Reference voltage for a battery

Abstract

Accumulator arrangement (100, 200, 300), with - a plurality of modules, each containing at least one accumulator cell (102-124); - a plurality of module monitoring devices (130, 132, 134; 230, 232; 234; 330, 332, 334), each monitoring at least one module; - an accumulator monitoring device (126; 226; 326) designed to monitor the accumulator arrangement (100, 200, 300); - a first reference voltage source (136; 335) configured to maintain a reference voltage within a tolerance range for a first period of time; and - a plurality of second reference voltage sources (138, 140; 337) configured to maintain a reference voltage within a tolerance range over a second period, wherein the first period is longer than the second period; - wherein the first reference voltage source (136; 335) is arranged in the accumulator monitoring device (326) or in one of the module monitoring devices (130; 230); and - wherein a second reference voltage source (138, 140; 337) is arranged in those module monitoring devices (132, 134; 232; 234; 330, 332, 334) in which no first reference voltage source (136; 335) is arranged; - furthermore comprising an adjustment device (128; 228;328) which is designed to determine and / or change the reference voltage of the second reference voltage source (138, 140; 337) on the basis of the reference voltage of the first reference voltage source (136; 335).

Description

[0001] The present invention relates to the generation of reference voltages in an accumulator arrangement that requires fewer high-precision components to meet safety requirements.

[0002] A high-voltage battery of an electric vehicle generally comprises several battery cells connected in series and a battery monitoring system, also known as a battery management system (BMS). The battery monitoring system comprises electronic hardware and software.

[0003] In a battery arrangement with a plurality of battery cells, particularly lithium-ion cells, the voltage of each battery cell or each module with a plurality of battery cells must be monitored separately for safety reasons, and a method for charge equalization between the battery cells must be provided. For this purpose, special monitoring devices with integrated circuits, also referred to as front-end chips (FE chips), are used. Such a monitoring device can typically monitor 4 to 16 battery cells. There are also monitoring devices that can monitor only one battery cell. Since a typical battery arrangement for an electrically powered motor vehicle can comprise more than 80 battery cells, several of the previously described monitoring devices are used.

[0004] It is known in the prior art that a plurality of the aforementioned monitoring devices are connected via a so-called daisy-chain bus, whereby these devices can exchange data with a battery monitoring device. There is no standardization for a daisy-chain bus. The daisy-chain bus is usually implemented manufacturer-specifically. Typically, monitoring devices and the battery monitoring device communicate via a plurality of daisy-chain buses arranged in a chain. The reference potential of each monitoring device is the potential of the negative pole of the battery cell with the lowest potential. This requires that communication be carried out by means of galvanic isolation or that the communication signal in each monitoring device be raised to the potential of the subsequent monitoring device, for example, using a charge pump.

[0005] As previously mentioned, for safety reasons, the voltage of each individual battery cell is measured using a monitoring device. The maximum permissible inaccuracy of such a voltage measurement is in the range of a few mV and must be guaranteed over the entire service life of the battery assembly. For this purpose, one or two highly accurate and stable reference voltage sources are integrated into each monitoring device, each of which can generate the reference voltage according to a different physical principle. Two reference voltages are typically required to meet the safety requirements of ISO 26262 corresponding to Automotive Safety Integrity Level (ASIL) C or D. Such reference voltage sources significantly increase the cost of the monitoring devices.

[0006] Soldering the monitoring devices onto a circuit board can affect the accuracy of the reference voltage sources. Therefore, calibration of the entire monitoring devices is often performed at the end of production. It goes without saying that calibration also significantly increases the cost of the monitoring device and thus the battery assembly.

[0007] DE 10 2006 005 334 A1 discloses a plurality of battery cells with a so-called rail line. The rail line serves as a power line, communication line, and reference voltage line for several cell groups. Several cell groups are connected in parallel to the rail line, and the rail line generates the same reference potential for all battery cell groups.

