Patent Publication Number: US-11031791-B2

Title: Electronic adjusting device for electric energy storing apparatus of the type provided with batteries

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a U.S. National Phase 35 U.S.C. § 371 Application based on International Patent Application No. PCT/EP2017/050454 filed on Jan. 11, 2017 and published as WO/2017121745A1 on Jul. 20, 2017, which claims benefit and priority to Italian Patent Application No. 102016000002586 filed on Jan. 13, 2016. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
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     INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC OR AS A TEXT FILE VIA THE OFFICE ELECTRONIC FILING SYSTEM (EFS-WEB) 
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     STATEMENT REGARDING PRIOR DISCLOSURES BY THE INVENTOR OR A JOINT INVENTOR 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of electric energy storing apparatus of the type provided with batteries. 
     More in particular, the present invention relates to an electronic adjusting device for electric energy storing apparatus with batteries that allows rapid and effective balancing of the feeding currents supplied to an electric load by the battery modules. 
     There are known numerous examples of electric energy storing apparatus for use in electric systems, either isolated or connected to the electric power network. 
     Among these, electric energy storing apparatus of the type provided with batteries are widely used. 
     An electric energy storing apparatus with batteries typically comprises a plurality of battery modules electrically connected to one another in series and/or in parallel and connectable, as a whole, with an electric load to feed this latter. Each battery module generally comprises a plurality of cells electrically connected in series and/or in parallel. 
     As is known, when a storing apparatus with batteries is electrically connected to an electric load, it is desirable for the currents supplied to the electric load by the battery modules to have the same or very similar intensity. 
     Unfortunately, the electric impedance (internal and of the electric connections) and the storing capacity of the battery modules are subject to variations linked to differences in construction, installation and/or operation. 
     Generally, this makes it impossible to obtain a natural balancing of the feeding currents supplied by the battery modules and, consequently, a uniform discharge process of the cells, resulting in a decrease in the total electric energy storing capacity and in the maximum current that can be supplied to the electric load. 
     Moreover, as amply demonstrated by experience in the field, in some circumstances the lack of balance of the feeding currents supplied can rapidly lead to interruptions in the operation of the battery modules. 
     In order to overcome the problems indicated above, many electric energy storing apparatus of the type provided with batteries are provided with electronic devices for adjusting the feeding currents supplied by the battery modules. 
     2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98 
     The patent application US2005/0275372A1 describes an electronic adjusting device that allows balancing of the currents supplied by disconnecting from the electric load, time by time, the battery module that has a too high a charge with respect to the other battery modules. The U.S. Pat. No. 6,208,039 describes an electronic adjusting device that comprises, according to control architecture of “master-slave” type, a centralized control unit intended to provide control signals for a plurality of DC/DC converter circuits, each of which is on a battery module to adjust the current it supplies to the electric load. 
     The U.S. Pat. No. 7,589,498 describes an electronic adjusting device that comprises, again according to control architecture of “master-slave” type, a centralized control unit intended to provide multiple reference signals for adjusting units on the battery modules. Each adjusting unit comprises a plurality of control loops concurrent with one another to adjust the current supplied to the electric load by the corresponding battery module. 
     The patent application US2012/112701A1 describes a further example of electronic adjusting device of the state of the art. 
     BRIEF SUMMARY OF THE INVENTION 
     In general, the prior art solutions, illustrated above, have limits in terms of effectiveness and/or promptness in the adjustment dynamics of the currents supplied to the electric load that are not negligible. 
     Moreover, these solutions are characterized by structures that are relatively complex to produce in practice with high manufacturing costs that have a significant influence on the total industrial costs of the electric energy storing apparatus. 
     The main task of the present invention is to provide an electronic adjusting device for electric energy storing apparatus of the type provided with batteries that allows the aforesaid problems to be solved and overcome. 
     Within this task, an object of the present invention is to provide an electronic adjusting device that makes it possible to obtain rapid and effective balancing of the currents supplied to the electric load by the battery modules. 
     A further object of the present invention is to provide an electronic adjusting device that is particularly reliable, has a particularly simple structure and that is easy to manufacture on an industrial scale, at competitive prices with respect to conventional adjusting devices. 
     This task and these objects, together with other objects that will be more apparent from the subsequent description and from the accompanying drawings, are achieved, according to the invention, by an electronic adjusting device for electric energy storing apparatus of the type provided with batteries, according to claim  1  below and to the related dependent claims. 
