeable electrical energy storage device is in the range of 6 V to 48 V. Advantageously, the capacity of the electrical energy storage device is in the range of 1 Ah to 200 Ah.

[0022] It should be noted at this point that the method described here is also applicable when several rechargeable electrical energy storage devices are connected in parallel or in series.

[0023] According to an advantageous development, the first current intensity can also be measured in step b1) and the second current intensity can also be measured in step b2), wherein in step b3) the internal resistance of the electrical energy store is also determined as a function of the first current intensity measured in step b1) and the second current intensity measured in step b2).

[0024] According to a further preferred aspect, according to claim 10, a device for regularly monitoring the state of a rechargeable electrical energy storage device is provided, which can have the following features: a charge controller that can be electrically connected to an electrical energy storage device and is designed to electrically charge the electrical energy storage device and / or to maintain it in a predetermined charge state, and a monitoring device that has the following features: an electrical resistance network that can be connected to the electrical energy storage device via at least a first and a second switching element, a voltage measuring device that can be electrically connected to the rechargeable electrical energy storage device and is designed to measure a terminal voltage applied to the rechargeable electrical energy storage device, a storage device,in which a program and a reference value for the internal resistance of the rechargeable electrical energy storage device are stored, a control device configured to cause the device to carry out the method described above upon execution of the stored program. The device can preferably be configured as a charger to which, for example, an external rechargeable electrical energy storage device can be connected.

[0025] Advantageously, a threshold value can be stored in the memory device, wherein the control device is designed to cause the device, upon execution of the stored program, to form the amount between the determined internal resistance and the stored reference value and to compare the amount formed with the threshold value in order to determine the state of the electrical energy storage device.

[0026] Advantageously, the device may further comprise a current measuring device designed to measure a discharge current which can be taken from the rechargeable electrical energy storage device.

[0027] Advantageously, the electrical resistance network can have at least one first electrical resistor, which can be electrically connected to the electrical energy store via the first switching element, and at least one second electrical resistor, which can be electrically connected to the electrical energy store via the second switching element. If, for example, during the first period of time only the at least one first electrical resistor is connected to the electrical energy store by means of the first switching element and subsequently during the second period of time only the at least one second electrical resistor is connected to the electrical energy store by means of the second switching element, the total resistance of the at least one first electrical resistor and the total resistance value of the at least one second electrical resistor are different, depending on whether the first or the second current intensity is greater than the other.

[0028] Preferably, the two switching elements can each be designed as a semiconductor switch or as an electromechanical switch.

[0029] According to a further aspect, an uninterruptible power supply is provided, which may comprise the device described above. The invention is explained in more detail below using an exemplary embodiment in conjunction with the accompanying drawings. In the drawings:

[0030] Figure 1 shows a schematic current-voltage curve diagram of an exemplary rechargeable electrical energy storage device during a regularly performed monitoring process for determining the state of a rechargeable electrical energy storage device,

[0031] Figure 2 is a schematic current-voltage curve diagram during a monitoring process shown in Figure 1 for determining the state of the rechargeable electrical energy storage device,

[0032] Figure 3 is a schematic block diagram of an exemplary uninterruptible power supply with an integrated monitoring device for regularly monitoring the state of a rechargeable electrical energy storage device,

[0033] Figure 4 is a schematic block diagram of an exemplary device with an integrated monitoring device for regularly monitoring the state of a rechargeable electrical energy storage device, and

[0034] Figure 5 is a schematic block diagram of an exemplary device with an integrated monitoring device for regularly monitoring the state of a rechargeable electrical energy storage device and with such a rechargeable electrical energy storage device.

[0035] Figure 3 shows an exemplary uninterruptible power supply 300, also referred to as a UPS for short, with which an electrical load (not shown) can be temporarily supplied with energy in a manner known per se, even if the main energy supply, preferably a mains voltage, has failed. The UPS 300 has, for example, two input connections 310 and 311, to which, for example, a mains voltage can be applied. Furthermore, the UPS 300 has, for example, two output connections 312 and 313, to which an electrical load to be supplied can be connected. During fault-free operation, the exemplary UPS 300 transmits a mains voltage applied to the input connections 310 and 311 directly to the output connections 312 and 313, for example via a switching device 340.According to an exemplary implementation, the exemplary UPS 300 includes a rechargeable electrical energy storage device, which may be referred to as a rechargeable battery or secondary battery, or simply as an accumulator. It should be noted that multiple rechargeable batteries 500 may be connected in series or parallel. The battery 500 is idealized in Figure 3 as a voltage source 520 connected in series with an internal electrical resistance 510 between two terminals 501 and 502 of the rechargeable battery 500. The terminals 501 and 502 function, for example, as the positive and negative poles of the rechargeable battery 500.

[0036] It should already be noted at this point that an essential aspect is that the condition of the rechargeable battery 500 is regularly monitored, in particular by regularly determining the electrical internal resistance 510 of the rechargeable battery 500 and comparing it with an ohmic reference value.

