WO2012172035A1

WO2012172035A1 - Method of managing and diagnosing a battery

Info

Publication number: WO2012172035A1
Application number: PCT/EP2012/061400
Authority: WO
Inventors: Henri Zara; David Brun-Buisson
Original assignee: Commissariat A L'energie Atomique Et Aux Energies Alternatives
Priority date: 2011-06-17
Filing date: 2012-06-15
Publication date: 2012-12-20
Also published as: FR2976743A1

Abstract

Method of managing a battery (10) comprising several accumultors A, connected in series, each accumulator being able to be bypassed, characterized in that it comprises the repetition of the following steps in a phase of charging or discharging of the battery, for all the accumulators of the battery: - as soon as an accumulator A reaches a predefined voltage threshold, it is bypassed; - continuation of the phase of charging or discharging of the battery as long as the last accumulator A is not bypassed.

Description

Method for managing and diagnosing a battery

The invention relates to a method of managing a battery, including in particular the realization of the diagnosis of its different subsets. It also relates to a battery as such comprising an arrangement for implementing this management method. Finally, it also relates to a battery management system implementing this battery management method. There are accumulator batteries consisting of an assembly of several accumulators, arranged in series, in order to provide a sufficient output voltage in certain demanding applications, such as for powering a drive motor of a motor vehicle . FIG. 1 thus schematically illustrates such a battery architecture 1, which comprises n accumulators A, arranged in series.

The document US2008072859 describes a battery whose architecture is of the previous type, but which also allows to arrange the different accumulators in series or in parallel, using switches inserted between the accumulators, controlled by a dedicated electronic circuit. This solution allows the implementation of a balancing between the accumulators by arranging them in parallel, which induces the automatic load balancing between the accumulators. This balancing of the different accumulators is done at the end of a charging period: it allows to position the battery in an ideal configuration before its next use.

The state of the art battery management uses a representative indicator of the aging of a battery, often called by its English name of "State of Health" for state of health, or more simply SOH. This indicator is commonly used in the diagnosis of a battery. The evaluation of this indicator is important for a good control of the functioning of the battery, as well as to better manage its end of life. The estimation of the SOH is carried out during a specific diagnostic operation during which the battery is not used. In addition, the solutions recommended for carrying out this diagnosis are however not optimal.

Thus, a general object of the invention is to propose a solution for managing a battery which makes it possible to improve its use during the charging and discharging phase, while at the same time making it possible to perform the diagnosis of the state of the battery. battery, and more particularly the calculation of his state of health SOH. For this purpose, the invention is based on a method of managing a battery comprising several accumulators A, linked in series, each accumulator being bypassed, characterized in that it comprises the repetition of the following steps in a phase of charge or discharge of the battery, for all accumulators of the battery:

as soon as an accumulator A reaches a predefined voltage threshold, it is bypassed;

continuation of the charging or discharging phase of the battery as long as the last accumulator A is not bypassed,

and in that it comprises simultaneous diagnosis of at least one accumulator A, of the battery during a charging or discharging phase of the battery, comprising an estimate of the state of health SOH of this at least one accumulator A, by comparing the value of a quantity representative of the charge or discharge of this at least one accumulator A, with the value of this same quantity taken for a another accumulator or taken in the initial state of said at least one accumulator A.

The predefined voltage threshold may correspond to a maximum voltage reached by an accumulator during a charging phase of the battery, corresponding to its maximum charge, and / or the predetermined voltage threshold may correspond to a low voltage threshold reached by an accumulator A, during a discharge phase of the battery, corresponding to its total discharge.

The method of managing a battery may comprise a prior step of putting in series all the accumulators and the bypass of an accumulator may comprise the opening of a series switch and the closing of a parallel switch.

The method of managing a battery may comprise a step of calculating the charge Qi received by a battery A during its charging or the discharge Qi supplied by a battery A during its discharge. The calculation of the charge or discharge Q i received or supplied by a battery i during its charging or discharging can be obtained by the following formula, integrated over the duration of the charge or discharge phase of the battery A,: X = / 1 dt, where I is the charging or discharging current.

