DE102007053726A1 - Method for open-circuit voltage measurement of battery of vehicle, involves determining defined time period after switching on ignition - Google Patents

Abstract

The method involves determining a defined time period (t-r) after switching on ignition. A voltage measurement (U-r1) at the battery is done. Another time period (t-mess 1) is determined for another voltage measurement (U-r2) at the battery, whereby the latter time period is many times smaller than the former time period. The result of the former voltage measurement is compaired with the latter voltage measurement. An independent claim is also included for a device for open-circuit voltage measurement of a battery of a vehicle.

Description

The The invention relates to a method and a device for quiescent voltage measurement a battery of a vehicle.

In Storage batteries, in particular lead-acid batteries, There is a very close relationship under certain conditions between the value of the rest voltage and the state of charge of the battery SOC (state of charge). Then, for example, a specific Voltage value of, for example, 12.7 V assigned an SOC = 100% with a reduction of 0.1 V to a reduction of approx. 10% SOC equals. The knowledge of a precise as possible Value of the state of charge is necessary in many situations, for example if a motor vehicle is not moved for a long time.

Therefore are various methods for determining the state of charge a known battery.

• – Erfassen von wenigstens zwei Messwertpaaren für Spannung und Strom;
• – Korrigieren der erfassten Messwertpaare für Spannung und Strom auf sich im eingeschwungenen Zustand ergehende Werte unter Berücksichtigung einer Batterieersatzschaltung;
• – Interpolieren der korrigierten Messwertpaare und Ermitteln eines Ruhespannungswerts beim Stromwert 0 und
• – Bestimmen des Ladezustandes mittels eines ersten vorbestimmten Zusammenhangs ermittelter Ruhespannung und Ladezustand.

From the DE 102 08 652 A1 is a method for determining the state of charge of a battery with at least one cell known, with the steps:

• - detecting at least two measured value pairs for voltage and current;
• - Correcting the detected measured value pairs for voltage and current to steady-state values taking into account a battery replacement circuit;
• - Interpolate the corrected measured value pairs and determine a rest voltage value at the current value 0 and
• - Determining the state of charge by means of a first predetermined relationship determined rest voltage and state of charge.

From the DE 10 2005 015 727 A1 a method for determining the rest voltage of a storage battery is known, wherein by determining operating parameters of the storage battery in the idle phase and determining the rest voltage, each having a selected in dependence on the operating parameters rest voltage determination routine.

From the EP 0 680 613 B1 a method for determining the state of charge of a battery is known, in which upon detection of certain operating conditions, the battery current and the rest voltage are measured and closed from the measured values by means of a computing device on the state of charge, the determined variables are linked with correction functions that depend on at least the battery temperature are formed, wherein the discharge current measured during a first period of time and the charge current measured during a second period are related to each other, from which a third period is determined, which characterizes the remaining time remaining, indicating how long the Battery can still deliver a predetermined power.

Of the Invention is based on the technical problem, an improved Method and device for rest voltage measurement of a battery To create a vehicle.

The Solution of the technical problem results from the procedure with the features of claim 1 and the device with the features of Claim 11. Further advantageous embodiments of the method emerge from the dependent claims.

The method for quiescent voltage measurement of a battery of a vehicle comprises the steps that after switching off the ignition, a first defined time period t _{R is} waited and carried out a first voltage measurement U _R1 to the battery, wherein after a second defined time t _{measurement 1} another voltage measurement U _{R2 is performed} on the battery, wherein the second time period t _{Mess 1 is} a multiple smaller than the first time period t _R. For example, the first period is two hours, whereas the second period 10 Minutes. Subsequently, the results of the first voltage measurement U _{R1 are} compared with the second voltage measurement U _R2 , wherein the method steps for determining U _R1 and U _{R2 are} repeated if the deviation | U _{R1 -U R2} | is greater than a predetermined threshold .DELTA.U. On the other hand, if the deviation was smaller, a third voltage measurement U _{R3 is} carried out after a third time interval t _{meas 2} , wherein the result of the third voltage measurement U _{R3 is} written into a register as the open circuit voltage of the battery. This ensures that the voltage at the battery is not taken over at a fixed time as a rest voltage, but their temporal change is taken into account, so that incomplete decay processes are detected. This leads to significantly realistic conditions of the quiescent voltage.

Preferably, the second time interval t _{meas 1 is selected} equal to the third time span t _{meas 2} .

In a further preferred embodiment, the third voltage measurement U _{R3 is} compared with the first voltage measurement, wherein the method steps b) to d) are repeated according to claim 1 if the deviation | U _R1 - U _R3 | is greater than the predetermined threshold ΔU, the result of the third voltage U _R3 being written into the register only if the deviation | U _R1 - U _R3 | is less than the predetermined threshold .DELTA.U. This further improves the quiescent voltage measurement, since it reacts even longer to a change over time.

