EP3245530A1

EP3245530A1 - Method for monitoring a battery and monitoring device

Info

Publication number: EP3245530A1
Application number: EP15822944.3A
Authority: EP
Inventors: Frank Stimm
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2015-01-13
Filing date: 2015-12-23
Publication date: 2017-11-22
Also published as: DE102015200321A1; CN107110917A; WO2016113099A1; CN107110917B

Abstract

The present invention discloses a method for monitoring a battery, wherein the method comprises the steps of measuring a cell voltage value during a current pulse, correcting the cell voltage value by a known maximum possible measurement accuracy, if a predefined relevant value for the cell voltage value is exceeded, in order to calculate a corrected cell voltage value, transferring the corrected cell voltage value to a table in a data memory and storing the values of a minimum cell temperature and a current value for the measured cell voltage for a predefined number of measurements and a current pulse duration in the table, incrementing a counter in a row/column combination assigned to the measurement of the cell voltage value in the table by a predefined value, comparing a sum of the counter values for the predefined number of measurements and current pulse duration with a predefined reference counter value, and outputting a signal if a predefined threshold value is reached or exceeded. A corresponding monitoring device is also disclosed.

Description

description

The present invention relates to methods for monitoring a battery having the features mentioned in the preamble of claim 1. Furthermore, a monitoring device for a battery with the features mentioned in the preamble of claim 9 is disclosed. State of the art

In electrically driven vehicles accumulators or batteries, which comprise a plurality of battery cells, are increasingly being used as the energy source. In this case, lithium-based battery cells are often used, so-called lithium-ion batteries, since these compared to on

Nickel or lead-based batteries have the largest available energy density with the lowest weight. In order to achieve the required power and energy data, typically several battery cells are connected in series. Due to the growing demands on the energy content or due to the required higher power, battery cells are also increasingly connected in parallel.

Lithium ion batteries have many advantages over batteries based on, for example, nickel or lead, but are also much more expensive than them. A battery for an automobile can cost several thousand euros. As a result, the customer is required to ensure that the batteries have a correspondingly long service life and robustness against errors, or that the driver is warned accordingly by the automobile when a fault occurs, for example by an indicator light in the vehicle interior.

Lithium-ion batteries are known to be sensitive to deep discharge, overcharge, high temperatures, and very low temperatures. External damage due to over-discharging, overcharging and excessively high temperatures is prevented in practice by appropriate regulation and control systems as well as warning systems. Furthermore, monitoring systems, so-called battery management systems, are used to monitor dangerous states of a battery such as overcharging or over-discharging and to initiate appropriate countermeasures. These systems can also be used to monitor the battery at low

Temperatures or high voltages are used.

Especially at very low temperatures from about -10 ° C and at high voltages, metallic lithium is deposited in the battery, which can reduce the life of the battery. Furthermore, at very low temperatures such as -10 ° C, only a low charging current of about 300 milliamperes compared to about 2-5 amperes in a normal temperature range of about 0-40 ° C can be applied. An optimum temperature range of lithium-ion batteries is approximately 18-25 ° C. The normal and optimum temperature ranges depend on other factors such as the materials used for anode, cathode and separator or the intended use and thus the design of the battery and are specified by the manufacturer.

The above-mentioned problem of lifetime reduction at critical

Conditions such as overloading are also addressed in DE 10 2010 040 031 AI.

DE 10 2010 040 031 A1 discloses a circuit for monitoring the voltage of a cell of a battery energy storage. In this case, a level of a voltage is measured, and when exceeding or falling below a reference value, a signal is generated, by which the operating state of the input stage is changed. As a result, the expenditure on equipment is to be optimized, since accurate knowledge of a cell voltage value is generally regarded as unnecessary. Rather, it is assumed that the monitoring of an overbzw. Underlying a reference value is sufficient to ensure a safe condition of the battery.

