GB2486310A - Method of determining the state of a battery pack - Google Patents
Method of determining the state of a battery pack Download PDFInfo
- Publication number
- GB2486310A GB2486310A GB1120442.7A GB201120442A GB2486310A GB 2486310 A GB2486310 A GB 2486310A GB 201120442 A GB201120442 A GB 201120442A GB 2486310 A GB2486310 A GB 2486310A
- Authority
- GB
- United Kingdom
- Prior art keywords
- battery pack
- characteristic value
- load characteristic
- temperature
- time
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
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]
- G01R31/382—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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/48—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte
-
- 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]
- G01R31/385—Arrangements for measuring battery or accumulator variables
- G01R31/387—Determining ampere-hour charge capacity or SoC
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Secondary Cells (AREA)
Abstract
A method of determining the state of a battery pack comprises the step of forming a load characteristic value (B) representing the discharge history of the battery pack by determining, during operation of the battery pack, the instantaneous operating temperature of the battery pack and increasing the load characteristic value (B) in steps in dependence on the respective instantaneous operating temperature.
Description
I
METHOD OF DETERMIN[NG THE STATE OF A BATTERY PACK The invention relates to a method of determining the state of a battery pack.
Various electrical apparatus are operated with the help of battery packs. The power capability of such a battery pack strongly decreases towards the end of its service life.
The power decrease in that case depends on, inter alia, the intensity of use of the battery pack, which in turn depends on the operating duration and the load during operation of the battery pack. Information with respect to operating duration and load are helpful for diagnosis of battery packs. The operating duration can in that regard be measured relatively simply. In order to assess the load, thereagainst, further data are necessary such as, for example, the profile of the current during the discharge process. Such a current profile is, however, very difficult to measure and can be measured only with considerable technical effort.
It is therefore an object of the invention to provide a possibility of determining the overall load of a battery pack by simplest possible means and as accurately as possible.
According to the present invention there is provided a method of determining the state of a battery pack, wherein a load characteristic value representing the intensity of use of the battery pack is formed in that during operation of a battery pack the instantaneous operating temperature of the battery pack is determined and the load characteristic value is increased in steps in dependence on the respective instantaneous operating temperature.
Since the instantaneous battery pack temperature is linked with the instantaneous load of the battery pack, the previous overall load of the battery pack can be estimated with the help of the load characteristic value directly increasing with the battery pack temperature.
A high load characteristic value points towards substantial use of the battery pack. A relatively accurate diagnosis of the state of the battery pack can therefore be carried out with the help of the load characteristic value.
In an advantageous ernbodimerft the load characterisUc vaftie is increased in steps during operation of the battery pack at predetermined intervals in time by a value dependent on the respective instantaneous battery pack temperature. ln this case the stepped increase in the load characteristic value takes place in each instance at the same time intervals.
The procedure can therefore be realised by particularly simple time transmitters.
In a further embodiment the load characteristic value is increased in steps during operation of the battery pack in each instance by a predetermined value at time intervals determined by the respective instantaneous battery pack temperature, wherein the time intervals are shorter the higher the respectively determined instantaneous operating temperature. In this case the load characteristic value is increased at varying intervals in time in each instance by the same amount. Summation can be realised in particularly simple manner.
In yet another embodiment the operating times of the battery pack are determined on the basis of the course over time of the voltage of the battery pack. The discharge phases of the battery pack can be determined in particularly simple manner on the basis of the battery pack voltage.
Finally, in a further embodiment the start of a discharge process of the battery pack is determined on the basis of a negative jump in the battery pack voltage and the end of the discharge process of the battery pack is determined on the basis of a positive jump in the battery pack voltage. Detection of the jumps in the battery pack voltage allow a particularly accurate detection of the start and end of a discharge phase.
Preferred examples of the method of the present invention will now be more particularly described with reference to the accompanying drawings, in which: Fig. 1 is a diagram showing the course over time of a battery voltage; Fig. 2 is a diagram showing the course over time of a battery pack temperature; Fig. 3 is a diagram showing the formation of a load characteristic value by stepped increase in accordance with a first example of the method according to the invention; and Fig. 4 is a diagram showing the formation ofa load characteristic vabje by stepped increase fr accordance with a second example of the method according to the invention. * 3
Referring now to the drawings, in a method exemplifying the invention a load characteristic value reflecting the intensity of use or the wear of a battery pack is formed over the entire period of use of the battery pack. A statement about the state of the battery pack can be made in relatively simple manner with the help of this load characteristic value. In that case, a high load characteristic value points towards a high intensity of use and thus a high degree of wear of the battery pack. Thereagainst, a low load characteristic value indicates a low intensity of use or a low degree of wear of the battery pack. In order to form the load characteristic value serving as a measurement magnitude for the wear of the battery pack the instantaneous operating temperature is measured during operation of the battery pack, i.e. during discharge phases, and the load characteristic value is increased in steps in dependence on the determined battery pack temperature. In that case, the greater the measured battery pack temperature, the more the load characteristic value is increased.
