Battery management system

Abstract

A battery management system (BMS) configured to control a discharge current of a battery is provided. The BMS is configured to: calculate a discharge energy of the battery within a time step based on the discharge current and a duration of the time step; and calculating the cumulative discharge energy of the battery based on the cumulative discharge energy calculated for the previous time step and the discharge energy for the time step. The BMS is further configured to determine a maximum discharge pulse current, calculate a discharge current limit, and control the discharge current of the battery such that the discharge current does not exceed the discharge current limit. The BMS may control the charging current of the battery in a similar manner.

Description

Technical Field

[0001] The present disclosure relates to a battery. In particular, the present disclosure relates to a battery for an electric working vehicle or the like. Background Art

[0002] Rechargeable batteries (e.g., cells or batteries) generate heat when they are charged or discharged. Therefore, the energy flow from / to the battery causes the battery to heat up due to the inherent resistance of the battery.

[0003] To prevent the battery from overheating, a battery management system ("BMS") may be provided to control the power input / output of the battery to a level of heat generation that the battery can safely dissipate.

[0004] Typically, a battery manufacturer will specify safe operating limits for continuous power flow from / to the battery. Additionally, a battery manufacturer may specify pulse power limits, where a higher amount of power may be output from / input to the battery for a specified period of time.

[0005] Against this background, the present disclosure aims to provide an improved or at least commercially valuable alternative battery management system. Summary of the invention

[0006] According to a first aspect of the present disclosure, a battery management system is provided, wherein the battery management system is configured to control a discharge current of a battery. The BMS is configured to:

[0007] Calculating the discharge energy of the battery within the time step based on the discharge current and the duration of the time step;

[0008] calculating a cumulative discharge energy of the battery based on the cumulative discharge energy calculated for a previous time step and the discharge energy for the time step;

[0009] Determining a maximum discharge pulse current of a pulse having a duration based on a discharge pulse current lookup table of the BMS;

[0010] Calculating the maximum accumulated discharge energy of the battery based on the maximum discharge pulse current and the duration of the pulse;

[0011] calculating a discharge current limit value based on a ratio of the cumulative discharge energy to the maximum cumulative discharge energy, wherein the discharge current limit value does not exceed the maximum discharge pulse current; and

[0012] The discharge current of the battery is controlled so that the discharge current does not exceed the discharge current limit.

[0013] The inventors have recognized that the maximum discharge current value provided by the battery manufacturer's lookup table provides a restrictive way to operate the battery. For example, the battery manufacturer may specify a value for the maximum pulse discharge current (where the pulses typically have a relatively short duration, such as 2 seconds or 30 seconds), and a separate value for the maximum discharge steady-state current (i.e., the safe operating limit for steady-state current discharge). Although the maximum discharge pulse current may be higher than the maximum discharge steady-state current, the increased current is only suitable for operation within the specified duration of the current pulse (e.g., according to the specified pulse duration of 2 seconds or 30 seconds). In some cases, the battery manufacturer specifies different maximum discharge pulse currents for pulses of different durations (e.g., a first maximum discharge pulse current is specified for a 2-second current pulse, and a lower second maximum discharge pulse current is specified for a 30-second current pulse). In such cases, it may be difficult to determine a suitable operating current for pulses of intermediate duration (e.g., operating with a 15-second current pulse), or a suitable operating duration for currents of intermediate amplitudes (i.e., currents between the maximum discharge pulse current and the maximum discharge steady-state current).

[0014] According to a first aspect, a BMS is provided that can determine a safe operating limit for a battery with a pulse current that lasts longer than the duration specified in a lookup table provided by a battery manufacturer. The BMS of the first aspect calculates a discharge current limit by comparing the energy accumulated by the discharge of the battery with the maximum accumulated energy. The maximum accumulated discharge energy is calculated based on the maximum discharge pulse current provided by the lookup table of the BMS. The difference between the accumulated discharge energy and the maximum accumulated discharge energy defines the remaining amount of energy that the battery can safely accumulate. Based on the energy difference, the BMS can determine the discharge current limit at which the battery can continue to operate. In fact, over a duration longer than the duration of the pulse associated with the maximum discharge pulse current, the BMS can allow the battery to safely operate at a discharge current higher than the maximum steady-state discharge current.

