Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
  • H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
  • H02J7/0031—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits using battery or load disconnect circuits
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
  • H02J7/0047—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with monitoring or indicating devices or circuits
  • H02J7/005—Detection of state of health [SOH]
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
  • H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
  • H02J7/00306—Overdischarge protection
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
  • H02J7/0047—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with monitoring or indicating devices or circuits
  • H02J7/0048—Detection of remaining charge capacity or state of charge [SOC]

Definitions

• the invention relates to a method for managing the end of discharge of a rechargeable battery.
• Electrochemical accumulators are used in many mobile applications, such as portable electronic, thermal, electric or hybrid vehicles, etc., or many stationary applications, such as telecommunication relay, electricity production from intermittent sources of energy, such as wind power or photovoltaics, etc., ensuring in each case an element that is as important as it is fragile.
• the voltage decreases in a conventional way to reach the value of 10, 8V, corresponding to the LVD low voltage threshold described above, the value at which the discharge must be stopped.
• these voltage thresholds take into account the battery technology or the sizing of the system, they are nevertheless maintained constant throughout the battery operation. Or 1 the voltage of a battery depends on both of its technology, but also of its operating conditions, namely the charging current or discharging current, the relaxation period, temperature, and to finish his health , or state of wear. In the case of a battery which may include a series of elements, inhomogeneity between the elements may itself have an impact on the voltage measured across the complete battery. In other words, there is no direct relationship, or at least an approximate relationship, between the voltage of a battery and its state of charge.
• a conventional control structure of a battery 1 is shown diagrammatically in FIG. 2.
• a battery 1 supplies a load 2, via, for example, a power source 3.
• the charging cycles and discharging the battery 1 are managed by a regulator 4, connected to the terminals of the battery 1 and measuring, for example, the voltage across the battery 1.
• the controller 4 controls, according to S1, the charge of the battery 1 by via a first switch 5, in particular for disconnecting the battery after discharge, and control, according to S2, the energy source 3 via a second switch 6.
• the voltage thresholds used to stop the discharge are very largely overvalued within such a regulator described above, so as to ensure never to fall below the threshold of state of charge really critical e.
• the low voltage threshold of these batteries is generally close to 1.9V7 element (or 11.4V for a battery of 6 elements), whatever the conditions of wear or operation of the batteries.
• lead-acid batteries could most often be used up to a threshold close to 1.8V / element (or 10.8V for a battery of 6 elements), without any harmful consequences for their use. This results in a lack of storage energy, which can reach up to 10% of the battery capacity. Management of the end of discharge of such rechargeable batteries is not optimal.
• the object of the invention is to provide a method for managing the end of discharge of a rechargeable battery, which is efficient, simple to perform, from the exploitation of data specific to complex impedance measurements. , which allows a diagnosis of the state of the batteries, while taking into account the impact of the past and current conditions of use and the state of health of the batteries, and which makes it possible to avoid any inadvertent reconnections of the batteries fully discharged.
• the method according to the invention is characterized in that it comprises the determination of the transition frequency of the battery and the determination of a criterion of end of discharge of the battery according to said transition frequency.
• the transition frequency is determined periodically during use of the battery, the discharge being interrupted by regulating means as a function of said transition frequency.
• said end of discharge criterion is determined from measurements of the transition frequency carried out during a calibration phase.
• said end of discharge criterion is readjusted from measurements of the transition frequency made during a maintenance phase.
• said end of discharge criterion is representative of a sudden change of slope of the transition frequency during discharge, a predetermined maximum value of the transition frequency or a maximum value. predetermined slope of the transition frequency.
• FIG. 1 is a graph showing the discharged quantity of a battery as a function of the voltage, respectively at three different current regimes (0.5A, 5A and 10A), according to the prior art.
• Figure 2 schematically shows a conventional control structure of a rechargeable battery according to the prior art.
• FIG. 3 represents, in flowchart form, a particular embodiment of a method for managing the end of discharge of a rechargeable battery according to the invention.
• FIG. 4 illustrates the identification of the transition frequency F HF in a Nyquist diagram, according to the prior art.
• FIG. 5 is a graph showing the state of charge SOC of a battery as a function of the transition frequency F HF , respectively at the three different current regimes according to FIG.
• FIG. 6 is a graph illustrating the slope of the transition frequency as a function of the voltage, respectively at two different current regimes (0.5A and 5A), according to the invention.
• the method of managing the end of discharge of a rechargeable battery according to the invention can be achieved by a conventional control structure, as shown in FIG. 2, with a regulator making it possible to manage the load and discharging the battery, for example, by controlling switches.
• the method of managing the end of discharge of a rechargeable battery consists in a first step F1 in determining the transition frequency F HF of the battery.
• the determination of the transition frequency F HF can be performed by dichotomy.
• a frequency of transition F HF in a frequency range of 3300HZ to 100Hz and considering the imaginary part of the impedance measured at the frequency f, denoted lm (Z ( f)), and considering s the sign of this magnitude, we can then write: if s ⁇ 0, then F HF > f and if s ⁇ 0, then F HF ⁇ f.
• an estimation of the time of determination of the transition frequency F HF by this method can be obtained by considering the realization of these seven successive measurements, all carried out at frequencies higher than 100 Hz. Considering that the measurements are moreover performed over five periods for each frequency studied, the realization of thirty-five measurements is then sufficient and much less than half a second, namely 0.35s if all the measurements are made at 100 Hz. This method by dichotomy therefore allows to monitor the frequency of transition F HF every second, or over a longer time step.
• the transition frequency F HF In the field of impedance measurements, it was already known to determine the transition frequency F HF . As shown in FIG. 4, illustrating the identification of the transition frequency F HF in a diagram of FIG. Nyquist, the transition frequency F HF conventionally corresponds to the frequency at which the complex impedance of the battery changes from an inductive behavior to a resistive behavior, that is to say the frequency with which the imaginary part of the complex impedance vanishes. . It is an impedance parameter measured in the high frequencies, continuously during the operation of the battery, whether at rest or in operation, in a completely non-intrusive manner.
• the method according to the invention proposes, for its part, to use this transition frequency F HF1 in order to manage the end of discharge of a rechargeable battery, the transition frequency F HF being connected to the state of the active substance and being usable to stop the discharge depending on the actual state of the active ingredient.
• the management method includes determining, in a second step F2, the slope of the transition frequency F HF .
• the slope is determined by the derivative of the transition frequency dF HF / dt.
• the derivative of the transition frequency dF HF / dt can in particular be determined from the graph of FIG. 5. Indeed, this illustrates the transition frequency F HF as a function of the state of charge SOC, when a constant current I discharge. However, the state of charge SOC is proportional to the current I multiplied by the time t. In FIG. 5, the current I being constant, the state of charge SOC is proportional to the time t. Thus, the derivative of each of the three curves shown in FIG. 5 thus corresponds, with a constant close which is the current I of discharge, to the slope of the transition frequency dF HF / dt.
• the management method consists of comparing the previously calculated slope with a maximum predetermined value Pmax, representative of the end of discharge criterion of the battery from which the battery must be disconnected. If the computed value of the slope is smaller than the maximum predetermined value Pmax, then the management method loops back before step F1 for determining the transition frequency F HF . If the calculated value of the slope is greater than the predetermined maximum value Pmax, the management method then proceeds to the next step F4, namely the interruption of the discharge of the battery, by R2007 / 001635
• the predetermined maximum value Pmax thus defines the end of discharge criterion, which is a function of the transition frequency, from which the battery must be disconnected.
• a stop of the discharge on a threshold of 11.5V to 5A (dashed lines in FIG. 6), which corresponds to a slope dF HF / dt of the transition frequency F HF of the order of 0.015, driven to maintain the same slope value dF HF / dt of the transition frequency F HF to stop the discharge at a threshold of the order of 11.25V to 0.5A.