For measurement of the temperature, use can in that case be made of, for example, devices already present in modern battery packs. Such devices are already integrated in many battery packs for, for example, temperature monitoring during the charging process.
A statement about the instantaneous intensity of use can be made by way of the measured operating temperature of the battery pack. On the one hand, by way of the battery pack temperature a conclusion can be indirectly made with respect to the mean discharge current and thus to the instantaneous load of this energy store. High discharge currents typically have the effect of shortening the service life of the battery cells. On the other hand, the battery pack temperature is directly linked with the wear of the pack, because the internal resistance of the pack increases with increasing wear. In order to obtain an indication which is as accurate as possible about the intensity of use and the wear connected therewith the load characteristic value is calculated as follows on the basis of the operating duration and battery pack temperature: As soon as the battery pack discharges, the operating duration counter starts. This counter stops as soon as the discharge process ends. The start and end of the discharge process can be determined by, for example, measuring the battery pack voltage. hi that case, a negative jump in the voltage indicates the start of a discharge process, whilst the end of a discharge process is indicated by a positive jump in the voltage. Fig. I shows by way of example the course of battery pack voltage V for a time period in which an electrical apparatus operated by means of the battery pack is placed in operation in total twice in succession. The electrical apparatus is initially in a switched-off state. The voltage V has in this state the value V1. Through the switching-on of the electrical apparatus at the time instant t1 the voltage V drops to the lower value V2. The negative jump in the voltage V resulting therefrom thus indicates the start of the discharge process of the battery pack extremely accurately. At the time instant t3 the apparatus is switched off again, whereupon the voltage V abruptly rises from the lower value V2 to the higher value V1. The positive jump in the voltage illustrated in Fig. 1 at the time instant t3 therefore marks the end of the first discharge process I. The second discharge process II taking place after a pause is similarly determined by a negative voltage jump at the time instant t4 as well as by a positive voltage jump at the time instant t7.
Since the battery pack serving as a voltage source has an internal resistance, the discharge current flowing in the closed circuit leads to a loss in power and thus to a temperature increase within the battery pack. This temperature increase is greater the higher the discharge current and the longer the discharge process. Fig. 2 shows by way of example the course of the battery pack temperature T during the two discharge processes I, II. As is apparent from Figure 2, the temperature T rises more or less linearly during the first discharge process I from a low value T1 substantially predetermined by the ambient temperature. The battery pack temperature T exceeds a first threshold value T2 at a time instant t2 and finally reaches a maximum at the time instant t3. With the switching-off of the apparatus at the time instant t3, the temperature T drops back to the ambient temperature T1. The temperature T also continuously rises during the second discharge process II from the value T1 predetermined by the environment.
Since the apparatus at the start of the second discharge phase II is operated with a lower load, the discharge current and also the temperature rise connected therewith are smaller at this point in time than at the start of the first discharge process I. The temperature plot during the second discharge process II therefore reaches the threshold value T2 somewhat later. Since, however, the discharge process II lasts longer than the first discharge process I, the temperature T ultimately rises significantly higher. At the time instant t6 the temperature T exceeds a second threshold value T3 and reaches its maximum at the time instant t7 before the battery pack cools down again after the end of the second discharge process II.
The temperature course, which is shown here, during the discharge and rest phases merely serves to illustrate typical use behaviour of an electrical machine. The temperature behaviour of the battery pack depends on many factors, such as, for example, the course of the discharge current, the internal resistance of the battery or the heat dissipation capability of the battery pack or the housing. For this reason, the temperature course can differ from battery pack to battery pack or from apparatus to apparatus.
In order to be able to make a statement about the previous intensity of use or the wear connected therewith, in accordance with the invention a use or load characteristic value representing the total load of the battery during its past service life is formed in dependence on the respective instantaneous measured temperature. In that case the increase in the load characteristic value takes place in each instance during the discharge processes, i.e. during the phases of use of the electric apparatus. The load characteristic value can, however, also be increased during a charging process in dependence on the charging current, the charging duration or the temperature increase during charging.