The document DE 100 45 622 AI further discloses a method for

Monitoring of the charge of gas-tight alkaline accumulators, whereby determined measured values, in particular the charging voltage at different temperatures, are filed in a battery management system as a parameter field. critical

Charge states can be measured by measuring temperature and charging current Reference values are calculated and compared with the current voltage value and thus used to control the accumulator.

Furthermore, from document EP 2 345 904 A1

Battery management system with a monitoring unit known which at

Occurrence of certain events decrements a counter. If the counter falls below a predetermined value, an alarm can be triggered. This monitoring system serves to alert the customer when the condition of the battery becomes critical, especially when the life of the battery is over, as measured by the state of charge. Furthermore, by the

Setting a counter and utilizing the data that led to the decrementing of the counter, the service personnel in the event of an error message at customer service relatively quickly by reading the battery management system to recognize what the real state of the battery is.

The above disclosures enable monitoring and even control of battery management based on measured values, in part compared to previously determined reference values. The focus is on preventing a total loss of the battery.

The focus in the present invention is placed on a

Monitoring of the temperature, voltage and current with appropriate warning occurs upon detection of a critical condition, by the

Operating range of the battery is not unnecessarily limited and also the battery management system can be designed more cost-effective.

Disclosure of the invention

The above objects are achieved by the subject-matter of the independent claims. More specifically, the requirements are exploited

Accuracy in terms of voltage, current and temperature monitoring for future ECUs reduced and thus more cost-effective

Battery management systems can be used. In this case, at least the operating range of the battery can still be used. According to the invention, a method is provided for monitoring a battery having a plurality of interconnected cell connections, comprising a plurality of interconnected battery cells, which is characterized by the following steps. In a first step, a cell voltage value is measured during a current pulse. In a second step, when a predefinable limit value for the cell voltage value is exceeded, the cell voltage value is corrected by a known maximum possible measurement accuracy for calculating a corrected cell voltage value. In a third step, the corrected cell voltage value is transferred to a table in a data memory, and the values of a minimum occurring cell temperature and a

Current value are stored in the measured cell voltage for a predetermined number of measurements and current pulse duration in the table. In a fourth step, a counter in a row / column combination assigned to the measurement is increased in the table by a predefinable value, and in a further step, a sum of the counter values for the predefinable number of measurements is compared with a predefinable reference counter value. In a further step, upon reaching or exceeding a predefinable

Threshold issued a signal. Preferably, the current pulse is a charge pulse or a discharge pulse. More preferably, the predetermined limit is 4.0 volts and the maximum possible

Measuring accuracy is 100 millivolts.

In a further advantageous embodiment, the table comprises, in addition to the predefinable number of measurements and current pulse duration, a predefinable number of voltage values to which the counter exceeds the predefinable value

Limit value assigned and increased by the predetermined value. Thus, a better clarity for the evaluation can be achieved and an even simpler version of the system can be achieved.

Furthermore, in a preferred embodiment, the signal is a warning signal indicating a critical condition of the battery by visual or audible indication. Alternatively, the signal may be a signal that is output to a device that triggers a shutdown of the battery or a portion thereof. More preferably, the threshold is 5 percent before exceeding the reference counter value. Thus, it can be ensured that the battery is not damaged, even if the output signal is disregarded. More preferably, when a final threshold value is exceeded, the battery or a part thereof is switched off. This ensures that if the warning is disregarded at the first threshold value, a further control means is available which, if exceeded, deactivates at least part of the battery in order to prevent damage to the same.

Furthermore, a monitoring device for a battery is provided, which is adapted to carry out the method according to the invention. Preferably, the monitoring device is integrated in a battery management system. This reduces the space requirement in the vehicle and allows integration into existing, also in the battery management system existing systems and thus the exploitation of any existing facilities such as sensors or measurement technology that can also be used for the purpose of performing the method according to the invention.

Brief description of the drawings

The invention and advantageous embodiments according to the features of the further claims are explained in more detail below with reference to the embodiments illustrated in the drawings, without limiting the invention in this respect.

