CALCULATING AT LEAST A WEAR PARAMETER

Technical field

The present invention relates to a method for calculating a wear parameter of a battery and/or single cell also inside a battery as well as a battery comprising sensors needed to implement such method and respective battery charger.

The device object of the present invention relates also a cell apt to be assembled with other cells to form a battery pack, and at the same time apt to be individually connected to a battery charger and respective control unit, and it is used to guarantee a longer useful life to battery packs, to reduce costs in case of breaking or performance; losses of one or more cells forming the battery pack, to avoid breaking, damages or weakening of the engine or any other user of a battery pack in case of damages or performance losses of one or more cells forming the battery pack.

The device allows also to know the wear level precisely in every moment and so the residual useful life of the battery pack and/or each single cell forming the battery pack, and as a consequence the wear level and the residual useful life of the battery pack formed by more assembled cells, and it guarantees that each cell is charged up to the maximum charge level or the charge level selected by the user.

Such device aims at eliminating one of the main reasons against the diffusion of electric vehicles and at improving the functioning of those users that need a battery pack. Nowadays, battery packs are formed by the assembly of more cells which, even if they form a sole battery pack so that they provide a sole battery, and even if they are charged in series, they maintain anyway their individual features of charge, duration, structure etc., so much that each one of them affects the duration and efficiency of the whole battery pack. It is known that when one or more cells break, battery pack voltage diminishes. Therefore, the battery pack has to supply more current in order to supply the same power.

This causes more damages since the still functioning cells of the battery pack discharge faster and so, they wear out faster thus reducing the duration of their useful life with a cascade effect: the more the cells wear out, the more the voltage of the whole battery pack diminishes, which so has to supply more current thus wearing out the ce11 s even faster .

On the other hand, the engine, if supplied by a voltage lower than the nominal one, absorbs greater current, overheats uselessly, thus reducing its useful life; in fact by increasing dissipated power in heat, with equal produced mechanical power the engine gets older earlier.

In addition, since it reduces strongly the duration of the whole battery pack the breaking of one or more cells implies after short time more costs needed to buy the whole battery pack.

And yet, when charging the battery pack containing one or more damaged cells, the good cells forming the same battery pack are charged beyond their maximum capacity with the risk of damaging or exp1os ion the eof .

On the other hand, if a cell forming the battery pack is damaged, it is needed more time to charge the battery pack, with an increase of recharging costs and the explosion risk.

State of the art

Currently, there are known methods to indicate the functioning condition of a single cell, shown for example in DE 102015002069, but not its wear level. At the state of the art there are known examples of batteries provided with devices for indicating the charge condition or for single cells charge condition optimization. A first embodiment is described in the document DE 102015002069A1 , wherein it is shown a battery provided with an indicator of its condition. A second example is described in the application EP2207221, wherein it is shown a battery formed by a series of cells removably coupled to each other. The document US2005/0029986 describes instead a plurality of cells connected in parallel for supplying a load, each cell being provided with an own recharging device. Yet another example is described in the application of the Italian patent MI2009A001868, wherein it is described a method for determining the variations of the charge condition. (SOC) of a battery in dynamic conditions by measuring the voltage of the same.

Technical problem.

The ones cited and many other examples known at the state of the art are limited since they do not allow to determine quantitatively a wear parameter of ai battery pack and/or single cell of the same that allows to evaluate its residual useful life. It is clear that the possibility to evaluate the residual useful life of a battery and/or single cell inside the same has important implications both technica1 , sinee it a11ows t o optim.i ze maintenance and duration of the useful life of the same, and economical, since it allows to assign an objective economical value to a battery or a used cell .

These results are yet more relevant when the wear level is determined with reference to the single cell constituting the battery pack, since besides an optimization of the charging process they allow to intervene, if needed, with a replacement of the single cell, thus avoiding the beginning of the above-described vicious cascade wear process.

Aim of the invention

Therefore, aim of the present invention is to provide a method for calculating a wear parameter of a battery.

According to another ai . the present invention provides a method for calculating a wear parameter of a single cell inside a battery pack.

Yet, according to another aim the present invention provides cells, a battery pack and respective charging means configured for implementing the method for calculating a wear parameter.

Brief description

The present invention realizes the prefixed aims since it is a battery pack comprising: at least a current sensor configured so that it measures the discharge current of said battery ^' pack, at least a current sensor configured so that it measures the charge current of said battery pack, at least a voltage sensor configured so that it measures the voltage of said battery pack, at least a temperature sensor, electronic means configured for measuring time as well as for acquiring and storing data measured by said current, voltage and temperature sensors, said electronic means being configured for calculating at least a wear parameter, wherein said at least wear parameter is calculated as the sum of the contribution of each single total or partial charging- and discharging cycle, and wherein said contribution of each single total or partial charging cycle is calculated as a function of the charging time, battery voltage during said charging time, charge current and temperature du i g the charging step and wherein said contribution of each single total or partial discharging cycle is calculated as ai function of the discharging time, battery voltage during said discharging time, discharge current and temperature duri ng the discharging step.

