Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J7/00—Circuit arrangements for charging or discharging batteries or for supplying loads from batteries
  • H02J7/865—Battery or charger load switching, e.g. concurrent charging and load supply
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J7/00—Circuit arrangements for charging or discharging batteries or for supplying loads from batteries
  • H02J7/50—Circuit arrangements for charging or discharging batteries or for supplying loads from batteries acting upon multiple batteries simultaneously or sequentially
  • H02J7/52—Circuit arrangements for charging or discharging batteries or for supplying loads from batteries acting upon multiple batteries simultaneously or sequentially for charge balancing, e.g. equalisation of charge between batteries
  • H02J7/54—Passive balancing, e.g. using resistors or parallel MOSFETs
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J7/00—Circuit arrangements for charging or discharging batteries or for supplying loads from batteries
  • H02J7/60—Circuit arrangements for charging or discharging batteries or for supplying loads from batteries including safety or protection arrangements
  • H02J7/61—Circuit arrangements for charging or discharging batteries or for supplying loads from batteries including safety or protection arrangements against overcharge

Definitions

• the present invention relates to a method and a device for balancing electric storage batteries.
• a field of application envisaged is in particular, but not exclusively, the charge management of lithium-ion batteries.
• This type of battery comprises a plurality of electric accumulators, or cells, including a rechargeable electrochemical system for supplying a nominal voltage.
• the charging or discharging of these accumulators respectively results in a growth or a decrease in the voltage across the accumulator.
• the accumulator is in the charged state or discharged when it has reached a voltage level defined by the electrochemical equilibrium of the system.
• the same current value flows through all the accumulators.
• the charge or discharge level of the accumulators depends on the intrinsic characteristics of said accumulators, namely, the intrinsic capacitance and the parasitic internal resistances of the electrolyte and / or electrodes of the electrochemical system. As a result, voltage differences between the accumulators may arise due to manufacturing and aging disparities.
• the accumulators of the same electrochemical system have a given maximum charge state, which should not be exceeded when charging the storage battery, otherwise they may be damaged.
• the device described in this document takes into account the maximum and minimum load thresholds of each of the accumulators to switch on and off the individual charge thereof.
• a disadvantage of this device lies in its cost, since it requires the use of as many chargers as accumulators of said battery.
• a problem that arises and that aims to solve the present invention is to provide a balancing method and a balancing device that are cheap.
• the present invention proposes, according to a first object, a method of balancing an electric storage battery, said method being of the type according to which on the one hand a battery of electric accumulators comprising accumulators connected to each other in series, and secondly a charging current having a charge value for charging said accumulators, said accumulators having a maximum state of charge, and charging said accumulators during a charging step to increase the charging said accumulators to their maximum state of charge.
• said charging step comprises in the following sub-steps: a) said accumulators are supplied in series with said charging current at said charge value until one of said accumulators of said battery reaches said maximum state of charge; b) torque during a coupling period said one of said accumulators at the terminals of an unloading member corresponding to discharge said one of said accumulators, while simultaneously lowering said charging current to a balancing value; and, c) returning to substep a) after a duration less than or equal to said coupling period.
• a feature of the invention lies in the supply of all accumulators connected in series with a single charging device as will be explained in the following description, and in paralleling on a discharging member during a predetermined coupling period, the accumulator which has reached the first, the maximum state of charge.
• the unloading member is advantageously a resistor. However, it may consist of a device for not dissipating energy, but to transfer it to other accumulators that have not yet reached the state of maximum load.
• step b) the unloading member, or the corresponding resistor, is traversed by a balancing current and said charging current is lowered to a value less than or equal to said balancing current.
• the charging current is at a value equivalent to the balancing current, it is then controlled in "proportional mode" and requires a complementary control element.
• said lowering charging current to a zero value, and the control is performed in "all or nothing mode", which significantly reduces the charging speed of the storage battery but on the other hand, simplifies the assembly.
• a higher state of charge is defined, said upper state of charge being lower than said maximum state of charge, and the accumulators are furthermore coupled to the sub-step b). whose state of charge is between said upper state of charge and said state of maximum load, corresponding unloading bodies so as to discharge.
• This higher state of charge although lower than the maximum state of charge, is very close. In this way, not only the charge of the most charged accumulator but also and simultaneously the charge of those whose charge state is close to said maximum state of charge is lowered. In this way, the next cycle is longer and therefore, over the cycles, the charging speed of the accumulators of the battery is faster.
• sub-step a) is returned to if and only if at least one accumulator has a state of charge lower than said higher state of charge.