     In a further aspect thereof, the present invention relates to an electric energy storing apparatus, according to claim  11  below and to the related dependent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
       Characteristics and advantages of the present invention will become more apparent with reference to the description given below and to the accompanying figures, wherein: 
         FIG. 1  schematically illustrates an electric energy storing apparatus with batteries comprising an electronic adjusting device according to the present invention; and 
         FIG. 2  schematically illustrates an electronic adjusting device according to the present invention, in a preferred embodiment; and 
         FIG. 3  schematically illustrates the operation of an example of electric energy storing apparatus with batteries comprising an electronic adjusting device according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to the cited figures, the present invention relates to an electronic adjusting device  1  for an electric energy storing apparatus  100  of the type provided with batteries. 
     The storing apparatus  100  comprises a plurality of battery modules  10  electrically connectable with an electric load (not illustrated) to provide this latter with electric power. 
     In general, the number of battery modules  10  of the apparatus  100  can be any, according to needs. By way of example,  FIG. 1  shows an apparatus  100  comprising N (N&gt;=2) battery modules connected in parallel to one another. 
     In some embodiments, however, the apparatus  100  can comprise a plurality of battery modules  10  connected to one another in a different way than illustrated, for example in series. Preferably, each battery module  10  is connected to a pair of output terminals OUT+, OUT−, at which it is electrically connectable with the electric load to feed this latter, and to a pair of input terminals IN+, IN−, at which it is electrically connectable with an electric power source for charging. 
     In some embodiments of the apparatus  100 , as illustrated in  FIG. 1 , the pairs of input terminals IN+, IN− and output terminals OUT+, OUT− of each battery module  10  can have a common terminal, for example the ground potential terminal. 
     Each battery module  10  advantageously comprises one or more cells  11  electrically connected to one another in series or in parallel. 
     The cells  11  can be of the lead-acid, nickel-cadmium, sodium-sulfur, nickel-metal hydride, sodium-metal chloride, redox, iron-ion, aluminum-ion or sodium-ion type and the like. 
     Preferably, the cells  11  are of lithium-ion type. 
     Preferably, each battery module  10  comprises an electronic control device  12  adapted to manage operation of the related cells  11 . 
     The electronic control device  12  is adapted to implement functions of detecting and managing the state of charge of the cells  11 , protective functions (such as from over-voltages, over-currents, over-temperatures and the like), communication functions with any other electronic devices of higher level, or the like. 
     An example of construction of a battery module  10  can be represented by a “smart battery pack” known with the trade name GENIOL™ 460. This battery module is provided with four groups of cells connected to one another in series. Each group of cells is in turn formed of 6 cells connected to one another in parallel. This battery module can, for example, have a rated storage capacity of 20-40 Ah, a rated voltage of 10-15 V and a rated discharge current of 10-30 A. 
     According to the invention, the apparatus  100  comprises an electronic adjusting device  1  adapted to adjust the feeding current supplied to the electric load by the battery modules  10 . 
     The electronic adjusting device  1  comprises a plurality of electronic adjusting units  2 . 
     Each electronic adjusting unit  2  is comprised in a corresponding battery module  10  and is adapted to adjust the feeding current IL provided to the electric load by the cells  11  of the corresponding battery module. 
     By way of example, each electronic unit  2  can be integrated in a circuit board together with the electronic control device  12  and positioned, together with the cells  11 , inside a protective enclosure of the corresponding battery module  10 . 
     Preferably, the electronic device  1  comprises an electronic adjusting unit  2  for each battery module  10  comprised in the apparatus  100 . 
     In some embodiments of the invention, however, the electronic device  1  could comprise a total number of electronic adjusting units lower than the total number of battery modules  10  present in the apparatus  100 . 
     In general, the relation 2&lt;=M&lt;=N is valid, where N and M are respectively the number of battery modules  10  and the number of electronic adjusting units  2  present in the apparatus  100 . 
     The electronic device  1  comprises an electronic bus  3  connected in parallel to the electronic adjusting units  2  to allow communication between these latter. 
     In particular, the electronic bus  3  is adapted to make available a bus signal VBUS to the electronic adjusting units  2 . 
     The bus signal VBUS is indicative of a minimum feeding current provided to the electric load by the battery modules of the apparatus  100 . 
     For clarity, it is specified that the term “minimum feeding current” identifies the feeding current provided to the electric load by one of the battery modules of the apparatus  100  when this feeding current is lower than the feeding currents provided by the other battery modules. Naturally, the bus signal VBUS can vary in time as a function of the operating status of the various battery modules of the apparatus  100 . 
