DE102020113498A1 - Method and device for monitoring a battery cell arrangement, battery cell arrangement and use in a vehicle, in particular an aircraft - Google Patents

Abstract

A method and a device are proposed for monitoring a battery cell arrangement (1) for temperature deviations of individual battery cells (2) from a normal operating temperature and for operating the battery cell arrangement (1), with the following steps: ), preferably at least a quarter or a third or half of the battery cells (2), most preferably at least three quarters of the battery cells (2), in particular all battery cells (2), in the battery cell arrangement (1) with an electrical resistance element (4) with a temperature-dependent electrical resistance value; b) connecting the resistance elements (4) in the form of at least one electrical series circuit (4a, 4b); c) during operation of the battery cell arrangement (1), continuous measurement of a series resistance of the resistance elements (4) in the series circuit (4a, 4b) and comparing the measured series resistance with a comparison value; d) Output of a monitoring signal (MS) as a function of a result of the comparison. In this way, the circuit complexity can be reduced with unchanged good measurement coverage compared to previously known methods.

Description

The invention relates to a method for monitoring a battery cell arrangement for temperature deviations of individual battery cells from a normal operating temperature and for operating the battery cell arrangement according to claim 1.

The invention further relates to a device for monitoring a battery cell arrangement for temperature deviations of individual battery cells from a normal operating temperature and for operating the battery cell arrangement according to claim 8.

The invention further relates to a battery cell arrangement with a plurality of battery cells according to claim 15 and a use of the device according to the invention according to claim 19.

For modern battery cell systems or batteries or accumulators, in particular for lithium-ion batteries, battery management systems (BMS) are used to monitor cell voltages and temperatures. Such battery management systems are in particular able to switch off a battery or prevent the use of a battery if deviations occur during operation, in particular if the operating temperature of a battery or individual battery cells is a temperature to be expected during normal operation ("normal operating temperature") ) exceeds.

For this purpose, a number of temperature sensors are provided within the battery cell arrangement and connected to the BMS. The temperature monitoring can in particular take place using temperature measuring elements which are designed as thermistors in the form of PTC or NTC resistors. PTC resistors are electrical resistors with a positive temperature coefficient, which means that when the temperature rises, they react with a sharp increase in electrical (ohmic) resistance. On the other hand, NTC resistors are resistors with a negative temperature coefficient, which accordingly react to increases in temperature with a sharp drop in electrical resistance.

For large batteries, especially for batteries with a large number of small, cylindrical battery cells, not every battery cell is equipped with a temperature sensor according to the state of the art, since the number of measuring channels that would be required on the BMS would be correspondingly very large, because hundreds or even thousands of sensors could be used.

This is in the attached 1 shown. 1 shows a battery cell arrangement 1 according to the prior art with a large number of battery cells 2 , which are each designed as cylindrical cells. For the sake of clarity, in 1 only a few battery cells 2 explicitly designated. Reference number 3 symbolizes a battery management system (BMS). Every battery cell 2 is with a temperature measuring element in the form of an electrical resistance element 4th provided as described above. Each of the resistance elements 4th is via a pair of electrical wires 5 with the BMS 3 tied together. For the sake of clarity, there are again only a few resistance elements 4th and wire pairs 5 explicitly designated. In this way, there is a disadvantageous high connection or wiring expenditure, and the BMS 3 is designed correspondingly complex and heavy, as there are a large number of measurement channels (one measurement channel per battery cell 2 ) needed.

Each temperature sensor (temperature measuring element) requires in BMS 3 associated evaluation electronics, either in the form of an analog-to-digital converter to obtain the temperature data, or - in the simplest case - in the form of a comparator that makes a comparison with a predefined threshold value. The effort and costs involved in integrating these electronic circuits into the BMS 3 connected so that it can work together with a large number of temperature sensors are very high.

To remedy this, the state of the art, as described in 2 is shown, proposed the number of temperature sensors or resistance elements 4th to reduce to a reasonable level, for example by only every fifth or only every twentieth battery cell 2 with a resistance element 4th is equipped. This reduces the coverage and accuracy of the temperature monitoring accordingly. A corresponding disadvantage is that there are a large number of battery cells 2 with unknown temperature.

The design according to 2 has opposite 1 the advantage of having fewer resistance elements 4th and wire pairs 5 are needed. In addition, the BMS 3 be designed more simply. The disadvantage here, however, is that due to the large number of battery cells 2 with an unknown temperature, there is an increased risk of catastrophic failure of the battery cell arrangement 1 altogether exists. As already mentioned, it is normally provided that in the event of an increased temperature even in only one battery cell 2 Protective measures are taken, for example switching off the battery cell arrangement 1 . However, if an increased cell temperature goes undetected, as in the case of the 2 can easily be done this performs possibly critical overheating and ignition of the battery cell arrangement 1 . The reduced temperature coverage according to the prior art in 2 therefore represents a significant security risk.