[0008] Such a prior-art system has the disadvantage that, due to the common reference potential, signals on the rail line can have a voltage of several hundred volts compared to the potential of the battery cells. Such a circuit requires galvanic isolation and boosting the signals to the potential of the corresponding battery cell. It is clear that such a circuit is complex.

[0009] US 2014 / 0 079 963 A1 discloses a control method for a battery system in which the total voltage of the battery cells is transmitted as information to a higher-level controller. The higher-level controller issues a discharge command or similar to a lower-level controller whose voltage is higher than that of the other controllers. Thus, the voltage curve of the respective battery cells is balanced.

[0010] The object of the invention is to provide an improved accumulator arrangement in which a reference voltage is generated in a more efficient manner.

[0011] The object of the invention is achieved by an accumulator arrangement according to claim 1. The dependent claims specify preferred embodiments.

[0012] A rechargeable battery arrangement according to the invention comprises a plurality of modules, each having at least one rechargeable battery cell, a plurality of module monitoring devices, each monitoring at least one module, and a rechargeable battery monitoring device designed to monitor the rechargeable battery arrangement. A first reference voltage source is designed to generate and / or maintain a reference voltage over a first period of time within a tolerance range. A plurality of second reference voltage sources are designed to generate and / or maintain a reference voltage over a second period of time within a tolerance range, wherein the first period of time is longer than the second period of time. The first period of time can extend over several years, preferably over the entire service life of the rechargeable battery arrangement. The second period of time can extend over at least one day, preferably over several days.

[0013] The first reference voltage source can be arranged in the battery monitoring device or in a module monitoring device. A second reference voltage source can be arranged in the battery monitoring device if no first reference voltage source is arranged in the battery monitoring device. A second reference voltage source can be arranged in those module monitoring devices in which no first reference voltage source is arranged.

[0014] The accumulator arrangement further comprises a calibration device configured to determine and / or change the reference voltage of the second reference voltage source based on the reference voltage of the first reference voltage source. The invention has the advantage that the second reference voltage source only has to maintain the output second reference voltage within the prescribed tolerance range for a shorter period of time. This allows the second reference voltage source to be designed with less complexity.

[0015] Based on the first reference voltage, a first value of a voltage source can be determined. Using the second reference voltage source, a second value of the voltage of the voltage source can be determined. By comparing the first value with the second value, the second reference voltage of the second reference voltage source can be determined and / or changed. The voltage measurement can be performed, for example, using an analog-to-digital converter, with a higher voltage being scaled down if necessary, for example, using a voltage divider with two resistors connected in series.If necessary, a voltage must be measured between two potentials, whereby, if one or both potentials are higher than the reference potential of a voltage measuring system, the voltage of each potential can be measured with respect to the reference potential of the voltage measuring system according to the principle described above, and then a difference can be calculated which corresponds to the desired voltage.

[0016] The first reference voltage source can be located in the battery monitoring device. A second reference voltage source can be located in each module monitoring device. In this embodiment, all module monitoring devices are identical.

[0017] The first reference voltage source can be arranged in one of the module monitoring devices. A second reference voltage source can be arranged in each module monitoring device in which no first reference voltage source is arranged. In this embodiment, no reference voltage source needs to be arranged in the battery monitoring device.

[0018] The calibration device can be configured to instruct the accumulator monitoring device, which has a first reference voltage source, to measure a first value of the cell voltage of a predetermined accumulator cell of a predetermined module, which has a second reference voltage source, based on the first reference voltage. The calibration device can instruct the module monitoring device of the predetermined module to measure a second value of the cell voltage of the predetermined accumulator cell of the predetermined module based on the second reference voltage. The calibration device can compare the first value with the second value and adjust the second reference voltage based on the first value and the second value.

[0019] The calibration device can be configured to instruct a first module monitoring device, which has a first reference voltage source, to measure a first value of the cell voltage of a predetermined battery cell of a second module, which has a second reference voltage source, based on the first reference voltage. The calibration device can instruct the module monitoring device of the second module to measure a second value of the cell voltage of the predetermined battery cell of the second module based on the second reference voltage. The first value can be compared with the second value. The second reference voltage can be adjusted based on the first value and the second value.