In a further preferred embodiment, the third voltage measurement U _{R3 is} repeated periodically after a time span t _{Mess 2} until the deviation | U _{R1 -U R3} | greater than the threshold ΔU or the ignition is switched on. This allows a continuous monitoring of the quiescent voltage, so that even creeping changes are detected, for example due to the quiescent current.

In a further preferred embodiment, the voltage measurement U _{R3 is} periodically updated in the register as long as the deviation | U _R1 - U _R3 | is less than the threshold ΔU.

In a further preferred embodiment, the voltage value U _R3 in the register is cleared if the deviation | U _R1 - U _R3 | is greater than the threshold .DELTA.U. On the other hand, this can be of further interest as a guideline if, after a detected deviation of | U _R1 - U _R3 | > ΔU shortly after the ignition is switched on. Therefore, both alternatives are conceivable, namely to delete the U _R3 value or leave it in the register first. Preferably, the value for U _{R3 is} first stored in an intermediate register, which is then adopted by the condition "ignition on" in a main register or measured value block MWB.

In a further preferred embodiment, the values U _{R3 of} preceding "ignition-off phases" stored as rest voltage are or remain stored in the main register, which allows an overview of the history of the rest voltage for analysis purposes.

In a further preferred embodiment, the number of operating phases is detected in which no voltage U _{R3 was written} into the register when the ignition was switched off.

In a further preferred embodiment, after switching on the ignition and / or a motor running a determined rest voltage U _{R3 is set} after a defined time as invalid. This prevents that the quiescent voltage value is deleted by only briefly switching on the ignition or engine and is no longer available for diagnostic or display purposes, although not much has changed in the state of charge of the battery. The defined time for "ignition on" and "engine run" can be selected differently.

In In another preferred embodiment, the determined Open circuit voltage displayed as voltage value or as SOC value.

The Invention will be described below with reference to a preferred embodiment explained in more detail. The figures show:

1 a schematic flow diagram of the method for determining the rest voltage and

2 a schematic block diagram of a device for determining the rest voltage.

block 10 represents the operating state "Ignition off" (s_operation = 3). When the ignition is switched off, a counter is activated, which is symbolized by t active. When a first defined time span t _R (t = t _R ) has elapsed, a first voltage measurement U _{R1 is} carried out on the battery. On the other hand, if a change in the operating state from "ignition off" (s_operation = 3) to "ignition on" (s_operation = 2) takes place before the expiration of t _R , then a counter is produced 20 counted up that no rest voltage U _{R3 was} detected. On the other hand, if the voltage measurement U _R1 was carried out, then a further counter is activated, after which a second voltage measurement U _{R2 is} carried out after a second defined time span t _{Mess 1 has} elapsed. If, on the other hand, a change in the operating state from "ignition off" (s_operation = 3) to "ignition on" (s_operation = 2) takes place before expiry of time span t _{measurement 1,} a value "invalid" for the rest voltage is written in a register MWB (Value 1 = invalid). Furthermore, the counter 20 elevated. If, on the other hand, the second voltage measurement U _{R2 was} carried out, then it is compared with the first voltage measurement U _R1 . If the deviation between the first voltage measurement U _R1 and the second voltage measurement U _{R2 is} greater than a threshold value ΔU (| U _R1 -U _R2 |> ΔU), then the first voltage measurement U _{R1 is} repeated. The reason is that a deviation above the threshold value suggests that the battery is not yet settled. If, however, the deviation is smaller than the threshold value .DELTA.U, a third voltage measurement _{U.sub.R3 is} carried out after a defined period of time _{t.sub.mess 2 has} elapsed. If, however, the ignition is switched on before t _{measurement 2 has} expired (s_operation = 2), the rest voltage is stored with the value "invalid" and the counter 20 incremented. If, however, the ignition is switched on after a measurement U _R3 , the voltage U _{R3 is} stored as a rest voltage in the register MWB (value 1 = s_U_R3). The value of the third voltage measurement U _R3 is also compared with the value of the first voltage measurement U _R1 . If the deviation is greater than the threshold ΔU (| U _R1 -U _R3 |> ΔU), then the first voltage measurement U _{R1 is} repeated and the method starts again. If, on the other hand, the deviation is smaller than the threshold value ΔU, the voltage measurement for U _{R3 is} repeated after the time span t _{meas 2 has} elapsed until either the ignition is switched on or the deviation is greater than the threshold ΔU. If the deviation was greater than the threshold value ΔU and no new U _R2 or U _{R3 was} determined yet, the quiescent voltage is preferably set to "invalid" when the ignition is switched on (value 1 = invalid). This can be realized, for example, by writing the value U _R3 to an intermediate register, the value of which is taken over into the register MWB only when the ignition is switched on, the intermediate register being deviated | U _{R1 -U R3} | > ΔU is cleared.

Furthermore, it can be seen that the values for U _{R3 of} preceding phases are stored in the register MWB, the storage preferably taking place in the form of a shift register, in which case the U _R values of the last three ignition-off phases are stored.