     In fact, the feeding current provided by any battery module of the apparatus  100  can vary according to the state of charge and any variations in the electric impedance of the related cells and of the related electric connections. 
     This means that the minimum feeding current value provided to the electric load can vary in time, as can the battery module that supplies this minimum feeding current. 
     According to the invention, each electronic adjusting unit  2  comprises a first electronic stage  21  arranged so as receive the bus signal VBUS and a first detection signal S 1 . 
     The detection signal S 1  is indicative of the feeding current IL provided to the electric load by the cells  11  of the corresponding battery module  10 . 
     The electronic stage  21  is configured so as to process the input bus signal VBUS and the input detection signal S 1  received, and to provide a new bus signal VBUS modified to make it available, through the electronic bus  3 , to the electronic adjusting units  2 . 
     The modified bus signal VBUS is provided by the electronic stage  21  only in the case in which the feeding current IL, provided by the cells  11  of the corresponding battery module  10 , is lower than the aforesaid minimum feeding current. 
     In other words, the electronic stage  21  is configured so as to provide a bus signal VBUS different from the bus signal VBUS initially made available by the electronic bus  3 , if the feeding current IL provided by the corresponding battery module  10  is, for any reason (for example due to variations in impedance of the cells  11 ), lower than the minimum feeding current value made available by the electronic bus  3 . 
     In practice, the electronic stage  21  is configured so as to provide a bus signal VBUS indicative of a new minimum feeding current value, in the case in which the feeding current IL provided by the corresponding battery module  10  has become the minimum feeding current provided to the electric load, i.e., is lower than the current value initially made available by the electronic bus  3  and, therefore, lower than the feeding current provided by part of the other battery modules of the apparatus  100 . 
     Preferably, each electronic adjusting unit  2  comprises a second electronic stage  22  configured so as to receive and process the bus signal VBUS and the detection signal S 1  and to provide a first control signal A based on the behaviour of the aforesaid signals. 
     Preferably, each electronic adjusting unit  2  comprises a third electronic stage  23  arranged so as to receive the control signal A and to provide, when enabled by the control signal A, a second control signal R. 
     Preferably, each electronic adjusting unit  2  comprises a fourth electronic stage  24  having terminals  241 ,  242  electrically connected to the electric line that connects the cells  11  to the electric load so that the feeding current IL provided to the electric load by the cells  11  of the corresponding battery module  10  flows through them. 
     The electronic stage  24  is adapted to adjust the feeding current IL, when it receives the control signal R from the electronic stage  23 . 
     In particular, the electronic stage  24  is configured so as to reduce the feeding current IL in response to an input control signal R possibly received from the electronic stage  23 . 
     In some embodiments of the invention, the electronic stage  24 , although part of the electronic adjusting unit  2 , can be used also for other purposes with respect to the purpose illustrated above. 
     For example, it can be intended also to act as electronic decoupling circuit to disconnect the corresponding battery module  10  from the electric load during charging of the respective cells  11  or in the event of an electrical fault. 
     According to a further example, the electronic stage  24  can be intended to act as protective electronic circuit to disconnect the corresponding battery module  10  from the electric load in the event of over-voltages on the electric load. 
     In the cases illustrated, the electronic stage  24  can receive further control signals also from other devices of the battery module  10  (for example, from the electronic control device  12 ) to control operation thereof in the absence of the control signal R. 
     In some embodiments of the invention, as illustrated in  FIG. 2 , the electronic stage  22  is arranged so as to receive a second detection signal S 2  indicative of the voltage at the ends of the electronic stage  24 , i.e., along the electric line that connects the cells  11  to the electric load, at the terminals  241 ,  242  through which the feeding current IL provided to the electric load by the cells  11  of the corresponding battery module  10  flows. 
     Preferably, the electronic stage  22  is configured so as to provide the control signal A based on the behaviour of the detection signal S 2 . 
     Preferably, each electronic adjusting unit  2  comprises a fifth electronic stage  25  arranged so as receive a first measuring signal M 1  of the feeding current IL provided to the electric load by the cells  11 . 
     Preferably, the electronic stage  25  is configured so as to provide the detection signal S 1 , obtained as a function of the measuring signal M 1 , at an output terminal  251 . 
     Preferably, the electronic stage  25  is arranged so as to receive a second measuring signal M 2  of the voltage at the ends of the electronic stage  24 , i.e., at the terminals  241 ,  242 . 