The method of managing a battery may comprise a step of calculating the state of health SOHi of at least one accumulator A, by the following calculation:

SOHi = ^

Ecc

Where Qo is the initial capacity of the accumulator i. The method of managing a battery may comprise an estimate of the state of health SOH of at least one accumulator A, by comparing the charge or discharge duration of this accumulator A, with the charge or discharge duration of the other accumulators .

The method of managing a battery may comprise an estimate of the state of health SOH of at least one accumulator A, by observing its stored energy and restored in a charging or discharging phase.

The invention also relates to a battery comprising several accumulators (A,) connected in series, characterized in that each accumulator (A,) can be bypassed, and in that the battery comprises a computer which implements the method battery management as previously described.

The battery may comprise a series switch arranged in series with each accumulator (A,) so as to be able to disconnect an accumulator (A,) from the rest of the battery by opening a series switch and may comprise a parallel switch disposed in parallel with each accumulator (A,) so as to bypass an accumulator (A,) by closing a parallel switch (14).

The battery may comprise a circuit for controlling the switches, and / or at least one voltage and / or current and / or temperature measurement sensor connected by a communication means to the computer.

The invention also relates to a battery management system, characterized in that it comprises at least one computer which implements the management method described above. The invention also relates to a computer medium readable by a management unit, characterized in that it comprises a registered computer program comprising computer program code means for implementing the battery management method as described above.

These objects, features and advantages of the present invention will be set forth in detail in the following description of a particular embodiment made in a non-limiting manner in relation to the appended figures among which:

Figure 1 shows schematically the architecture of a battery according to a state of the art.

FIG. 2 schematically represents the architecture of a battery according to one embodiment of the invention.

The method of the invention, an embodiment of which will be described below, applies both when charging a battery and during a discharge. The following embodiment relates to a battery charge but it is easy to transpose it to a discharge of a battery.

FIG. 2 represents a battery 10 according to one embodiment of the invention, which comprises, as previously, the combination of n accumulators A, arranged in series. The connection between these accumulators comprises a branch 1 1 disposed between their terminals of opposite sign, on which is disposed a first switch 13, which we will call "series switches". Then, a branch 12 of bypass including a switch 14, which we will call "parallel switch", is associated with each accumulator.

According to an advantageous embodiment, each accumulator is an elementary battery. Such an elementary battery is for example in a cylindrical form, comprises a multitude of positive and negative electrodes, in the form of nested concentric cylinders or coiled spiral layers, separated by layers of electrolytes and electrodes. membranes. These elements represent the active part of the structure of the elementary battery, that is to say they form a set that participates directly in the function of storage and return of electrical energy. In this example, this active part is chemical in nature. As a remark, such an elementary battery may comprise an active part based on other chemical components, or an active part of capacitive nature. On the other hand, the active part of the elementary battery is disposed in a housing, a first outer face forms the positive terminal or first current collector and a second outer face forms the negative terminal or second current collector. This housing has the function of maintaining and supporting the active part of the elementary battery, and its sealing vis-à-vis the outside. It encloses a physical assembly that forms a fixed monolithic assembly, indissociable, whose electrical connection is unmodifiable for a user of the elementary battery, which sees an outgoing current equal to the current entering on its two terminals.

Alternatively, each battery can be in the form of a combination of several elementary batteries.

The battery is also associated with a management system, which comprises hardware (hardware) and / or software (software), at least one calculator, to implement the battery management method that will be detailed later. This management system controls the switches 13, 14 of the battery. It can also receive measurements such as the voltage of each accumulator, from a not shown voltage sensor disposed at each accumulator. Alternatively, it could receive current and / or temperature measurements. This battery management system is preferably integrated within the structure of the battery, and even partially distributed at the level of accumulators. For this, a control circuit can be arranged at each accumulator and can directly control the switches, from control exchanged with a central computer, possibly through a galvanic isolation. The various electronic components arranged locally, such as a control circuit of the switches, any measurement sensors, such as current, voltage, temperature, etc. sensors, may be arranged on a printed circuit arranged within the structure of the battery. , to the nearest accumulators to avoid complex wiring. In addition, according to an advantageous embodiment, these local electronic components can be supplied locally, that is to say by the voltage supplied by a battery of the battery.