Moreover, a simple load characteristic value can also be formed during charging. In principle, a combination of different methods for formation of a characteristic value reflecting the state of the battery can also be used. For illustration that the formation of the load characteristic value can in principle be undertaken in different ways, two possible procedures are presented by way of example in the following.
According to a first procedure the load characteristic value is increased in steps in each instance by a predetermined amount. In this regard, the step width -thus the time between two increases -is selected in dependence on the instantaneous battery pack temperature 1. The load characteristic value B can in that case be increased in each instance by a predetermined fixed amount AB, for example by 1'. Fig. 3 clarifies the increase in the load characteristic value B in accordance with this first method. As is shown in Fig. 3 the load characteristic value B at the start of the observation period is three points. At the start of the first discharge phase I at the time instant t1, which is indicated by the negative jump in the voltage curve in accordance with Fig. 1, the operating time counter of the battery pack is set in motion. In addition, the instantaneous for increase of the load characteristic value B is determined on the basis of the instantaneous operating temperature T. In the present example the temperature T lies below the first threshold value temperature T2. A step width of three time units, for example, is associated with this temperature region. As a consequence thereof the load characteristic value B of all three time units is increased in each instance by one'. As time units, use can be made basically of different time periods such as, for example, 1 second, seconds, 30 seconds. Time units lasting 1 minute and even several minutes are also possible depending on the respective use. As is shown in Fig. 3, the increase of the load characteristic value B takes place only after expiry of the time period At determined by the instantaneous temperature T. In principle, the load characteristic value increase can, however, also take place at the start of the time period At or at a mean point in time of the time period At.
Since the battery pack temperature T, as is illustrated in Figure 2, exceeds the first threshold value T2 at the time instant t2 the increase of the load characteristic value B is accelerated from the time instant t2. The higher intensity of use accompanying the higher temperature and the higher level of wear connected therewith of the battery pack can thus be documented. In the first procedure this acceleration takes place by shortening the step width, thus the time period between two increases. In the present example the step width is increased to two time units.
With the end of the first discharge process I at the time instant t3 the increase of the load characteristic value B is also set. During the inactive phase from the time instant t3 up to the time instant t4 marking the start of the second discharge phase lIthe load characteristic value B therefore remains constant.
Since during the rest phase the battery pack in the meanwhile is cooled down to the ambient temperature T1, the step width at the start of the second discharge phase II is similarly three time units. Only from the time instant t5 at which the battery pack temperature I exceeds the first threshold value T2 is the step width reduced to two time units. Finally, from the time instant t6 at which the temperature I of the battery pack exceeds a second threshold value 13 the step width is now reduced to one time unit.
Finally, the battery pack temperature I at the end of the second discharge process II reaches its maximum at the time instant t7 before the battery pack cools down again. As dicatethn Hg. 3, the load charactedstk vakeBfrom the time kistant t7 therefore remains constant up to a fresh discharge process.
The increase of the load characteristic value B can in principle also take place at predetermined fixed step widths At. The load characteristic value B is then increased in each instance by a variable amount AB which depends on the instantaneous battery pack temperature T. Fig. 4 shows by way of example the course of such a load characteristic value increase. In this example as well the load characteristic value B is increased in each instance at the end of the predetermined time period At, wherein the increase can in principle also be already carried out at an earlier or later point in time. As Fig. 4 shows, the load characteristic value B at the start of the first discharge phase I is increased in steps of four time units in each instance by one point. On reaching the first temperature threshold T2 at the time instant t2 the load characteristic value B is now increased in each instance by two points until the load characteristic value increase on reaching the end of the first discharge phase I at the time instant t3 is suspended. The load characteristic value is also increased in each instance by one point at the start of the second discharge phase II. After exceeding the first temperature threshold T2 at the time instant t5 the load characteristic value B is now increased in each instance by two points per step. Finally, the load characteristic value increase from the time instant t6 at which the battery pack temperature T exceeds the second temperature threshold value 13 amounts in each instance to three points per four time units.
As is apparent from comparison of Figs. 3 and 4, substantially similar end values arise even in the case of use of different summation methods, so that with the help of the load characteristic value B according to the invention and depending on the respective procedure for forming the load characteristic value the temperature load of the battery pack can be satisfactorily imaged during its entire operational life. The thus-formed load characteristic value can be filed within a memory device (for example EPROM) of the battery pack and read out again from this memory device for diagnostic purposes. For diagnosis, use can also be made -apart from the summated load characteristic value -of the measured operating duration of the battery pack.