[0020] The predetermined battery cell may be the battery cell with the lowest potential of a plurality of battery cells of the predetermined module or the first module.

[0021] The communication between the module monitoring devices and with the battery monitoring device as well as the transmission of voltage values ​​between them can be carried out by means of the daisy chain structures and / or a daisy chain bus.

[0022] The comparison device can be configured to instruct the battery monitoring device, which has a first reference voltage source, to generate a comparison voltage relative to a predetermined battery cell of a first module. The adjustment device can instruct the battery monitoring device to measure a first value of the comparison voltage based on the first reference voltage. The adjustment device can instruct the module monitoring device of a predetermined module to measure a second value of a comparison voltage based on the second reference voltage. The first value can be compared with the second value, and the second reference voltage can be adjusted based on the first value and the second value. The comparison voltage can be generated relative to the battery cell with the lowest potential of the module with the lowest potential.

[0023] The adjustment device can be configured to instruct a first module monitoring device of a first module, which has a first reference voltage source, to generate a comparison voltage with respect to a predetermined battery cell of a first module. The adjustment device can instruct the first module monitoring device to measure a first value of the comparison voltage based on the first reference voltage. The adjustment device can instruct the module monitoring device of a second module to measure a second value of the comparison voltage based on the second reference voltage. The adjustment device can compare the first value with the second value and adjust the reference voltage based on the first value and the second value. The comparison voltage can be generated with respect to the battery cell with the highest potential of the first module.

[0024] The invention will now be explained in more detail with reference to the accompanying figures, which are given for illustrative purposes and are not to be construed as limiting. Fig. 1 shows a first embodiment of the invention with additional voltage taps; Fig. 2 a second embodiment of the invention with a generated reference voltage; and Fig. 3 a third embodiment of the invention, in which the reference voltage source is arranged in the battery monitoring device.

[0025] It will be Fig. 1, which shows a first embodiment of the invention. A battery assembly 100 according to the first embodiment of the invention comprises a plurality of battery cells 102-124 connected in series. The plurality of battery cells 102-124 are connected via a battery monitoring device 126 to an electrical system of an electrically powered vehicle having an electric machine and an inverter. The operation of an electrically powered vehicle is known to those skilled in the art and need not be repeated here.

[0026] In Fig. 1 shows that the battery cells 102-108 are connected to a first module monitoring device 130, the battery cells 110-116 to a second module monitoring device 132, and the battery cells 128-124 to a third module monitoring device 134. A module monitoring device can measure the voltage of each battery cell connected to it. The module monitoring devices 130, 132, 134 are connected to each other and to the battery monitoring device 126 via a bus 142, for example, a daisy-chain bus.

[0027] The first module monitoring device 130 comprises a first reference voltage source 136 that generates a first reference voltage. The second module monitoring device 132 comprises a second reference voltage source 138 that generates a second reference voltage, and the third module monitoring device 134 comprises a second reference voltage source 140 that generates a second reference voltage. The first reference voltage source 136 is designed such that the reference voltage remains within a predetermined tolerance band for a longer period of time than the second reference voltage generated by the second reference voltage source 138, 140. Preferably, the first reference voltage source 136 maintains the reference voltage within the predetermined tolerance band over the entire service life of the first module monitoring device 130 or the accumulator arrangement 100. The tolerance band can cover a range of a few mV.The first reference voltage source 136 may include a plurality of voltage sources that generate the reference voltage using a different physical principle.

[0028] Since the second reference voltage source 138, 140 can only maintain the second reference voltage within a predetermined tolerance band for a short period of time, the second reference voltage source 138, 140 must be calibrated regularly. The second reference voltage source 138, 140 is calibrated relative to or with the first reference voltage source 136, since the latter can maintain the reference voltage within a tolerance band for a longer period of time. The second reference voltage source 138, 140 is preferably calibrated when the vehicle is switched on or before the accumulator arrangement 100 is connected to the drive system and / or on-board electrical system of the motor vehicle using contactors (not shown). This time is preferred because at this time, fewer potential sources of interference within the motor vehicle are supplied with power.

