SYSTEMS AND METHODS FOR BATTERY CHARGE CONTROL

Abstract

A charging control system for a battery includes temperature sensing means configured to provide temperature value associated with the battery, voltage sensing means configured to provide a battery's voltage value, pressure sensing means configured to provide the battery's internal portion pressure value, and a controller. The controller is configured to determine a threshold pressure change associated with a full charge of the battery based on map data selected from a predetermined data map associated with the battery monitor, during the charging process, a present voltage value obtained by the voltage sensing means and a total pressure change based on a present pressure value obtained by the pressure sensing means, continue the charging process when the present voltage value exceeds an upper limit voltage value, and total pressure change is less than threshold pressure change and terminate the charging process when the present voltage value exceeds the upper limit voltage value

Claims

1-21. (canceled)

22. A charging control system for a battery, comprising: a temperature sensor configured to provide a temperature value associated with the battery; a voltage sensor configured to provide a voltage value associated with the battery; a pressure sensor configured to provide a pressure value associated with an internal portion of the battery; and a controller configured to: determine, before a charging process is started, a threshold pressure change associated with a full charge of the battery based on map data selected from a predetermined data map associated with the battery; monitor, during the charging process, a present voltage value obtained by the voltage sensor and a total pressure change based on a present pressure value obtained by the pressure sensor; continue the charging process when the present voltage value exceeds an upper limit voltage value, and the total pressure change is less than the threshold pressure change; and terminate the charging process when the present voltage value exceeds the upper limit voltage value, and the total pressure change is greater than or equal to the threshold pressure change.

23. The charging control system according to claim 22, wherein the selection of the map data is based on a pre-charging temperature value obtained from the temperature sensor, a pre-charging voltage value obtained from the voltage sensing means, and a pre-charging pressure value obtained from the pressure sensor.

24. The charging control system according to claim 22, wherein the controller is configured to increase the upper limit voltage value when the present voltage value exceeds the upper limit voltage value, and the total pressure change is less than the threshold pressure change.

25. The charging control system according to claim 22, wherein the controller is further configured to compensate for creep in one or more portions of the battery by modifying the selected map data based on an initial internal pressure measurement, the pre-charging process pressure value, and the pre-charging temperature value.

26. The charging control system according to claim 25, wherein the controller is configured to compare the initial internal pressure measurement and the pre-charging pressure value, and when the initial internal pressure measurement is greater than the pre-charging process pressure value, select new map data associated with the pre-charging pressure value.

27. The charging control system according to claim 26, wherein the predetermined map comprises a collection of experimentally measured internal pressures, open circuit voltages, and temperatures of a representative battery under representative conditions of use of the battery.

28. The charging control system according to claim 22, wherein the pressure sensor comprises at least one tactile sensor embedded in the battery.

29. The charging control system according to claim 28, wherein the at least one tactile sensor is positioned parallel to a laminated direction of a battery cell of the battery.

30. The charging control system according to claim 22, further comprising a state of charge sensor configured to determine a state of charge of the battery.

31. The charging control system according to claim 22, wherein the voltage sensor comprises a dummy cell connected to one or more battery packs associated with the battery.

32. The charging control system according to claim 22, wherein the voltage value is an open circuit voltage of the battery.

33. The charging control system according to claim 22, wherein the battery comprises at least one of a lithium-ion solid-state battery and a lithium-ion liquid electrolyte battery.

34. A vehicle comprising the charging control system according to claim 22.

35. A method for charging a battery, comprising: determining a temperature value associated with the battery; determining a voltage value associated with the battery; determining a pressure value associated with an internal portion of the battery; determining, before a charging of the battery is started, a threshold pressure change associated with a full charge of the battery based on map data selected from a predetermined data map associated with the battery; charging the battery; monitoring, during the charging, a present voltage value obtained by the voltage sensor and a total pressure change based on a present pressure value obtained by the pressure sensor; continuing the charging when the present voltage value exceeds an upper limit voltage value, and the total pressure change is less than the threshold pressure change; and terminating the charging when the present voltage value exceeds the upper limit voltage value, and the total pressure change is greater than or equal to the threshold pressure change.