[0015] According to a second aspect of the present disclosure, a battery management system (BMS) is provided, wherein the battery management system (BMS) is configured to control a charging current of a battery. The BMS is configured to:

[0016] Calculating a charge energy of the battery within the time step based on the charge current of the battery and the duration of the time step;

[0017] calculating a cumulative charge energy of the battery based on the cumulative charge energy calculated for a previous time step and the charge energy for the time step;

[0018] Determining a maximum charging pulse current of a pulse having a duration based on a charging pulse current lookup table of the BMS;

[0019] calculating a maximum accumulated charging energy based on the maximum charging pulse current and the duration of the pulse;

[0020] calculating a charging current limit based on a ratio of the accumulated charging energy to the maximum accumulated charging energy, wherein the charging current limit does not exceed the maximum charging pulse current; and

[0021] The charging current of the battery is controlled so that the charging current does not exceed the charging current limit.

[0022] Accordingly, it should be understood that a BMS may be provided to control the charging current of the battery. The BMS may control the charging current by comparing the accumulated charging energy with the maximum accumulated charging energy. Therefore, the BMS may follow a strategy similar to that of the BMS of the first aspect to control the charging current.

[0023] According to a third aspect of the present disclosure, a machine is provided. According to the first aspect and / or the second aspect of the present disclosure, the machine may include a battery and a BMS. In some embodiments, the machine may be an electric working vehicle.

[0024] According to a fourth aspect of the present disclosure, a method for controlling a discharge current of a battery is provided. The method comprises:

[0025] Calculating the discharge energy of the battery within the time step based on the discharge current and the duration of the time step;

[0026] calculating a cumulative discharge energy of the battery based on the cumulative discharge energy calculated for a previous time step and the discharge energy for the time step;

[0027] Determining a maximum discharge pulse current of a pulse having a duration based on a discharge pulse current lookup table of the BMS;

[0028] Calculating the maximum accumulated discharge energy of the battery based on the maximum discharge pulse current and the duration of the pulse;

[0029] calculating a discharge current limit value based on a ratio of the cumulative discharge energy to the maximum cumulative discharge energy, wherein the discharge current limit value does not exceed the maximum discharge pulse current; and

[0030] The discharge current of the battery is controlled so that the discharge current does not exceed the discharge current limit.

[0031] It should be understood that the method of the fourth aspect of the present disclosure may be executed by the BMS of the first aspect and / or by the machine of the third aspect.

[0032] According to a fifth aspect of the present disclosure, a method for controlling a charging current of a battery is provided. The method comprises:

[0033] Calculating a charge energy of the battery within the time step based on the charge current of the battery and the duration of the time step;

[0034] calculating a cumulative charge energy of the battery based on the cumulative charge energy calculated for a previous time step and the charge energy for the time step;

[0035] Determine the maximum charging pulse current of the pulse having the duration based on the charging pulse current lookup table of the BMS;

[0036] calculating a maximum accumulated charging energy based on the maximum charging pulse current and the duration of the pulse;

[0037] calculating a charging current limit based on a ratio of the accumulated charging energy to the maximum accumulated charging energy, wherein the charging current limit does not exceed the maximum charging pulse current; and

[0038] The charging current of the battery is controlled so that the charging current does not exceed the charging current limit.

[0039] It should be understood that the method of the fifth aspect of the present disclosure may be executed by the BMS of the second aspect and / or the machine of the third aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Embodiments of the present disclosure will now be described with reference to the following non-limiting drawings, in which:

[0041] - Figure 1 A graph showing a discharge current controlled by a BMS according to the present disclosure;

[0042] - Figure 2 A graph showing cumulative discharge energy and maximum cumulative discharge energy calculated by a BMS according to the present disclosure;

[0043] - Figure 3 A graph showing cumulative discharge energy and maximum cumulative discharge energy calculated by the BMS;

[0044] - Figure 4 A graph showing a discharge current limit value calculated by a BMS according to the present disclosure;

[0045] - Figure 5 A graph showing a discharge current limit value calculated by a BMS according to the present disclosure;

[0046] - Figure 6 A graph showing a discharge current controlled by a BMS according to the present disclosure;

[0047] - Figure 7 A graph showing battery current controlled by a BMS according to the present disclosure;

[0048] - Figure 8 A graph showing cumulative energy and maximum cumulative charging energy calculated by a BMS according to the present disclosure;

[0049] - Fig. 9 A graph showing battery current controlled by a BMS according to the present disclosure;

[0050] - Fig.10 A graph showing a charge current limit calculated by a BMS according to the present disclosure;