     Preferably, the electronic stage  25  is configured so as to provide the detection signal S 2 , obtained as a function of the measuring signal M 2 , at an output terminal  252 . 
     Preferably, the electronic stage  25  comprises one or more amplification circuits configured, according to known design techniques, so as to process the measuring signals M 1 , M 2  and to provide the detection signals S 1 , S 2  (preferably in voltage) at the respective output terminals  251 ,  252 . 
     Preferably, the electronic stage  25  receives the measuring signal M 1  from a first measuring circuit  27  configured to detect the feeding current IL, along the electric line that connects the cells  11  and the electric load, and to generate the measuring signal M 1 . 
     The measuring circuit  27  can comprise, for example, a resistive shunt arranged along the electric line that connects the cells  11  and the electric load so as to provide a voltage signal M 1  indicative of the feeding current IL. 
     Preferably, the electronic stage  25  receives the measuring signal M 2  from a second measuring circuit  28  configured to detect the electric voltage between the terminals  241 ,  242  of the electronic stage  24  and to generate the measuring signal M 2 . 
     The measuring circuit  28  can, for example, comprise a pair of electrodes connected to the terminals  241 ,  242 , along the electric line that connects the cells  11  and the electric load, so as to provide a voltage signal M 2  indicative of the voltage between the terminals  241 ,  242  of the electronic stage  24 . 
     According to some embodiments of the invention, illustrated for example in the cited figures, the measuring circuits  27 ,  28 , although part of the electronic unit  2 , can also be used for other purposes (for example as passive protection from over-currents or over-voltages) or also to send the measuring signals M 1 , M 2  to other electronic devices of the battery module  10 , for example to the electronic device  12 . 
     According to preferred embodiments of the invention, the electronic device  1  (in particular the electronic bus  3  and the electronic adjusting units  2 ) is formed of electronic circuits of analog type so as to ensure reduced response times (in the order of 10-50 ms) in adjusting the feeding current IL. 
     According to preferred embodiments of the invention (illustrated in the cited figures), the electronic bus  3  and the electronic adjusting units  2  are arranged so that the bus signal VBUS, the detection signals S 1 , S 2  and, more generally, the input/output signals to the electronic stages  21 - 25  are electric voltage signals. This makes it possible to simplify the circuit structure of the electronic device  1 , in particular of the electronic adjusting units  2 . 
     Hereunder, with reference to  FIG. 2 , a preferred embodiment of the invention will be described in greater detail. 
     Preferably, as illustrated in the cited figures, the electronic stage  21  comprises a first input terminal  211 , a second input terminal  212  and a first output terminal  213 . 
     Preferably, the input terminal  211  is connected to the electronic bus  3  to receive the bus signal VBUS (voltage) made available by this latter, the input terminal  212  is connected to the electronic stage  25  (at the terminal  251  of this latter) to receive the detection signal S 1  (voltage) and the output terminal  213  is connected to the electronic bus  3  and to the electronic stage  22  to provide, if necessary, a new bus signal VBUS (voltage) to the electronic bus  3  and to the electronic stage  22 . 
     Preferably, the electronic stage  21  comprises a first circuit section  214  having the terminals  211 ,  212  as input terminals and a first connection terminal  216  as output terminal. 
     Preferably, the circuit section  214  is configured to compare the bus signal VBUS, made available by the electronic bus  3 , and the detection signal S 1  with each other. 
     Preferably, the circuit section  214  comprises a first operational amplifier A 1  arranged in configuration of unit gain amplifier and provided with suitable input and output electric power networks (which can be produced with known design techniques) advantageously configured so as to allow the amplifier to absorb current to ground and not to supply output current. 
     The operational amplifier A 1  is advantageously arranged so as to have the non-inverting and inverting inputs connected respectively to the input terminals  211 ,  212  and the output connected with the connection terminal  216 . 
     The circuit section  214  provides, at the connection terminal  216 , a first control signal P 1  (voltage) that assumes a “high” or “low” logic state respectively in the cases in which the detection signal S 1  is lower or higher than the bus signal VBUS. 
     Preferably, the electronic stage  21  comprises a second circuit section  215  connected in cascade with the circuit section  214 . 
     Preferably, the circuit section  215  has the connection terminal  216  as input terminal and the terminal  213  as output terminal. 
     Preferably, the circuit section  215  is configured to provide a signal indicative of the feeding current IL provided to the electric load by the corresponding battery module  10  in the case in which the detection signal S 1  is lower than the input bus signal VBUS received. 