The invention is based on the object of providing a remedy here and of specifying a method and a device for monitoring battery cell arrangements, which is associated with increased operational reliability with a reduced structural effort compared to the prior art. The invention is also based on the object of specifying an improved battery cell arrangement and a preferred use of the device according to the invention and the method according to the invention.

The above-mentioned objects are achieved according to the invention by a method for monitoring a battery cell arrangement with the features of claim 1, by a device for monitoring a battery cell arrangement with the features of claim 8, by a battery cell arrangement with the features of claim 15 as well as by the uses defined in claim 19. Advantageous further developments are given in the subclaims.

1. a) Versehen einer Vielzahl der Batteriezellen, vorzugsweise zumindest von einem Viertel oder einem Drittel oder der Hälfte der Batteriezellen, höchst vorzugsweise zumindest von drei Vierteln der Batteriezellen, insbesondere aller Batteriezellen, in der Batteriezellen-Anordnung mit einem elektrischen Widerstandselement mit einem temperaturabhängigen elektrischen Widerstandswert;
2. b) Verbinden der Widerstandselemente in Form wenigstens einer elektrischen Reihenschaltung;
3. c) im Betrieb der Batteriezellen-Anordnung, fortlaufendes Messen eines Reihenwiderstands der Widerstandselemente in der Reihenschaltung und Vergleichen des gemessenen Reihenwiderstands mit einem Vergleichswert;
4. d) Ausgeben eines Überwachungssignals in Abhängigkeit von einem Ergebnis des Vergleichs.

A method according to the invention for monitoring a battery cell arrangement for temperature deviations of individual battery cells from a normal operating temperature and for operating the battery cell arrangement comprises the following steps:

1. a) Providing a plurality of the battery cells, preferably at least a quarter or a third or half of the battery cells, most preferably at least three quarters of the battery cells, in particular all battery cells, in the battery cell arrangement with an electrical resistance element with a temperature-dependent electrical resistance value;
2. b) connecting the resistance elements in the form of at least one electrical series circuit;
3. c) during operation of the battery cell arrangement, continuously measuring a series resistance of the resistance elements in the series circuit and comparing the measured series resistance with a comparison value;
4. d) outputting a monitoring signal as a function of a result of the comparison.

A device according to the invention for monitoring a battery cell arrangement for temperature deviations of individual battery cells from a normal operating temperature and for operating the battery cell arrangement has: a plurality of electrical resistance elements, each with a temperature-dependent electrical resistance value, the plurality of preferably at least a quarter, at least a third, corresponds to at least one half, at least three quarters or all of the battery cells from a number of battery cells to be monitored, which resistance elements are connected to one another in the form of at least one electrical series circuit; and a measurement and comparison device connected to the series circuit via an electrical conductor pair for measuring a series resistance of the resistance elements in the series circuit and for comparing the measured series resistance with a comparison value, which measurement and comparison device is further designed to generate and output a monitoring signal as a function of a result of the comparison.

A battery cell arrangement according to the invention comprises a multiplicity of battery cells, preferably essentially identical battery cells, and a device according to the invention.

A use according to the invention of the device according to the invention or the arrangement according to the invention includes the use in a vehicle, preferably an aircraft. The aircraft can preferably be a multi-rotor aircraft, most preferably an aircraft that takes off and lands vertically. This aircraft can have distributed and preferably electrically driven drive units, which drive units are supplied with electrical energy from at least one battery cell arrangement according to the invention. For this purpose, at least one battery cell arrangement can preferably be provided per drive unit.

Since according to the invention the resistance elements used for temperature measurement, which in turn can be PTC or NTC resistance elements or other suitable, temperature-dependent resistance elements, are connected in the form of at least one electrical series circuit and combined in terms of circuitry, each individual Battery cell (in contrast to the configuration according to 2 ) manage the monitoring with a greatly reduced number of measuring channels and evaluation units. Contrary to the design according to 1 the number of measurement channels is greatly reduced compared to the number of battery cells. Advantageously, only one measuring channel is used for about 20 to 50 battery cells.