[0051] - Fig.11 A graph showing battery current controlled by a BMS according to the present disclosure;

[0052] - Fig.12 A graph showing a charge current weight and a discharge current weight calculated by a BMS according to the present disclosure;

[0053] - Fig.13a , Fig.13b and Fig.13c A diagram showing different arbitration strategies for a BMS;

[0054] - Fig.14 A block diagram showing a method for controlling a discharge current of a battery according to an embodiment of the present disclosure;

[0055] - Fig.15 A block diagram showing a method for controlling a charging current of a battery according to an embodiment of the present disclosure; and

[0056] - Fig.16 A block diagram of a BMS connected to a battery according to the present disclosure is shown. DETAILED DESCRIPTION

[0057] According to an embodiment of the present disclosure, a battery management system (BMS) 10 is provided. The BMS 10 is configured to control a discharge current of a battery 20. Fig.16 A block diagram of a BMS 10 and a battery 20 is shown. According to this embodiment, the battery 20 may be a rechargeable battery. The battery 20 and the BMS 10 may be provided as part of a machine 30 (eg, an electric working machine), or connected to the machine.

[0058] The BMS 10 may include various sensors (e.g., current sensors, voltage sensors, temperature sensors) to determine various operating parameters of the battery 20 (e.g., state of charge, battery temperature, discharge / charge voltage, discharge / charge current, etc.). The BMS 10 may also include a processor or a controller, etc., which is configured to control the power output of the battery 20. In order to control the power output of the battery 20, the BMS 10 may also include a suitable circuit (e.g., a transistor and a resistor, etc.), which is configured to control the power output of the battery 20 in response to the power demand of the external load (e.g., the power demand from the machine connected to the BMS 10 and the battery 20).

[0059] Now refer to Figures 1 to 6 Describing a method of controlling the discharge current of a battery 20 using a BMS 10, these figures show various graphs of different variables of the BMS 10 and the battery 20 over time. Figures 1 to 6 In the graph of , the current for charging the battery 20 (charging current) is shown as a positive current, and the current for discharging the battery 20 (discharging current) is shown as a negative current.

[0060] Figure 1 A graph showing the discharge current (D) of the battery 20 is shown. The discharge current of the battery 20 varies over time in response to the square wave required current (S). Figure 1 In the example shown, the required discharge current for the square wave is 3500A over a duration of 60 seconds. Figure 1 The maximum discharge steady-state current (M SS ) and the maximum discharge pulse current (M P ).exist Figure 1 In the embodiment, a maximum discharge pulse current M is provided within a pulse duration of 30 seconds. P .

[0061] The maximum steady-state discharge current (M SS ) may be a value stored in the BMS 10 associated with the battery 20. In some embodiments, the maximum discharge steady-state current (M SS ) may be a value that varies with one or more of the following: battery state of charge (SOC), battery temperature, and battery life. Accordingly, in some embodiments, the BMS 10 may use a discharge steady-state lookup table of the BMS 10 to determine the maximum discharge steady-state current (M SS ) value.

[0062] Similarly, the maximum discharge pulse current (M P ) may be a value stored in the BMS 10 associated with the battery 20. In some embodiments, the maximum discharge pulse current (M P) can be a value that varies with one or more of the following: battery state of charge (SOC), battery temperature, battery life. It can be combined with a specified pulse duration T p Provide the maximum discharge pulse current (M P ), the maximum discharge pulse current (M P ) operates the battery 20. In some embodiments, the BMS 10 may include a plurality of maximum discharge pulse currents (M P ), each maximum discharge pulse current (M P ) with an associated pulse duration T p , where the pulse durations are of different lengths (having different associated M p ). Accordingly, in some embodiments, the BMS 10 may use a discharge pulse lookup table of the BMS 10 to determine the maximum discharge pulse current (M P ) and the pulse duration T p .

[0063] It should be understood that for the battery 20 to be used with the BMS 10, the maximum discharge steady-state current (M SS ) and the maximum discharge pulse current (M P ) can be provided by the battery manufacturer.

[0064] from Figure 1 It can be understood that the required current S is greater than the maximum discharge steady-state current M SS , but less than the maximum discharge pulse current (M P When the required current S is required for a duration longer than the specified length of the maximum discharge pulse current, the BMS 10 is configured to determine that the battery 20 can be discharged at a current higher than the maximum steady-state current M. SS The length of time the discharge current works and at what discharge current amplitude. Figure 1 It will be appreciated that initially the BMS 10 allows the battery 20 to discharge 100% of the required current. As this demand continues, the BMS 10 reduces the discharge current to ensure that the total energy (i.e., heat energy) accumulated by the battery 20 does not become excessive. According to the present disclosure, the BMS 10 reduces the discharge current based on the maximum discharge pulse current M of the battery. P Calculate the maximum energy to be accumulated.