36. The method according to claim 35, wherein the selection of the map data is based on a pre-charging temperature value obtained from the temperature sensor, a pre-charging voltage value obtained from the voltage sensor, and a pre-charging pressure value obtained from the pressure sensor.

37. The method according to claim 35, comprising increasing the upper limit voltage value when the present voltage value exceeds the upper limit voltage value, and the total pressure change is less than the threshold pressure change.

38. The method according to claim 35, comprising compensating for creep in one or more portions of the battery by modifying the selected map data based on an initial internal pressure measurement, the pre-charging process pressure value, and the pre-charging temperature value.

39. The method according to claim 38, comprising comparing the initial internal pressure measurement and the pre-charging pressure value; and when the initial internal pressure measurement is greater than the pre-charging process pressure value, selecting new map data associated with the pre-charging pressure value.

40. The method according to claim 39, wherein the predetermined map comprises a collection of experimentally measured internal pressures, open circuit voltages, and temperatures of a representative battery under representative conditions of use of the battery.

41. The method according to claim 35, comprising determining a state of charge of the battery and modifying the threshold pressure change based on the state of charge of the battery before the charging is started.

42. The method according to claim 35, wherein the battery comprises at least one of a lithium-ion solid-state battery and a lithium-ion liquid electrolyte battery.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG. 1A is a schematic diagram of a charging system for a battery according to embodiments of the present disclosure;

[0032] FIG. 1B is a schematic diagram of an exemplary open circuit voltage measuring configuration;

[0033] FIG. 2 shows an exemplary representation of an internal portion of a battery including pressure sensors;

[0034] FIG. 3 is a flowchart showing one exemplary method for charge control according to embodiments of the present disclosure;

[0035] FIG. 4 is a flowchart showing one exemplary method for creep compensation;

[0036] FIGS. 5A and 5B are representations of an exemplary data maps according to embodiments of the disclosure; and

[0037] FIG. 6 is an exemplary graph showing a relationship between pressure, voltage, and available energy during a charging process.

DESCRIPTION OF THE EMBODIMENTS

[0038] Reference will now be made in detail to the present exemplary embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

[0039] FIG. 1A is a schematic diagram of a charging system for a battery according to embodiments of the present disclosure. The system may include a battery 5, one or more sensors 27, battery control unit 70, and a charging control unit 20. Battery 5 may include one or more battery packs 10, one or more pressure sensing membranes 15, and a dummy cell 25, among others. Battery 5 may be any suitable type of battery, for example, a lithium ion battery, a NIMH battery, lead acid battery, etc.

[0040] Battery 5 may be connected to an inverter 100 which may in turn be connected to one or more motors 105, to permit energy stored in battery 5 during a charging process to be stepped up by inverter 100 and fed to motor 105 during a discharging process, thereby resulting in movement of the vehicle.

[0041] Battery packs 10 may be installed within a housing associated with battery 5. For example, battery 5 may include a housing 11 comprising any suitable material for housing battery packs 10, e.g., of metal, plastic, composite, etc. Such a housing 11 may be configured to have one or more battery packs 10 placed and connected therein, and subsequently the housing 11 may be closed, e.g., by fastening (e.g., bolting) a cover onto an open portion of the housing 11.

[0042] According to some embodiments, one or more bolts (not shown) may extend over a length or width of the housing and following placement of a cap (not shown) over the open portion of housing 11, a nut may be affixed to the one or more bolts and tightened, resulting in closure of the housing 11. One of ordinary skill in the art will understand that bolted configurations of this type may undergo a creep phenomenon in which changing stresses applied to the bolts over time result in permanent deformation of the bolts used for the fastening, and an expansion/enlarging of space within the internal cavity of battery 5 housing the battery packs 10. Therefore, pressure within the internal cavity of battery 5 changes based on expansion of the battery packs 10 and as a function of creep. Embodiments of the present disclosure take such creep and expansion into account as described below.