• 1) eine Temperaturmessung, die wie im Stand der Technik (vgl. 2) mit einer reduzierten Anzahl von Temperatursensoren (Widerstandselementen) durchgeführt wird, und
• 2) das Erkennen einer erhöhten Temperatur, was mit einer zweiten Anzahl von Temperatursensoren (Widerstandselementen) erreicht wird, wobei jede Batteriezelle ein solches Widerstandselement aufweist (vgl. 1), während das BMS erfindungsgemäß aufgrund der verwendeten Reihenschaltung mit einer stark reduzierten Anzahl von Messkanälen auskommt.

In a further development of the invention, the temperature monitoring function of the BMS can effectively be divided into two sub-functions:

• 1) a temperature measurement that, as in the prior art (cf. 2 ) is carried out with a reduced number of temperature sensors (resistance elements), and
• 2) the detection of an increased temperature, which is achieved with a second number of temperature sensors (resistance elements), each battery cell having such a resistance element (cf. 1 ), while the BMS according to the invention gets by with a greatly reduced number of measurement channels due to the series connection used.

The present description essentially deals with the second-mentioned aspect (the second sub-function), because the first-mentioned aspect is known as such from the prior art.

During operation of the battery cell arrangement, according to the invention, a continuous measurement of a series resistance of the resistor elements in the series circuit takes place, and the measured series resistance value is compared with a comparison value, so that a monitoring signal can be output as a function of a result of this comparison. This monitoring signal can in particular indicate whether the measured series resistance is above or below the comparison value. Depending on the type of electrical resistance elements used, a sharp increase in the series resistance (with PTC elements) or a sharp decrease in the series resistance (with NTC elements) can indicate a deviation of a single battery cell from the normal operating temperature. Because a plurality of resistance elements are combined to form a series circuit, the battery cell arrangement can be completely metrologically covered without increasing the structural effort, particularly in the wiring and / or in the design of the BMS.

In the course of a further development of the method according to the invention, it is provided that the monitoring signal is used to output a warning message (e.g. to a pilot) or even to switch off the battery cell arrangement directly if the measured series resistance exceeds the comparison value. In this way, destruction of the battery cell arrangement can be effectively prevented. The development presented above relates specifically to the use of PTC elements as resistance elements. If NTC elements are used, provision can accordingly be made for the battery cell arrangement to be switched off if the measured series resistance falls below the comparison value.

In a particularly preferred development, it is provided that the battery cells in step a) are each provided with essentially identical electrical resistance elements, ie within the scope of customary manufacturing tolerances, or with resistance elements with essentially identical thermal resistance coefficients. This facilitates the evaluation and reduces the design effort.

In yet another further development of the method according to the invention, a maximum and minimum series resistance of the resistor elements in the series circuit can be measured at the normal operating temperature or within the limits of a normal operating temperature range and used to establish the comparison value before step c). In this way, harmful temperature increases can then easily be detected during operation. Here and in the following, “normal operating temperature” is understood to mean an operating temperature that may be (slightly) higher than an initial or resting temperature, but to an extent that is harmless to the individual battery cells. For example, the normal operating temperature or the normal operating temperature range in a typical lithium-ion battery cell arrangement can be between -20 ° C and 60 ° C, whereas a critical temperature increase to be detected would be around 80 ° C and above.

• i) ein erster Absolutwert, MA1, eines einzelnen Widerstandselements bei einer erhöhten Betriebstemperatur bestimmt wird, vorzugsweise vor dem Verbinden der Widerstandselemente; und
• ii) ein zweiter Absolutwert, MA2, als lokales Extremum, d.h. als Maximum (bei PTC-Elementen) oder Minimum (bei NTC-Elementen) des Widerstandswerts eines einzelnen Widerstandselements in dem Normalbetriebstemperaturbereich bestimmt wird, vorzugsweise vor dem Verbinden der Widerstandselemente; und
• iii) höchstens eine solche Anzahl, N oder Nmax, von Widerstandselementen 4 zu einer elektrischen Reihenschaltung 4a, 4b verbunden werden, für welche Anzahl gilt: $$\text{MA}2*\left(\text{N}-1\right)<\text{MA}\mathrm{1,}$$
  
  $$\text{N}<\text{MA}1\text{/MA}2+\mathrm{1,}$$
  
  $${\text{N}}_{\text{max}}=\text{INT}\left(\text{MA}1\text{/MA}2\right),$$
  

wobei INT einen ganzzahligen Anteil von (MA1/MA2) bezeichnet.Another development of the method according to the invention provides that