[0065] like Figure 2 As shown, BMS10 calculates the cumulative discharge energy E of the battery D and the maximum cumulative discharge energy M ED .

[0066] For the maximum discharge pulse current M P and the maximum discharge pulse current M PThe duration of the associated pulse is used to calculate the maximum cumulative discharge energy M ED According to this embodiment, it is assumed that the maximum energy that the battery 20 can accumulate is the energy that the battery 20 can accumulate during the specified duration T of the pulse. P Internal release maximum discharge pulse current M P Therefore, the maximum cumulative discharge energy M can be calculated according to the following formula: ED :

[0067] M ED =M P 2 x T p

[0068] In some embodiments, the maximum cumulative discharge energy of the battery 20 may also take into account the steady-state energy loss associated with the battery 20. Therefore, in some embodiments, the maximum cumulative discharge energy may be calculated based on the maximum discharge pulse current, the duration of the pulse, and the steady-state energy loss of the battery 20 during the duration of the pulse. In some embodiments, the steady-state energy loss may be a predetermined value associated with the battery 20 or the BMS 10.

[0069] In some embodiments, the steady-state energy loss can be calculated by the BMS 10 based on the maximum discharge steady-state current M SS For example, in Figures 1 to 6 In the embodiment of FIG. 1 , it is assumed that the battery 20 can be used for the duration T of the pulse. p The maximum steady-state discharge current M SS The energy generated by the discharge current at M SS 2 x T P Calculate this steady-state energy loss.

[0070] Therefore, in Figures 1 to 6 In the embodiment of FIG. 5 , the maximum cumulative discharge energy can be calculated as:

[0071] M ED =(M P 2 x T p )-(M SS 2 x T p )

[0072] exist Figures 1 to 6 In the embodiment of the present invention, the cumulative discharge energy E when the BMS 10 controls the battery 20 is calculated. D The BMS 10 updates the discharge current to be controlled at regular time steps. Therefore, the accumulated discharge energy E is updated in each time step (Δt). D Therefore, based on the cumulative discharge energy (ED (n-1)) (where n is an integer) and the discharge energy (E) for that time step Δt ), calculate the cumulative discharge energy E for the nth time step D (n).

[0073] exist Figures 1 to 6 In the embodiment of the present invention, the discharge energy (E) in the time step is calculated based on the square value (D) of the discharge current currently output by the battery 20 and the duration of the time step Δt. Δt ). For example, in Figures 1 to 4 In the embodiment of , the time step Δt may have a duration of 0.1 seconds. Therefore, the cumulative discharge energy may be calculated as:

[0074] E D (n)=(E D (n-1))+E Δt

[0075] In some embodiments, the cumulative discharge energy E is calculated based on the discharge energy, the cumulative discharge energy in the previous time step, and the steady-state energy loss of the battery 20 in the time step. D (n). By considering the steady-state energy loss, in some cases, between time steps, the accumulated discharge energy E D (n) May decrease.

[0076] For example, in Figures 1 to 6 In the embodiment, based on the maximum discharge steady-state current M of the battery SS Calculate the steady-state energy loss of the battery 20 in the time step. Therefore, the steady-state energy loss can be calculated as M SS 2 xΔt.

[0077] Accordingly, in Figures 1 to 6 In the embodiment of FIG. 5 , the accumulated discharge energy can be calculated as:

[0078] E D (n)=(E D (n-1))+(D 2 xΔt)–(M SS 2 xΔt.)

[0079] from Figure 2 It will be understood that when the discharge current (D) is output from the battery 20, the accumulated discharge energy E D When the discharge current drops below the maximum steady-state discharge current, the accumulated discharge energy decreases as the battery 20 dissipates the accumulated energy. Figure 1 and Figure 2It can be understood that as the accumulated discharge energy E D As the current flowing through the battery 20 increases, the BMS 10 begins to limit the discharge current output by the battery 20. The process of implementing this control will be further discussed below.

