EP2396838A1

EP2396838A1 - Method and device for classifying a battery

Info

Publication number: EP2396838A1
Application number: EP10707604A
Authority: EP
Inventors: Denis Porcellato
Original assignee: Peugeot Citroen Automobiles SA
Current assignee: PSA Automobiles SA
Priority date: 2009-02-13
Filing date: 2010-01-28
Publication date: 2011-12-21
Also published as: FR2942323B1; FR2942323A1; CN102318103A; WO2010092275A1; US20110295533A1; CN102318103B

Abstract

The invention relates to a device for classifying a battery produced by assembling electricity-accumulating elements (1, 2, 3, 4, 5) divided into groups. In the device, a component (22) is provided for evaluating the degrees of ageing, each of which is associated with a distinct group, and for allocating, to the battery, in accordance with statistical distribution parameters of the evaluated degrees of ageing, a classification level that is representative of the potential performances of the battery during use.

Description

"Method and device for classifying a battery."

The present invention relates to a method and a device for classifying a battery, in particular a battery for a motor vehicle.

During its use, the battery of a vehicle gradually loses its performance, with consequences that can be detrimental to the operation of a vehicle, including a vehicle with electric traction.

In order to control this loss of performance, devices and methods have already been considered to calculate a degree of deterioration of a battery.

Thus, the document FR2841385 provides for calculating several degrees of deterioration, each associated with a detected state quantity. A total degree of deterioration is then calculated based on the degrees of deterioration associated with the state variables. The disadvantage of the device and method disclosed in this document is that each of the degrees of deterioration relates to the battery as a whole.

An automobile traction battery generally consists of several modules themselves made up of several cells.

Thus, document US7075194 describes a system that makes it possible to configure a battery in real time by connecting the elements differently to one another according to usage. A parallel connection of elements is favorable for a consumer-intensive use. A series connection of elements, is favorable for a demanding use of high voltages. However the aging of the elements is not uniform because it depends on the thermal environment specific to each element, initial characteristics elements, drifts in the manufacturing process sources of early aging, the situation in the vehicle which can cause an imbalance in the power circuit from the point of view for example of the interconnection impedance.

The dispersion of characteristics specific to each element, amplifies over time and the battery loses all or part of these performances. The loss of performance of the battery has a direct effect on the performance of the vehicle, its consumption and therefore the emission of greenhouse gases.

In the prior art, it is envisaged to analyze the entire battery and judge its state according to its overall characteristics, without taking into account the dispersion of the characteristics of the elements that compose it. Following this approach, we are led to change the battery while it would be enough to change some elements.

However, abandoning the knowledge of global characteristics of the battery to focus locally on individual states of elements, is not possible because the overall characteristics directly impact the outside of the battery, including the operation of the vehicle.

To overcome the drawbacks of the prior art, the subject of the invention is a method of classifying a battery made by assembling accumulators of electricity distributed in groups, comprising the steps of:

- evaluate degrees of aging, each associated with a distinct group; and

assigning to the battery, according to statistical distribution parameters of the aging levels evaluated, a classification level which is representative of the potential performance of the battery in use. In particular, the degree of aging of at least one group is evaluated by an impedance measurement method or a method of estimating the internal resistance as a function of a current measurement that passes through the group of elements and a measurement. Of voltage .

Advantageously, the method comprises a step of replacing at least a first group by a second group so as to maintain the classification level of the battery.

Particularly, the first group is replaced by permutation in the battery with the second exposed group, before permutation, to lower utilization constraints than the first group. More particularly, the use constraints include a temperature.

Alternatively, the first group is replaced by a second group from another battery with a lower degree of aging. Alternatively again, the first group is replaced by a second group with a zero degree of aging.

Among various possible implementation modes, a group includes all the elements of the battery, some elements or a single element of the battery.

Preferably, the statistical distribution parameters comprise an average of the degrees of aging and / or a higher value of the estimated degrees of aging.

The subject of the invention is also a device for classifying a battery made by assembling accumulators of electricity distributed in groups, comprising a component arranged to: - evaluate degrees of aging, each associated with a distinct group; assigning to the battery, according to statistical distribution parameters of the aging levels evaluated, a classification level which is representative of the potential performance of the battery in use.

In particular, the component is arranged to evaluate the degree of aging of at least one group by an impedancemetry method or a method of estimating the internal resistance as a function of a measurement of current that passes through the group of elements and a measurement of tension.

Advantageously, the device comprises slides that hold the accumulators of electricity to achieve the battery and that replace at least a first group by a second group so as to maintain the classification level of the battery.

More particularly, the component comprises communication means of the classification level and the degrees of aging evaluated.

In the device, a group may comprise all the elements of the battery, some elements or a single element of the battery.