• i) a first absolute value, MA1, of an individual resistance element is determined at an elevated operating temperature, preferably prior to connecting the resistance elements; and
• ii) a second absolute value, MA2, is determined as a local extreme, ie as a maximum (for PTC elements) or minimum (for NTC elements) of the resistance value of an individual resistance element in the normal operating temperature range, preferably before connecting the resistance elements; and
• iii) at most such a number, N or Nmax, of resistance elements 4th to an electrical series connection 4a , 4b connected, for which number applies: $$\text{MA}2*\left(\text{N}-1\right)<\text{MA}\mathrm{1,}$$
  
  $$\text{N}<\text{MA}1\text{/ MA}2+\mathrm{1,}$$
  
  $${\text{N}}_{\text{Max}}=\text{INT}\left(\text{MA}1\text{/ MA}2\right),$$
  

where INT denotes an integer part of (MA1 / MA2).

In this way, it is easy to computationally determine how many resistance elements can usefully be combined to form a series circuit. Said second absolute value, MA2, of the resistance value can include an increase in the resistance value and a decrease in the resistance value and accordingly represent a (local) maximum value or a (local) minimum value, depending on the type of resistance elements used (in particular PTC or NTC).

The consideration is preferably based on a reference temperature for the resistance elements, for example a reference temperature of 25 ° C. (without restriction). First of all, it is determined how the resistance value of an individual resistance element changes when its temperature is increased from the reference temperature to the increased operating temperature (overheating, for example 80 ° C.). Correspondingly, it is determined for each resistance element how the resistance value changes based on the reference temperature when the normal operating temperature is present. This normal operating temperature can - as already stated - be between -20 ° C and 60 ° C without restriction.

Advantageously, those resistance elements are selected within the scope of the invention, which experience a particularly strong change in their resistance value in a range between the (highest) normal operating temperature and the increased operating temperature to be recognized, preferably by a factor of about 100 (without restriction). The greater this change, the more resistance elements can be combined in a series circuit, and the more the circuitry effort can be reduced.

$$\text{N}<\text{MA}1\text{/MA}2+\mathrm{1,}$$

$${\text{N}}_{\text{max}}=\text{INT}\left(\text{MA}1\text{/MA}2\right),$$

wobei INT einen ganzzahligen Anteil von (MA1/MA2) bezeichnet. Mit anderen Worten: Je größer der Quotient aus dem ersten Absolutwert MA1 und dem zweiten Absolutwert MA2 ausfällt, desto mehr Widerstandselemente können in einer Reihenschaltung verbunden werden. Die Absicht dahinter ist, dass eine übermäßige Temperaturerhöhung an nur einer einzelnen Batteriezelle zu einer solch starken Änderung des elektrischen Widerstands eines dort angeordneten Widerstandselements führt, dass dies den Einfluss aller anderen Widerstandselemente in der Reihenschaltung (wobei diese anderen Widerstandselemente an normal funktionierenden Batteriezellen angeordnet sind) übersteigt und entsprechend erkennbar ist.In the context of the invention, it has been found to be particularly advantageous if at most such a number, N or Nmax, of resistance elements are connected to form an electrical series circuit, for which number applies: $$\text{MA}2*\left(\text{N}-1\right)<\text{MA}\mathrm{1,}$$

$$\text{N}<\text{MA}1\text{/ MA}2+\mathrm{1,}$$

$${\text{N}}_{\text{Max}}=\text{INT}\left(\text{MA}1\text{/ MA}2\right),$$

where INT denotes an integer part of (MA1 / MA2). In other words: the greater the quotient of the first absolute value MA1 and the second absolute value MA2, the more resistance elements can be connected in a series circuit. The intention behind this is that an excessive increase in temperature on only one single battery cell leads to such a strong change in the electrical resistance of a resistance element arranged there that this affects all other resistance elements in the series circuit (these other resistance elements being arranged on normally functioning battery cells) exceeds and is accordingly recognizable.

In yet another further development of the method according to the invention, it can be provided that a plurality, n, of series connections is generated so that the product n * N or n * N _max corresponds to a total number, G, of the battery cells in the battery cell arrangement. Each of the series connections preferably comprises an equal number of resistance elements or battery cells. In practice, the number n will turn out to be much smaller than the number G, so that complete monitoring of all battery cells is possible with less structural effort.

Another preferred development of the method according to the invention provides that the series circuit is connected to a battery management system, which battery management system carries out the measurement of the series resistance and the comparison with the comparison value and then also generates and outputs the monitoring signal. This has already been pointed out above. The monitoring signal can in particular be used to switch off the battery cell arrangement if the comparison shows that at least one of the battery cells has an excessive temperature.

The repeatedly mentioned reduced design effort is reflected in the device according to the invention in the fact that an electrical conductor pair is not required for each individual battery cell because only the series circuits need to be connected to the associated measuring and comparison device.