[0043] Each battery pack 10 present in battery 5 may be connected in series or in parallel to other battery packs 10 present in battery 5. One of skill in the art will recognize that various criteria such as a desired voltage, a desired maximum current, etc. may be considered when designing a battery and connections as described herein.

[0044] One or more pressure sensors 15 may be provided within battery 5. For example a pressure sensor 15 may be placed in between each battery pack 10 within battery 5, such that pressure arising due to expansion of each battery pack 10 may exert a force on the one or more pressure sensors 15 based on the amount of expansion. In addition, pressure sensors 15 may further be provided between an end of the housing 11 of battery 5 and the terminal battery pack 10 within battery 5.

[0045] According to some embodiments, pressure sensors 15 may be positioned parallel to a laminated direction of the battery packs 10 within battery 5 (see FIG. 2).

[0046] The number of pressure sensors included within battery 5 may be determined based on the number of battery packs 10, and/or any other criteria one of skill in the art may determine suitable. For example, where to battery packs 10 are present within battery 5, one pressure sensor 15 may be placed between these two battery packs 10. Similarly where three battery packs are present within battery 5, two pressure sensors 15 may be placed within battery 5, a first pressure sensor 15 in between the first battery pack any secondary pack, and a second pressure sensor 15 placed in between the second battery pack and the third battery pack.

[0047] Pressure sensor 15 may comprise any suitable pressure sensing device, and may be, for example, a tactile sensor having a thickness suitable for measuring expansion and contraction of battery packs 10. According to some embodiments a thickness of pressure sensor 15 may range between for example, 0.01 mm to 1 mm, and according to some embodiments, 0.1 mm.

[0048] Once the battery 5 has been assembled and closed, for example with a cover bolted to battery housing 11 as described above, an initial pressure P.sub.initial inside battery 5 may be measured at a plurality of open circuit voltages (e.g., OCVs corresponding to SOCs of between 10 and 100 percent at increments every 5 percent), and these values stored in memory of battery ECU 70. This value may be used throughout the life of battery 5 as a comparison to a current pressure P within battery 5, as measured by pressure sensors 15 and pressure detector 30.

[0049] FIG. 2 shows an exemplary representation of an internal portion of a battery including pressure sensors. Arrows shown at FIG. 2 represent application of pressure forces on pressure sensors 15 as well as, at the external portion of the left and right battery packs 10, forces exerted on the walls of housing 11 battery 5 based on expansion of battery packs 10. One of skill in the art will understand that while battery packs 10 may also exert forces in the Y direction, for purposes of the present disclosure forces exerted in the X direction will be considered for determination of pressure within battery 5.

[0050] Battery 5 may also include one or more dummy cells 25 conductively linked to battery packs 10 to permit measurement of an open circuit voltage V.sub.ocv across the totality of battery packs 10 present within battery 5. For example, a dummy cell 25 configured to provide a dummy load may be connected in parallel with each of battery packs 10 present within battery 5, and the output (i.e., open circuit voltage) may be provided to sensor bank 27, and more particularly voltage detector 35. One of skill in the art will recognize that more than one dummy cell 25 may be provided, for example one dummy cell for each battery pack 10 present in battery 5, and such a configuration may aid in determination of a faulty or failing battery pack 10.

[0051] FIG. 1B shows an exemplary schematic including dummy cell 25 connected with battery 5 and a switch 6 configured to close a connection of dummy cell 25 thereby engaging circuit 2. Closing of switch 6 thereby enables measuring an open circuit voltage V.sub.ocv across circuit 2 shown in FIG. 1B, while normal operation of battery 5 (i.e. while not measuring an open circuit voltage V.sub.ocv of battery 5) utilizes circuit 1.

[0052] In addition to pressure sensors 15 and dummy cell 25, battery 5 may include additional sensors, for example one or more temperature sensors, current sensors, etc. Sensors present in battery 5 may be configured to provide signals to sensor bank 27, thereby enabling sensor bank 27 to monitor information associated with battery 5 during a charging and/or discharging process (e.g. open circuit voltage V.sub.ocv, pressure, temperature, etc.) and to provide the information to battery ECU 70, among others.