The invention further provides a battery pack comprising a plurality of cells electrically connected in series and/or parallel and assembled to each other so that they can be individually removed from said battery pack, each one of said ce11 s compri s ing :

- electrical terminals which allow charging thereof independently to the other cells of said battery pack,

- a current sensor configured so that it measures single cell charge current values,

- a voltage sensor configured so that it measures single cell voltage values,

a temperature sensor configured so that it measures single cell temperature values

- electronic means configured for measuring time as well as for acquiring and storing data measured by said current, voltage and temperature sensors of the single cell, as well as for acquiring and storing data measured by said current sensor which measures the discharge current of the battery pack, said electronic means being configured for processing a wear parameter relating to the single cell, wherein said wear parameter relating to the single cell is calculated as the sum of the contribution to wear of the cell of each single total or ^' partial charging and discharging cycle and wherein said contribution of each single total or partial charging cycle is calculated as a function of the charging time and voltage, current and temperature of the cell during the charging step and wherein said contribution of each single total or partial discharging cycle is calculated as a function of discharging time and current and temperature of the cell during the discharging step.

As it is briefly described and shown in figures, according to a first embodiment the present device comprises cells apt to be assembled so that they form a battery pack.

The feature of these cells is that, even if they can be assembled in the number desired (according to need} so that they form a sole battery pack, in case one or more cells of such battery pack do not function, it is possible to replace only the not functioning cells, for which a performance loss or damage has been detected, thus maintaining all the cells in good or optimum condition, which form the same battery pack.

According to another embodiment the battery pack according to the invention comprises at least a sensor configured for measuring charge current, at least a sensor configured for measuring battery voltage and at least a sensor configured for measuring battery temperature, so that the calculation of the wear parameter is allowed according to the logic described in the following in the present document.

Moreover, preferably the battery according to the present invention comprises electronic means for acquiring data detected by said sensors, for calculating a battery wear parameter as a function of said data and for storing the same.

According to an alternative embodiment the battery comprises electronic means configured so that the data detected by said sensors are transmitted to an outer processing control unit, which, as a way of example, can be ^' provided in the battery charger or in the cell or in the battery or elsewhere.

According to another embodiment each cell forming the battery pack is provided with a battery charger with a control unit able to determine the cell condition, with indication of all the parameters relating to the functioning of the same and which allows that each cell of the battery pack is charged up to its individual maximum charge level or the one selected by the human operator .

Therefore, while currently used battery chargers measure only temperature and/or voltage and/or current absorbed by the battery pack as a whole but do not consider the cell history to determine the kind of charge needed and the residual useful life of every single cell, in the present device instead, even if there are battery charger and control unit for each cell forming the battery pack, such battery charger and control units (which can be arranged in different places or in a sole place) are controlled by a global control unit (fig, 8 n° φ) which manages both the charging and the functioning condition of the cells forming the battery pack and transmits the information to indicators arranged near the user.

In addition,, another feature of the ^' present device is that all voltage, current, temperature and time values relating to the cell are read by appropriate measuring devices suitably connected inside the circuit (5, 6, 7) and sent to the control unit which processes them for determining a "F" wear parameter of the cell.

As yet said, such values can be measured for the whole battery or with reference to the single cell. Hence, the features of such devices are used to solve all the above described ^' problems.

In fact thanks to this device, in case it breaks up or there is a performance loss of only one or more cells forming the battery pack, it will be possible to replace inside the same battery pack the single broken cell (whose breaking is suitably signaled by a detector arranged for example near the human operator) with a new one or with one in good condition.

This allows that the battery pack of the present device guarantees to the engine supplied thereby the same useful power, since it is sufficient to replace the only damaged cell so that the voltage is not reduced and so that the battery pack has not to supply greater current .

In this way, since with the replacement of the only damaged cell in the battery pack the voltage will not be reduced and so greater current will not be supplied, the good cells of the battery pack will continue to supply the current they have been dimensioned for and will neither discharge faster, nor their useful life will be reduced.

Much less they will worsen the battery pack performance.

And, in this way, in the engine there will not be problems of overheating, damaging or reduction of its useful life either.

In addition, the pure replacement of the only damaged cell leads to low costs limited to the replacement of the only damaged cell and not of the whole battery pack.

On the other hand, with such device there will be neither an increase in recharging costs nor an explosion problem of the good cells, since the same will be supplied up to their charge level.