A further development of the device according to the invention provides that the monitoring signal has a first value assumes when the measured series resistance does not exceed the comparison value, and that the monitoring signal assumes a second value different from the first value when the measured series resistance exceeds the comparison value. This development also relates specifically to the case of using PTC resistance elements, which leads to an increase in the resistance value for each individual resistance element when the temperature increases. If, on the other hand, NTC elements are used, the effect would be exactly the opposite, so that the monitoring signal then assumes the first value when the measured series resistance exceeds the comparison value, and vice versa.

In order to keep the circuit complexity as low as possible, a further development of the device according to the invention also provides that the electrical resistance elements are designed essentially identically.

In a further development of the device according to the invention, the comparison value is preferably established according to a series resistance of the resistance elements in the series circuit measured at normal operating temperature. This has already been pointed out above.

$$\text{N}<\text{MA}1\text{/MA}2+\mathrm{1,}$$

$${\text{N}}_{\text{max}}=\text{INT}\left(\text{MA}1\text{/MA}2\right),$$

wobei INT einen ganzzahligen Anteil von MA1/MA2 bezeichnet, wenn MA1 einen ersten Absolutwert des Widerstandswerts eines einzelnen Widerstandselements bei einer erhöhten Betriebstemperatur bezeichnet, und wenn MA2 einen zweiten Absolutwert als Maximum (bei PTC-Elementen) oder Minimum (bei NTC-Elementen) des Widerstandswerts eines einzelnen Widerstandselements in dem Normalbetriebstemperaturbereich bezeichnet.According to the development of the method according to the invention, a simple formula-based relationship for determining the number of resistance elements in an electrical series circuit also results in a further development of the device according to the invention. The following applies to this number N or Nmax: $$\text{MA}2*\left(\text{N}-1\right)<\text{MA}\mathrm{1,}$$

$$\text{N}<\text{MA}1\text{/ MA}2+\mathrm{1,}$$

$${\text{N}}_{\text{Max}}=\text{INT}\left(\text{MA}1\text{/ MA}2\right),$$

where INT denotes an integer part of MA1 / MA2, when MA1 denotes a first absolute value of the resistance value of an individual resistance element at an increased operating temperature, and when MA2 denotes a second absolute value as the maximum (for PTC elements) or minimum (for NTC elements) of the Denotes the resistance value of an individual resistance element in the normal operating temperature range.

With a corresponding development, the device according to the invention can comprise a plurality, n, of series connections so that the product n * N or n * N _max corresponds to a total number, G, of battery cells in the battery cell arrangement, while preferably an electrical conductor pair for each series connection Connect to the measuring and comparison device is provided.

With a corresponding development, the device according to the invention advantageously furthermore has a battery management system, which battery management system is operatively connected to the measuring and comparison device or comprises the measuring and comparison device. The battery management system is designed to allow continued operation of the battery cell arrangement as a function of the monitoring signal, preferably at the first value of the monitoring signal, or to prevent it, preferably at the second value of the monitoring signal.

In a further development of the battery cell arrangement according to the invention, provision is accordingly made for the plurality of electrical resistance elements to correspond to the plurality of battery cells and for such a resistance element to be assigned to each battery cell. Consequently, the battery cell arrangement does not suffer like the configuration according to the prior art ( 2 ) including that the temperature monitoring is only carried out infrequently.

In order for the temperature monitoring to work as well as possible, a further development of the battery cell arrangement according to the invention provides that each resistance element is connected to a respective battery cell in a thermally conductive manner. In particular, a force-fit or material connection, for example by clamping or gluing, comes into consideration here.

In a corresponding development of the same, the battery cells of the battery cell arrangement are advantageously designed as lithium-ion cells. Such battery cells have proven to be particularly efficient in the past.

With all of its aspects described above, the present invention is particularly suitable for use in a vehicle, preferably an aircraft. The applicant produces so-called multirotor aircraft in the form of multicopters which have a plurality of electrically operated drive units. Advantageously, each of these drive units can be assigned at least one battery cell arrangement according to the present invention.

It has already been pointed out that within the scope of the present invention, in addition to the approaches described above, a basic measurement of the temperature of the battery cell arrangement can also take place, as is exemplified in FIG 2 is shown. This does not need to be discussed further at this point because such a function is basically known from the prior art. In addition or as an alternative to this, can the inventive monitoring of a battery cell arrangement described in detail above for temperature deviations of individual battery cells from a normal operating temperature take place. It is particularly advantageous to implement both functionalities and thus create a particularly safe and powerful battery cell arrangement. This has already been pointed out above.