[0029] The module monitoring devices 130, 132, 134 can include a calibration device 128. The calibration device 128 can also be distributed. It is also possible for the calibration device 128 to be located at least partially within the battery monitoring device 126.

[0030] The balancing device 128 of the first module monitoring device 130 is connected via a first balancing line 144 to the higher potential of the accumulator cell 110 with the lowest potential, which is connected to the second monitoring device 132. The lower potential of the accumulator cell 110 corresponds to the higher potential of the accumulator cell 108 with the highest potential, which is connected to the first module monitoring device 130. The first module monitoring device 130 measures the voltage of the accumulator cell 110 with the lowest potential, which is connected to the second module monitoring device 132, using the first reference voltage of the first reference voltage source 136. For this purpose, for example, an analog-to-digital converter can be used, which measures the voltage between the lowest potential of the cell 108 and the highest potential of the cell 110 via a voltage divider with two resistors connected in series.By using a voltage divider with a suitable division ratio, it is avoided that a voltage with a potential higher than the highest potential of all cells connected to the module monitoring device 130 must be measured. The voltage of cell 108, which is already measured by the module monitoring device 130, is subtracted from the voltage measured in this way to obtain the desired voltage of cell 110. The voltage value thus measured and / or calculated is stored as a first voltage value. The first voltage value can be transferred to the second module monitoring device 132 as a digital or analog value.

[0031] The second module monitoring device 132 uses the calibration device 128 to measure the voltage of the accumulator cell 110 with the lowest potential, which is connected to the second module monitoring device 132, using the second reference voltage generated by the second reference voltage source 138. This measured voltage value is stored as a second voltage value. The first voltage value and the second voltage value are then compared. Based on the difference between the first voltage value and the second voltage value, the reference voltage of the second reference voltage source 138 can be calibrated, for example, adjusted proportionally to the difference between the first voltage value and the second voltage value.

[0032] By means of the adjustment devices 128 of the second module monitoring device 132 and the adjustment device 128 of the third module monitoring device 134, the second reference voltage source 140 of the third module monitoring device 134 is adjusted as previously described with regard to the second reference voltage source 138 of the second module monitoring device 132.

[0033] The first embodiment has the advantage that only one reference voltage source with a high accuracy is required. Furthermore, there is no galvanic isolation of the module monitoring devices 130, 132, 134 from communication signals. Fig. 2, which shows a second embodiment of a rechargeable battery arrangement 200. The second embodiment of the rechargeable battery arrangement 200 essentially corresponds to the first embodiment of the rechargeable battery arrangement 100, with the exception that the first module monitoring device 230, the second module monitoring device 232, and the third module monitoring device 234 have a second embodiment of a balancing device 228. Furthermore, the second embodiment of the rechargeable battery arrangement 200 additionally has a voltage transfer line 244, with which a voltage can be transferred from the first module monitoring device 230 to the second module monitoring device 232, and a voltage transfer line 246, via which a voltage can be transferred from the second module monitoring device 232 to the third module monitoring device 234.The operation of the second embodiment of the accumulator arrangement 200 differs from the operation of the first embodiment of the accumulator arrangement 100 only with regard to the adjustment, so that for the sake of conciseness, only the adjustment will be described. The first module monitoring device 230 generates a voltage that is higher than the highest voltage of the accumulator cell 108, which has the highest potential connected to the first module monitoring device 230. The generated voltage is measured as a first voltage value based on the first reference voltage of the first reference voltage source. The generated voltage is transferred to the second module monitoring device 232 via the voltage transfer line 244. Furthermore, the first voltage value is transferred to the second module monitoring device 232, for example digitally, via the bus 142.Subsequently, the calibration device 228 of the second module monitoring device 232 measures the voltage generated by the first module monitoring device 230, which was transferred via the voltage transfer line 244, as the second voltage value. The calibration device 228 of the second module monitoring device 232 compares the measured voltages on the transfer line 244 with the first voltage value transferred by the bus 140. The second voltage value was measured using the second reference voltage of the second reference voltage source 138. The second voltage value is compared with the first voltage value. Based on the difference between the first voltage value and the second voltage value, the second reference voltage of the second reference voltage source 138 can be calibrated.