[0080] Figure 3 The cumulative discharge energy E D and a graph of the maximum cumulative discharge energy over time (also in Figure 2 ). Figure 4 Shows that along with Figures 1 to 3 On the same time axis, the discharge current limit (L D ) versus time. Based on the maximum cumulative discharge energy M ED With the accumulated discharge energy E D The discharge current limit L is calculated by the ratio D The BMS10 also ensures that the discharge current limit L D Do not exceed the maximum discharge pulse current specified by the BMS 10 / battery manufacturer.

[0081] In some embodiments, the accumulated discharge energy E D With the maximum cumulative discharge energy M ED The ratio (i.e., E D / M ED ) can be used as a reserve of the remaining energy that can be accumulated by the battery 20 without causing excessive heat accumulation (ie, 1-E D / M ED ). Therefore, in some embodiments, the ratio E D / M ED Can be used to scale the maximum discharge pulse current M P , in order to calculate the discharge current limit L D .

[0082] In some embodiments, the ratio E D / M ED Used to scale the maximum discharge pulse current M P and the maximum discharge steady-state current M SS In some embodiments, the BMS 10 can ensure that the magnitude of the discharge current limit is not reduced to a value lower than the maximum discharge steady-state current M. SS Therefore, in some embodiments, the discharge current limit L D It can be calculated as:

[0083] L D =(1-E D / M ED )x(M P –M SS )+M SS

[0084] Therefore, as the accumulated discharge energy E D Starting from zero, the discharge current limit L D From the maximum discharge pulse current M P To this maximum steady-state discharge current M SS reduce.

[0085] In some embodiments, when the current demand exceeds the maximum discharge steady-state current M SS When the BMS 10 changes the way in which the BMS 10 limits the discharge current, the BMS 10 may change the way in which the BMS 10 limits the discharge current. For example, in some embodiments, it may be desirable for the BMS 10 to smoothly change the discharge current limit from the maximum discharge pulse current M to the maximum discharge pulse current M. P Drop to the maximum discharge steady-state current M SS Therefore, the BMS 10 can advantageously reduce the instantaneous required current in order to maintain a current above M for an extended period of time. SS In the example of the BMS 10 attached to an electric working vehicle, when the battery 20 is used to perform the driving operation of the vehicle, it may be desirable to achieve a smooth change. That is, since the maximum accumulated discharge energy M is reached ED The resulting sudden drop in acceleration may provide a "jerkier" operating experience for the user. In other embodiments, it may be desirable for the BMS 10 to facilitate increased instantaneous power output. Such a strategy may then require a sharp reduction in the discharge current limit in order to avoid exceeding the maximum cumulative discharge energy M ED In practice, the BMS 10 may provide a discharge pulse limit value M at one or more maximum discharge pulse limits. P and the maximum steady-state discharge current M SS The arbitration strategy followed may be selected / modified to provide different power output profiles, where the different power output profiles may be tailored for various tasks to be performed by the machine.

[0086] Therefore, in some embodiments, the maximum discharge pulse current M P The discharge current limit is calculated by combining the discharge current weight W. The discharge current weight can be provided by the arbitration strategy lookup table.

[0087] The arbitration strategy lookup table may be based on the ratio E of the cumulative discharge energy to the maximum cumulative discharge energy. D / M ED Output discharge current weight W D .

[0088] In some embodiments, the ratio E can also be combined D / M ED The arbitration strategy parameter (K) is input into the arbitration strategy lookup table to determine the discharge current weight WD arbitration strategy.

[0089] In some embodiments, the arbitration strategy can control how the BMS 10 changes the discharge current from the maximum discharge pulse current M P (no accumulated discharge energy) drops to the maximum discharge steady-state current M SS (E D =M ED ).

[0090] In a possible strategy that is favorable for instantaneous output power, the BMS 10 may specify that for cumulative discharge energies less than the maximum cumulative discharge energy, the discharge current limit is equal to the maximum discharge pulse current (ie, where E D <M ED ; L D =M P ). When the accumulated discharge energy is equal to the maximum accumulated discharge energy, the BMS 10 implements a step change to the discharge current limit value, changing the discharge current limit value to the maximum discharge steady-state current M. SS (i.e., where E D =M ED ; L D =M SS ). Such arbitration strategies may allow the battery 20 to deliver a discharge current higher than the maximum discharge steady-state current for as long as possible. Once the accumulated discharge energy reaches the maximum M ED , the arbitration strategy then implements a step change to the discharge current limit. Fig.13a Shows E D / M ED and discharge current weight W D Such step size changes to the discharge current may not be suitable for some applications, and therefore it may be desirable to provide other arbitration strategies that provide a smoother transition (or rise and fall) between the maximum discharge pulse current and the maximum discharge steady-state current.