It shows:

Figure 1 is an exemplary table for carrying out the invention according to a

Embodiment.

Embodiments of the invention

Batteries according to the invention are preferably in electrical or

Hybrid vehicles used. Preferably, lithium-ion batteries are used, since these compared to nickel or lead-based batteries the have the largest available energy density at the lowest weight and are thus most suitable for driving a vehicle. However, lithium-ion batteries are expensive and also sensitive to very high and very low temperatures as well as high voltages, which can greatly affect their life and performance. That is why it is a goal of

Invention to provide a monitoring device and a method that provides a cost-effective monitoring of critical conditions of the battery and thus contributes to extending the life of a battery. For this purpose, the knowledge is used that the requirements for accuracy with respect to voltage, current and temperature monitoring for future

Control units by the monitoring device according to the invention and the inventive method reduces and thus cheaper

Battery management systems can be used. More specifically, the invention is based on the finding that despite a lower accuracy of the measurement of the voltage, current and temperature values, the specifiable cell limits, ie the values up to which a cell still functions safely and does not become defective, can be maintained. This will be clarified by the method according to the invention described below.

In a first step, a cell voltage of a battery during a current pulse, for example, a charging pulse, so applied current l> 0 amps, measured. If this measured cell voltage exceeds a predeterminable limit value, for example 4.0 volts, the measured cell voltage is corrected by a so-called "worst-case value." This "worst-case value" is the maximum possible measurement accuracy which corresponds to the measured voltage Cell voltage is added so that a corrected reading results. The measurement accuracy can be in the range of a few millivolts, depending on which meter is used. This corrected measured value is then stored in a data memory. This

Data storage may be provided in or external to a battery management system, as long as it is ensured that the data can be stored thereon and retrieved.

All other values also measured at the measured cell voltage, such as the corresponding minimum occurring temperature and current, are in the Data store collected in a table and prepared, ie it is a

Parameter field generated. In this parameter field, these measured values, ie the minimum occurring temperature and the current are respectively plotted for a predefinable number of measurements and a predefinable duration of a current pulse. As soon as the measured cell voltage exceeds the predefinable limit value, the corrected measured value is transferred to the table and a counter, which is assigned to this corrected value in the parameter field in the corresponding row / column combination, is increased by one value, usually by the value "1 ".

If the sum of the values of the counters exceeds a predefinable reference counter value for a certain number of measurements or reaches a predefinable threshold value, a signal or a warning is output. Failure to comply with this warning may result in the shutdown of all or part of the battery. This depends on the design of the system. Thus, it can be ensured that before reaching the

Appropriate measures are taken to protect the battery from damage.

According to the invention, a measurement is defined as a run, beginning with the measurement of a cell voltage value during a current pulse via the correction of the cell voltage value by a known maximum possible

Measuring accuracy for calculating a corrected cell voltage value when exceeding a predefinable limit value for the cell voltage value, continuing with the transfer of the corrected cell voltage value to a table in a data memory and storing the values of a minimum occurring cell temperature and a current value at the measured cell voltage for a predeterminable number of measurements and Current pulse duration in the table, the

Increase a counter in one of the measurements of the cell voltage value

associated row / column combination in the table by a predetermined value, and the comparison of a sum of the counter values for the predetermined number of measurements and current pulse duration with a predetermined reference counter value, to the output of a signal upon reaching or exceeding a predetermined threshold value. A monitoring device which can carry out the method according to the invention can comprise, for example, a data memory in which the parameter field is stored, as well as an evaluation device which stores the data

Comparison of the measured values with the predefinable limit value and the evaluation whether the sum of the counter values for a certain number of measurements has exceeded the reference counter value. The monitoring device may be connected to or part of a battery management system.

