WO2020029117A1

WO2020029117A1 - Method and device for monitoring an electric energy store

Info

Publication number: WO2020029117A1
Application number: PCT/CN2018/099389
Authority: WO
Inventors: Sylvain Guenon; Christoph Fischer; Jochen BOHNE; Stephan Leuthner; Thomas Klaus-Juergen FROEHLICH
Original assignee: Robert Bosch Gmbh
Priority date: 2018-08-08
Filing date: 2018-08-08
Publication date: 2020-02-13
Also published as: CN112514194A

Abstract

In a method for monitoring an electric energy store, comprising at least one electric energy storage unit, an electronic battery management unit and an interface for communication with external devices, the method comprises the steps: a) determining at least one state variable of the electric energy store, particularly a voltage quantity and/or a state of charge quantity, by the electronic battery management unit; b) transmitting the determined state variable via the interface for communication with external devices to a monitoring device (40, 50) being installed externally to the electric energy store; c) evaluating a state of the electric energy store by the monitoring device (40, 50) depending on the determined at least one state variable; d) performing a charging process of the electric energy store by a charging device that is situated externally to the electric energy store depending on the evaluation by the monitoring device (40, 50) and/or performing a voltage balancing process inside of the electric energy store by an internally installed voltage balancing device. The monitoring device (40, 50) comprises a communication device (41, 51) and evaluation device (42, 52).

Description

Method and device for monitoring an electric energy store

The present disclosure relates to a method and a device for monitoring an elec-tric energy store, the electric energy store having at least one electric energy storage unit, an electronic battery management unit and an interface for commu-nication with external devices.

State of the art

Electric energy stores, especially batteries and accordingly battery cells, often have to be stored for a certain amount of time, sometimes years, before they are used. In particular, when they are used as replacement or spare parts in an al-ready existing energy store, the storage time of electric energy stores can reach up to several years. Preferably, electric energy stores are kept at a low state of charge when stored to slow down aging processes.

As they are stored at a low state of charge, the state of charge of the electric en-ergy stores has to be monitored. In many cases, the electric energy stores com-prise several electric energy storage units, e.g. battery cells. Therefore, it is ad-visable to monitor each of these energy storage units as well because they may differ in several characteristics, e.g. their self-discharge rate. This means that af-ter a certain storage time, the electric energy storage units in an electric energy store may show differing voltage behavior. To operate the energy store safely af-ter some storage time, its state of charge must not fall below a certain state of charge threshold. The same holds for the electric energy storage units comprised in the electric energy store. Furthermore, it is advisable that they do not show voltage behaviors and voltage values that differ strongly.

Therefore, it is advisable to monitor the electric energy store and respectively its electric energy storage units regularly so that they do not to fall below certain state of charge thresholds. If these state of charge thresholds are reached or ap-proached, the electric energy store has to be charged or an internal voltage bal-ancing process on electric energy storage unit level within the electric energy store has to be performed.

The balancing process equalizes the voltage levels of the electric energy storage units. Afterwards, the electric energy store and respectively its electric energy storage units can be charged so that the electric energy store can be safely stored without being in use for a certain period. The charging process ensures that no critical states of charge are reached during the storage period.

The publication GB 2550282A discloses a monitoring device with a communica-tion device that is operable to give instructions to a control arrangement to per-form a charge transfer between battery cells.

The publication US 2017/0021738 discloses a method for the battery manage-ment of a battery which comprises carrying out charge state balancing.

Disclosure of the invention

Advantages of the invention

The present disclosure describes a method for monitoring an electric energy store, the electric energy store having at least one electric energy storage unit, an electronic battery management unit and an interface for communication with external devices. The electronic battery management system may incorporate the interface for communication. The disclosed method comprises several steps.

A state variable of the electric energy store is determined by the electronic bat-tery management unit, the state variable being or comprising a voltage quantity and/or a state of charge quantity of the electric energy store respectively the electric energy storage unit.

Furthermore, the determined state variable is transmitted via the interface for communication to a monitoring device being installed externally to the electric en-ergy store. The interface may be designed for wired or wireless data transmis-sion. In particular, it may be designed as a CAN interface or wireless LAN inter-face.

Depending on the determined state variable, the monitoring device evaluates a state of the electric energy store. For example, the state of the electric energy store can be evaluated as needing maintenance when the determined voltage quantity falls below a predefined voltage level or when a certain state of charge threshold is reached or underrun.

Depending on the evaluation by the monitoring device, a charging device that is situated externally to the electric energy store performs a charging process for the electric energy store. Alternatively or additionally a voltage balancing process inside of the electric energy store on the level of the electric energy storage units may be performed by an internally installed voltage balancing device, i.e. the volt-age balancing device is installed inside of the electric energy store.