• the charge of the accumulators of the battery can be interrupted when all the accumulators have a state of charge between the maximum state of charge and the state of charge higher.
• the power supply and the balancing of the accumulators are interrupted when it is no longer necessary.
• the present invention proposes a balancing device for charging an electric storage battery, said electric storage battery comprising accumulators connected to each other in series, said accumulators having a state of charge. maximum load, said balancing device comprising charging means for supplying a charging current having a charge value, said charging current being for charging said accumulators during a charging step so as to increase the charging of said accumulators to a charge current; at their maximum state of charge.
• the balancing device comprises: control means and control means for controlling said charging means to supply said accumulators in series with said charging current at said charge value until said control means controls one of said accumulators said battery at its maximum state of charge; coupling means adapted to be controlled by said control means for coupling during a coupling period said one of said accumulators to the terminals of a corresponding discharging member so as to discharge said one of said accumulators, while said control means simultaneously lowering said charging current; and said control means is adapted to control the supply of said accumulators with said charging current to said charge value, after a duration less than or equal to said coupling period.
• said coupling means comprise switches and corresponding discharging members, for each of said accumulators, said switches being connected to said control means.
• the corresponding unloading members are resistors.
• said control means comprise first control means connected to said control means, for each of said accumulators.
• the first control means communicate to the control means the state of charge of the accumulators, and as soon as one of the accumulators reaches the maximum state of charge, the control means control the switch to connect the corresponding discharge or for example the resistance, across said one of the accumulators.
• said control means further comprise second control means for each of said accumulators, said second control means being able to control a higher state of charge, said upper state of charge being less than said maximum state of charge. Thanks to the first and second control means, the accumulators of said battery converge more rapidly to their maximum state of charge.
• each control means consists of a voltage comparator.
• These voltage comparators offer the advantage of being much less expensive than an analog / digital converter allowing it to provide the precise value of the current.
• FIG. 1 is a block diagram of a first elementary unit of a balancing device according to the invention, and according to a first embodiment
• FIG. 2 is a graph illustrating the operating mode of the balancing device according to the first embodiment
• FIG. 3 is a block diagram of a second elementary unit of a balancing device according to the invention, and according to a second variant embodiment;
• FIG. 4 is a graph illustrating the operating mode of the balancing device according to the second embodiment.
• FIG. 1 illustrates a battery 10 of n accumulators 12, or cells, connected in series, between two terminals A, B, and a balancing device 14 according to a first embodiment, shown partially.
• the accumulators 12 are for example of the lithium-ion type. They each have a maximum state of charge corresponding, for example, to 3.6 V for an electrochemical lithium-ion system based on iron phosphate, and whose nominal voltage is 3.3 V. It will also be observed that the charge or the discharge of an accumulator corresponds respectively to a high voltage and a low voltage across this accumulator around the nominal voltage. As a result, the state of charge or discharge of an accumulator can be measured by monitoring the voltage at its terminals.
• FIG. 1 shows an elementary unit balancer 16 mounted in parallel to the i th elementary accumulator 12.
• This balancing unit 16 essentially comprises a first controller or comparator 18 and a resistor 20 as corresponding unloading member, both coupled at the terminals of the accumulator 12.
• the resistor 20 is part of a balancing circuit 22 adapted to be closed by a controllable switch 24 and which constitute coupling means.
• FIG. 1 also shows, on the one hand, control members 26 connected to the controllable switch 24 and the first comparator 18, and, on the other hand, a charger 28 connected to the two terminals A, B, of the battery 10, - Even being also connected to the control members 26.
• the control members 26 comprise, for example, a microcontroller.
• the first comparator 18 is connected to the control members 26 at a time by a first connection 30 intended to transmit an upper threshold signal when the maximum state of charge, for example 3.6 V, is reached and a second connection 32 for transmitting a lower threshold signal when the state of maximum discharge, for example 2 V, is reached.
• Each of the accumulators 12 of the battery 10 is equipped with basic balancing units 16 connected in parallel, while the balancing device 14 comprises a single charger 28 and the only control members 26 to which are connected all the basic units of the battery. balancing 16.
• the operating mode of the balancing device is intended to charge all the accumulators 12 of the battery 10 in series, with the single charger 28, and whose individual states of charge are different, without any of these accumulators 12 maximum state of charge.
• the control members 26 control the charger 28 to supply the battery 10 with a charging current of a given value of charge.
• all the accumulators 12 receive an identical charging current, while their own charge state is not necessarily equivalent and that, moreover, their charging capacity is also not equivalent.