The advantage of a monitoring device according to the invention is that a cost-effective device can be used by applying the method according to the invention, since no devices such as sensors, components or evaluation must be used, which have a high or very high measurement accuracy. Furthermore, by using the "worst-case value", ie the correction of the measured cell voltage to the maximum possible accuracy, at least the operating range of the battery can be used, so there are much fewer restrictions in this area, as it Solutions according to the prior art is the case.

FIG. 1 shows a table which shows by way of example how values associated with a measured cell voltage can be stored as a parameter field. Furthermore, by way of example, a filled-in area with a number of counters is shown, which have been entered into the respectively appropriate row by a corrected measured value exceeding the reference value. The sum shown in the bottom row is compared with a reference count value, and based on this result, a signal is generated if the reference count value or a

predetermined threshold has been exceeded. The signal can be in the form of a warning light in the interior of the vehicle or as an acoustic signal

be issued. The signal can also be issued immediately as a control signal, for example, triggers a shutdown of the battery or parts thereof to prevent damage. The configuration of the signal depends on how the system as a whole is designed, in which

Threshold is to be warned at which threshold, which may possibly be a second value, a shutdown should be made, or how high the counter sum, etc. Thus, it is clear that, depending on the field of application and Design of the system and type of battery a corresponding selection of the reference counter value or the threshold value can and must occur.

More specifically, in the first column of the table, a temperature T, more precisely a minimum occurring cell temperature is entered at the measured cell voltage, here for example 25 ° C and 40 ° C. Here could be more different

Temperatures may be recorded, such as -10 ° C or other measured minimum temperatures. These depend on the environmental conditions in the measurement, e.g. Measurement in winter or summer, from.

In the second column, a current value occurring at the measured cell voltage is plotted in this table by way of example for values greater than or less than 100 amps at 40 ° C and for values greater or less than 80 amps at 25 °.

In the third column, the number of measurements, here 26000, and the duration of a current pulse, here 0-2 seconds, and four voltage values, here 4.22 volts, 4.25 volts, 4.3 volts and 4.35 volts, specified. If the measured cell voltage, corrected by the maximum possible measuring accuracy, in this case 100 mV, exceeds the predeterminable limit value, here 4.0 volt, an increase of

For example, the corrected reading is 4.3 V. This value was measured at a minimum temperature of 25 ° C. and a current pulse duration of 1 second, the measured current being 100 Thus, in the third column, below the value for 4.3 volts in the row which represents the values for the

Temperature of 25 ° C and the current of> 80 amps, the counter increased by the value "1".

In the last line of the third column, the sum of the counter values, ie the measurements which have delivered a corrected measured value above the predefinable limit value and for which the counter has been increased by the value "l", is formed of 26000 measurements measured above the allowable preset limit This sum of counts is compared to a reference count If the sum of the counts reaches or exceeds a predefined threshold, here is 5% Exceeding the reference counter value, a signal is generated. This signal may be a warning in the form of a warning light in the interior of the automobile, but it may also be an audible signal or other warning signals warning the driver that the battery could be defective. Furthermore, as a further measure, the signal can be output to a device that triggers a shutdown of the battery or a part thereof, if the warning was ignored, ie if the vehicle was not brought to service and the defect was checked and corrected. The same principle as described above for the third column applies to columns four to six, but for other basic parameters, ie number of measurements and pulse duration.

Become more precise in the fourth column as well, as for the third column

described, the number of measurements, here 12000, as well as the duration of one

Current pulse, here 2-10 seconds, and four voltage values, here 4.22 volts, 4.25 volts, 4.3 volts and 4.35 volts, given. For this specification, an increase of the counter by "1" in the corresponding row / column combination

made if the measured cell voltage, corrected by the maximum possible accuracy, here 100m V, the predetermined limit, here 4.0 volts, exceeds. Furthermore, the sum of the counter values is also formed in the last row of the fourth column, here 16, and compared with a reference counter value. Should the sum of the counter values reach or even exceed a predefinable threshold, here 5% before exceeding the threshold

Reference counter value, a signal is generated. This signal can be configured as described above.