This is advantageous because an external monitoring device performs the evalu-ation of the state of the electric energy store and the monitoring process so that the electric energy store and respectively its electronic battery management unit are not charged with method steps that are energy-intensive and would lead to an unnecessary discharging of the electric energy store. A further advantage is that the monitoring device typically features a higher computing power and more memory capacity.

Further illustrative embodiments of the present invention are given in the sub-claims.

It is advisable to transmit a status report on the determined state variable to a user and/or a computer by the monitoring device. This is advantageous because it gives the user the possibility to respond appropriately depending on the deter-mined state variable respectively the outcome of the evaluation result. Further-more, this has the advantage that the transmitted status report can be stored on the computer and combined with other status reports to allow for more detailed and in-depth analyzes.

It is advisable to the at least one battery management unit for determining the at least one state variable and correspondingly deactivate the electronic battery management unit for reducing the consumption of electric energy from the elec-tric energy store. This is advantageous because the battery management unit only consumes energy when it is necessary to perform the monitoring steps. Dur-ing the rest of the time, it is in a deactivated state and does not consume electric energy from the electric energy store. This results in a longer storage time of the electric energy store without needing maintenance and charging. As a further ad-vantage, the lifespan of the electric energy store respectively the electric energy storage unit is prolonged.

It is advisable to determine an environmental temperature of the electric energy store by the monitoring device and to adapt the environmental temperature by controlling a heating and/or cooling device depending on the determined environ-mental temperature. The heating and cooling device may be combined in a heat-ing and cooling circuit, where an appropriate liquid, for example a mixture of wa-ter and glycol, is circulated. Another embodiment of the heating device may be a heating resistor that may be installed inside or outside of the electric energy store. This is advantageous because the electric energy store respectively the electric energy storage unit typically have a recommended storage temperature where aging processes are reduced to a minimum. Determining, monitoring and controlling the environmental temperature therefore serves to keep the actual temperature very close to the recommended storage temperature. If the deter-mined environmental temperature is above the recommended storage tempera-ture of the electric energy store, the environmental temperature is lowered, for example by controlling the cooling circuit to circulate more cooling liquid inside the circuit and vice versa.

It is advisable to determine an environmental humidity by the monitoring device and to adapt the environmental humidity by controlling a drying device and/or a humidifier depending on the environmental humidity. This is advantageous be-cause as regards the environmental temperature, there is a recommended stor-age humidity where aging phenomena of the electric energy store respectively the electric energy storage unit related to humidity are reduced to a minimum. Determining, monitoring and controlling the environmental humidity therefore serves to keep the actual humidity very close to the recommended storage hu-midity. If the determined environmental humidity is above the recommended stor-age humidity of the electric energy store, the environmental humidity is lowered, for example by controlling the drying device to perform at a higher rate and vice versa.

It is advisable to perform the evaluation of the state of the electric energy store by the monitoring device by means of a method of artificial intelligence. For exam-pie, a neural network that has been trained by means of training data and an opti-mization method, e.g. gradient descent, can be used to evaluate the state of the electric energy store. Appropriate training data for the neural network may be gained either by laboratory experiments or actual usage data of electric energy stores, e.g. in cars. Part of this artificial intelligence is to compare the condition of the electric energy stores to each other. In this case it is important to control their electric voltages and to derive the right measures. It is for example possible to determine the rate at which the electric voltages of the electric energy stores drift apart in order to evaluate by when a further checking procedure is necessary and by when a balancing procedure is necessary. Is the period for the checking pro-cedure foreseen all 6 months and the evaluation shows that the cell voltages drift apart stronger than foreseen, the period of the checking procedure has to be shortened, e.g. to 3 months. By this means, the effort for the checking procedure can be optimized. This is advantageous because the evaluation can be per-formed in an automated manner and taking into account past evaluations and ex-pert knowledge while in the meantime optimizing evaluation intervals.

The presented order of the method steps is only a preferred order. Other method step sequences are possible depending on the specific application. For example, the status report may be transmitted to the user and/or the computer system after evaluating the state of the electric energy store or after performing the charging process.

Furthermore, a device for monitoring an electric energy store -a monitoring de-vice -is disclosed where the electric energy store has at least one electric en-ergy storage unit, an electronic battery management unit and an interface for communication with external devices. The monitoring device comprises a com-munication device configured to receive a state variable of the electric energy store that is transmitted via the interface for communication with external devices. Additionally, the monitoring device has an evaluation device that is configured to perform an evaluation of the state of the electric energy store depending on the determined state variable and is configured to initiate a charging process of the electric energy store by a charging device depending on the evaluation result. Additionally or alternatively, the monitoring device is configured to initiate a volt-age balancing process inside of the electric energy store by an internally installed voltage balancing device depending on the evaluation result.