Such a battery architecture allows the implementation of an advantageous battery management method during a charge of the battery. This charge comprises a preliminary step consisting in putting all the accumulators in series, by closing all the series switches 13 and opening all the parallel switches 14, before sending a charge current into the battery, which therefore passes through all these accumulators. In addition, this charge phase begins advantageously after the total discharge of all the accumulators of the battery.

Next, the method of charging the battery 10 comprises repeating the following steps, for all the accumulators of the battery:

As soon as an accumulator i reaches its maximum voltage, it is bypassed (shunted), that is to say that its series switch 13 is open and that its parallel switch 14 is closed;

- Charging then continues without this battery, for the remaining batteries only.

As a remark, the term "bypassed or shunted accumulator" means an accumulator whose current is totally deflected by another electrical path.

The battery management method therefore comprises a measurement or an estimate of the voltage at the terminals of each accumulator, repeated periodically during a charging or discharging phase. Advantageously, this method thus makes it possible to obtain the full charge of all the accumulators of the battery (ie a state of charge, often called SOC from the English name of "State Of Charge", of 100%). It therefore has the advantage of perfectly balancing the battery, taking into account the differences between its various accumulators, and for example avoids the decline in overall performance of the battery as soon as an accumulator fails. The method can also be applied for partial charges or discharges in the case where the battery is used in intermediate ranges. On the other hand, this method of charging the battery advantageously allows the simultaneous realization of its diagnosis and in particular the calculation of the state of health SOH of all its accumulators. For this, it comprises an additional step of calculating the charge Qi received by a battery i during its charging.

This charge is for example obtained by the following formula, integrated over the duration of the charging phase of the battery i: X = / 1 dt, where I is the charging current. This current can be measured by a sensor, or alternatively, it can be estimated by any model or other method.

This charge Qi can be stored in an electronic memory associated with the battery, for example a memory of the management system associated with the battery.

Then, the state of health of the accumulator i is obtained by the following calculation:

Qi

SOHi = -

Ecc

Where Qo is the initial capacity of the accumulator i, i.e. the initial load considered, which may be the charge stored in the new state or another state chosen as a reference. As a variant, the state of health SOH can be estimated without calculating the current and the load, but by comparing the charging duration of each accumulator with the charging time of the other accumulators. This study makes it possible, for example, to determine that an accumulator whose charging time is less than 80% of the total charge time of the battery is faulty and needs to be changed. According to another variant, this state of health could also be evaluated by the observation of other electrical quantities, for example as the powers offered by an accumulator, and therefore the stored energy and restored, which evolves decreasing with the aging of the battery. The implementation of this approach can be carried out on the basis of voltage and current measurements.

Thus, more generally, the diagnosis of at least one accumulator A, of the battery during a charging or discharging phase of the battery, comprises an estimate of the state of health SOH of this at least one accumulator A, by comparing the value of a quantity representative of the charge or discharge of this at least one accumulator A, with the value of this same quantity taken for another accumulator or taken to the initial state of said at least one accumulator A ,.

The method of diagnosing an accumulator is implemented during the charging or discharging phases of the battery and has the advantage of not requiring a separate phase, which would immobilize the battery for a certain specific period of diagnosis.

As a note, the method of charging the battery described above makes it possible to obtain the total charge of all the accumulators. Then, the charging process is continued by a complementary phase, often called by its English name of "floating", which consists in maintaining a constant charging voltage until the current falls below a predetermined value, in general low compared to the rated load current. For this, the different accumulators are again all positioned in series. The invention also relates to a battery as such, presenting itself as illustrated in FIG. 2, and further comprising a control circuit for its switches, as well as at least one calculator for implementing the explicit calculations. Alternatively, these components may be external to the battery, belonging to an external battery management system. According to another mixed variant, the various components mentioned are partly distributed within the battery and partly within an external management system. Naturally, the operating principle of the battery previously described for a charging phase is similarly reproduced for a discharge phase, that is to say an operating phase in which the battery restores the stored energy. For this, the method of discharging the battery 10 comprises the repetition of the following steps, for all the accumulators of the battery:

As soon as an accumulator i reaches a low voltage threshold, it is bypassed, that is to say that its series switch 13 is open and that its parallel switch 14 is closed;

- The discharge then continues without this accumulator, for the remaining accumulators only.