And yet, thanks to a control unit, it is possible to individuate the wear level of each single cell forming the battery pack and its residual useful life, since sometimes the cells ca be charged and/or discharged faster, thus reducing their residual life.

On the other hand, the provision of a battery charger for each single cell forming the battery pack allows that each cell is charged up to its maximum individual charge level.

Obviously, in case voltage and current parameters are detected with reference to the whole battery, these advantages will be relating to the evaluation of the residual life of the whole battery, and not of the single cell.

The present invention can be better understood from the detailed description of some embodiments provided in the following as a way of not limiting examples and with reference to the appended drawings. In the drawings:

Fig. 1 shows the single cell; fig. 2 shows two assembled cells with respective electrical connections; fig. 3 shows the recharging system of the assembled cells in a battery pack and the supplying system of an engine or a user through the assembled cells i a battery pack; fig. 4 sho s the case in which the cells forming the battery pack are electrically connected and in several available spaces; fig. 5 shows the whole recharging system of the single cell with also the user connected, with the switches positioned for carrying out the cell charging; fig. 6 shows the whole recharging system of the single cell with also the user connected, with the switches positioned for supplying a user, for example an engine; fig- 7 shows the whole recha ging system of the single cell with also the user connected, with the switches positioned for supplying a known load and so for determining the current or power which said cell is able to store; fig. 8 shows more recharging systems of the assembled single cells for supplying the user- connected, with the switches positioned for supplying a user, for example an engine; fig. 9 shows a detail of the second embodiment; figure 10 shows an embodiment of the battery pack configured so that a wear parameter for the whole battery pack is calculated; figures 11 to 13 show electrical schemes of further embodiments of the device according to the invention.

An embodiment of the present invention relates to a device, comprising:

- cells (If) which can be assembled so that a sole battery pack is formed, which can be connected to a battery charger which takes current from an outer electric source, and provided with a control unit for managing cell charging and/or discharging;

- an indicator of the functioning condition (3d) of each cell, near the human operator; - voltage, current, temperature sensors which send acquired signals to the control unit.

Such embodiment comprises a plurality of cells (fig. 1) connected in series and/or in parallel to each other, apt to form, a sole battery pack (3a) , each cell comprising:

means apt to assemble more cells, which for example can be realized with complementary guides (la), an abutment (lb) and a housing for the abutment (lc) ;

poles ha ing the configuration of a holed parallelepiped (Id) apt to realize both the electrical (2b) and mechanical connection by means of fixing means (2a) among the various cells forming the battery pack, and apt to realize the electrical connection (3b) between each cell and its own battery charge with respective co trol unit, and apt, the poles of the cells being arranged at the ends of the battery pack, to realize the electrical connection (3c) between the battery pack and the engine or any other user;

a sensor (12) apt to detect cell temperature values .

In this embodiment each cell comprises also an electrical circuit provided with switches thanks to which it can take three different configurations, shown in figure 5 to 7, depending on whether the cell forming the battery pack is considered:

- as single unit when it is charged, and in such case the charging contact (5n) is closed and the other 2 contacts (5m, 5o) are open;

- as an unit connected in series (fig. 8) with the other cells of the battery pack when the battery pack supplies the engine or any other user, and in such case the supplying contact of the outer load (5o) is closed and the other 2 contacts (5n, 5m) are open;

- as a single unit when the self-test of the cell is carried out, and in such case the supplying contact of the test electric load (5m) is closed and the other 2 contacts (5n, 5o) are open.

According to this embodiment, i the first step a battery charger (5a) (supplied by an outer electric source) is arranged for charging each si gle cell autonomously and independently for each cell, considering the cell temperature (suitably signaled by a sensor (le) provided on the cell) and until it receives such charging command by the control unit (5f) . The control unit determines firstly voltage and charge current and threshold values on the basis of battery features, on the basis of the slow or fast charging mode set by the human user, on the basis of cell voltage and on the basis of a parameter "F" value which indicates the cell wear condition. During charging the control unit- controls continuously if such parameters are reached so that it interrupts charging (because the cell is charged or overheated) at the right time. All voltage, current, temperature and time values relating to the cell are read by appropriate measuring devises (5g, 5i, 5e, 5h) suitably connected inside the circuit (figs. 5, 6, 7} and sent to the control unit (5f) which processes them for determining the cell wear parameter "F".

In particular, the parameter "F" is stored and calculated by the control unit by processing values of the charge current (lc) measured by the amperometer (5i) , of the charge voltage (V) measured by the voltmeter (5g) , of the temperature of the cell (T) measured by the temperature sensor (5h) , besides to the charging time (T charging} and the discharging time (Tdischarge) · The battery discharge current is read by a suitable sensor (5i) and it is the same for all cells thanks to their connection i series. It is to be specified that as a function of the needs connected to the specific application, the cells forming the battery pack can be connected in series, in parallel or in a plurality of strings, each string being formed by more cells connected in parallel to each other, and the various strings connected in series to each other .