[0091] For example, in another possible strategy that is conducive to smooth variation of discharge current, the discharge current weight W D Trackable D / M ED changes. Fig.13b An example of such a relationship is shown. Once the battery 20 begins to accumulate energy, Fig.13a The opposite of the strategy, Fig.13b The arbitration strategy sets the discharge current limit L D This provides a smoother transition to a steady-state discharge current, but may limit the power output by the battery 20 if the required power drops before the maximum accumulated discharge energy is reached.

[0092] Fig.13c Another possible arbitration strategy is shown, where the discharge current weight W D The breakpoints decreasing from 1 to zero will change. Fig.13a In the strategy of D / M ED = 1 (one step change). Fig.13b In the strategy of D / M ED = 0. Fig.13c In the embodiment, the breakpoint is at E D / M ED =0.5. In each case, the discharge current weight W D From the breakpoint W D = 1 linearly scaled to E D / M ED =W at 1 D =0.

[0093] In some embodiments, the arbitration policy parameter k D Can be used to select the discharge current weight W D The breakpoint of scaling towards zero. Thus, in some embodiments, the arbitration strategy may be:

[0094] For E D / M ED <k D :W D = 1; and

[0095] For E D / M ED ≥k D :W D =(1-E D / M ED ) / (1–k D ).

[0096] In some embodiments, an arbitration strategy lookup table may be generated based on the above relationship, wherein the arbitration strategy lookup table is based on k D and E D / M ED Generate discharge current weight W D It should be noted that Figures 13a to 13c In the example, a linear relationship is used to scale the breakpoints k and E D / M ED = 1. In other embodiments, different relationships (such as polynomials or other nonlinear functions) may be used to scale W D .

[0097] exist Figures 1 to 6 In the embodiment of the present invention, the discharge current weight W is used. D To scale the maximum discharge pulse current M P and the maximum discharge steady-state current M SS Therefore, in some embodiments, the discharge current limit L D It can be calculated as:

[0098] L D =W D x(M P –M SS )+M SS

[0099] Figure 4 shows the discharge current limit L D The discharge current limit value increases from the maximum discharge pulse current M to the maximum discharge pulse current M as the accumulated discharge energy increases. P Reduce (such as Figure 3 shown).

[0100] The BMS 10 is configured to control the discharge current of the battery 20 so that the discharge current D does not exceed the discharge current limit L D Therefore, if Figure 5 and Figure 6 As shown, due to the discharge current limit L D falls below the required current S (see Figure 1 ), BMS10 limits the discharge current D to the discharge current limit value L D Once the discharge current decreases to below the maximum discharge steady-state current M SS , the discharge current limit L D Start to increase, such as Figure 5 shown.

[0101] It should be understood that although the above description focuses on the calculation of the discharge current limit, the ratio E D / M ED It can also be used to calculate the discharge voltage limit for the battery 20. Therefore, based on the ratio E D / M ED and the maximum discharge pulse current M P The voltage limit is calculated by the associated maximum discharge pulse voltage. The maximum discharge pulse voltage may be provided by the battery manufacturer and stored in a suitable lookup table of the BMS 10.

[0102] The BMS 10 according to the present disclosure may also be used to control the charging current of the battery 20. In some embodiments, the BMS 10 may be used to control the charging current and the discharging current of the battery 20. That is, the BMS 10 may control the current input to the battery 20 and the current output from the battery. Figures 7 to 12 Describing a method of controlling the charging and discharging currents of the battery 20 using the BMS 10, the figures show various graphs of different variables of the BMS 10 and the battery 20 over time. Figures 7 to 12 In the graph of FIG. 1 , the current (charging current) for charging the battery 20 is shown as a positive current, and the current (discharging current) for discharging the battery 20 is shown as a negative current. According to the following description, the charging current and associated variables of the BMS 10 are different from the discharging current and associated variables of the BMS 10 because the BMS 10 can apply different control strategies to charge and discharge the battery 20.