[0034] The second reference voltage of the second reference voltage source 140 of the third module monitoring device 234 is calibrated by the calibrating device 228 of the second module monitoring device 232 and the calibrating device 228 of the third module monitoring device 234 using a voltage value generated by the second module monitoring device 232, which is transferred via the transfer line 246, as previously described with regard to the second reference voltage of the second reference voltage source 138. For the sake of conciseness, the description will not be repeated.

[0035] The generated voltage can be generated, for example, using a charge pump. This embodiment has the advantage that fewer high-precision reference voltage sources are required. It has the disadvantage that galvanic isolation of the module monitoring device 330, 332, 234 from the communication path cannot be achieved without the use of additional components, such as an isolation transformer. In this case, the charge pump must generate an AC voltage signal. The AC voltage signal can be measured with respect to peak values ​​or any desired average value.

[0036] It will be Fig.3, which shows a third embodiment of a battery assembly 300, the operation of which essentially corresponds to the operation of the first embodiment of the battery assembly 100 or the second embodiment of the battery assembly 200. For this reason, only the structural differences between the third embodiment of the battery assembly 300 and the first embodiment of the battery assembly 100 or the second embodiment of the battery assembly 200 will be described.

[0037] A first reference voltage source 335 is arranged in a battery monitoring device 326, which generates a reference voltage that remains within a predetermined tolerance band over a long period of time. A second reference voltage source 337 is arranged in a first module monitoring device 330, a second reference voltage source 138 is arranged in a second module monitoring device 332, and a second reference voltage source 140 is arranged in a third module monitoring device 334. The reference voltages of the second reference voltage sources 138, 140, and 337 remain within a tolerance band for a shorter period of time than the reference voltage of the first reference voltage source 335.

[0038] To enable the second reference voltage sources 138, 140, 337 to be calibrated, a calibrating device 328 is arranged in the module monitoring device 326, a calibrating device 328 in the first module monitoring device 330, a calibrating device 328 in the second module monitoring device 332, and a calibrating device 328 in the third module monitoring device 334. The calibrating of the second reference voltage sources of a module monitoring device 330, 332, 334 can be performed as previously described with regard to the first embodiment of the accumulator arrangement 100 and the second embodiment of the accumulator arrangement 200.

[0039] This embodiment has the advantage that all module monitoring devices are identical, which, depending on the number of units, means lower production costs. Furthermore, the high-precision reference voltage source in the battery monitoring device can also be used for other purposes, for example, for current measurement, measurement of the total voltage of the battery arrangement, or the like. This embodiment has the disadvantage that additional calibration is required between the battery monitoring device and the first module monitoring device 330.

[0040] The invention has the advantage that fewer highly accurate and thus complex reference voltage sources are required. This can reduce the manufacturing costs of a battery assembly.