The invention will be better understood, and other objects, features, details and advantages thereof will appear more clearly in the explanatory description which follows, with reference to the appended schematic drawings given solely by way of example, illustrating a mode of embodiment of the invention and in which: - Figure 1 is a schematic view of the device according to the invention; FIG. 2 shows process steps according to the invention; Fig. 3 is a statistical distribution curve as a function of a characteristic value; FIG. 4 shows an example of possible classification as a function of a displacement of the curve of FIG. 3.

With reference to FIG. 1, a battery is made by assembling accumulator elements 1, 2, 3, 4, 5 between two output terminals.

15 and 16. Each electricity storage element 1, 2,

3, 4, 5, provides an electric voltage and an internal impedance between two pads 20 and 21. The accumulator elements 1, 2, 3, 4, 5 are distributed in groups in which they can be connected to each other. parallel or in series and the groups can in turn be connected to each other respectively in series or in parallel.

In the example illustrated in FIG. 1, the stud 20 of an element is connected to the terminal 15 or to the stud 21 of a previous element. We can thus observe the battery represented as a group comprising five elements connected in series or five groups connected in series and each comprising a single element. An ammeter 13 upstream of the terminal 16 makes it possible to measure the current generated by the battery when it is used. If the elements of the battery in total are five in the example illustrated, it will be understood that all the elements can be in any number indifferently less than or greater than five.

Each element accumulator of electricity 1, 2, 3,

4, 5, is inserted on rails or between slides 18 which can easily slide the elements to facilitate disassembly individually or in groups.

The rails or slides 18 are mounted on the vertical walls of a not shown locker and on the bottom of which is printed a bus to connect the pad of an element to the pad of another element, for example as shown in thick line in Figure 1. Ideally the pads 20, 21, are directed down to make contact with the bus when the elements are pushed between the slides in the bin. The arrangement of the studs 20, 21, under the elements and directed downwards, makes it possible to avoid short circuits, in particular by means of a lid, not shown, which by closing the top of the rack, presses on the accumulator elements electricity 1, 2, 3, 4, 5 to ensure good electrical contact of the pads with the bus. A loop 19 disposed on the top of each element, allows to lift the element after opening the lid and thus disconnect the bus element. During the lifting operation, there is no risk of short circuit with the other elements because they are protected by the orientation of their pads, directed towards the bottom of the rack. A component 22 is arranged to implement process steps explained now with reference to FIG. 2.

A step 101 is to evaluate a degree of aging individually associated with a distinct group, including a group comprising a single element.

The degree of aging of an element, taken individually, can be evaluated in different ways. It can be evaluated while the battery is being used by measuring the current delivered by the battery by means of the ammeter 13 and by connecting a voltmeter on the studs 20, 21 to measure the voltage delivered by the element so as to to deduce the degree of aging. It can be evaluated by means of a clock that measures a time that separates the present moment from a previous moment in which the element has been inserted in the battery basket with a known degree of aging.

The degree of aging is advantageously evaluated by an impedancemetry method. The impedancemetry method consists in injecting a variable current of known values into the element or group of elements to be monitored and measuring the resulting variations of voltage across the element or group of elements. The variable current is injected to add only in the element or group of elements, the zero or non-zero base current flowing normally in the battery. It is thus possible to measure the impedance of each element or group of elements, taken in isolation without having to know the no-load voltage or the voltage drop on element pads which is caused by a flow of the base current.

The component 22 is arranged to inject the variable current by means of a current generator 23. The current generator 23 is produced in a known manner, for example by means of a bipolar electrical generator controlled by current by operational amplifiers, with safety saturation in tension.

In a first embodiment (not shown), the component 22 is a portable instrument (not on board) which comprises measuring lugs, each connected to a pole of the current generator 23. The lugs of the component 22 are then connected. on the studs 20 and 21 of an element or at the ends of a group of elements. From a measurement of voltage variation between the lugs, the component 22 deduces the impedance of the element or group of elements, from which it estimates a degree of aging, directly equal to or in function the deduced impedance. The estimated degree of aging is stored in a memory 24 in association with a mark of the controlled element or group of elements. The degree of aging is indicated on a display by a communication means 17. It is then connected the measuring lugs of the component 22 on the pads 20 and 21 of a next element or at the ends of a next group of elements. In a second embodiment, illustrated in Figure 1, the component 22 is embedded in the vehicle. One pole of the generator 23 is connected to a first series of relays 6, 8, 10 and another pole of the generator 23 is connected to a second series of relays 7, 9, 11. For purely illustrative and non-limiting purposes in FIG. , the relay 6 is connected to a bus portion which connects the terminal 15 to the pad 20 of the element 1. The relay 8 is connected to a bus portion which connects the pad 21 of the element 2 to the pad 20 of the element 3. The relay 10 is connected to a bus part which connects the pad 21 of the element 4 to the pad 20 of the element 5. The relay 7 is connected to a bus part which connects the pad 21 of the 1 to the stud 20 of the element 2. The relay 9 is connected to a bus portion which connects the stud 21 of the element 3 to the stud 20 of the element 4. The relay 11 is connected to a part of bus that connects the pad 21 of the element 5 to the terminal 16.

