Patent Application
20100094575
The present invention concerns the technical area of start-up batteries of lead-acid type.
The subject of the invention finds particularly advantageous, but not exclusive application, to a start-up battery for automotive vehicle.
One of the major causes of immobilization of an automotive vehicle is ill-functioning of the start-up battery. It is therefore necessary to know the functioning status of the battery so that the user can be warned of any battery failure.
In the state of the art, it is known to determine the state of ageing or health of a battery by evaluating the internal resistance of the battery, which is determined by applying an alternate electric signal to the battery terminals. Said principle is difficult to implement for an in-vehicle battery.
For an in-vehicle battery it is known to measure permanently the characteristics of the battery, such as voltage, current and temperature so as to deduce its charge status. In relation to the logging of state of charge, it is possible to deduce the functioning status of the battery. In practice, this method proves to be relatively complex and cumbersome to implement.
Also, an energy management system for the battery of an automotive vehicle is known from document US 2003/025481 capable of determining the state of charge and state of health of the battery on the basis of measurements of voltages, currents and temperatures taken during a forcing phase of the battery. Said system proves to be relatively difficult and costly to use, since said system must be provided with a control module to place the battery in a forced operating phase.
The objective of the invention is therefore to overcome the disadvantages of known technical solutions by proposing a novel method which, in reliable, simple and low-cost manner and through direct use of normal operating points of the vehicle and hence without any particular prompting of the battery, can diagnose a lead-acid battery equipping an automotive vehicle.
To reach this objective, the method of the invention comprises the following steps:
during an experimentation phase, of carrying out parameterization of the state of health of a lead-acid battery for different state of charge values of the battery, for each of the state of charge values there are values representing the state of health of the battery for pairs of values including battery temperature and at least one battery parameter which is determined on the basis of battery voltage and current, the temperature, current and voltage being measured during the vehicle start-up phase over a given range of current variation and after the first discharge,
during a diagnosis phase of the battery equipping the vehicle:
By way of example, the values representing the state of health correspond to values of the Ah capacity of the battery or to chemical characteristics of the battery.
Also by way of example, the battery parameter is determined on the basis of characteristics of the battery such as the voltage and current delivered by the battery and their changes over time.
According to one preferred characteristic of embodiment, the battery parameter is determined from characteristics of the battery such as a considered voltage or current value for a threshold voltage and current respectively, a ratio between the peak voltage and current values, a current or voltage value respectively corresponding to a peak voltage or peak current or to changes in voltage and current over time.
According to one preferred characteristic of embodiment, for calculation of the state of health, a distinction is made between the nominal capacity Qn defined as battery capacity when new, and real capacity Qr which takes ageing into account:
Qr(Ah)=(1−% ageing)*Qn(Ah).
According to one preferred characteristic of the invention, the dynamic parameter linked to nominal capacity is calculated from current-voltage characteristics under strong current, and the parameter related to ageing is calculated from current-voltage characteristics under low current.
According to another characteristic of the invention, the nominal capacity may form an input data item for the system (prior calibration) thereby enabling calculation of real capacity by estimating ageing.
According to one preferred variant of embodiment, the method consists of determining the state of charge of the battery from measurement of battery characteristics taken during stoppage of the vehicle, and from matrices giving the percentage state of charge in relation to pairs of voltage and temperature values.
Advantageously, the method consists of taking the measurements after a stoppage time of the vehicle necessary for physicochemical stabilization of the battery.
A further object of the invention is to propose a method allowing determination of the diagnosis of the start-up capability of a lead-acid battery in an automotive vehicle.
To attain this objective, the method of the invention consists of determining the start-up capability of the battery in relation to the value representing state of health.
According to a first variant of embodiment, the method consists of determining the start-up capability of the battery by recording changes in the value representing state of health determined during repeat of the operating phase of the battery, and by providing information on battery start-up capability when the value representing state of health reaches a determined threshold value or when changes come to exceed a determined variation range.
According to one characteristic of the invention, a distinction can be made between two different evaluations of start-up capability, one evaluation at the current functioning cycle and a predictive evaluation which depends on changes in state of charge and temperature.
According to this example, the method consists of determining battery start-up capability by determining a start-up index, in relation to the state of health of the battery, for the parameter value and at the measured temperature.
According to another variant of embodiment, the method consists:
for the value representing state of health and by means of the parameterization, of deducing a value of the parameter at the measured temperature value to which a safety factor is applied and at the determined state of charge to which a safety factor is applied;
establishing a predictive determination of battery start-up capability in relation to the value of the battery parameter and to changes in battery operating conditions.
According to this example, the method consists of calculating the start-up index on several occasions during the battery operating phase, and of monitoring changes in this index to provide a diagnosis on the start-up capability of the battery.
Advantageously, in relation to the start-up index, the method consists of providing information either on problem-free start-up, or on difficult start-up, or on impossible start-up.
Preferably, for a difficult start-up index, the method consists of providing information on recommended heating, charging or change of battery.