[0103] Figure 7 A graph showing the current (I) of the battery is shown. The current of the battery 20 changes over time in response to the square wave required current (S). Figure 7 In the example, the square wave current S includes Figure 1 A similar square wave of discharge current is required, as is a square wave of charge current. The amplitude of the square wave of current required is 750A over a duration of 60 seconds. Figure 7 The maximum discharge pulse current (M P ), maximum charging steady-state current (M SSC ) and the maximum charge pulse current (M PC ).exist Figure 7 In the embodiment, the pulse duration T of 30 seconds P Each provides the maximum discharge pulse current M P and the maximum charging pulse current M PC In other embodiments, the maximum discharge pulse current M P and the maximum charging pulse current M PC The pulse duration may be different.

[0104] The maximum steady-state charging current (M SSC ) may be a value stored in the BMS 10 associated with the battery 20. In some embodiments, the maximum charging steady-state current (M SSC ) may be a value that varies with one or more of the following: battery state of charge (SOC), battery temperature, and battery life. Accordingly, in some embodiments, the BMS 10 may use a charge steady-state lookup table of the BMS 10 to determine the maximum charge steady-state current (M SSC ) value.

[0105] Similarly, the maximum charging pulse current (MPC ) may be a value stored in the BMS 10 associated with the battery 20. In some embodiments, the maximum charge pulse current (M PC ) can be a value that varies with one or more of the following: battery state of charge (SOC), battery temperature, and battery age. Figure 7 As shown, as the battery 20 discharges (ie, as the SOC of the battery decreases), the maximum charge pulse current (M PC ) increases. It can be combined with the specified pulse duration T p Provides the maximum charging pulse current (M PC ), the specified maximum charging pulse current (M PC ) operates the battery 20. In some embodiments, the BMS 10 may include a plurality of maximum charge pulse currents (M PC ), each maximum charging pulse current (M PC ) with an associated pulse duration T p , where the pulse durations are of different lengths (having different associated M PC ). Accordingly, in some embodiments, the BMS 10 may use a charging pulse lookup table of the BMS 10 to determine the maximum charging pulse current (M PC ) and the pulse duration T p .

[0106] It should be understood that for a battery to be used with the BMS 10, the maximum charging steady-state current (M) provided in the associated lookup table is SSC ) and the maximum charge pulse current limit (M PC ) can be provided by the battery manufacturer.

[0107] from Figure 7 It will be understood that when charging the battery 20, the required current S is greater than the maximum charging steady-state current M SS , and is also greater than the maximum charging pulse current (M PC ). When the duration of the required current S is longer than the specified duration T of the maximum charging pulse current P When the battery 20 is longer, the BMS 10 is configured to determine that the battery 20 can be charged at a current higher than the maximum steady-state current M SSC The length of time the charging current works and at what charging current amplitude. Figure 7 It will be understood that initially, the BMS 10 allows the battery 20 to charge at the maximum charging pulse current M PC As this demand continues, the BMS 10 reduces the charging current S to ensure that the total energy (ie, heat energy) accumulated by the battery 20 does not become excessive. According to the present disclosure, the BMS 10 reduces the charging current S based on the maximum charging pulse current M of the battery. PC Calculate the maximum energy to be accumulated.

[0108] like Figure 8 As shown, the BMS 10 calculates the accumulated energy E and the maximum accumulated charging energy M of the battery. EC Based on the accumulated discharge energy E of the battery D (as discussed above) and the accumulated charge energy E of the battery C Calculate the accumulated energy E of the battery (i.e., E = E C +E D ). Thus, when calculating the charge current limit (or indeed the discharge current limit as discussed above), both the charging and discharging of the battery 20 may be taken into account.

[0109] For the maximum charging pulse current M PC and the maximum charging pulse current M PC The duration of the associated pulse is T P , calculate the maximum cumulative charging energy M EC Therefore, the maximum cumulative discharge energy M can be calculated similarly to that discussed above. ED The maximum accumulated charging energy M is calculated by EC For example, the maximum accumulated charging energy M can be calculated according to the following formula: EC :

[0110] M EC =M PC 2 x T p

[0111] In some embodiments, the maximum cumulative charging energy of the battery 20 may also take into account the steady-state energy loss associated with the battery 20. Therefore, in some embodiments, the maximum cumulative charging energy may be calculated based on the maximum charging pulse current, the duration of the pulse, and the steady-state energy loss of the battery 20 during the duration of the pulse. In some embodiments, the steady-state energy loss may be a predetermined value associated with the battery 20 or the BMS 10.