This is advantageous because the monitoring device performs the evaluation of the state of the electric energy store and the monitoring process so that the elec-tric energy store and respectively its electronic battery management unit are not charged with method steps that are energy-intensive and would lead to an un-necessary discharging of the electric energy store. A further advantage is that the monitoring device typically features a higher computing power and more memory capacity.

It is advisable that the monitoring device comprises a charging device, which has the advantage that the charging process of the electric energy store can be easily performed without resorting to additional devices.

It is advisable that the monitoring device comprises an energy supply interface that is configured to supply electric energy to the electronic battery management unit. This is advantageous, as no external power supply for the electronic battery management unit is needed. The monitoring device is sufficient to perform all necessary actions.

In a preferred embodiment, the energy supply interface is designed as a plug connection and is configured to supply a voltage of 12 V to the electronic battery management unit. This has the advantage that typical electronic battery manage-ment units can be supplied with electric energy because they normally need a voltage level of 12 V. As a result, the monitoring device has a wide range of ap-plication.

An electric energy storage unit may be embodied by an electrochemical battery cell and/or a battery module with at least one electrochemical battery cell and/or a battery pack with at least one battery module. For example, the electric energy storage unit may be a lithium based battery cell, in particular a lithium ion battery cell. Furthermore, the battery cell may be of the type lithium polymer, lithium air or lithium sulfur. A capacitor may also be used as electric energy storage unit.

The monitoring device may be an electronic control unit, comprising a microcon-troller and/or a microprocessor. A personal computer or otherwise adapted com-puter with appropriate interfaces may also be used.

Description of the figures

Advantageous embodiments of the invention are given in the figures and de-scribed in detail in the description below.

Figure 1 shows a flow diagram of a first embodiment of a method according to the invention.

Figure 2 shows a flow diagram of a second embodiment of a method according to the invention.

Figure 3 shows a flow diagram of a third embodiment of a method according to the invention.

Figure 4 shows a schematic illustration of a first embodiment of a device for mon-itoring an electric energy store according to the invention.

Figure 5 shows a schematic illustration of a second embodiment of a device for monitoring an electric energy store according to the invention.

Embodiments of the invention

Identical reference signs refer to identical features of identical method steps in all figures.

Figure 1 shows a flow diagram of a first embodiment of a method according to the invention. An electric energy store is monitored which comprises at least one electric energy storage unit, an electronic battery management unit and an inter-face for communication with external devices. In a first step S11, an electric volt-age of the electric energy store is determined, preferably between terminals of the electric energy store, by an electronic battery management unit.

In a second step S12, the determined voltage respectively the determined volt-age value is transmitted via an interface for wireless communication with external devices, e.g. a wireless LAN interface, to a monitoring electronic control unit be-ing installed externally to the electric energy store.

In a third step S13, a state of the electric energy store is evaluated by the moni-toring electronic control unit based on the electric voltage value, which results in the electric energy store being assessed as needing maintenance in the form of being charged which results in a fourth step S14.

In the fourth step S14, a charging process of the electric energy store is per-formed by an external charger that is situated outside of the electric energy store. The charging process is performed until a predefined voltage level is reached. As a result, the state of charge and hence the voltage of the electric energy store is increased which ensures a safe distance from critical voltage levels.

Figure 2 shows a flow diagram of a second embodiment of a method according to the invention. An electric energy store is monitored which comprises several electric energy storage units, an electronic battery management unit and an inter-face for communication with external devices.

In a first step S21, the electronic battery management unit is activated to be able to determine at least one state variable that means it is switched on from a switched off status or a very low power status where only very low currents are drawn from the electric energy store, e.g. in the range of several microamperes.

In a second step S22, the electronic battery management unit determines a state of charge value of the electric energy store. Alternatively or additionally, state of charge values of the electric energy storage units can be determined.

In a third step S23, this state of charge value is transmitted via the interface for communication to the disclosed monitoring device. Alternatively or additionally, the state of charge values of the electric energy storage units can be transmitted.

In a fourth step S24, the monitoring device evaluates a state of the electric en-ergy store whether it requires maintenance in the form of being charged. This evaluation is performed based on the state of charge value of the electric energy store. Alternatively or additionally, the evaluation may be based on the state of charge values of the electric energy storage units.

In a fifth step S25, it is assumed that the fourth step S24 gave the result that the electric energy store needs maintenance in the form of being charged. In order to prepare the charging process, in the fifth step S25, the electric energy store un-dergoes a voltage balancing process among the electric energy storage units, which results in the electric energy storage units having the same voltage level. To do this, the electric energy store features an internally installed voltage bal-ancing device. After that, the electric energy store is charged by a charger that is situated externally of the electric energy store until a predefined state of charge threshold is reached.

In a sixth step S26, the electronic battery management unit is deactivated in or-der to reduce the consumption of electric energy of the electric energy store. The deactivation and/or the activation in step S21 may be performed by the monitor-ing device. To this end, the electronic battery management unit and the monitor-ing device may be able communicate via the interface for communication.