     If the feeding current IL value, provided by the cells  11  of the corresponding battery module  10 , is lower than the current value (minimum feeding current) of the bus signal VBUS, the output signal (voltage) provided by the circuit section  215  will be indicative of a new minimum feeding current value provided to the electric load. 
     Given that the output terminal  213  is connected to the electronic bus  3 , the output signal provided by the circuit section  215  will form a new bus signal VBUS to be made available to the electronic units  2  through the electronic bus  3 . 
     Preferably, the circuit section  215  is configured not to provide any output signal in the case in which the feeding current IL value, provided by the cells  11  of the corresponding battery module  10 , is higher than the current value (minimum feeding current) of the bus signal VBUS made available by the electronic bus  3 . 
     Preferably, the circuit section  215  comprises a first switching device Q 1  (preferably a transistor of BJT type) arranged, through a suitable filter and polarization network that can be produced with known design techniques, so as to have the terminals (in the example illustrated base, collector and emitter) connected respectively to the terminals  216 ,  213  and to ground. 
     In this way, if the control signal P 1  at the terminal  216 , is in a “low” or “high” logic state, the switching device Q 1  is in an off-state (OFF) or on-state (ON), respectively. 
     The operation of the electronic stage  21 , according to the embodiment illustrated above, will now be described in greater detail. 
     The circuit section  214  receives the bus signal VBUS and the detection signal S 1  and performs a comparison between them. 
     If the current value provided by the detection signal S 1  is higher than the current value provided by the bus signal VBUS, the operational amplifier A 1  provides, with a response dynamic that depends on the related feedback network, a control signal P 1  (voltage) having a “low” logic value at the connection terminal  216 . 
     In this case, the transistor Q 1  of the circuit section  215  is taken to an off-state (OFF) with a response dynamic that depends on the related polarization and filter network. 
     Therefore, the electronic stage  21  is not able to provide any output signal at the terminal  213 . The bus signal VBUS, made available by the electric bus  3  and imposed by the electronic adjusting unit of another battery module of the apparatus  100  that provides the minimum feeding current to the electric load, is not modified by the electronic stage  21 . 
     If the current value provided by the detection signal S 1  is lower than the current value provided by the bus signal VBUS, the operational amplifier A 1  provides, with a response dynamic that depends on the related feedback network, a control signal P 1  (voltage) having a“high” logic value. 
     In this case, the transistor Q 1  of the circuit section  215  is taken to an on-state (ON) with a response dynamic that depends on the related polarization and filter network. 
     After a short transient period, the electronic stage  21  is able to provide, at the terminal  213 , an output signal (voltage) indicative of the feeding current IL value supplied to the electric load by the battery module  10 . 
     This output signal (in this case corresponding to the detection signal S 1 ) forms a new bus signal VBUS that is imposed on the electric bus  3 . This is made possible by the fact that the other electronic adjusting units  2 , connected to the electronic bus  3 , are not able to provide any bus signal given that the feeding current IL, supplied by the battery module  10 , is the minimum feeding current provided to the electric load. 
     The arrangement of the electronic stage  21  in the electronic units  2  makes it possible to considerably simplify the overall structure of the adjusting device  1  and of the apparatus  100 , according to the invention. 
     In fact, unlike what occurs in prior art storing apparatus, it is not necessary to arrange an electronic control unit that acts as “master” device to send reference signals to the adjusting units on the battery modules. 
     In the electronic device  1 , according to the invention, the bus signal VBUS, in a given instant of operation, is imposed, automatically, by the electronic stage  21  of the battery module  10  that supplies the minimum feeding current to the electric load. 
     Each electronic adjusting unit  2  can therefore automatically become, in relation to the operating state of the cells of the corresponding battery module, a “master” device for the electronic adjusting units of the other battery modules or a “slave” device controlled by the electronic adjusting unit of another battery module. 
     Preferably, the electronic stage  22  is connected to the electronic bus  3  and in cascade with the electronic stage  21  and is connected to the electronic stage  23  to provide this latter with the control signal A. 
     Preferably, the electronic stage  22  comprises a third circuit section  224  adapted to receive the bus signal VBUS and to provide a reference signal VR as a function of the bus signal VBUS. Preferably, the reference signal VR is a voltage signal defined by the relation VR=VO+VBUS, where VO is a predefined offset signal (voltage). 
     Preferably, the circuit section  224  comprises a third input terminal  221  of the electronic stage  22  connected to the output terminal  213  of the electronic stage  21  and to the electronic bus  3  to receive the bus signal VBUS made available by this latter or directly by the electronic stage  21 . 
     Preferably, the circuit section  224  comprises a fourth input terminal  224 A of the electronic stage  22  connected to a feeding circuit (not illustrated) to receive the offset signal VO. Preferably, the circuit section  224  comprises a second connection terminal  224 B at which to provide the reference signal VR. 
     Preferably, the circuit section  224  comprises a second operational amplifier A 2  arranged, through a suitable feedback electric power network that can be produced with known design techniques, in configuration of non-inverting summing amplifier. 
     The operational amplifier A 2  is advantageously arranged so as to have, through the aforesaid feedback network, the non-inverting input connected to the input terminals  221  and  224 A, the inverting input connected to ground and output connected to the connection terminal  224 B. Being in configuration of non-inverting summing amplifier, the operational amplifier A 2  provides an output reference signal (voltage) VR=VO+VBUS. 
     In practice, the circuit section  224  is configured to sum a predefined offset value (voltage) to the value (voltage) of the input bus signal VBUS received. This offset value VO can be, for example, about 2% of the maximum value of the signal VBUS. 
     The circuit section  224  advantageously makes it possible to reduce the influence of any disturbances superimposed on the bus signal VBUS making adjustment of the feeding current IL provided by the battery module  10  much more robust, in relation to negligible measurement errors (for example lower than 4% of the maximum value). 
     Preferably, the electronic stage  22  comprises a fourth circuit section  225  connected in cascade with the circuit section  224 . 
     Preferably, the circuit section  225  has the connection terminal  224 B as input terminal and comprises a fifth input terminal  223  of the electronic stage  22  connected to the electronic stage  25  (at the terminal  251  of this latter) to receive the detection signal S 1  (voltage). 
     Preferably, the circuit section  225  comprises a second output terminal  222  of the electronic stage  22  at which there is provided the control signal A for the electronic stage  23 . 
     Preferably, the circuit section  225  comprises a third operational amplifier A 3  arranged in configuration of proportional-integrator, through a suitable feedback electric power network that can be produced with known design techniques. 
     The operational amplifier A 3  is advantageously arranged so as to have, through the aforesaid feedback network, the non-inverting and inverting inputs connected respectively to the input terminals  223 ,  224 B and the output connected with the output terminal  222 . 
     When the reference signal S 1  (voltage) is lower than the reference signal VR, i.e., when the feeding current IL value supplied by the battery module  10  is lower than the reference value VR (indicative of the minimum feeding current value added to the offset value), the operational amplifier A 3  provides an output signal (voltage) that progressively decreases as a function of the difference between the input signals S 1 , VR. 
     When the reference signal S 1  is higher than the reference signal VR, i.e., when the feeding current IL value supplied by the cells  11  is higher than the reference value VR, the operational amplifier A 3  provides an output signal (voltage) that increases progressively as a function of the difference between the input signals S 1 , VR. 
     The circuit section  225  thus provides, at the output terminal  222 , a control signal A that varies as a function of the difference between the feeding current IL value supplied by the cells  11  and the reference value VR. 
     Preferably, the electronic stage  23  is connected in cascade with the electronic stage  22  and is connected to the electronic stage  24  to provide this latter with the control signal R, when enabled by the input control signal A received by the electronic stage  22 . 
     Preferably, the electronic stage  23  comprises a sixth input terminal  231  connected to the output terminal  222  of the electronic stage  22  and a third output terminal  232  connected to the electronic stage  24 . 
     Preferably, the electronic stage  23  comprises a second switching device Q 2  (preferably a transistor of BJT type) arranged, through a suitable filter and polarization network that can be produced with known design techniques, so as to have the terminals (in the example illustrated base, collector and emitter) connected respectively to the terminals  231 ,  232  and to ground. 
     In this way, if the control signal A, at the terminal  231 , is in a “low” or “high” logic state, the switching device Q 2  is in off-state (OFF) or on-state (ON), respectively. 
     Preferably, the electronic stage  24  comprises a third switching device F 1  (preferably of FET type) arranged, through a suitable filter and polarization network that can be produced with known design techniques, so as to have a pair of terminals (in the example illustrated the “source” and “drain” terminals) connected with the terminals  241 ,  242 , so that the feeding current IL flows through them, and a further terminal (in the example illustrated the “gate” terminal) connected to the terminal  232  of the electronic stage  23 . 
     The switching device F 1  is advantageously arranged so as to operate constantly in saturation state. It can thus adjust the feeding current IL, in the example illustrated flowing between the “source” and “drain” terminals, as a function of an input control voltage, in the example illustrated the voltage between the “gate” and “source” terminals. 
     When the control signal A is in “low” logic state, the switching device Q 2  is in an off-state and the electronic stage  23  is unable to provide any second control signal R at the terminal  232 . The terminal  232  can, for example, remain at the potential imposed by another electronic circuit connected thereto, for example by the electronic control device  12 . 
     Therefore, the electronic stage  23  is not able to interact with the electronic stage  24  to adjust the feeding current IL. 
     When the control signal A is in “high” logic state, the switching device Q 2  is in an on-state and the electronic stage  23  provides the control signal R (voltage) at the terminal  232 . 
     This control signal R consists substantially in imposing on the terminal  232  a control voltage having a value lower than the voltage that would have been imposed by another electronic circuit connected to the same terminal  232 , for example the control device  12 . 
     When the terminal  232  is held at an increasingly lower voltage, the “gate-source” voltage of the transistor F 1  decreases progressively with consequent progressive reduction of the feeding current IL flowing across the terminals  241 ,  242  (increase of the equivalent resistance of the transistor F 1 ). 
     It is pointed out that when the terminal  232  is held at a gradually decreasing voltage, the voltage between the terminals  241 ,  242  (in the example illustrated the “drain” and “source” terminals of the transistor F 1 ) of the electronic stage  24  increases progressively, given that the reduction of the feeding current IL flowing through the transistor F 1  is obtained at the expense of an increase in the equivalent resistance of this latter. 
     From the above, it is evident that the electronic unit  2  (in particular the electronic stage  25 , the circuit sections  224 - 225 , the electronic stage  23  and the electronic stage  24 ) implements a first control loop that adjusts the feeding current IL as a function of the bus signal VBUS. 
     More specifically, this control loop is configured so as to reduce the feeding current IL provided to the electric load by the cells  11 , when the value of this latter exceeds the minimum feeding current value provided by the signal VBUS. 
     The adjusting action, performed by the aforesaid first control loop, stabilizes when the feeding current IL value provided to the electric load by the cells  11  is more or less equal (except for an error introduced by the offset voltage VO) to the minimum feeding current value provided by the signal VBUS. 
     In the case in which, in a given instant, the feeding current IL value provided to the electric load by the cells  11  is, for any reason, lower than the minimum feeding current value provided by the signal VBUS, the aforesaid first control loop does not provide any adjusting action (electronic stage  23  in an off-state). In fact, in this circumstance the feeding current IL provided by the cells  11  is the minimum feeding current supplied to the electric load. 
     According to some embodiments of the invention (illustrated in the cited figures), the electronic stage  22  comprises a fifth circuit section  226 . 
     Preferably, the circuit section  226  comprises a seventh input terminal  227  of the electronic stage  22  connected to the electronic stage  25  (at the terminal  252  of this latter) to receive the detection signal S 2  (voltage). 
     Preferably, the circuit section  226  comprises an eighth input terminal  228  of the electronic stage  22  connected to a supply circuit (not illustrated) to receive a threshold signal VT (voltage). 
     Preferably, the circuit section  226  comprises a third connection terminal  229  connected to the output terminal  222 , at which the control signal A for the electronic stage  23  is provided. 
     Preferably, the circuit section  226  is configured to receive the detection signal S 2  and to provide, as a function of the detection signal S 2  and in substitution of the fourth circuit section  225 , the electronic stage  23  with a control signal A having a predefined value such as to disable the electronic stage  23 . 
     Preferably, the circuit section  226  comprises a fourth operational amplifier A 4  arranged in configuration of proportional-integrator, through a suitable feedback electric power network that can be produced with known design techniques. 
     The operational amplifier A 4  is advantageously arranged so as to have, through the aforesaid feedback network, the non-inverting and inverting inputs respectively connected to the input terminals  228 ,  227  and the output connected with a fourth connection terminal  226 A. 
     The operational amplifier A 4  provides, at the terminal  226 A, a second control signal P 2  (voltage) that varies as a function of the difference between the detection signal S 2  and the threshold signal VT. 
     When the reference signal S 2  (voltage) is lower than the threshold signal VT, i.e., when the voltage between the terminals  241 ,  242  of the electronic stage  24  (in the example illustrated above, the “drain-source” voltage of the transistor F 1 ) is lower than the threshold value VT, the operational amplifier A 4  provides an output control signal P 2  that decreases progressively as a function of the difference between the input signals S 1  and VT. 