[0053] Sensor bank 27 may include a pressure value detector 30, a state of charge detector 45, a voltage detector 35, a temperature detector 40, among others. For example pressure sensors 15 may be configured to provide information to pressure value detector 30, in order to enable pressure value detector 30 to determine a pressure force being exerted on pressure sensor 15.

[0054] Similarly voltage detector 35 may receive input from dummy cell 25 in order to determine an open circuit voltage V.sub.ocv of battery 5, and/or of each individual battery pack 10 within battery 5.

[0055] State of charge detector 45 may be configured to receive current information from a current sensor as well as voltage information from dummy cell 25 in order to determine a state of charge (SOC) of battery 5.

[0056] Temperature detector 40 may be configured to receive information from a temperature sensor within battery 5 in order to determine the temperature of battery 5.

[0057] Values from sensor bank 27 may be provided to battery ECU 70, with battery ECU 70 providing command signals battery controller 20 (e.g. charging control commands). For example battery ECU 70 may include a calculation unit 65 for determining a threshold pressure differential P.sub.T which may be calculated based on an open circuit voltage V.sub.ocv of battery 5 as measured by voltage detector 35 and a current pressure P within battery 5 as measured by pressure value detector 30 during a pre-charging process (i.e., before battery 5 begins charging). This will be described in greater detail below with reference to FIGS. 4, 5A and 5B.

[0058] Battery ECU 70 may further include a voltage comparison unit 60 configured for comparing a current voltage V as measured by voltage detector 35 (i.e., the open circuit voltage V.sub.ocv of battery 5) with a predetermined initial maximum voltage V.sub.max of battery 5. One of skill in the art understands that an intial maximum voltage V.sub.max of battery 5 may be determined in advance based on a design of the battery, and stored in, for example, a read-only memory (ROM) associated with battery ECU 70, or another computer present on the vehicle. Further, for purposes of the present disclosure, it will be assumed that the current voltage V and open circuit voltage V.sub.ocv of battery 5 at any particular point in time are equal.

[0059] Pressure comparison unit 55 may also be provided in ECU 70 for comparing a pressure differential P measured during the charging process by pressure value detector 30 (e.g. via repeated sampling by pressure value detector 30 of pressure sensors 15), with threshold pressure differential P.sub.T.

[0060] Battery ECU 70 may include memory configured to store values obtained from sensor bank 27, among others. For example, battery ECU 70 may store pressure values obtained from pressure value detector 30, voltage values obtained from voltage detector 35, temperature values obtained from temperature detector 40, etc. as well as map values associated with data experimentally obtained from an exemplary battery design corresponding to the battery 5 installed in the vehicle.

[0061] A history of values may be compiled and stored over the life of the battery 5 during use of the vehicle, and according some embodiments when the vehicle is stored (i.e., not being driven). By compiling such data it may be possible to determine the history of temperatures, voltages, pressures, etc. to which battery 5 has been subjected. Such a history may be used to augment processes described below for determining values to be used when compensating for creep.

[0062] One of skill in the art will understand that the memory associated with battery ECU 70 may be comprised within battery ECU 70, or may be present on and or in other systems of the vehicle providing communication access to battery ECU 70.

[0063] Battery controller 20 may comprise any suitable battery controller configured to control a charging process resulting in the recharging the battery packs 10 associated with battery 5. As one of skill in the art understands, lithium ion batteries in particular require relatively strict charging circumstances to be maintained during a battery charging process in order to avoid dangerous conditions such as overheating and overcharging. Therefore, battery controller 20 may be configured to control current and voltage provided to battery 5 during the charging process, among others. For example, when it is determined that a battery is not fully charged battery controller 20 may provide a predetermined current I at a predetermined voltage suitable for charging battery 5.

[0064] FIG. 3 is a flowchart showing one exemplary method for charge control according to embodiments of the present disclosure. In a pre-charging process (i.e. before charging a battery 5 begins) battery ECU may initially obtain a temperature of battery 5 as determined by temperature detector 40 based on information provided by a temperature sensor present in battery 5 (step 305).