The embedded component 22 is programmed to sequentially close the relays 6 and 7 so as to measure the impedance of the element 1, the relays 7 and 8 so as to measure the impedance of the element 2, the relays 8 and 9 in order to measure the impedance of the element 3, the relays 9 and 10 so as to measure the impedance of the element 4, the relays 10 and 11 so as to measure the impedance of the element 5. Measurement of impedance is carried out by measurement of voltage in module and in phase by means of voltmeter 14. The degrees of aging correlated with each impedance measurement are successively stored in an associative table indexed by an element reference. The associative table is for example stored in the memory 24 of the component 22. In the associative table, it is interesting to match each element reference, a date expressed in terms of the kilometers traveled by the vehicle since the element belongs to the battery, a date expressed in terms of Ah exchanged by the element or a date expressed in terms of duration since commissioning of the element.

We have just developed the case where the impedance, for example at a given current frequency which varies in alternative form, constitutes a characteristic value of degree of aging. Other characteristic values may be envisaged such as, for example, a temporal integral of the temperature undergone by the element or an age of the element. On the other hand in the case where each element is individually controlled voltage, for example in the case of a Li-ion battery, knowing the value of the current flowing through the element and measuring its voltage, we can deduce its internal resistance which can then be a characteristic to determine the degree of aging of the element. This operation can be done in both driving and parking mode at the garage.

The communication means 17 are arranged to transfer information contained in the memory 24, for example to a diagnosis socket of the vehicle (not shown). Incidentally, the communication means 17 are arranged to transfer information to the memory 24, for example since the diagnosis of the vehicle.

A step 102 consists in assigning a classification level to the battery. The potential performance of the battery in use, depend on all the elements that constitute it but also elements considered individually. To be representative, the level of classification explained now takes into account these two components on which the performance of the battery depends. FIG. 3 shows a distribution curve D of the elements or groups of elements of a battery as a function of a characteristic variable Vc of degree of aging. The elements are generally distributed around an average value M with a frequency of occurrence generally higher in the vicinity of the average value and decreasing on both sides. The more homogeneous the set of elements, the more the values of their characteristic variable will be grouped around the average. On the other hand, the more heterogeneous the set of elements, the more the values of their characteristic variable will be dispersed with the effect of flattening the curve centered on the average.

Considering degrees of aging for which the characteristic variable is the impedance of the element, its age, or the amount of its charge and discharge cycles, performance will be higher for the values of the weakest characteristic variable on the left. of the curve and lower for the values of the highest characteristic variable to the right of the curve.

The component 22 contains an arithmetic and logic unit and a few program lines for calculating the average M of the values contained in the memory 24 and measured in the previous step.

The component 22 contains in memory 24, different possible values M _A , M _B , M _c , of average. With reference to FIG. 4, a distribution of elements corresponding to the average value M _A is statistically represented by the left curve. The statistical distribution D of average M _A corresponds to a classification level from which one can expect the best performances in use of the battery because the values of the characteristic variable Vc which represents the degree of aging, are mainly the weakest. A distribution of the elements corresponding to the average value M _c is statistically represented by the curve of right. The statistical distribution D of mean M _c corresponds to a classification level from which it can be expected that passable performances in use of the battery because the values of the characteristic variable Vc which represents the degree of aging, are mostly the highest. A distribution of elements corresponding to the average value M _B is statistically represented by the central curve. The statistical distribution D of mean M _B corresponds to a classification level from which one can expect performances in use of the battery lower than those obtained with the average M _A but better than those obtained with the average M _c .

The component 22 contains a few program lines for comparing the calculated average value M with the possible values M _A , M _B and M _c , within a predetermined tolerance range so as to assign an NC classification level to the battery, using formulas of type: M _< 3M _{A +} M _B ^ _{NC: = A}

2 _ ^ _{xNτ (-} -_ ._ _β,

^{3MB + MC} <M => NC: = C

2

An additional requirement may also be that, in addition, not only must the average belong to one of the ranges defined above, but no element must have a characteristic that exceeds a certain threshold.

If the classification level is A, B or respectively C and the component 22 detects an element whose value of the characteristic variable is greater than a threshold S _A , S _B , or respectively S ₀ , the component 22 generates an alarm and communicates the mark of the characteristic value element which is too high for the class to which it belongs. The number of classification levels may be higher than three. The ranking may be based on other methods than those based on the average of the characteristic variable followed by the different elements or groups of elements constituting the battery and where each class corresponds to a value range of this characteristic.

Another example of a method is that the classification is based on the value of the characteristic of the weakest element or the average of the x weakest elements. There are many other methods of classification.

If the control shows that the battery has passed from class A (new battery) to class B, the user has the choice of accepting a battery classification or asking to exchange the most important elements. weak to maintain the battery in class A.

If the control shows that the Battery is classified C, the customer has the choice to accept this classification of the battery or ask to exchange the weakest elements to maintain the battery in class B or possibly pass it in class A.

A step 103 consists in replacing the defective elements with elements that have already been used and which are recycled and whose classification has been determined beforehand at a level a, b, c as being the most suitable respectively for being integrated into a level battery. A take the example of a removed element to maintain a battery in class A, the characteristic followed by the element showing a state of aging higher than the criterion of class A. Suppose this element is classified b. This element can then be used later to mount a class C battery in class B. The standard exchange of elements or groups of elements by new or used elements, is facilitated by the mechanical design of the battery basket shown in Figure 1, which is optimized in terms of volume, weight and safety.

The individual control of each element or group of elements and the design of the battery basket designed to replace the elements or groups of the most degraded elements, keeps the battery to the best of its performance. By removing the battery throughout its life, the most degraded elements, all elements age homogeneously.

In the case for example of a Li-ion battery, it is necessary not to exceed a low voltage threshold for each element constituting it during the discharge and a high threshold for each element during charging. Therefore, it is the element that will have for example the highest impedance or internal resistance that will limit the capacity of the Li-ion battery. For this reason, it is important to have a mapping of the characteristics related to the performance of each component of the battery to be able to exchange elements limiting the performance of the overall battery.

On the other hand, depending on their location in the vehicle, the thermal environment of each element can vary greatly from one element to another and therefore the degree of aging of each can be very different. One solution is to change the most degraded elements by the temperature. Another solution is as a preventive measure, to periodically switch the elements of the hottest locations, for example closer to the engine, with those of the coldest locations, for example the farthest from the engine, to allow a more homogeneous aging possible drums. This is also facilitated by an individual control of each element or each group of elements and a battery basket design that allows the permutation of elements.

Claims

A method of classifying a battery made by assembling accumulators of electricity distributed in groups, comprising the steps of:

- evaluate degrees of aging, each associated with a distinct group;

assigning to the battery, according to statistical distribution parameters of the aging degrees evaluated, a classification level that is representative of the potential performance of the battery in use; said method being characterized in that the degree of aging of at least one group is evaluated by an impedancemetry method as a function of a current measurement which passes through the group of elements and a voltage measurement.

2. Method according to claim 1, characterized in that it comprises a step consisting of:

replace at least one first group with a second group so as to maintain the classification level of the battery.

3. Method according to claim 2, characterized in that the first group is replaced by permutation in the battery with the second group exposed, before permutation, to lower utilization constraints than the first group.

4. Method according to claim 3, characterized in that the constraints of use comprise a temperature.

5. Method according to claim 2, characterized in that the first group is replaced by a second group from another battery with a lower degree of aging.

6. Method according to claim 2, characterized in that the first group is replaced by a second group with a zero degree of aging.

7. Method according to one of claims 1 and 2 or 5 and 6, characterized in that a group comprises all the elements of the battery.

8. Method according to one of claims 1 to 6, characterized in that a group comprises a single element of the battery.

9. Method according to one of the preceding claims, characterized in that the statistical distribution parameters comprise an average of the degrees of aging and / or a higher value of the degrees of aging evaluated.

10. Device for classification of a battery made by assembling electrically accumulating elements (1, 2, 3, 4, 5) distributed in groups, comprising a component (22) arranged for:

- evaluate degrees of aging, each associated with a distinct group;

assigning to the battery, according to statistical distribution parameters of the aging degrees evaluated, a classification level that is representative of the potential performance of the battery in use; said device being characterized in that the component (22) is arranged to evaluate the degree of aging of at least one group by an impedancemetry method as a function of a current measurement which passes through the group of elements and a measure of tension.

11. Device according to claim 10, characterized in that it comprises slides (18) which hold the accumulator elements (1, 2, 3, 4, 5) to achieve the battery and which allow to replace at least a first group by a second group so as to maintain the classification level of the battery.

12. Device according to one of claims 10 and

11, characterized in that the component (22) comprises communication means of the classification level and the degrees of aging evaluated.

13. Device according to one of claims 10 to

12, characterized in that a group comprises all the elements of the battery.

14. Device according to one of claims 10 to 12, characterized in that a group comprises a single element of the battery.

15. Device according to one of claims 10 to 14, characterized in that the statistical distribution parameters comprise an average of the degrees of aging and / or a higher value of the degrees of aging evaluated.