• 1 zeigt eine Batteriezellen-Anordnung nach dem Stand der Technik;
• 2 zeigt eine weitere Batteriezellen-Anordnung nach dem Stand der Technik;
• 3 zeigt eine erfindungsgemäße Batteriezellen-Anordnung;
• 4 zeigt Widerstandswerte in Abhängigkeit von der Betriebstemperatur im Rahmen der Erfindung; und
• 5 zeigt die Verwendung von erfindungsgemäßen Batteriezellen-Anordnungen bei einem Multirotor-Fluggerät.

Further properties and advantages of the invention emerge from the following description of exemplary embodiments with reference to the drawing.

• 1 shows a battery cell arrangement according to the prior art;
• 2 shows a further battery cell arrangement according to the prior art;
• 3 shows a battery cell arrangement according to the invention;
• 4th shows resistance values as a function of the operating temperature within the scope of the invention; and
• 5 shows the use of battery cell arrangements according to the invention in a multi-rotor aircraft.

On the previously known configurations according to 1 and 2 has already been discussed above.

3 shows a battery cell arrangement according to the invention 1 with battery cells 2 , BMS 3 and PTC resistance elements 4th , with each individual battery cell 2 a PTC resistor element 4th assigned. The resistance elements 4th are in two series connections 4a , 4b summarized, which is a series connection 4a across the two front rows of battery cells 2 extends while the other series connection extends 4b over the two back rows of battery cells 2 extends. Overall, the battery cell arrangement comprises 1 according to 3 without limitation a number of 48 battery cells 2 (i.e. G = 48) which battery cells 2 are designed as lithium-ion cells and each have the shape of a straight circular cylinder. In the design according to 3 includes each of the series connections 4a , 4b so 24 individual battery cells 2 , each with a PTC resistor element 4th are provided. For connection to the BMS 3 are only two pairs of lines 5a , 5b required, one per series connection 4a , 4b , as shown.

The BMS 3 has a measuring and comparison device 3a on that with each of the series connections 4a , 4b via an associated electrical line pair 5a respectively. 5b connected is. The measuring and comparison device 3a is for measuring a series resistance of the resistance elements 4th in the respective series connection 4a , 4b and configured to compare the measured series resistance with a comparison value. In addition, the measuring and comparison device 3a designed to generate and output a monitoring signal MS, the monitoring signal MS being dependent on a result of said comparison. As in 3 shown, the monitoring signal MS can be used to the battery cell arrangement 1 act, in particular to switch them off when it is found that at least one of the battery cells 2 has an excessive operating temperature. Additionally or alternatively, the monitoring signal MS can be used to inform a pilot or a higher-level control point (not shown) about a (mal) function of the battery cell arrangement 1 to display.

As those skilled in the art will recognize, the design of the series connections 4a , 4b not according to the specific embodiment 3 limited. Of course, the series connections 4a , 4b be designed geometrically different, and they can have different numbers of battery cells 2 or resistance elements 4th include. In particular, the numbers of battery cells 2 or resistance elements 4th be different from series connection to series connection (with appropriate adaptation of the measuring and comparison device 3a) . In any case, it is crucial that all battery cells are covered 2 with resistance elements 4th a significantly reduced number of line pairs 5a , 5b is required to the resistance elements 4th with the BMS 3 or the measuring and comparison device 3a connect to.

In 4th the physical relationships are shown on which the invention is based or in the case of a specific embodiment of the invention for determining the number N of resistance elements 4th in a series connection 4a , 4b can be used.

Is shown in 4th the change in the electrical resistance or the resistance value (in any units) as a function of the temperature in degrees Celsius. PTC resistance elements are considered here, that is to say resistance elements with a positive temperature coefficient, which accordingly show a strong increase in their resistance value towards increased temperatures. The in 4th The resistance value shown is related to a reference value "R25", which indicates a reference resistance value at a temperature of 25 ° C. The specification of, for example, “10” on the ordinate accordingly indicates that the resistance value compared to the reference value R25 by a factor 10 is increased.

The lower curve shows the development of resistance for a single resistance element with temperature. The increase in resistance with temperature is quite moderate up to about 60 ° C (corresponding to a maximum normal operating temperature), and then increases by leaps and bounds. This is the typical behavior of a PTC resistance element, as is the case with reference symbols 4th according to 3 is used.

The middle, dashed curve shows the cumulative behavior of 25 such resistance elements, which are connected in series and all have the same (operating) temperature. The dashed curve is obtained simply by multiplying the lower curve by a factor of 25.