In the fifth column are also, as described for the third and fourth column, the number of measurements, here 4000, and the duration of a

Current pulse, here 10-30 seconds, and four voltage values, here 4.22 volts,

4.25 volts, 4.3 volts and 4.35 volts, given. For this requirement is a

Increase of the counter by "1" in the corresponding row / column combination, if the measured cell voltage, corrected by the maximum possible measuring accuracy, here 100 mV, exceeds the predefinable limit value, in this case 4.0 volts Row of the fourth column the Sum of counter values formed here 25, and compared with a reference counter value. Should the sum of the counter values reach or even exceed a predefinable threshold, here 5% before exceeding the threshold

In the sixth column also, as described for the third to fifth column, the number of measurements, here 5000, and the duration of a

Current pulse, here greater than 30 seconds, and four voltage values, here 4.22 volts, 4.25 volts, 4.3 volts and 4.35 volts, given. For this requirement is a

Increase of the counter by "1" in the corresponding row / column combination, if the measured cell voltage, corrected by the maximum possible measuring accuracy, here 100mV, exceeds the predeterminable limit, in this case 4.0 V. Further, also in the last line In the fourth column, the sum of the counter values is formed, here 3, and compared with a reference counter value If the sum of the counter values reaches or even exceeds a predefinable threshold, here 5% before exceeding the counter value

The table shown in FIG. 1 merely serves as an illustrative example. The values for the minimum temperature, the current, the number and duration of the

Measurements as well as the measured voltage and the predeterminable limit as well as the measuring accuracy can vary independently depending on the given parameters, e.g. which type of battery is chosen, how many

Battery cell can be used or which device or method is used or which environmental conditions prevail.

With the present inventive method and the monitoring device according to the invention, a cost-effective system is provided, which at the same time makes it possible to use at least the operating range of the battery used and thus extend the service life of the battery.

Claims

claims

1. A method of monitoring a battery having a plurality of each other

connected cell interconnections comprising a plurality of interconnected battery cells,

characterized in that the method comprises the steps of:

a) measuring a cell voltage value during a current pulse, b) when a predefinable limit value for the

Cell voltage value, the cell voltage value is corrected by a known maximum possible measurement accuracy for calculating a corrected cell voltage value,

c) transferring the corrected cell voltage value to a table in a data memory and storing the values of a minimum occurring cell temperature and a current value at the measured cell voltage for a predeterminable number of measurements and current pulse duration in the table, d) incrementing a counter in one of the measurements of

Cell voltage value associated row / column combination in the table by a predetermined value,

e) comparing a sum of the counter values for the predeterminable number of measurements and current pulse duration with a predetermined reference counter value, and

f) outputting a signal when a predefinable threshold value is reached or exceeded.

2. The method according to claim 1, characterized in that the current pulse a

Charge pulse or a discharge pulse is.

3. The method according to any one of the preceding claims, characterized

characterized in that the predetermined limit value is 4.0 volts and the maximum possible measurement accuracy is 100 millivolts.

4. The method according to any one of the preceding claims, characterized

in that, in addition to the predefinable number of measurements and current pulse duration, the table comprises a predefinable number of voltage values to which the counter exceeds the predefinable limit value assigned and for which the counter is increased by the predetermined value.

5. The method according to any one of the preceding claims, characterized

characterized in that the signal is a warning signal indicating a critical condition of the battery by visual or audible indication.

6. The method according to any one of the preceding claims, characterized

characterized in that the signal is a signal that is output to a device that triggers a shutdown of the battery or a part thereof.

7. The method according to any one of the preceding claims, characterized

characterized in that the threshold is 5 percent before the reference counter value is exceeded.

8. The method according to any one of the preceding claims, characterized

characterized in that when a final threshold is exceeded, the battery or a part thereof is turned off.

9. Battery monitoring device adapted to carry out the method according to claims 1-8.

10. Monitoring device according to claim 9, wherein the

Monitoring device is integrated in a battery management system.