[0037] Depending on the implementation, the UPS 300 can, for example, have a charge controller 600 and a rectifier 320. The rectifier 320 can be electrically connected on the input side to the input terminals 310 and 311 and on the output side to the charge controller 600. The charge controller 600 is electrically connected to the two terminals 501 and 502 of the rechargeable battery. For example, the rechargeable battery 500 can be recharged via the rectifier 320 and the charge controller 600 electrically connected to the output of the rectifier 320, for example, after use or, as will be shown below, maintained in a predetermined charge state, also called a trickle charge state, between each two monitoring processes. It should be noted at this point that, depending on the implementation of the UPS 300, the rechargeable battery 500 can also be connected to the UPS 300 as an external battery.For clarity of illustration only, only one electrical connection is shown between the rectifier 320 and the charge controller 600 and between the charge controller 600 and the rechargeable battery instead of two electrical connections.

[0038] Furthermore, an exemplary monitoring device 400 is implemented in the exemplary UPS 300. The exemplary monitoring device 400 has an electrical resistance network 420, which, according to an exemplary implementation, has at least a first electrical resistor 421 that can be electrically connected to the terminals 501 and 502 of the rechargeable battery 500 via a switching element 411. For this purpose, the monitoring device 400 can, for example, have two connection points 401 and 402, wherein the connection point 401 is electrically connected, for example, via an electrical supply line to the terminal 501 of the battery 500, while the connection point 402 is electrically connected to the terminal 502 of the rechargeable battery 500 via a second supply line.The exemplary electrical resistance network 420 has, for example, at least one second electrical resistor 422, which can be electrically connected to the terminals 501 and 502 of the rechargeable battery 500 via a switching element 410. The switching elements 410 and 411 can be designed, for example, as semiconductor switches or as electromechanical switches, which can be opened, i.e., electrically blocked, or closed, i.e., electrically conductive, via a control device 450. The control device 450 can be designed, for example, as a microcontroller.

[0039] As shown by way of example in Figure 3, one terminal of the switching element 410 and one terminal of the switching element 411 are each electrically connected to the connection point 401 of the monitoring device 400, while the common connection point of the two electrical resistors 421 and 422 is connected to the other connection point 402 of the monitoring device 400. In this way, the two electrical resistors 421 and 422 can be electrically connected alternately or simultaneously to the terminals 501 and 502 of the rechargeable battery 500. In order to be able to measure, for example, the terminal voltage of the rechargeable battery 500 between the terminals 501 and 502, the monitoring device 400 has a voltage measuring device 430, which, according to the exemplary implementation, can be connected, for example, via a switching element 412, between the terminals 401 and 402 of the monitoring device 400.

[0040] It should already be noted at this point that, according to an advantageous embodiment, the resistance value of the electrical resistor 421 is greater than the resistance value of the electrical resistor 422. For example, the resistance value of the electrical resistor 421 is 7.5 ohms, while the resistance value of the electrical resistor 422 is 3.75 ohms. In this way, when the switching element 411 is closed and the switching element 410 is open, the rechargeable battery 500 is discharged with a current of a first current intensity that is smaller than a second current intensity of a discharge current that is drawn from the rechargeable battery 500 when the switch 410 is closed and the switch 411 is open. It is also conceivable that the two switching elements 410 and 411 are closed simultaneously in order to be able to discharge the rechargeable battery 500 with a current of a second current intensity.In this case, the electrical resistors 421 and 422 can have the same resistance value.

[0041] It should be noted at this point that the electrical resistance network 420 can have a plurality of electrical resistors connected to one another, wherein, for example, a plurality of electrical resistors 421 can be connected in parallel or in series and / or a plurality of electrical resistors 422 can be connected in parallel or in series, which can be specifically connected to the terminals 501 and 502 of the rechargeable battery via the switching element 410 or 411.

[0042] It is also conceivable that at least one further electrical resistor can be electrically connected to the terminals 501 and 502 of the rechargeable battery 500 via a third switching element (not shown), wherein the battery 500 can then be discharged with a current of third current intensity.

[0043] Optionally, the monitoring device 400 can comprise a device 440 for measuring a discharge current, which is connected, for example, between the connection point 402 of the monitoring device 400 and the common connection point of the two electrical resistors 421 and 422. Alternatively, the discharge current can also be measured via a voltage measurement using the voltage measuring device 430, which, when an electrical resistor 421 is included, can measure its voltage drop or the voltage drop across the electrical resistor 422. If the two resistors 421 and 422 are known, the corresponding discharge current can be determined.

[0044] It should be noted at this point that the respective resistance value of the electrical resistors 421 and 422 can be stored, for example, in a memory device 460. It should already be noted at this point that software containing, for example, firmware and / or other programs for controlling the UPS 300 can be stored in the memory device 460.

[0045] It should also be noted that a predetermined threshold value can be stored in the memory device 460, which, as explained below, is used to determine the battery state. Furthermore, a reference value for the internal resistance 510 of the rechargeable battery can be stored in the memory device 460. The reference value can, for example, be entered manually or, as explained below, determined with the aid of the monitoring device 400 before the actual monitoring of the operating state of the rechargeable battery 500 begins.