The topmost curve in 4th illustrates the case in which 25 (identical) PTC resistance elements are connected in series, with 24 of these resistance elements having the same (normal operating) temperature, while a single PTC resistance element has the temperature 80 ° C, which represents an excessive operating temperature. Due to the fact that the one overheated resistance element according to the lower curve in 4th has a resistance value that is approximately 1000 times higher than the reference resistance value, the upper curve is in 4th for each temperature higher than the middle, dashed curve, which results in the event that none of the resistance elements or an associated battery cell is overheated. The special resistance behavior of the resistance elements used means that even if several such resistance elements are combined in a series circuit, the overheating of an individual resistance element or the associated battery cell can still be clearly identified.

What is essential here is that the increase in the resistance value for an individual resistance element between a maximum permissible operating temperature (here 60 ° C) and an overheating temperature that can be detected (here 80 ° C) is greater than the total increase in resistance of all other resistance elements in the series connection in the permissible temperature range (here up to 60 ° C). As long as this criterion is met, an excessive increase in temperature at an individual resistance element can be recognized without problems with reduced circuit complexity according to the invention.

As also shown above in terms of a formula, the course of the curves according to 4th also derive a possible maximum number of resistance elements in a series circuit.

5 shows schematically the preferred use of battery cell arrangements according to the invention 1 on a multirotor aircraft 10 . This has a variety of motor / rotor arrangements 11 on, without limitation any motor / rotor arrangement 11 a battery cell arrangement according to the invention 1 is assigned to the relevant motor / rotor assembly 11 to be supplied with electrical energy. Reference number 12th denotes a higher-level control unit, which in particular receives the monitoring signals MS from the individual measuring and comparison devices of the measuring and comparison device (not designated) of the individual battery cell arrangement 1 receives and is accordingly able, among other things, to detect defective (overheated) battery cell arrangements 1 switch off and, if necessary, further emergency measures for the aircraft 10 initiate.

In the context of the introductory description it has already been pointed out that a battery cell arrangement according to the invention, in particular according to 3 , can also contain a functionality, as it is, for example, in 2 for the state of the art. This enables a basic determination of the operating temperature of the battery cell arrangement with reasonable effort 1 , while the additional provision of an embodiment according to 3 the targeted monitoring of all battery cells 2 allowed on possible heating. Such a combined configuration is therefore particularly advantageous.

Claims (19)

A method for monitoring a battery cell arrangement (1) for temperature deviations of individual battery cells (2) from a normal operating temperature and for operating the battery cell arrangement (1), comprising the steps: a) Providing a large number of battery cells (2), preferably at least a quarter or a third or half of the battery cells (2), most preferably at least three quarters of the battery cells (2), in particular all battery cells (2), in the battery cells - Arrangement (1) with an electrical resistance element (4) with a temperature-dependent electrical resistance value; b) connecting the resistance elements (4) in the form of at least one electrical series circuit (4a, 4b); c) during operation of the battery cell arrangement (1), continuously measuring a series resistance of the resistance elements (4) in the series circuit (4a, 4b) and comparing the measured series resistance with a comparison value; d) outputting a monitoring signal (MS) as a function of a result of the comparison. Procedure according to Claim 1 , in which the monitoring signal (MS) is used to output a warning message or to switch off the battery cell arrangement (1) if the measured series resistance exceeds the comparison value. Procedure according to Claim 1 or 2 , in which the battery cells (2) in step a) are each provided with electrical resistance elements with essentially identical thermal resistance coefficients (4). Method according to one of the Claims 1 until 3 , in which, before step c), a maximum and minimum series resistance of the resistance elements (4) in the series circuit (4a, 4b) is measured within the limits of a normal operating temperature range and used to establish the comparison value. Method according to one of the Claims 1 until 4th in which i) a first absolute value, MA1, of an individual resistance element (4) is determined at an elevated operating temperature, preferably before the resistance elements (4) are connected; and ii) preferably before connecting the resistance elements (4), a second absolute value, MA2, is determined as the maximum or minimum of the resistance value of an individual resistance element (4) in the normal operating temperature range; and iii) at most such a number, N or Nmax, of resistance elements (4) are connected to form an electrical series circuit (4a, 4b), for which number applies: $$\text{MA}2*\left(\text{N}-1\right)<\text{MA}\mathrm{1,}$$