• one of the accumulators 12 necessarily reaches the maximum state of charge before the others.
• the first comparator 18, via its first connection 30, transmits a signal upper limit value to the control means 26. In receiving this signal, the microcontroller 26 simultaneously controls the switch 24 and the closing of the circuit 22, and the lowering of the charging current.
• This coupling operation is preprogrammed for a given coupling period.
• the accumulator 12 discharges across the resistor 20, for example between 1/10 and 1/100 of the maximum state of charge, while the charging current is lowered so that other accumulators 12 do not reach, during this coupling period, their own maximum state of charge.
• a first mode of implementation says: "in all or nothing”, the charging current is brought to zero during this coupling period, which simplifies the mounting of the device and, above all, makes it possible to avoid another accumulator does not reach its maximum state of charge, especially when the coupling period is relatively long.
• a second mode of implementation said: “proportional”, the charging current is brought to a value equivalent to the value of the balancing current which passes through the resistor.
• the microcontroller 26 controls the opening of the circuit 22 and the charger 28 so that the latter returns to said given load value.
• the accumulators 12 are successively charged to be brought to a state of charge close to their maximum state of charge.
• FIG. 2 showing a first graph showing the progress of the state of charge of four of the accumulators of a battery, which battery comprises ten accumulators, according to the charging cycles.
• the maximum state of charge is here 4.2 V.
• Battery No. 10 is also close to the maximum state of charge, while Battery No. 2 is at a charging state corresponding to 4.12 V and Battery No. 8 at 4.06 V.
• the battery No. 9 reaches the first state of maximum charge. Also, it is partially discharged while the other accumulators continue either to be loaded during the coupling periods, according to the proportional mode, or not to be charged during this period, according to the all or nothing mode.
• Battery No. 10 is the second to reach maximum state of charge. It is in turn partially discharged during the coupling period.
• the accumulators Nos. 9 and 10 which have already reached their maximum state of charge, oscillate between their maximum state of charge and their state of charge after coupling on the resistor during the coupling period, while the other accumulators No. 2 and 8, converge to their maximum state of charge.
• the accumulator # 2 reaches to the seventh cycle, while the 8 reaches to the 30th cycle.
• the balancing is carried out charging in the manner of a sampled system whose sampling period corresponds to the coupling period.
• the states of charge of the accumulators, or the corresponding voltages oscillate between the state of maximum charge and the state of charge to which a balanced accumulator falls during the coupling period.
• the microcontroller 26 controls the charger 28. In this way, no accumulator can see its state of charge decrease below a certain threshold, which could damage it.
• the elementary balancing unit 16 that is found further comprises a second controller, or comparator 36, also mounted in parallel on the accumulator 12 and connected to the microcontroller 26.
• the entire balancing device is identical to that of the previous variant embodiment, and all the elementary balancing units 16 comprise a second comparator 36.
• This second comparator 36 is connected to the control members 26 by a third connection 38 intended to transmit a threshold signal when a higher state of charge, in this case 3.5 V, is achieved.
• a higher state of charge in this case 3.5 V
• the control members 26 control the charger 28 to supply the battery 10 with a charging current of a given value of charge.
• the first comparator 18 via its first connection 30 always transmits an upper threshold signal to the control means 26.
• the microcontroller 26 Upon receipt of this signal, the microcontroller 26 not only controls the switch 24 and the simultaneous lowering of the charging current for the ith accumulator 12, but also of all the accumulators 12 for which the second comparator 36 has also transmitted a threshold crossing signal, that is to say for which the state of charge corresponds to a voltage between 3.5 V and 3.6 V.
• the accumulators of the battery 10 whose state of charge is close to the state of maximum charge will also be partially discharged. This allows faster balancing of the accumulators 12 of the battery 10, because, compared with the first embodiment, the accumulators whose state of charge is close to the maximum state of charge are discharged simultaneously.
• the microcontroller 26 stops the charging cycle, as soon as all the accumulators have a state of charge corresponding to a voltage of between 3.6 V and 3.5 V, ie, when the state of charge of all the accumulators is between the maximum state of charge and the higher state of charge. With this second comparator 36, the load is stopped when it has become unnecessary.
• the balancing control algorithm may be more advanced.
• the balancing device described above is applicable to other components, such as capacitors.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Charge And Discharge Circuits For Batteries Or The Like (AREA)
• Secondary Cells (AREA)

Applications Claiming Priority (2)

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• 2011
  • 2011-07-25 FR FR1156742A patent/FR2978625B1/fr not_active Expired - Fee Related
• 2012
  • 2012-07-12 US US14/234,734 patent/US20140191725A1/en not_active Abandoned
  • 2012-07-12 CN CN201280041359.2A patent/CN103765720A/zh active Pending
  • 2012-07-12 KR KR1020147004857A patent/KR20140050691A/ko not_active Withdrawn
  • 2012-07-12 JP JP2014522134A patent/JP2014522222A/ja active Pending
  • 2012-07-12 EP EP12744088.1A patent/EP2737592A2/de not_active Withdrawn
  • 2012-07-12 WO PCT/FR2012/051656 patent/WO2013014358A2/fr not_active Ceased

Non-Patent Citations (1)

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