[0046] As further shown in Figure 3, depending on the implementation, the UPS 300 can, for example, have an inverter 330 that is electrically connected to the terminals 501 and 502 of the rechargeable battery. On the output side, the inverter 330 can be connected to the switching device 340, which has the task of electrically connecting the input terminals 310 and 311 to the output terminals 312 and 313 during normal operation. However, in the event of a mains voltage failure, the switching device 340 ensures that the outputs of the inverter 330 are electrically connected to the output terminals 312 and 313. The corresponding switching of the switching device 340 is controlled, for example, by the control device 450.

[0047] It should be noted that the memory device 460 and the control device 450 may be separate components or part of a microcontroller.

[0048] Furthermore, the charge controller 600 is preferably implemented in the UPS 300, which is electrically connectable to the electrical energy storage device 500 and is preferably configured to electrically charge the electrical energy storage device 500 and / or maintain it at a predetermined charge level. The predetermined charge level preferably corresponds to the fully charged state of the rechargeable battery 500, which in turn corresponds to a so-called trickle charge, which depends on the respective battery type. The rechargeable battery 500 can be, for example, a lead-acid or lithium-ion battery.

[0049] The charge controller 600, the monitoring device 400, and, if implemented, preferably also the rectifier 320 can be considered a device 700 for regularly monitoring the condition of the rechargeable battery 500. Such a device 700 is illustrated schematically and by way of example in Figure 4. Preferably, the device 700 is designed as an example. For the sake of simplicity of illustration and explanation, the same reference numerals are used for the same components in Figures 3 and 4. This also expresses that these components can be identical or essentially the same in function and structure.

[0050] The device 700 comprises a monitoring device 400, a charging controller 600, and, depending on the implementation, for example, a rectifier 710. The charging device 700 can have two input terminals 701 and 702 for applying an external supply voltage, for example, a mains voltage, and two output terminals 703 and 704 for electrically connecting to an external rechargeable battery 500 to be monitored. If a DC voltage is applied to the input terminals as the supply voltage, a voltage converter can be provided instead of the rectifier 320. The charging controller 600 and the rectifier 320 can form a single component. Terminals 401 and 402 of the monitoring device 400 are electrically connected to the output terminals 703 and 704 and thus also to the rechargeable battery 500. The charging controller 600 is connected to the rectifier 710 and to the output terminals 703 and 704.The charge controller 600 is preferably controlled by the control device 450 or a separate control device to preferably fully charge the rechargeable battery and to maintain it in a predetermined trickle charge state depending on the application.

[0051] The monitoring device 400 and the charge controller 600 shown in Figure 4 correspond in structure and function to the monitoring device 400 shown in Figure 3 and the charge controller 600 shown there, so that in this regard, reference is made to the description of the monitoring device shown in Figure 3 and the charge controller 600 shown there in order to avoid repetition.

[0052] It is conceivable that, as Figure 5 shows by way of example, a rechargeable electrical energy storage device 500 and a monitoring device 400, which preferably corresponds in structure and function to the monitoring device 400 shown in Figure 3, can be designed, for example, as a separate device 800, which can preferably be accommodated in a common housing. The device 800 has two connections 801 and 802, which are electrically connected to connections 501 and 502 of the rechargeable electrical energy storage device 500 and to connections 401 and 402 of the monitoring device 400. If such a device 800 is used, for example, in the UPS 300 shown in Figure 3, the connections 801 and 802 are electrically connected to the charge controller 600.

[0053] In the following, the functioning of the monitoring device 400 is explained in more detail using an example in conjunction with the UPS 300.

[0054] By way of example, it is now assumed that a first time period and a second time period are stored in the memory device 460 or in a separate memory (not shown) assigned to the control device 450, which are, for example, the same and, for example, each amount to 2 ms. Furthermore, a third time period is stored in the memory device 460 or in a separate memory assigned to the control device 450, which defines the duration between each two consecutive monitoring processes. In Figure 1, this time period is provided with the reference symbol 2. The third time period is, for example, 24 hours. This means that the condition or internal resistance of the rechargeable battery 500 is monitored or determined by the monitoring device 400 every 24 hours.The start and expiration of the first, second and third time periods is controlled or monitored by the control device 450 or a separate timer (not shown) electrically connected to the control device.

[0055] Furthermore, at least one parameter n can be stored in the memory device 460, which parameter indicates how often, during a monitoring process or, where appropriate, a process for determining a reference value, switching should take place between a discharge current of the first current intensity and a discharge current of the second current intensity, which are to be drawn from the rechargeable battery 500 via the resistor network 420. For the sake of simplicity of explanation, it is initially assumed that n is set equal to 1, so that switching between a discharge current of the first current intensity and a discharge current of the second current intensity occurs only once.