In case of cells connected in parallel it is sufficient a voltmeter for measuring all the cells voltage. Concerning amperoraeters configured so that the cells charge current is measured, according to the specific needs there can be used:

- a sole amperemeter for the whole battery pack or

- an amperometer for each cells string or

- an amperometer for each cell.

The control unit determines also the number of charging and discharging cycles (Nc, Ns) by analyzing if there is current passage and in what direction by means of amperoraeters positioned in dif ferent points in the charging circuit (5e, 5i) , and calculates also the current generated by the engine when the engine is used as regenerative brake, thus becoming a generator itself. The wear parameter "F" is calculated by processing the above described values since such values are those affecting the cell duration the most.

Such parameter "F" can be stored in the cell or in the battery charger or in both of them., or on any other medium known at the state of the art. Preferably, the electronic means are configured so that they guarantee that said parameter "F" cannot be modified in fraudulent way. Therefore, there can be used one of the anti-fraud methods known at the state of the art, for example used for storing the kilometers covered by automobiles .

According to a preferred embodiment the wear parameter (F) is calculated as the sum of the contribution to wear of the battery pack (or of the single cell) of each total or partial charging and discharging cycle. Said contribution of each total or partial charging cycle is calculated as a function of the charging time, battery voltage during said charging time, charge current and temperature during the charging step, said contribution of each single total or partial discharging cycle is calculated as a function of the discharging time, battery voltage during said discharging time, discharge current and temperature during the discharging step.

A formula example for determining the parameter "F" is the following, which can be referred, with equal formulation, both to cell and battery pack:

F -

F = parameter indicating wear condition Vj Vk = voltage at the ends of cell or battery pack [ V ] Ic = charge current of cell or battery pack [A] = temperature of cell or battery pack [C°]

Tcharging: charging time [s]

Nc = number of charging cycles

Ns = number of discharging cycles Is = discharge current [A]

Tdischarging = discharging time [s]

The maximum wear level, i.e. the maximum limit which, on the average for a certain battery model, the parameter "F" can reach, is determined experimentally by working out an average of a remarkable number of cells when performance diminishes .

Then there is the step (shown in figure 6} in which the cell, whether single or assembled with the other ones, supplies the engine or any other user and at the same time sends voltage (5g) , current (5i) ancl temperature data of the cell (5h) to the control unit (5f) , which data are needed to calculate the above cited parairieter "F".

A single cell is generally assembled in series with other cells so that a sole battery pack is formed and in such case {fig. 8) the engine is supplied by all the cells assembled in a sole battery pack. All the control units of the assembled single cells send the cells functio ing parameters to an indicator arranged near the human operator, so that it is possible to individuate the possible cell functioning with reduced performance or damaged or which determines the bad functioning of the whole battery pack which is no more able to supply the engine with the correct voltage and current, thus safeguarding the useful life of the other cells forming the whole battery pack and the engine supplied by such battery pack.

It is to be specified that, with reference to the embodiment in which a wear parameter is calculated for the whole battery shown in figure 10, the elements needed are indicated with references having the number 6 followed by a letter equal to the one of same elements shown in figures 5, 6 and 7. In figure 10 the cells are shown enclosed inside an envelope (6p).

Optionally (fig, 4), with still the same electrical elements, the single cells, even if they form a sole battery pack as a whole, they can be displaced in more places according to dimensions and/or weight balancing needs.

With the ust described device, it is possible to carry out a test of the cha ge which can be really stored by a cell. To such aim the cell is first charged to its maximum, charge limit, then it is discharged on a fictitious load (5d) and time, voltage and current are measured during the discharging step, until voltage goes under a certain threshold level. So, it is determined how much energy the cell can yet store.

Obviously, and as yet said, a similar speech can be done with reference to the whole battery pack. The needed elements are shown in figure 10, where it is observed a battery ^' pack formed by a plurality of cells connected in series to each other for supplying an electric load, as for example an engine. The battery pack is provided with a sensor for measuring charge current, a sensor for measuring discharge current, a sensor for measuring battery pack voltage and a sensor for measuring temperature, as well as a control unit for acquiring data detected by said sensors. The battery pack is also configured so that it can be connected to a test electrical load, for measuring the electric current storable according to the just described logic.

A secondo embodiment (fig. 9) of the present invention relates to a device which is different from the first embodiment only because the cells are introduced in a container for cells apt to allow the electric connection among all cells forming the battery pack.

All the different modifications and variants to the above described embodiment are considered comprised in the present invention .