[0065] A current pressure P within battery 5 is then obtained from pressure value detector 30 based on information provided by pressure sensors 15 within battery 5 and an open circuit voltage V.sub.ocv obtained by placing switch 6 in a position such that circuit 2 is engaged thereby permitting measurement of open circuit voltage V.sub.ocv by voltage detector 35 (step 310).

[0066] A threshold pressure differential P.sub.T may then be determined based on at least one of a temperature, open circuit voltage V.sub.ocv, and the present pressure P of battery 5 (step 315). The process for determining the threshold pressure differential P.sub.T and compensating for creep will be discussed with reference to FIGS. 4, 5A, and 5B.

[0067] FIG. 4 is a flowchart showing one exemplary method for creep compensation using a current temperature T of battery 5, while FIGS. 5A and 5B are representations of an exemplary experimentally determined data map relating temperature, pressure, and open circuit voltage V.sub.ocv of an exemplary battery. As will be discussed, such maps may be used for determining a threshold pressure differential P.sub.T.

[0068] The data map of FIGS. 5A and 5B may be created in advance based on experimental data obtained on an exemplary battery 5 in an assembled condition and stored in memory of ECU 70. For example an assembled battery 5 may be subjected to various temperatures T (e.g. at increments of 10 degree C., between 40 degrees C. and 60 degrees C.) at predetermined intervals of open circuit voltages (e.g., an interval of 0.01 V).

[0069] An internal pressure P of battery 5 may then be measured at each of these temperatures T and open circuit voltages. For each 10 degree C. increment, a collection of map points demonstrating a relationship between open circuit voltage V.sub.ocv and internal pressure of battery 5 at the particular temperature may be created and stored based on the measured pressure P at the open circuit voltage V.sub.ocv increment. Such a collection of map points corresponds, to each of lines T1-Tx shown in FIG. 5A. Notably, temperatures falling between lines of the 10 degrees C. lines (or any other selected interval) may then be interpolated by, for example, linear interpolation.

[0070] In order to determine a threshold pressure differential P.sub.T, ECU 70 may obtain a current temperature T of battery 5 from temperature detector 40 (step 405). Based on the determined current temperature T of battery 5, ECU 70 may refer to the data map as generated above, see FIG. 5A, to select map data (i.e., an initial temperature line) for example, T1.

[0071] Voltage comparison unit 60 may then obtain the current open circuit voltage V.sub.ocv of battery 5, thereby enabling identification of a point along the selected map data (e.g., temperature line T1) shown at 5A.

[0072] Pressure comparison unit 55 may then obtain a current pressure P within battery 5 from pressure value detector 30 and compare the current pressure P to determine whether it is less than the initial pressure P.sub.initial as measured at the same temperature following completion of battery assembly (step 410). If the current pressure P is equal to or within a reasonable tolerance (e.g., 5 bar, 10 bar, etc.) of the initial pressure P.sub.initial, then the initially selected map data (e.g., temperature line T1) is used for determination of the applicable threshold pressure differential P.sub.T (step 420).

[0073] Where the current pressure P is determined to be less than the initial pressure P.sub.initial for the current temperature and open circuit voltage V.sub.ocv, creep has likely occurred and therefore new map data should be selected from the data map to compensate for creep (step 415).

[0074] This compensation for creep may be performed, according to some embodiments, by traversing the y-axis directly from the initial pressure P.sub.initial to the point at the current pressure P and current open circuit voltage V.sub.ocv. The intersection of this point on a collection of map data (e.g., temperature line Tx) may then be selected as the new map data. An exemplary representation of this determination can be seen at FIG. 5B. If the point P does not fall directly on a predetermined collection of mapped data, a temperature line Tx falling outside of a 10 degree C. increment may be interpolated by, for example, linear interpolation at the current pressure P and the current open circuit voltage V.sub.ocv.

[0075] To determine the threshold pressure differential P.sub.T, a pressure change from the current pressure on the selected temperature line to a maximum pressure P.sub.max on the same temperature line is calculated based on equation 1.