[0056] Furthermore, it is assumed that the rechargeable battery is being put into operation for the first time and is in a fully charged state. Figure 1 shows an example of a charging process for fully charging the rechargeable battery. According to an exemplary charging process, the charge controller 600 can be prompted by the control device 450 or a separate control device of the UPS 300 to fully charge the rechargeable battery 500 using a direct current and a direct voltage during a charging phase 1 and then to maintain the charge state of the rechargeable battery 500 at a predetermined value, the so-called trickle charge. This transition occurs at the time designated by reference numeral 3. The rechargeable battery 500 is then maintained in the predetermined charge state for the third period of time, designated by reference numeral 2 in Figure 1.During this time, the monitoring device 400 is preferably not electrically connected to the rechargeable battery 500, i.e., the switching elements 410, 411, and 412 of the exemplary monitoring device 400 are then open or switched to an electrically blocking state. The self-discharge current then only flowing can be seen in Figure 1. The charging and charge maintenance process explained above by way of example is known per se. As already mentioned, the expiration of the third time period, which is, for example, 24 hours, can be detected by the control device 450 in order to initiate, in response thereto, a monitoring process and, if appropriate, a process for determining a reference value for the internal resistance of the rechargeable battery 500.

[0057] Note that a monitoring operation or an operation for determining a reference value for the internal resistance of the rechargeable battery 500 may preferably take from 1 to several seconds.

[0058] To monitor the condition of the rechargeable battery 500, a reference value for the internal resistance 510 of the rechargeable electrical energy storage device 500 is required. The reference value can be stored in advance in the storage device 460. Alternatively, as explained below, a reference value can also be determined by the monitoring device 400.

[0059] Let us now assume that the third time period has elapsed since the rechargeable battery 500 was fully charged and only a small self-discharge current is still flowing, as can be seen in Figure 1 at time t1. The expiration of the third time period has been detected by the control device 450. The control device 450 can, for example, be configured to execute the program stored in the memory device 460 in response to the expiration of the third time period in order to carry out a method for determining a reference value, according to which: a1) the at least two switching elements 410, 411 are switched to a first switching state for a predetermined first time period, so that the electrical energy storage device 500 is connected to the electrical resistance network 420 in such a way that the electrical energy storage device 500 is discharged with a current of a first current intensity during the first predetermined time period,and a first terminal voltage between the terminals 501, 502 of the electrical energy storage device 500 is measured while the electrical energy storage device 500 is being discharged with the current of the first current intensity; a2) subsequently, the at least two switching elements 410, 411 are switched to a second switching state for a predetermined second time period, so that the electrical energy storage device 500 is connected to the electrical resistance network 420 such that the electrical energy storage device 500 is discharged with a current of the second current intensity during the second predetermined time period, and a second terminal voltage between the two terminals 501, 502 of the electrical energy storage device 500 is measured while the electrical energy storage device 500 is being discharged with the current of the second current intensity; wherein the first and second current intensities are different,and wherein the first and second time periods are the same or different; a3) the internal resistance 510 of the electrical energy storage device 500 is determined as a function of the first terminal voltage measured in step a1) and the second terminal voltage measured in step a2), wherein the determined internal resistance 510 is stored as a reference value for the internal resistance of the rechargeable electrical energy storage device 500, for example, in the storage device 460.

[0060] It should be noted that in the exemplary embodiment, as already mentioned above, the first and second time periods can be the same, and the current of the first current intensity is preferably smaller than the current of the second current intensity. Applied to the exemplary monitoring device 400 shown in Figure 3, the control device 450 is designed, for example, to execute the program stored in the memory device 460 in response to the expiration of the third time period in order to control a method according to which: a1) for the predetermined first time period, the switching element 410 is opened and the switching element 411 is closed, so that the electrical energy storage device 500 is connected only to the electrical resistor 421 and the electrical energy storage device 500 is discharged with a current of the first current intensity during the first predetermined time period, and a first terminal voltage between the terminals 501,502 of the electrical energy storage device 500 is measured by means of the voltage measuring device 430 while the electrical energy storage device 500 is being discharged with the current of the first current intensity; a2) subsequently, for the predetermined second time period, the switching element 411 is opened and the switching element 410 is closed, so that the electrical energy storage device 500 is only connected to the electrical resistor 422 and the electrical energy storage device 500 is discharged with a current of the second current intensity during the second predetermined time period, and a second terminal voltage between the two connections 501, 502 of the electrical energy storage device 500 is measured by means of the voltage measuring device 430,while the electrical energy storage device 500 is discharged with the current of the second current intensity; a3) the internal resistance 510 of the electrical energy storage device 500 is determined as a function of the first terminal voltage measured in step a1) and the second terminal voltage measured in step a2), wherein the determined internal resistance 510 is stored as a reference value for the internal resistance of the rechargeable electrical energy storage device 500, for example, in the storage device 460.

[0061] In order to be able to determine a more precise value for the reference value for the internal resistance of the rechargeable battery 500, the parameter n can be set to a larger number instead of 1, so that during a process for determining the reference value, switching can be carried out several times between a current of first current intensity and a current of second current intensity. In this case, the control device 450 is designed to periodically repeat steps a1) and a2) n times while executing the program stored in the memory device 460 and, in step a3), to determine the internal resistance of the electrical energy storage device as a function of at least some of the first terminal voltages measured n times and at least some of the second terminal voltages measured n times.