In the 2 schematically is a possible embodiment of a device 1 for resting voltage measurement of a battery 2 shown. The device 1 includes a tension measuring device 3 and a control and evaluation unit 4 , The control and evaluation unit 4 includes a microprocessor 5 , a store 6 and a register 7 (or MWB). The microprocessor 5 controls, for example, a switch 8th on, for example, is designed as a relay, so that when the switch is closed 8th a voltage measurement is performed and with the switch open 8th the battery 2 is not charged. The results of the voltage measurements are stored in the memory 6 written and following the procedure described in the microprocessor 5 evaluated. The result of the third voltage measurement U _R3 or other status signals are then stored in the register 7 written, with the register 7 is preferably designed as a non-volatile memory, whereas the memory 6 can be designed as a volatile memory and also by the main memory of the microprocessor 5 can be formed. Not shown is that the control and evaluation unit 4 a status signal is supplied to the ignition and the microprocessor 5 has an internal time measurement.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10208652 A1 [0004]
• DE 102005015727 A1 [0005]
• - EP 0680613 B1 [0006]

Claims (11)

A method for rest voltage measurement of a battery of a vehicle, comprising the following method steps: a) after switching off the ignition, a first defined period of time t _{R is} awaited, b) a first voltage measurement U _R1 is performed on the battery, c) after a second defined period t _{Mess 1} , a second voltage measurement U _{R2 is performed} on the battery, wherein the second time interval t _{Mess 1 is} a multiple smaller than the first time period t _R , d) comparing the result of the first voltage measurement U _R1 with the second voltage measurement U _R2 , wherein the method steps b) and c) are repeated if the deviation | U _R1 - U _R2 | is greater than a predetermined threshold .DELTA.U or after a third time span t _{Mess 2} a third voltage measurement U _{R3 is} performed, if the deviation | U _R1 - U _R2 | was less than the threshold .DELTA.U, wherein the result of the third voltage measurement U _{R3 is written} as a rest voltage of the battery in a register. A method according to claim 1, characterized in that the second time span t _{Mess 1 is selected} equal to the third time span t _{Mess 2} . Method according to Claim 1 or 2, characterized in that the third voltage measurement U _{R3 is} compared with the first voltage measurement U _R1 , the method steps b) to d) being repeated as in Claim 1 if the deviation | U _R1 - U _R3 | is greater than the predetermined threshold ΔU, the result of the third voltage measurement U _R3 being written into the register only if the deviation | U _R1 - U _R3 | is less than the predetermined threshold .DELTA.U. Method according to one of the preceding claims, characterized in that the third voltage measurement U _{R3 is} repeated periodically after a time span t _{Mess 2} until the deviation | U _R1 - U _R3 | greater than the threshold ΔU or the ignition is switched on. A method according to claim 4, characterized in that the voltage measurement U _{R3 is} periodically updated in the register, as long as the deviation | U _R1 - U _R3 | is less than the threshold ΔU. Method according to claim 4 or 5, characterized in that the voltage value U _R3 in the register is canceled if the deviation | U _R1 - U _R3 | is greater than the threshold .DELTA.U. Method according to one of the preceding claims, characterized in that the values stored as rest voltage U _R3 previous "ignition-off-phases" are stored or remain. Method according to one of the preceding claims, characterized in that the number of operating phases is detected in which no voltage U _{R3 was written} into the register with the ignition off. Method according to one of the preceding claims, characterized in that after switching on the ignition and / or a motor running a determined rest voltage U _{R3 is set} only after a defined time as invalid. Method according to one of the preceding claims, characterized in that the determined rest voltage as the voltage value or displayed as SOC value. Contraption ( 1 ) for resting voltage measurement of a battery ( 2 ) of a vehicle, comprising a tension measuring device ( 3 ), a control and evaluation unit ( 4 ) for the voltage measuring device ( 3 ) and a register ( 7 ), the control and evaluation unit ( 4 ) or in the control and evaluation unit ( 4 ), wherein after switching off the ignition, a defined period of time t _{R is} awaited before a first voltage measurement U _R1 on the battery ( 2 ) is carried out, wherein after a further defined period t _MESS1 a second voltage measurement U _R2 on the battery ( 2 ), wherein the second time period t _{MESS1 is} a multiple smaller than the first time period t _R , wherein the results of the first voltage measurement U _{R1 are} compared with the second voltage measurement U _R2 , wherein the first and second voltage measurement is repeated if the sign | U _R1 - U _R2 | is greater than a predetermined threshold .DELTA.U or after a third time period t _MESS2 a third voltage measurement U _{R3 is} performed if the deviation | U _R1 - U _R2 | was smaller than the threshold value ΔU, the result of the third voltage measurement U _R3 being the open-circuit voltage of the battery ( 2 ) in the register ( 7 ) is written.