     When the reference signal S 2  is higher than the threshold signal VT, i.e., when the voltage between the terminals  241 ,  242  of the electronic stage  24  is higher than the threshold value VT, the operational amplifier A 4  provides an output signal that increases progressively as a function of the difference between the input signals S 1 , VT. 
     Preferably, the circuit section  226  comprises a third switching device Q 3  (preferably a transistor of BJT type) arranged, through a suitable filter and polarization network that can be produced with known design techniques, so as to have the terminals (in the example illustrated base, collector and emitter, respectively) connected respectively to the terminals  226 A,  229  and to ground. 
     In this way, if the control signal P 2 , at the terminal  226 , is in a “low” or “high” logic state, the switching device Q 3  is in an off-state (OFF) or on-state (ON), respectively. 
     The operation of the circuit section  227  is now described in greater detail. 
     The circuit section  226  receives the detection signal S 2  and the threshold signal VT and performs a comparison between them. 
     If the value indicative of the voltage between the terminals  241 ,  242  of the electronic stage  24  is lower than the threshold value VT, the operational amplifier A 4  provides, with response dynamics that depend on the related feedback network, an output control signal P 2  that decreases progressively until the transistor Q 3  is taken to an off-state (OFF). 
     Therefore, the circuit section  226  is notable to provide any output signal at the terminal  229  and hence to interact with the circuit section  225 . 
     If the value indicative of the voltage between the terminals  241 ,  242  of the electronic stage  24  is higher than the threshold value VT, the operational amplifier A 4  provides an output control signal P 2  (voltage) that increases progressively until the transistor Q 3  is taken to an on-state (ON). 
     When the transistor Q 3  is in an on-state, the connection terminal  229  necessarily assumes a predefined voltage that is also imposed on the output terminal  222  of the circuit section  225 , given that this latter is connected to the terminal  229 . 
     The above substantially means that a control signal A having a predefined value is provided at the output terminal  222  of the electronic stage  22 . 
     It is pointed out that when the circuit section  226  operates (transistor Q 3  in on-state), the control signal A assumes the aforesaid predefined value, regardless of the adjusting action performed by the circuit section  225 . 
     Therefore, the circuit section  226  substitutes the circuit section  225  in providing the control signal A to the electronic stage  23 , when the voltage between the terminals  241 ,  242  of the electronic stage  24  is higher than the threshold value VT. 
     From the above it is evident that the electronic stage  25  and the circuit section  226  implement a second voltage control loop that operates only when the voltage between the terminals  241 ,  242  of the electronic stage  24  is higher than the threshold value VT. 
     The aforesaid second control loop substantially maintains the voltage between the terminals  241 ,  242  of the electronic stage  24  at the value VT and makes the action of the first control loop (illustrated above) ineffective, when the voltage between the terminals  241 ,  242  of the electronic stage  24  tends to exceed the threshold value VT. 
     The action of the aforesaid second control loop causes a reduction of the voltage between the terminals  241 ,  242  of the electronic stage  24 , given that the equivalent resistance offered by this latter decreases. 
     With reference to  FIG. 3 , there is illustrated an example of operation of an electric energy storing apparatus  100 , according to the present invention, comprising four battery modules  10  connected in parallel to the load. 
     Initially, the battery modules  10  provide feeding currents having values IL 1 , IL 2 , IL 3 , IL 4  very different to one another. 
     As can be seen, as a result of the action of the adjusting device  1 , the feeding currents provided by the battery modules rapidly reach (in around 9 ms) a common value ILM corresponding approximately to the mean value of the initial currents (with a maximum error lower than 1%). 
     It has been found in practice how with the storing apparatus  100  and the related electronic adjusting device  1 , according to the invention, the foregoing objects can be attained. 
     The adjusting device  1  allows very rapid balancing of the feeding currents provided to the electric load ensuring effective equal sharing of the load among the various battery modules. The adjusting device  1  is capable of automatically adapting the balancing action of the feeding currents provided to the electric load to the effective operating conditions of the battery modules, in particular of the cells of these latter. 
     The adjusting device  1  has a relatively simple circuit structure and can be easily arranged on an electric energy storing apparatus, without any appreciable increase in the overall dimensions thereof. 
     The adjusting device  1  and the apparatus  100  are easy and inexpensive to manufacture on an industrial scale. 
     SEQUENCE LISTING 
     Not Applicable