[0062] In Figure 1, the start of the process for determining a reference value is identified by reference numeral 4, the duration of the process by 5, and the start of the expiration of the third time period by 6. The start of the renewed expiration of the third time period is triggered, for example, by the control device 450.

[0063] The expiration of the third time period, see time t2 in Figure 1, is detected by the control device 500. The control device 450 can, for example, be configured to execute the program stored in the memory device 460 in response to the renewed expiration of the third time period in order to control a method according to which: b) a monitoring process for monitoring the state of the rechargeable electrical energy storage device 500 is carried out by b1) switching the at least two switching elements 410, 411 to a first switching state for a predetermined first time period, so that the electrical energy storage device 500 is connected to the electrical resistance network 420 in such a way that the electrical energy storage device 500 is discharged with a current of a first current intensity during the predetermined first time period, and a first terminal voltage between the two terminals 501, 502 of the electrical energy storage device 500 is measured,while the electrical energy storage device 500 is discharged with a current of a first current intensity; b2) subsequently, the at least two switching elements 410, 411 are switched to a second switching state for a predetermined second time period, so that the electrical energy storage device 500 is connected to the electrical resistance network 420 in such a way that the electrical energy storage device 500 is discharged with a current of a second current intensity during the predetermined second time period, and a second terminal voltage is measured between the two connection terminals of the electrical energy storage device 500 while the electrical energy storage device 500 is discharged with the current of a second current intensity,wherein the first and second current strengths are different; b3) the internal resistance 510 of the electrical energy storage device 500 is determined as a function of the first terminal voltage measured in step b1) and the second terminal voltage measured in step b2); b4) the state of the rechargeable electrical energy storage device 500 is determined as a function of the internal resistance determined in step b3) and the reference value provided in step a); and c) step b) is repeated regularly, preferably after each expiration of a third time period, wherein the electrical energy storage device 500 is maintained in a predetermined charge state, i.e., at a predetermined maintenance charge, between two successive monitoring processes.

[0064] It should be noted again that in the exemplary embodiment, as already mentioned above, the first and second time periods can be the same, and the current of the first current intensity is preferably smaller than the current of the second current intensity. This is achieved by the electrical resistance 421 being greater than the electrical resistance 422. Applied to the exemplary monitoring device 400 shown in Figure 3, the control device 450 is designed, for example, to execute the program stored in the memory device 460 in response to the expiration of the third time period in order to control a method according to which: b) a monitoring process for monitoring the state of the rechargeable electrical energy storage device 500 is carried out by b1) closing the switching element 411 and opening the switching element for the predetermined first time period,so that the electrical energy storage device 500 is connected only to the electrical resistor 421 and the electrical energy storage device 500 is discharged with a current of a first current intensity during the predetermined first time period, and a first terminal voltage between the two terminals 501, 502 of the electrical energy storage device 500 is measured by the voltage measuring device 430 while the electrical energy storage device 500 is discharged with a current of a first current intensity; b2) subsequently, for a predetermined second time period, the switching element 411 is opened and the switching element 410 is closed, so that the electrical energy storage device 500 is connected only to the electrical resistor 422 and the electrical energy storage device 500 is discharged with a current of a second current intensity during the predetermined second time period,and a second terminal voltage between the two connection terminals of the electrical energy storage device 500 is measured by means of the voltage measuring device 430 while the electrical energy storage device 500 is being discharged with the current of the second current intensity; b3) the internal resistance 510 of the electrical energy storage device 500 is determined as a function of the first terminal voltage measured in step b1) and the second terminal voltage measured in step b2); b4) the state of the rechargeable electrical energy storage device 500 is determined as a function of the internal resistance determined in step b3) and the reference value provided in step a); and c) step b) is repeated regularly, preferably after each expiration of a third period of time, wherein the electrical energy storage device 500 is maintained in a predetermined charge state, i.e., at a predetermined maintenance charge, between two successive monitoring processes.

[0065] It should be noted that if the reference value is not determined as described above but is specified, a monitoring process as described above can be carried out at time t1 of the current-voltage curve shown in Figure 1.

[0066] It should also be noted that, depending on the implementation, after completion of each monitoring process and, if applicable, after completion of a process for determining a reference value, the voltage measuring device 430 can be electrically separated from the terminals 501 and 502 of the rechargeable battery 500 via a switching element 412.

[0067] For the sake of simplicity, Figure 1 only shows one additional monitoring process at time t3. It should be noted that Figure 1 shows error-free operation of the UPS 300, i.e., there is no power failure at the input terminals 310 and 311 during the period shown, so that the rechargeable battery 500 is operating in standby mode, so to speak.

[0068] However, if the UPS 300 detects a mains voltage failure at the input terminals 310 and 311, the rechargeable battery 500 is connected to the output terminals 312 and 313 via the switch 340. As soon as the mains voltage is again present at the input terminals 310, 311, the battery 500 can be recharged during phase 1 as described above. To determine the state of the rechargeable battery 500, a threshold value can be provided or stored in the memory device 460, for example, whereby step b4) executable by the control device 450 can comprise the following steps:

[0069] - Forming the value between the internal resistance determined in step b3) and the reference value provided in step a); and

[0070] - Comparing the amount formed in step b4) with the threshold value in order to determine the state of the electrical energy storage device.

[0071] A faulty state of the electrical energy storage device 500 can be determined by the control device 450 in step b4) if the calculated amount is greater than or equal to the threshold value. A faulty state of the rechargeable battery 500 can occur, for example, if the rechargeable battery 500 is deeply discharged or if, due to age, the internal resistance exceeds or reaches a predetermined value.

[0072] Preferably, the execution of step c), ie the regular repetition of the monitoring process, is terminated when a faulty state of the electrical energy storage device 500 has been determined.

[0073] At this point, it should be noted that the current of the first current intensity of step a1) and / or step b1) and the current of the second current intensity of step a2) and / or step b1) is preferably each a constant low current and, for example, forms a rectangular current waveform.

[0074] The first and second discharge currents are, for example, between 1 A and 15 A, depending on the capacity or nominal voltage of the rechargeable battery 500 used. The nominal voltage can, for example, be between 6 V and 48 V.

[0075] Furthermore, it should be noted that the internal resistance 510 of the rechargeable battery 500 can be calculated with the monitoring device 400 shown as an example in Figure 1 or the control device 450 in step b3) and / or in step a3) with a parameter n equal to 1 during a monitoring process, for example, according to the following equation:

[0076] Trough resistance (510) = (V1 -V2) / (I1 -I2), where V1 is the measured first terminal voltage, V2 is the measured second terminal voltage, I1 is a measured current of the first current strength and I2 is a measured current of the second current strength.

[0077] In this case, in step b1) or in step a1), a current of first current intensity and in step b2) and / or a2), a current of second current intensity can be measured, for example, with the current measuring device 440, wherein in step b3) or in step a3), the internal resistance of the electrical energy store 500 is thus also determined as a function of the first current intensity measured in step b1) or in step a1) and the second current intensity measured in step b2) or in step a1).

[0078] Alternatively, the internal resistance 510 of the rechargeable battery 500 can be calculated with the monitoring device 400 shown as an example in Figure 1 or the control device 450 in step b3) or step a3) with a parameter n equal to 1 during a monitoring process, for example according to the following equation:

[0079] Trough resistance (510) = R 1 *R2 *(V1 -V2) / (V2*R 1 - V1*R2), where R1 is the value of the electrical resistance 421 , R2 is the value of the electrical resistance 422, V1 is the measured first terminal voltage and V2 is the measured second terminal voltage.

[0080] In this case, the corresponding resistance values ​​of the electrical resistors 421 and 422 are stored, for example, in the memory device 460.

[0081] In order to be able to determine a more precise value for the internal resistance of the rechargeable battery 500, the parameter n can be set to a larger number instead of 1, so that switching between a current of first current intensity and a current of second current intensity can be carried out several times during a monitoring process. In this case, the control device 450 is designed to periodically repeat steps b1) and b2) n times while executing the program stored in the memory device 460 and, in step b3), to determine the internal resistance of the electrical energy storage device 500 as a function of at least some of the first terminal voltages measured n times and at least some of the second terminal voltages measured n times.

[0082] For example, in step b3) or also in step a3), the internal resistance of the rechargeable battery 500 can be determined according to the following formula

[0083] Here, Ri is the internal resistance in ohms of the rechargeable battery 500, n is the number of switching cycles between a current of first intensity and a current of second intensity of a monitoring process, m is the number of evaluated switching cycles, dU is the voltage difference between the first terminal voltage measured at a first current intensity and the second terminal voltage measured at a second current intensity, dl is the current difference between the measured first current intensity and the measured second current intensity, and Rverb is the ohmic resistance of the connecting elements between the terminals 501 and 502 of the rechargeable battery 500 and the connection points 401 and 402 of the monitoring device 400.

[0084] The selection of the m switching cycles to be evaluated, ie the first terminal voltages, measured second terminal voltages and the associated measured first currents and measured second currents measured during the m selected switching cycles, can be made based on a specific selection criterion.

[0085] The control device 450 can be configured to determine the internal resistance, i.e., an ohmic resistance, or the impedance of the rechargeable battery 500 in steps a1) to a3) or b1) to b3), for example, according to a method described in patent application DE 102022 110451.6, filed on April 29, 2022. For further explanation of an exemplary monitoring process, which includes a measuring process for measuring the first and second terminal voltages of the battery 500, reference is now made to Figure 2. In the exemplary monitoring process, steps b1) and b2) are repeated periodically n times, where n is greater than 1, for example, 40. In step b3), the internal resistance of the electrical energy storage device is determined as a function of at least some of the first terminal voltages measured n times and at least some of the second terminal voltages measured n times.