$$\text{N}<\text{MA}1\text{/ MA}2+\mathrm{1,}$$

$${\text{N}}_{\text{Max}}=\text{INT}\left(\text{MA}1\text{/ MA}2\right),$$

where INT denotes an integer part of (MA1 / MA2). Procedure according to Claim 5 , in which a plurality, n, of series connections (4a, 4b) is generated, so that the product n * N or n * N _max corresponds to a total number, G, of battery cells (2) in the battery cell arrangement (1). Method according to one of the Claims 1 until 6th , in which the series circuit (4a, 4b) is connected to a battery management system (3), which battery management system (3) measures the series resistance and compares it with the comparison value and generates and outputs the monitoring signal (MS). Device for monitoring a battery cell arrangement (1) for temperature deviations of individual battery cells (2) from a normal operating temperature and for operating the battery cell arrangement (1), comprising: a plurality of electrical resistance elements (4) each with a temperature-dependent electrical resistance value, which plurality preferably corresponds to at least one quarter, at least one third, at least one half, at least three quarters or all battery cells (2) from a number of battery cells (2) to be monitored, which resistance elements (4) are connected to one another in the form of at least one electrical series circuit (4a, 4b); and a measuring and comparison device (3a) connected to the series circuit (4, 4b) via an electrical conductor pair (5a, 5b) for measuring a series resistance of the resistance elements (4) in the series circuit (4a, 4b) and for comparing the measured series resistance with a comparison value, which measuring and comparison device (3a) is also designed to generate and output a monitoring signal (MS) as a function of a result of the comparison. Device according to Claim 8 , in which the monitoring signal (MS) assumes a first value if the measured series resistance does not exceed the comparison value, and in which the monitoring signal (MS) assumes a second value different from the first value if the measured series resistance exceeds the comparison value. Device according to Claim 8 or 9 , in which the electrical resistance elements (4) are formed essentially identically. Device according to one of the Claims 8 until 10 , in which the comparison value is determined according to a series resistance of the resistance elements (4) in the series circuit (4a, 4b) measured at normal operating temperature. Device according to one of the Claims 8 until 11 , in which at most such a number, N or Nmax, of resistance elements (4) is connected to an electrical series circuit (4a, 4b), for which number applies: $$\text{MA}2*\left(\text{N}-1\right)<\text{MA}\mathrm{1,}$$

$$\text{N}<\text{MA}1\text{/ MA}2+\mathrm{1,}$$

$${\text{N}}_{\text{Max}}=\text{INT}\left(\text{MA}1\text{/ MA}2\right),$$

where INT denotes an integer part of (MA1 / MA2), when MA1 denotes a first absolute value of the resistance value of an individual resistance element (4) at an increased operating temperature, and when MA2 denotes a second absolute value of the resistance value of an individual resistance element (4) as a local extreme ( Maximum for PTC elements or minimum for NTC elements) in the normal operating temperature range. Device according to Claim 12 which comprises a plurality, n, of series connections (4a, 4b), so that the product n * N or n * N _max corresponds to a total number, G, of battery cells (2) in the battery cell arrangement (1), and in which an electrical conductor pair (5a, 5b) for connection to the measuring and comparison device (3a) is preferably provided for each series connection (4a, 4b). Device according to one of the Claims 8 until 13th , further comprising a battery management system (3), which battery management system (3) is operatively connected to the measurement and comparison device (3a) or comprises the measurement and comparison device (3a), which battery management system (3) is designed for this to allow continued operation of the battery cell arrangement (1) as a function of the monitoring signal (MS), preferably at the first value of the monitoring signal (MS) according to FIG Claim 9 , or to prevent, preferably at the second value of the monitoring signal (MS) according to Claim 9 . Battery cell arrangement (1) with a plurality of battery cells (2), preferably essentially identical battery cells (2), and with a device according to one of the Claims 8 until 14th . Battery cell arrangement (1) according to Claim 15 , in which the plurality of electrical resistance elements (4) corresponds to the plurality of battery cells (2) and in which such a resistance element (4) is assigned to each battery cell (2). Battery cell arrangement (1) according to Claim 16 , in which each resistance element (4) is thermally conductively connected to a respective battery cell (2). Battery cell arrangement (1) according to one of the Claims 15 until 17th , in which the battery cells (2) are designed as lithium-ion cells. Use of the device according to one of the Claims 8 until 14th or the arrangement (1) according to one of the Claims 15 until 18th in a vehicle, preferably an aircraft (10), in particular a multi-rotor aircraft, preferably a vertical take-off and landing aircraft, most preferably with distributed, preferably electrically driven drive units (11), which drive units (11) by means of at least one battery cell arrangement (1) , preferably at least one battery cell arrangement (1) per drive unit (11) are supplied.

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