Figure 3 shows a flow diagram of a third embodiment of a method according to the invention. An electric energy store is monitored which comprises at least one electric energy storage unit, an electronic battery management unit and an inter-face for communication with external devices. A first step S31, a second step S32 and a third step S33 resemble steps S11, S12 and S13 respectively.

In a fourth step S34, an environmental temperature of the electric energy store is determined by the monitoring device. For example, this may be performed via a temperature sensor, which is connected to the monitoring unit.

In a fifth step S35, it is assumed that the environmental temperature has been assessed as being too low, so the storage conditions for the electric energy store are not optimal. Hence, in the fifth step S35, the environmental temperature is changed by controlling a heating device via the monitoring device. The monitor-ing device initiates a heating process by means of the heating device, which in the end creates the optimal storage temperature for the electric energy store.

A sixth step S36 resembles step S14.

In a seventh step S37, a status report indicating the state of the electric energy store and the respective taken measures, i.e. temperature determination, heat control and charging, is sent to a computer for easy access via the internet.

Figure 4 shows a schematic illustration of a first embodiment of a device 40 for monitoring an electric energy store according to the invention. The monitoring de-vice 40 comprises a communication device 41 configured to receive a state varia-ble of an electric energy store. An evaluation device 42 is configured to perform an evaluation of the state of the electric energy store depending on a respective determined state variable and is additionally configured to initiate a charging pro-cess of the electric energy store by a charging device depending on the evalua-tion result. Furthermore, the evaluation device 42 may be configured to initiate a voltage balancing process inside of the electric energy store by an internally in-stalled voltage balancing device depending on the evaluation result.

Figure 5 shows a schematic illustration of a second embodiment of a device 50 for monitoring an electric energy store according to the invention. A communica-tion device 51 resembles the communication device 41 and an evaluation device 52 resemble the evaluation device 42. Furthermore, the monitoring device 50 comprises an energy supply interface 53, which is configured to supply electric energy to the electronic battery management unit and which is designed as a plug connection.

Claims

Method for monitoring an electric energy store, comprising at least one elec-tric energy storage unit, an electronic battery management unit and an inter-face for communication with external devices, comprising the steps:

a) Determining at least one state variable of the electric energy store, partic-ularly a voltage quantity and/or a state of charge quantity, by the electronic battery management unit;

b) Transmitting the determined state variable via the interface for communi-cation with external devices to a monitoring device (40, 50) being installed externally to the electric energy store;

c) Evaluating a state of the electric energy store by the monitoring device (40, 50) depending on the determined at least one state variable;

d) Performing a charging process of the electric energy store by a charging device that is situated externally to the electric energy store depending on the evaluation by the monitoring device (40, 50) and/or performing a volt-age balancing process inside of the electric energy store by an internally installed voltage balancing device.
Method according to claim 1, further comprising:

e) Transmitting a status report based on the determined state variable to a user and/or a computer by the monitoring device (40, 50) .
Method according to any one of the preceding claims, further comprising:

f) Activating the electronic battery management unit for determining the at least one state variable;

g) After this, deactivating the electronic battery management unit for reducing the consumption of electric energy of the electric energy store.
Method according to any one of the preceding claims, further comprising:

h) Determining an environmental temperature of the electric energy store by the monitoring device (40, 50) ;

i) Adapting the environmental temperature by controlling a heating and/or cooling device depending on the determined environmental temperature.
Method according to any one of the preceding claims, further comprising:

j) Determining an environmental humidity by the monitoring device (40, 50) ;

k) Adapting the environmental humidity by controlling a drying device and/or a humidifier depending on the determined environmental humidity;
Method according to any one of the preceding claims in which the evaluation in step c) is performed by means of a method of artificial intelligence.
Monitoring device (40, 50) for monitoring an electric energy store, the electric energy store having at least one electric energy storage unit, an electronic battery management unit and an interface for communication with external devices, the monitoring device comprising:

A communication device (41, 51) configured to receive a state variable of the electric energy store, which is transmitted via the interface for communication with external devices;

An evaluation device (42, 52) configured to perform an evaluation of the state of the electric energy store depending on the determined state variable and configured to initiate a charging process of the electric energy store by a charging device depending on the evaluation result and/or configured to initi-ate a voltage balancing process inside of the electric energy store by an inter-nally installed voltage balancing device depending on the evaluation result.
Monitoring device (40, 50) according to claim 7, the monitoring device (40, 50) comprising a charging device.
Monitoring device (40, 50) according to claim 7 or 8, the monitoring device (40, 50) comprising an energy supply interface which is configured to supply electric energy to the electronic battery management unit.
Monitoring device (40, 50) according to any one of the claims 7 to 9, the en-ergy supply interface being designed as a plug connection and configured to supply a voltage of 12 V.