[0086] Figure 2 schematically shows a current-voltage curve diagram 200 of an ideal rechargeable battery 400 during a monitoring process 208 for determining the internal resistance of the rechargeable battery 500 with a first current intensity 212, in Figure 2 also with I O NI, and a second current intensity 214, also designated ION2 in Figure 2. The monitoring process 208 considered in Figure 2, which comprises a measurement process of at least the terminal voltages, is an enlarged representation, for example, of the monitoring process shown schematically in Figure 1 at time t2.

[0087] The first current 212 is drawn from the rechargeable battery 500, for example, when initially only the resistor 421 is electrically connected to the rechargeable battery 500 by means of the switching element 411 during the first period of time, whereas the second current 214 is drawn from the rechargeable battery 500 when only the resistor 422 is electrically connected to the rechargeable battery 500 by means of the switching element 410 during the second period of time. This is achieved by the electrical resistance 421 being greater than the electrical resistance 422. Alternatively, the second current 214 can be drawn from the rechargeable battery 500 by electrically connecting both resistors 421 and 422 in parallel and simultaneously to the rechargeable battery 500 during the second period of time. In this case, the two resistors 421 and 422 can have the same resistance value.

[0088] For the sake of clarity, the exemplary rectangular waveform of the current 204 drawn from the battery 50 during the monitoring process 208, with periodically alternating first and second current intensities, and the corresponding first and second terminal voltages measured at the terminals 501 and 502 of the rechargeable battery 500, are shown in separate diagrams, in which the time abscissas 206 correspond to one another. The first time period during which the first current is drawn and the second time period during which the second current is drawn are the same in the current waveform shown in Figure 2.

[0089] As shown in Figure 2, at the beginning of the monitoring process 208, the first current 212 is drawn from the rechargeable battery 500, followed by the second current 214, with the alternation of the currents being repeated n times. The output voltage 202 of the battery 400 is reduced correspondingly to the current 204. At the first (smaller) current 212, the open-circuit voltage 220 of the battery 400 is reduced by a first amount to the first terminal voltage 222. At the second (larger) current 214, the open-circuit voltage 220 of the battery 400 is reduced by a further amount to the second terminal voltage 224. After the measurement process 208 has ended, the current 204 is zero again and the open-circuit voltage 220 of the battery is (approximately) back to its original value. The changes in voltage 202 correspond to the changes in current 204.

[0090] For example, the control device 450 can be configured to use only a predetermined subset, rather than all of the first and second terminal voltages measured during, for example, 40 measurement periods, to determine the internal resistance. It should be noted that each measurement period during which a first and second terminal voltage of the battery 500 is measured also includes the withdrawal and, if applicable, the measurement of the first current, followed by the withdrawal of the second current. For example, only the last 10 measurement periods, or the terminal voltages and, if applicable, the currents measured during the last 10 measurement periods, can be considered when determining the internal resistance of the rechargeable battery 500.Since the first terminal voltage and the second terminal voltage can vary during the respective current draw, the measurement accuracy can optionally be further improved by averaging the individual measured voltages during the respective current draw. For example, averaging can be performed using the RMS (root mean square) method. Criteria for selecting a suitable subset of measurement periods to be used, or the associated measured terminal voltages and, if applicable, measured currents, are disclosed, for example, in DE 102022 110451.6.

[0091] It should be noted that the preceding exemplary explanations of the functioning of the monitoring device 400, in particular in connection with Figure 2 and the UPS 300, are also valid in connection with the device 700, so that a corresponding repetition of the explanations can be dispensed with.

Claims

1. Method for regularly monitoring the state of a rechargeable electrical energy store (500) which can be connected to an electrical resistance network (420) via at least two switching elements (410, 411) which can be controlled by a control device (450), comprising the following method steps: a) providing a reference value for the internal resistance of the rechargeable electrical energy store (500);b) carrying out a monitoring process for monitoring the state of the rechargeable electrical energy store (500) by b1) switching the at least two switching elements (410, 411) into a first switching state for a predetermined first time period, so that the electrical energy store (500) is connected to the electrical resistance network (420) in such a way that the electrical energy store (500) is discharged with a current of first current intensity during the predetermined first time period, and a first terminal voltage between two connections (501, 502) of the electrical energy store (500) is measured while the electrical energy store (500) is discharged with the current of first current intensity;b2) subsequently, the at least two switching elements (410, 411) are switched to a second switching state for a predetermined second period of time, so that the electrical energy store (500) is connected to the electrical resistance network (420) in such a way that the electrical energy store (500) is discharged with a current of a second current intensity during the predetermined second period of time, and a second terminal voltage is measured between the two connections (501, 502) of the electrical energy store (500) while the electrical energy store (500) is discharged with the current of a second current intensity, wherein the first and second current intensity are different; b3) the internal resistance of the electrical energy store (500) is determined as a function of the first terminal voltage measured in step b1) and the second terminal voltage measured in step b2);b4) the state of the rechargeable electrical energy store (500) as a function of the internal resistance determined in step b3) and that in; step a) is determined; and c) regularly repeating step b), wherein the electrical energy store (500) is kept in a predetermined charge state between two successive monitoring processes.