P.sub.T=P.sub.maxP (1)

[0076] Where maximum pressure P.sub.max is determined experimentally at a range of temperatures for an exemplary new battery 5 having 100 percent state of charge (i.e. an open circuit voltage V.sub.ocv equivalent to the battery's full charge open circuit voltage V.sub.ocv). Based on this, one of skill will recognize that P.sub.max will be changed in accordance with which SOC is to be associated as V.sub.max.

[0077] Once the threshold pressure differential P.sub.T has been calculated by calculation unit 65, a charging process may begin, and battery controller 20 may allow current to begin flowing to battery 5 (step 320).

[0078] During the charging process battery 5 may be continuously monitored (e.g., at a predetermined sampling rate) and voltage comparison unit 60 may receive information from voltage detector 35 indicating a current open circuit voltage V.sub.ocv of battery 5. Voltage comparison unit 55 may compare the voltage V with an initial maximum voltage V.sub.max determined based on the design characteristics of battery 5 and its intended 100 percent charged maximum voltage (step 325). This initial maximum voltage V.sub.max may be stored in memory associated with battery ECU 70 for access by voltage comparison unit 60. Where the current voltage V is not greater than the initial maximum voltage V.sub.max (step 325: no), battery controller 20 causes the charging process to continue uninterrupted for the present sample.

[0079] When it is determined that the current voltage V is greater than or equal to the initial maximum voltage V.sub.max (step 325: yes) a current pressure differential P is determined based on equation 2.

P=P.sub.xP (2)

[0080] P.sub.x being a current internal pressure of the battery 5 at a time t where the current voltage V has exceeded the initial maximum voltage V.sub.max, and P being the pressure determined during the pre-charging process at step 315.

[0081] Pressure comparison unit 55 may then compare the current pressure differential P to the threshold pressure differential P.sub.T to determine whether the current pressure differential P is greater than the determined threshold pressure differential P.sub.T (step 330). Where the current pressure differential P is determined to be greater than or equal to the threshold pressure differential P.sub.T (step 330: yes), battery controller 20 may stop the charging process (i.e. stop flow of current to the battery 5).

[0082] If it is determined that the current pressure differential P is less than the threshold pressure differential P.sub.T (step 330: no) the initial maximum voltage V.sub.max may be increased for the present charging cycle to V.sub.max. In other words based on the fact that the threshold pressure differential P.sub.T has not been exceeded, it can be reasonably assumed that the battery 5 has not reached a 100 percent state of charge, and therefore the maximum voltage V.sub.max is currently too low to reflect 100% SOC with a present condition of battery 5. By basing the charge cycle on both V.sub.max and P.sub.T, it becomes possible to better enable the battery to reach a 100% state of charge 100 and avoids loss of energy storage.

[0083] FIG. 6 shows exemplary graphs indicating a relationship between pressure, voltage, and available energy during a charging process, as described above.

[0084] As shown in the lower graph FIG. 6 although the maximum voltage V.sub.max may be reached, the current pressure differential P has not exceeded the threshold pressure differential P.sub.T as determined at step 315. Therefore the maximum voltage V.sub.max is increased (see 3 in the bottom graph of FIG. 6), and the battery 5 permitted to charge for an additional period of time, this additional charging corresponding to an otherwise lost amount of energy stored in battery 5.

[0085] Throughout the description, including the claims, the term comprising a should be understood as being synonymous with comprising at least one unless otherwise stated. In addition, any range set forth in the description, including the claims should be understood as including its end value(s) unless otherwise stated. Specific values for described elements should be understood to be within accepted manufacturing or industry tolerances known to one of skill in the art, and any use of the terms substantially and/or approximately and/or generally should be understood to mean falling within such accepted tolerances.

[0086] Where any standards of national, international, or other standards body are referenced (e.g., ISO, etc.), such references are intended to refer to the standard as defined by the national or international standards body as of the priority date of the present specification. Any subsequent substantive changes to such standards are not intended to modify the scope and/or definitions of the present disclosure and/or claims.

[0087] It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims.