Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
  • G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
  • G01R31/367—Software therefor, e.g. for battery testing using modelling or look-up tables
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
  • G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
  • G01R31/382—Arrangements for monitoring battery or accumulator variables, e.g. SoC
  • G01R31/3828—Arrangements for monitoring battery or accumulator variables, e.g. SoC using current integration
  • G01R31/3832—Arrangements for monitoring battery or accumulator variables, e.g. SoC using current integration without measurement of battery voltage

Definitions

• the invention relates to the field of lead-acid type electric batteries, used as sources of electrical energy in various vehicles or vehicles, in association with a main source of energy, generally consisting of an alternator driven by a heat engine. It relates more particularly to a method of evaluating the state of charge of a battery.
• state of charge or “SOC” for “state of charge”
• SOC state of charge
• SOD state of discharge
• the object of the invention is therefore to propose a method of evaluating the state of charge, which gives reliable results in real time over a wide range of state of charge values.
• the invention therefore relates to a method for evaluating the state of charge of an electric battery.
• a "coulometric" charge state obtained by temporally integrating the intensity of the charging and discharging current of the battery, is calculated.
• this method is characterized in that, during the discharge phases of the battery, the difference between the coulometric charge state value and a predetermined value of a charge state is calculated.
• theoretical which is calculated based on the voltage across the battery, the discharge current, the battery temperature, and its rated capacity. This difference is then used to modify the calculation of the coulometric charge state. In particular, if this difference exceeds a first predetermined threshold, the current value of the coulometric charge state can be modified by the value corresponding to the theoretical state of charge.
• the invention consists in recalibrating the coulometric model by a theoretical model, the value of which depends, for a given type of battery, only on three measured parameters, namely the voltage at the battery terminals, the intensity of the current discharge and the temperature of the battery.
• This theoretical model is relevant in situations of battery discharge, that is to say in practice on a vehicle, when the power consumed by the different devices powered by the battery is greater than the power that can provide the device. charge usually consisting of an alternator.
• the Applicant has identified that it is possible, for a given discharge current and a given battery temperature, to determine the state of charge from the voltage measured across the battery.
• this second threshold can be set to a value greater than the value of the theoretical state of charge.
• this second threshold can be adapted according to the minimum level of health considered acceptable.
• a state of no-load determined from the measurement of the no-load voltage across the battery, after a predetermined stopping time.
• a predetermined intensity typically less than a few amperes
• SOC C coulometric charge state value
• SOC C current value of the coulometric charge state
• This threshold may be identical to or different from the threshold chosen for the registration described above. In other words, a second coulometric pattern registration means is then used, which can be used when the consumption of the battery has been minimal for a sufficient length of time.
• FIG. 1 is a simplified diagram illustrating the various elements involved in the process according to the invention
• FIG. 2 is a flowchart illustrating the various steps of the method according to the invention.
• Figures 3, 4 and 5 are curve beams illustrating at three different temperatures, the variation of the state of charge of the same battery as a function of the voltage measured at its terminals, for different values of discharge current. Way of realizing the invention
• an electric battery (1) is intended to supply a plurality of loads (2,3) consuming electrical energy in variable and / or various powers.
• the terminal (5) of the battery (1) is connected to the electrical circuit (6) on which is also connected the alternator (7) for charging the battery (1) when it is driven by a source of mechanical energy , and in particular by the engine of the vehicle.
• the state of charge of the battery (1) is measured by means of a computer (8) interface with a current sensor (10), a voltage measuring device (11) and a sensor temperature (12).
• the current sensor (10) is a probe used for measuring the charge and discharge current of batteries. This probe (10) is capable of delivering a signed signal, making it possible to identify whether the current I is a charging or discharging current.
• the current sensor is arranged on the electrical circuit (6) upstream of any consumer of electrical energy, with the exception of the voltage sensor (11). More precisely, the voltage sensor (11) is mounted on the electric circuit (6) as close as possible to the terminal (5) of the battery, in order to give a most accurate image of the voltage at the terminals of the battery ( 1).
• the voltage sensor (11) is not connected directly to the terminal (5) of the battery (1), it is possible to take into account the measured current and the resistance of the fraction of the electric circuit ( 6) separating the terminal (5) of the battery from the connection point (13) of the voltage sensor (11), to correct the value of the measured voltage, and obtain an estimate of the voltage across the battery.
• the computer (8) is also interfaced with a temperature sensor (12), intended to give an image of the temperature of the battery (1). Since it is not possible to install the temperature sensor directly inside the battery (1), this sensor (12) is arranged in close proximity to the latter, or at least in a zone in which there is a temperature comparable to the temperature of the battery (1).