Claims

[1] Accumulator arrangement (100, 200, 300), with - a plurality of modules, each having at least one accumulator cell (102-124); - a plurality of module monitoring devices (130, 132, 134; 230, 232; 234; 330, 332, 334), each monitoring at least one module; - an accumulator monitoring device (126; 226; 326) designed to monitor the accumulator arrangement (100, 200, 300); - a first reference voltage source (136; 335) configured to maintain a reference voltage within a tolerance range over a first period of time; and - a plurality of second reference voltage sources (138, 140; 337) configured to maintain a reference voltage within a tolerance range over a second period of time, the first period of time being longer than the second period of time; - wherein the first reference voltage source (136; 335) is arranged in the accumulator monitoring device (326) or in one of the module monitoring devices (130; 230); and - wherein a second reference voltage source (138, 140; 337) is arranged in those module monitoring devices (132, 134; 232; 234; 330, 332, 334) in which no first reference voltage source (136; 335) is arranged; - further comprising an adjustment device (128; 228; 328) which is designed to determine and / or change the reference voltage of the second reference voltage source (138, 140; 337) on the basis of the reference voltage of the first reference voltage source (136; 335). [2] Accumulator arrangement (300) according to claim 1, characterized bythat the first reference voltage source (335) is arranged in the accumulator monitoring device (326) and a second reference voltage source (138, 140; 337) is arranged in each module monitoring device (330, 332, 334). [3] Accumulator arrangement (100; 200) according to claim 1, characterized by that the first reference voltage source (136) is arranged in one of the module monitoring devices (130; 230) and a second reference voltage source (138, 140) is arranged in each module monitoring device (132, 134; 232, 234) in which no first reference voltage source (136) is arranged. [4] Accumulator arrangement (300) according to claim 1 or 2, characterized by that the adjustment device (328) is designed to - instructing the accumulator monitoring device (326), which has a first reference voltage source (335), to measure a first value of the cell voltage of a predetermined accumulator cell (102-124) of a predetermined module, to which a module monitoring device (330, 332, 334) is connected, which has a second reference voltage source (138, 140, 337), on the basis of the first reference voltage; - instructing the module monitoring device (330, 332, 334) of the predetermined module to measure a second value of the cell voltage of the predetermined accumulator cell of the predetermined module (330, 332, 334) based on the second reference voltage; - compare the first value with the second value; and - adjust the second reference voltage based on the first value and the second value. [5] Accumulator arrangement (100) according to claim 1 or 3, characterized by that the adjustment device is designed to - instructing a first module monitoring device (130) having a first reference voltage source (136) to measure a first value of the cell voltage of a predetermined accumulator cell (110-116) of a second module, to which a module monitoring device (132) having a second reference voltage source (138) is connected, on the basis of the first reference voltage; - instructing the module monitoring device (132) of the second module to measure a second value of the cell voltage of the predetermined accumulator cell of the second module based on the second reference voltage; - compare the first value with the second value; and - adjust the second reference voltage based on the first value and the second value. [6] Accumulator arrangement according to claim 5, characterized bythat the predetermined accumulator cell is the accumulator cell (102; 110) with the lowest potential of a plurality of accumulator cells of the predetermined module or the first module. [7] Accumulator arrangement (300) according to claim 1 or 2, characterized by that the adjustment device (328) is designed to - instructing the accumulator monitoring device (326), which has a first reference voltage source (335), to generate a comparison voltage with respect to a predetermined accumulator cell (102) of a first module; - instruct the battery monitoring device (326) to measure a first value of the comparison voltage based on the first reference voltage; - instructing the module monitoring device (330) of a predetermined module to measure a second value of the comparison voltage based on the second reference voltage; - compare the first value with the second value; and - adjust the second reference voltage based on the first value and the second value. [8] Accumulator arrangement (300) according to claim 7, characterized by that the reference voltage is generated relative to the accumulator cell (102) with the lowest potential of the module with the lowest potential. [9] Accumulator arrangement (200) according to claim 1 or 3, characterized by that the adjustment device (228) is designed to - instructing a first module monitoring device (230) of a first module, which has a first reference voltage source (136), to generate a comparison voltage with respect to a predetermined accumulator cell (102-108) of a first module; - instruct the first module monitoring device (230) to measure a first value of the comparison voltage based on the first reference voltage; - instruct the module monitoring device (232) of a second module to measure a second value of the comparison voltage based on the second reference voltage; - compare the first value with the second value; and - adjust the second reference voltage based on the first value and the second value. [10] Accumulator arrangement (200) according to claim 9, characterized by that the reference voltage is generated relative to the accumulator cell (108) with the highest potential of the first module.

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