For example, for a difficult start-up index, the method consists of recommending:
charging the battery if the state of charge is low
changing the battery if state of charge is high.
A further objective of the invention is to propose a system for implementing the diagnosis method according to the invention.
To reach this objective, in a casing equipped with assembly means, the system comprises:
a sensor to measure the current delivered by the battery,
a sensor to measure battery voltage,
a sensor to measure battery temperature,
an acquisition and processing unit linked to the measuring sensors and comprising:
For example, an acquisition and processing unit comprises means to determine the start-up capability of the battery in relation to the value representing the state of health, and the information means give information on battery start-up capability.
Advantageously the sensor measuring the current delivered by the battery is of contactless type.
For example, the sensor measuring battery temperature is mounted inside or outside the casing.
Various other characteristics will become apparent from the description given below with reference to the appended drawings which, as non-limiting examples, illustrate embodiments of the subject of the invention.
As arises from
As is conventional, a battery 2 comprises a positive 3 and a negative 4 terminal to which a connection cable 5 and ground cable are respectively connected.
The system 1 is in the form of a casing 8 equipped with assembly means, not shown, allowing its securing preferably onto the cables of the battery. The system 1 comprises a sensor 10 to measure the current I delivered by the battery 2. According to one preferred example of embodiment, the measuring sensor 10 is a magnetic sensor of contactless type mounted around the ground cable 6. For example, the current measuring sensor 10 is of resistive type or of magnetic field type such as a sensor with hall effect, magnetic resistance, GMR or flux gate.
The system 1 is connected to the terminals 3 and 4 via cables 11 and comprises a sensor 12 to measure the voltage U delivered by the battery 2. Evidently, the voltage U delivered by the battery 2 may be measured at a different point to the terminals 3, 4. The system 1 also comprises a sensor 14 to measure the temperature T of the battery 2. Preferably, the sensor 14 measuring temperature is mounted inside the casing 8 making the sensor less sensitive to variations in outside temperature. Evidently, the temperature sensor 14 may be mounted outside the casing 8.
As can be seen more clearly
It is to be considered that the method of the invention comprises an experimentation phase which precedes the diagnosis phase properly so-called to diagnose a battery 2 of a vehicle equipped with a system 1 such as described above. According to the invention, the experimentation phase and the diagnosis phase are conducted for the same operating phase of the battery. It is to be noted, that a battery comprises several functioning phases, namely a charge phase φc, a discharge phase φd, start-up phase φdm and a “floating” phase φf i.e. a phase in which the battery is maintained charged in an electric circuit. According to the invention, the diagnosis phase and the experimentation phase are performed for the start-up phase φdm of the vehicle.
In the experimentation phase, the method consists of carrying out parameterization of the state of helath SOH of a lead-acid battery, called an experimentation phase for different values of state of charge SOC of the battery. For example, this experimentation phase uses a battery having the same nominal capacity as the battery 2 to be diagnosed.
For memory, the state of health also called SOH of a battery reflects ageing of the battery. The state of health SOH of a battery is characterized by representative values e.g. corresponding to values of the Ah capacity of the battery or to chemical characteristics of the battery.
According to one preferred characteristic of embodiment, for calculation of the state of health, a distinction is made between the nominal capacity Qn defined as being the capacity when new, and a real capacity Qr which takes ageing into account:
Qr(Ah)=(1% ageing)*Qn(Ah).
This parameterization of the state of health SOH is performed for different values of state of charge also called SOC of the experimentation battery. For memory, the state of charge SOC of a battery corresponds to a percentage of the real capacity of the battery.
For each of the values of the state of charge SOC there are determined values representing the state of health of the battery for pairs of values including battery temperature T and at least one battery parameter γ. Parameter γ is determined on the basis of characteristics of the battery.
According to the subject-matter of the invention, parameter γ is determined from the measurements taken during the start-up phase of the vehicle. As can be seen more clearly
After processing, said measurements can be used to deduce a value of parameter γ of the battery.
For example, parameter γ corresponds to:
In one particular embodiment, the state of health SOH is defined using two dynamic parameters γ, one with a strong current at the start of discharge to estimate the nominal capacity of the battery, and one with low current at the end of discharge to estimate ageing.
The experimentation phase therefore consists of establishing tables or match matrices giving characteristic values of the state of health SOH of the battery, for different values of the state of charge SOC and for pairs of values of temperature T and parameter γ.
The parameterization thus conducted is advantageously memorized in the diagnosis system 1 intended to equip a battery 2 to be monitored.
The system 1 of the invention is adapted to implement a diagnosis phase for which the battery 2 is to be monitored to allow determination of the diagnosis of the battery 2.
The system 1 repeatedly determines the state of charge SOC of the battery. The state of charge SOC of the battery can be determined in any known manner.
According to one preferred characteristic of the invention, the state of charge SOC of the battery is determined from measurements taken during stoppage of the vehicle i.e. with zero current I and from matrices giving the percentage state of charge SOC as a function of pairs of values of voltage U and temperature T.
During the diagnosis phase, the state of charge SOC of the battery is determined when current is zero. Preferably measurements of voltage U and temperature T are performed after a stop time of the vehicle needed for physicochemical stabilization of the battery.
During the diagnosis phase, the method of the invention on several occasions measures the temperature and at least the current and voltage of the battery, and processes the measured values. As explained with reference to
The method then consists of using the parameterization and on the basis of this value of parameter γ and measured temperature for the determined value of state of charge SOC, to determine the value representing the state of health of the battery 2. According to one variant of embodiment, the method consists of determining the state of health by taking into account the nominal capacity of the battery which is calculated from current-voltage characteristics with high current values whilst percentage ageing is calculated from current-voltage characteristics for low current values. In the example illustrated
According to another variant of embodiment, the method consists of comparing the nominal capacity of the battery with a recommended value so as to deliver an alert signal when the battery shows a nominal capacity lower than the recommended value. This recommended value given by the vehicle manufacturer can be used to alert the vehicle user if an unsuitable battery is mounted on the vehicle.
This value representing the state of health is used to diagnose the battery. This diagnosis can evaluate the functioning capacities of the battery. It is to be noted that the diagnosis method of the invention is performed using solely normal operating characteristics of the battery equipping a vehicle. In particular, the measurements of current I and voltage U correspond directly to the values delivered by the battery which is not connected to an additional utilization source.
According to one preferred characteristic, this diagnosis which gives the value representing the state of health of the battery allows determination of the start-up capability of the battery.
The objective of the method of the invention, after determining battery operating state, is therefore to provide information on the capability of the battery to allow start-up of the vehicle. This predictive diagnosis can therefore alert the vehicle user before failure of the battery.
According to a first example of embodiment, the start-up capability of the battery is determined by recording changes in the value representing the state of health as determined during repetition or succession of the battery operating phase. The method consists of providing information on start-up capability in relation to changes in this representative value V of state of health. As can be seen more clearly
According to a second example of embodiment, the start-up capability is established from the value of battery parameter γ. Therefore for the value representing state of health and using parameterization, a new value of parameter γ is determined for the value of the measured temperature to which a safety factor is applied and for the determined state of charge SOC to which a safety factor is applied. It effectively appears judicious to take into account a drop in temperature which may occur between the time when the vehicle is stopped and the next start-up (night-time temperature drop). In other words, parameter γ is deduced for the value of the measured temperature to which a safety factor is applied. Similarly in the event of discharge of the battery a safety factor is applied to the determined state of charge SOC. Therefore, using parameterization and for the measured temperature value to which a safety factor is applied and for the determined state of charge SOC to which a safety factor is applied, the value of parameter γ is deduced. In relation to this parameter value γ of the battery, predictive determination can be made of the battery's start-up capability. By way of example, provision may be made to break down the variation range of parameter γ into several zones whether or not these are equal, each corresponding to a different qualification of start-up capability. For example the variation range of parameter γ is broken down into three zones corresponding to low, medium and strong values of parameter γ and for which start-up is considered to be respectively impossible, difficult and problem-free.
As can be seen
According to another example of embodiment, the start-up capability of the battery 2 is established by determining a start-up index d which relates to the state of health of the battery for the value of parameter γ and at the measured temperature T.
These indices d are monitored to deduce there from the diagnosis of the battery's start-up capability. In other words, on several occasions during the battery's operating phase a start-up index d is calculated and changes in this index are examined to provide diagnosis of the battery's start-up capability.
The index can be broken down so as preferably to provide information either on problem-free start-up or difficult start-up or impossible start-up.
A further objective of the invention is to propose a method to measure characteristics of the battery according to the operating modes of the battery in the vehicle.
To reach this objective, with this method it is possible to detect the battery's operating phase. As can be more clearly seen
According to one variant of the invention, during charge or floating the method measures state of charge by coulometry (Ah count) and calculates the temperature of the battery using a thermal model.
According to this same variant, during the rest phase, the sensor measures the no-load voltage of the battery and the method links this with the state of charge. Placing the sensor on standby is activated during this phase, and periodic reactivation is programmed for calculation of state of charge using the no-load voltage, for calculation of the internal temperature of the battery and for prediction of start-up capability SOF2. Changes in voltage are therefore calculated during this phase. Reactivation of the sensor during this phase is performed after detecting a variation in voltage exceeding a given threshold, or using a LIN network (Local Interconnect Network) of the vehicle or any other communication network.
According to this same variant of the invention, during this discharge phase, the sensor is reactivated and the algorithm calculates state of charge by coulometry, calculates a predictive start-up capability and measures the internal temperature.
According to this same variant of the invention, during the vehicle start-up phase, the method calculates the state of health of the battery, the start-up capability at the current operating cycle SOF1, calculates the state of charge by coulometry and the internal temperature of the battery using the thermal model.
The invention is not limited to the described, illustrated examples since various modifications may be made thereto without departing from the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0753298 | Feb 2007 | FR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/FR2008/050253 | 2/15/2008 | WO | 00 | 9/16/2009 |