• the method according to the invention is to calculate (20) the state of charge of batteries by temporal integration of the current (I) measured by the current sensor (10), from an initial value (SOC 0 ). This state of coulometric charge (SOQ) increases as the battery charges, and decreases when it discharges. As long as the battery is charging, the computation continues (30) to be done by applying the coulometric model.
• the determination (22) of a theoretical state of charge (SOQ) is carried out. This determination (22) takes into account a set of parameters (23) giving the variation of the state of charge (SOC) as a function of the voltage U, for different given temperatures and currents. The manner of determining these various settings (23) is described in detail below.
• the calculation of the state of charge can be done either from the aforementioned settings (23), or again from the law (24) giving the value of the state of charge as a function of the voltage empty at the battery terminals.
• this last law (24) can only be used in a relevant way when the discharge current has remained (31) at a very low value ( ⁇ ), typically less than a few amperes, for a long time (t), typically greater than several (n) hours (32).
• the difference ( ⁇ ) between the state of charge (SOQ) measured by coulometry, and the theoretical state of charge (SOQ), is then evaluated (25), and compared (35) with a first predetermined threshold (Si). . If this difference exceeds this threshold, the current value of the state of coulometric load (SOC 0 ) is then modified (26) to adopt the value of the theoretical state of charge (SOC t ). Subsequently, the temporal integration calculation of the current I is then continued, after this readjustment (34).
• the second threshold (S 2 ) can be set to a relatively large value, typically of the order of one half of the theoretical state of charge (SOC t ). In the case where this difference is frequently exceeded, typically after 4 or 5 successive readjustments, it is reasonable to deduce that the battery (1) is degraded to such a point that its charge is difficult, and that it should therefore be replaced . Accounting (28), however, makes it possible to avoid triggering nuisance alerts, in the case where the value measured by coulometry occasionally deviates too much from the theoretical value, for example in cases following a prolonged and very significant load. Indeed, we saw in this case that the charge efficiency tended to fall, and that the coulometric model deviated from reality.
• the coulometric model continues to integrate the incoming current, which suggests that the state of charge continues to grow, and can reach a value close to 100%.
• This is not critical in the case of new batteries, because after a prolonged charge, the state of charge approaches the nominal value. But for used batteries, the value of the actual state of charge may remain stuck at a lower level, which may not be very far from the level below which it is not certain to ensure a restart of the vehicle. It is therefore important to be able to identify these situations.
• the occasional appearance of a gap may not be an alarming sign, because even with a new battery, a prolonged charge results in hydrolysis phenomena, which deflect the coulometric model of reality. On the contrary, it is appropriate to generate an alert only when this situation persists.
• the invention therefore allows to recalculate the coulometric model, without generating nuisance alerts.
• the theoretical state of charge (SOC t ) is determined in the discharge phase by a parameterization giving the state of charge of a battery of nominal capacity (Q), for a voltage (U ) measured at its terminals, a charging current (I) and a temperature ( ⁇ ).
• FIGS. 3, 4 and 5 Examples of this parameterization are illustrated in FIGS. 3, 4 and 5, for a battery with a nominal capacity of 170 A.h.
• the table below gives the numerical reference of the curve in FIGS. 3 to 5 as a function of the temperature and the discharge current.
• the battery In a second phase, the battery is brought to the desired temperature, for a time sufficient for the temperature of the mass of lead that composes it is stabilized. This heating can last several hours.
• the voltage at the terminals of the battery, under different discharge currents is measured between 2 and 200 amps (see the curves illustrated in FIGS. 3 to 5). This discharge current is applied for ten seconds, after which the voltage across the battery is measured.
• this setting can be programmed inside the computer (8) in different ways. It is thus possible for a battery of nominal capacity Q, to record in a reference table the values of the state charge, corresponding to a temperature, a discharge current and a voltage across the given battery.
• the current measured is the same for each battery.
• the theoretical model described above applies using for the common nominal capacity of one of the batteries, and the overall voltage divided by the number of batteries.
• the method of the invention it is also possible to apply the method of the invention to each battery individually, to evaluate the state of charge of each battery.
• the voltage measurement is carried out at the terminals of each battery, for example from the global voltage and from the voltages measured at the midpoints between the batteries.
• the method according to the invention can generate an alert when one of the batteries appears as degraded.
• the method according to the invention has the advantage of allowing frequent recalibration of the calculation of the state of charge carried out by coulometry, so that the estimated state of charge is more reliable than those elaborated with existing solutions. Risks of malfunction, for example the risk of not being able to ensure the starting of a vehicle, are reduced.
• the invention finds a direct application in the measurement of the charge of the battery of a motor vehicle, of the truck type, car, but also of ships, and in general, in all systems using an electric battery supplying different electrical consumers, and recharged by a mechanism of the alternator type transforming mechanical energy into electrical energy.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Secondary Cells (AREA)
• Tests Of Electric Status Of Batteries (AREA)

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• 2004
  • 2004-11-30 WO PCT/FR2004/050630 patent/WO2006058970A1/fr active Application Filing
  • 2004-11-30 EP EP04805868A patent/EP1820039A1/de not_active Ceased

Patent Citations (5)

Non-Patent Citations (1)

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