The method steps can be realised by way of hardware, software or a combination of hardware and software.
Mhough flip xl characteristic value is preferabjy formed for Jith iuni-ion batteries of electric power tools such as, for example, battery screwdriver/drills, the method described here is in principle also usable for other types of batteries and apparatus.
Claims (5)
- cLAIMS 1. A method of determining the state of a battery pack, comprising the step of forming a load characteristic value representing the intensity of use of the battery pack by determining, during operation of the battery pack, the instantaneous operating temperature of the battery pack and increasing the load characteristic value in steps in dependence on the respective instantaneous operating temperature.
- 2. A method according to claim 1, wherein the load characteristic value is increased in steps, during operation of the battery pack, at predetermined intervals in time by a value dependent on the respective instantaneous operating temperature.
- 3. A method according to claim I or claim 2, wherein the load characteristic value is increased in steps, during operation of the battery pack, in each instance by a predetermined value at intervals in time determined by the respective instantaneous operating temperature, the intervals in time being shorter the higher the respective instantaneous operating temperature.
- 4. A method according to any one of the preceding claims, comprising the step of determining the operating times of the battery pack on the basis of the course over time of the voltage of the pack.
- 5. A method according to claim 4, wherein the step of determining operating times comprises determining the start of a discharge process of the battery pack on the basis of a negative jump in the pack voltage and the end of the discharge process of the battery pack on the basis of a positive jump in the pack voltage.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE102010062441A DE102010062441A1 (en) | 2010-12-06 | 2010-12-06 | Method for determining the state of a battery pack |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB201120442D0 GB201120442D0 (en) | 2012-01-11 |
| GB2486310A true GB2486310A (en) | 2012-06-13 |
| GB2486310B GB2486310B (en) | 2013-01-09 |
Family
ID=45508825
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB1120442.7A Expired - Fee Related GB2486310B (en) | 2010-12-06 | 2011-11-25 | Method of determining the state of a battery pack |
Country Status (2)
| Country | Link |
|---|---|
| DE (1) | DE102010062441A1 (en) |
| GB (1) | GB2486310B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US11955830B2 (en) | 2021-04-27 | 2024-04-09 | Techtronic Cordless Gp | Battery temperature based tool power reduction |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0712233A (en) * | 1993-06-24 | 1995-01-17 | Sekisui Chem Co Ltd | Seal device by o-ring |
| US20030016023A1 (en) * | 2001-07-11 | 2003-01-23 | Vb Autobatterie Gmbh | Method for determining the state of charge of rechargeable batteries |
| KR20070006953A (en) * | 2005-07-07 | 2007-01-12 | 삼성에스디아이 주식회사 | Method for resetting soc of secondary battery module |
| US7348763B1 (en) * | 2002-12-20 | 2008-03-25 | Linvatec Corporation | Method for utilizing temperature to determine a battery state |
| WO2009004009A1 (en) * | 2007-07-05 | 2009-01-08 | Robert Bosch Gmbh | Method for determining the quiescent voltage of a motor vehicle battery |
-
2010
- 2010-12-06 DE DE102010062441A patent/DE102010062441A1/en active Pending
-
2011
- 2011-11-25 GB GB1120442.7A patent/GB2486310B/en not_active Expired - Fee Related
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0712233A (en) * | 1993-06-24 | 1995-01-17 | Sekisui Chem Co Ltd | Seal device by o-ring |
| US20030016023A1 (en) * | 2001-07-11 | 2003-01-23 | Vb Autobatterie Gmbh | Method for determining the state of charge of rechargeable batteries |
| US7348763B1 (en) * | 2002-12-20 | 2008-03-25 | Linvatec Corporation | Method for utilizing temperature to determine a battery state |
| KR20070006953A (en) * | 2005-07-07 | 2007-01-12 | 삼성에스디아이 주식회사 | Method for resetting soc of secondary battery module |
| WO2009004009A1 (en) * | 2007-07-05 | 2009-01-08 | Robert Bosch Gmbh | Method for determining the quiescent voltage of a motor vehicle battery |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2486310B (en) | 2013-01-09 |
| DE102010062441A1 (en) | 2012-06-06 |
| GB201120442D0 (en) | 2012-01-11 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20151125 |