2. The method according to claim 1, wherein a threshold value is provided and step b4) comprises the following steps: - Forming the value between the internal resistance determined in step b3) and the reference value provided in step a); and - comparing the amount formed in step b4) with the threshold value in order to determine the state of the electrical energy storage device (500).

3. The method according to claim 2, wherein in step b4) a faulty state of the electrical energy storage device (500) is determined if the amount formed is greater than or equal to the threshold value.

4. Method according to one of claims 1 to 3, wherein Step a) includes the following steps: Before carrying out step b), determining the reference value by a1) switching the at least two switching elements (410, 411) into a first switching state for a predetermined first time period, so that the electrical energy store (500) is connected to the electrical resistance network (420) in such a way that the electrical energy store (500) is discharged with a current of first current intensity during the first predetermined time period, and a first terminal voltage between two connections (501, 502) of the electrical energy store (500) is measured while the electrical energy store (500) is discharged with the current of first current intensity;a2) subsequently, the at least two switching elements (410, 411) are switched into a second switching state for a predetermined second period of time, so that the electrical energy store (500) is connected to the electrical resistance network (420) in such a way that the electrical energy store (500) is connected to a second switching state during the second predetermined period of time; current of second current intensity is discharged, and a second terminal voltage is measured between the two connections (501, 502) of the electrical energy store (500) while the electrical energy store (500) is discharged with the current of second current intensity; wherein the first and second current intensity are different; a3) the internal resistance of the electrical energy store (500) is determined as a function of the first terminal voltage measured in step a1) and the second terminal voltage measured in step a2), wherein the determined internal resistance is stored in a storage device (460) as a reference value for the internal resistance of the rechargeable electrical energy store (500).

5. The method according to claim 4, wherein the current of the first current intensity of step a1) and the current of the second current intensity of step a2) are each a constant low current, and / or the current of the first current intensity of step a1) and the current of the second current intensity of step a2) form a rectangular current waveform, and / or the first current intensity is less than the second current intensity, and / or the first and second time periods are the same or different and / or steps a1) and a2) are repeated n times periodically, wherein in step a3) the internal resistance of the electrical energy store (500) is determined as a function of at least some of the first terminal voltages measured n times and at least some of the second terminal voltages measured n times.

6. Method according to one of the preceding claims, wherein steps b1) and b2) are repeated n times periodically, and wherein in step b3) the internal resistance of the electrical energy store (500) is determined as a function of at least some of the first terminal voltages measured n times and at least some of the second terminal voltages measured n times.

7. Method according to one of the preceding claims, wherein the current of first current intensity of step b1) and the current of second current intensity of step b2) are each a constant low current, and / or the current of the first current intensity of step b1) and the current of the second current intensity of step b2) form a rectangular current waveform, and / or the first current intensity is smaller than the second current intensity, and / or the predetermined first and predetermined second time periods are the same or different.

8. Method according to one of the preceding claims, wherein in step b1) the first current intensity is further measured and in step b2) the second current intensity is further measured, wherein in step b3) the internal resistance of the electrical energy store (500) is also determined as a function of the first current intensity measured in step b1) and the second current intensity measured in step b2).

9. Method according to one of the preceding claims, wherein Step c) is terminated when a faulty state of the electrical energy storage device (500) has been detected.

10. Device (700), in particular a charging device, for regularly monitoring the state of a rechargeable electrical energy storage device (500), comprising: a charging controller (600) electrically connectable to a rechargeable electrical energy storage device (500) and designed to electrically charge the rechargeable electrical energy storage device (500) and / or to maintain it in a predetermined charge state, and a monitoring device (400) having the following features: an electrical resistance network (420) connectable to the rechargeable electrical energy storage device (500) via at least a first and a second switching element (410, 411), a voltage measuring device (430) electrically connectable to the rechargeable electrical energy storage device (500) and designed to measure a terminal voltage applied to the rechargeable electrical energy storage device (500), a storage device (460),in which a program and a reference value for the internal resistance of the rechargeable electrical energy storage device (500) are stored, and, a control device (450) which is designed to cause the device to carry out the method according to one of the preceding claims by executing the stored program.

11. Device according to claim 10, wherein a threshold value is stored in the memory device (460), and wherein the control device (450) is designed to cause the device, upon execution of the stored program, to form the amount between the determined internal resistance and the stored reference value and to compare the amount formed with the threshold value in order to determine the state of the electrical energy storage device (500).

12. Device according to claim 10 or 11, further comprising a current measuring device (440) which is designed to measure a discharge current which can be taken from the rechargeable electrical energy storage device (500).

13. Device according to one of claims 10 to 12, wherein the electrical resistance network (420) has at least one first electrical resistance (421) which is electrically connectable to the electrical energy store (500) via the first switching element (411), and at least one second electrical resistance (422) which is electrically connectable to the electrical energy store (500) via the second switching element (410).

14. Device according to one of claims 10 to 13, wherein the first and second switching elements (410, 411) are each designed as a semiconductor switch or electromechanical switch 15. Uninterruptible power supply (300) comprising a device according to one of claims 10 to 14.

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