Thus, it appears in all operating cases that the battery is managed by comparing the voltage across each battery, so as to disconnect each battery from the rest of the battery when the voltage reaches a preset threshold, high or low depending on charging and discharging phases.

Claims

claims

1. A method of managing a battery (10) comprising several accumulators A, connected in series, each shunted accumulator, characterized in that it comprises the repetition of the following steps in a charging or discharging phase of the battery, for all battery accumulators:

as soon as an accumulator A reaches a predefined voltage threshold, it is shunted;

continuation of the charging or discharging phase of the battery as long as the last accumulator A is not shunted,

and in that it comprises simultaneous diagnosis of at least one accumulator A, of the battery during a charging or discharging phase of the battery, comprising an estimate of the state of health SOH of this at least one accumulator A, by comparing the value of a quantity representative of the charge or discharge of this at least one accumulator A, with the value of this same quantity taken for another accumulator or taken to the initial state of said at least one accumulator A.

2. Method for managing a battery according to the preceding claim, characterized in that the predetermined voltage threshold corresponds to a maximum voltage reached by an accumulator during a charge phase of the battery, corresponding to its maximum charge, and / or in that the predetermined voltage threshold corresponds to a low voltage threshold reached by an accumulator A, during a discharge phase of the battery, corresponding to its total discharge.

3. Method for managing a battery according to one of the preceding claims, characterized in that it comprises a preliminary step of placing all accumulators in series and in that the bypass of an accumulator comprises opening a series switch (13) and closing a parallel switch (14).

4. A method of managing a battery according to one of the preceding claims, characterized in that it comprises a step of calculating the charge Qi received by a battery A during charging or discharge Qi supplied by a battery A, during his discharge.

5. A method of managing a battery according to the preceding claim, characterized in that the calculation of the charge or discharge Qi received or supplied by a battery i during charging or discharge is obtained by the following formula, integrated over time the charging or discharging phase of the battery A, X = / 1 dt, where I is the charging or discharging current.

6. A method of managing a battery according to claim 4 or 5, characterized in that it comprises a step of calculating the state of health SOHi of at least one accumulator A, by the following calculation:

Qi

SOHi = -

Ecc

Where Qo is the initial capacity of the accumulator i.

7. A method of managing a battery according to one of claims 1 to 3, characterized in that it comprises an estimate of the state of health SOH of at least one accumulator A, comparing the charging time or discharge of this accumulator A, with the charging or discharging time of the other accumulators.

8. Method for managing a battery according to one of claims 1 to 3, characterized in that it comprises an estimate of the state of health SOH at least one accumulator A, by observing its stored energy and restored in a charging or discharging phase.

9. Battery comprising several accumulators (A,) connected in series, characterized in that it comprises switches able to shunt each accumulator (A,), and in that the battery comprises a computer which implements the method of Battery management according to one of the preceding claims.

10. Battery according to the preceding claim, characterized in that it comprises a series switch (13) arranged in series with each battery (A,) so as to be able to disconnect an accumulator (A,) from the rest of the battery by the opening of a series switch (13) and in that it comprises a parallel switch (14) arranged in parallel with each accumulator (A,) so as to be able to shunt an accumulator (A,) by closing a switch parallel (14).

1 1. Battery according to the preceding claim, characterized in that it comprises a control circuit of the switches (13, 14), and / or at least one sensor for measuring voltage and / or current and / or temperature connected by means communication to the calculator.

12. Battery management system, characterized in that it comprises at least one computer that implements the method of managing a battery according to one of claims 1 to 8.

13. Computer support readable by a management unit, characterized in that it comprises a registered computer program comprising computer program code means for implementing the battery management method according to one of claims 1 to 8.