• the transition frequency is determined (F1), for example, periodically during use of the battery in operation, the discharge then being interrupted (F4) by the regulator (FIG. function of the calculated transition frequency (F1).
• the end of discharge criterion applied to the management method can be determined from measurements of the transition frequency F HF made during a calibration phase of the battery.
• the end of discharge criterion corresponding to the calibration is then entered into the regulator (FIG. 2).
• the process consists then, as before, to determine the transition frequency F HF (F1) and, for example, the slope (F2), the battery being disconnected (F4) when the end of discharge criterion calculated during the calibration is reached (F3) during battery operation.
• the criterion of end of discharge can also be adjusted from the transition frequency F HF measurements carried out during a maintenance phase of the battery. As before, the calculation of the transition frequency F HF and the corresponding end of discharge criterion is then done during this maintenance phase and the battery is disconnected when the end of charge criterion is reached during the operation of the battery.
• the end of discharge criterion calculated as a function of the transition frequency F HF and allowing the disconnection of the battery is preferably constituted by the voltage at the terminals of the battery measured by the regulator (FIG. 2), thus defining a fixed voltage stop instruction (FIG. 6).
• the criterion of the end of discharge of the battery can be representative of a sudden change of slope of the transition frequency F HF being discharged.
• the abrupt change of slope is defined by the second derivative of the transition frequency dF HF 2 / dt 2 and the management method then consists in using this calculated value of the second derivative as a value representative of the end of discharge criterion, the battery being disconnected via the regulator ( Figure 2) when this criterion is reached.
• the criterion of end of discharge of the battery may be representative of a predetermined maximum value of the transition frequency F HF .
• the management method then consists in determining the transition frequency F HF and comparing the value obtained with the predetermined maximum value. If this calculated value is lower than the predetermined maximum value, then the process loops back before the determination step F1 of the transition frequency F HF and a new transition frequency F HF is measured. If the calculated value is greater than the predetermined maximum value, then the end of discharge criterion has been reached and the controller interrupts the discharge by disconnecting the battery.
• such a management method is very efficient and simple to perform, while allowing a diagnosis of the state of discharge of the batteries and taking into account the impact of the conditions of past and current use and health status of the batteries.
• Such a method also makes it possible to avoid any inadvertent reconnection of fully discharged batteries.
• the management of the discharge of a battery is optimal and the operation of the rechargeable battery, as well as its life, are optimized.
• the invention is particularly applicable, thanks to the use of such end of discharge criterion according to the various embodiments of the management method described above, the determination and development of a new series of products. , the easy and inexpensive determination of end-of-discharge thresholds and its indication to users for all discharge regimes.
• the invention also applies to the direct use in a regulator of such a new end of discharge criterion, for the adjustment of the end of discharge of the battery, so that the end of discharge takes consider the state of the battery in terms of aging or past use.
• the invention is still applicable to the use, in a system comprising a battery and its regulator, of the new end of discharge criterion, so as to recalibrate the thresholds of said regulator during maintenance operations.
• the invention is not limited to the various embodiments described above.
• the term battery used in the description above includes including both rechargeable batteries and rechargeable electrochemical accumulators.
• the management method described above applies in particular to any type of rechargeable batteries.

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

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• 2006
  • 2006-10-13 FR FR0608986A patent/FR2907272B1/fr not_active Expired - Fee Related
• 2007
  • 2007-10-05 EP EP07858404A patent/EP2076953A2/fr not_active Withdrawn
  • 2007-10-05 JP JP2009531868A patent/JP5421111B2/ja not_active Expired - Fee Related
  • 2007-10-05 CN CN2007800381961A patent/CN101523689B/zh not_active Expired - Fee Related
  • 2007-10-05 WO PCT/FR2007/001635 patent/WO2008046980A2/fr active Application Filing
  • 2007-10-05 US US12/310,683 patent/US8159190B2/en not_active Expired - Fee Related

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