[0112] In some embodiments, the steady-state energy loss can be calculated by the BMS 10 based on the maximum charging steady-state current M SSC For example, in Figures 7 to 12 In the embodiment of FIG. 1 , it is assumed that the battery 20 can be used for the duration T of the pulse. p dissipated by the maximum steady-state charging current M SSC The energy generated by the charging current at M SSC 2 x T P Calculate this steady-state energy loss.

[0113] Therefore, in Figures 7 to 12 In the embodiment of FIG. 5 , the maximum accumulated charging energy can be calculated as:

[0114] M EC =(M PC 2 x T p )-(M SSC 2 x T p )

[0115] exist Figures 7 to 12 In the embodiment of FIG. 1 , the accumulated energy E is calculated when the BMS 10 controls the battery 20. The BMS 10 updates the charging current to be controlled at regular time steps. Therefore, the accumulated energy E is updated in each time step (Δt). Therefore, based on the accumulated discharge energy (E D (n-1)) (where n is an integer) and the accumulated charge energy (E) calculated for the previous time step C (n-1)) and the discharge / charge energy for that time step (E Δt ), calculate the cumulative energy E(n) for the nth time step.

[0116] exist Figures 7 to 12 In the embodiment of the present invention, the charging energy (E) of the time step is calculated based on the square value (I) of the (charging) current currently output by the battery and the duration of the time step Δt. Δt ). For example, in Figures 7 to 12 In an embodiment of the invention, the time step Δt may have a duration of 0.1 seconds.

[0117] Therefore, the cumulative energy can be calculated as:

[0118] E(n)=(E(n-1))+E Δt

[0119] In some embodiments, the cumulative energy E(n) is calculated based on the discharge / charge energy, the cumulative energy in the previous time step, and the steady-state energy loss of the battery 20 in the time step. By taking into account the steady-state energy loss, the cumulative energy E(n) may decrease between time steps in some cases.

[0120] For example, in Figures 7 to 12 In the embodiment of the present invention, the maximum discharge steady-state current M of the battery can be used as the basis. SS Or the maximum steady-state charging current of the battery M SSC , respectively, according to whether the battery 20 is discharging or charging, the steady-state energy loss of the battery 20 in the time step is calculated. When the battery 20 is charging, the steady-state energy loss can be calculated as M SSC 2 xΔt.

[0121] from Figure 8It will be appreciated that the accumulated energy E increases when the battery 20 is charged and when the battery 20 is discharged. SS and the maximum steady-state charging current M SSC When the defined threshold is reached, the accumulated energy decreases as the battery 20 dissipates the accumulated energy. Figure 7 and Figure 8 It will be appreciated that as the accumulated energy E increases, the BMS 10 begins to limit the current I output by the battery 20. The process of implementing this control will be further discussed below.

[0122] Fig. 9 and Fig.10 Shows that along with Figure 7 and Figure 8 On the same time axis, the battery current I and the charge current limit (L C ) versus time. Based on the accumulated charging energy E C With the maximum accumulated charging energy M EC The charging current limit L is calculated by the ratio C .exist Figures 7 to 12 In the embodiment, the charging current limit L C It is also possible to consider any accumulated discharge energy E D Therefore, in Figures 7 to 12 In the embodiment of the present invention, the accumulated energy E is used instead of the accumulated charging energy E C The BMS10 also ensures that the charging current limit L C Do not exceed the maximum charge pulse current specified by the BMS 10 / battery manufacturer.

[0123] The accumulated charging energy E C With the maximum accumulated charging energy M EC The ratio (i.e., E C / M EC ), or the accumulated energy E and the maximum accumulated charging energy M EC The ratio (i.e., E / M EC ), can be used as an indication of the remaining energy that can be accumulated by the battery 20 without causing excessive heat accumulation. Therefore, in some embodiments, the ratio (E C / M EC or E / M EC ) can be used to scale the maximum charging pulse current M PC , in order to calculate the discharge current limit L C .

[0124] In some embodiments, the ratio (E C / M EC or E / M EC) is used to scale the maximum charging pulse current M PC and the maximum charging steady-state current M SSC Therefore, in some embodiments, the charging current limit L C It can be calculated as:

[0125] L C =(E C / M EC )x(M PC –M SSC )or

[0126] L C =(E / M EC )x(M PC –M SSC ).

[0127] Therefore, as the accumulated charging energy E C Starting from zero, the charging current limit L C From the maximum charging pulse current M PC The maximum charging steady-state current M SSC reduce.

[0128] Similar to Figures 1 to 6 An embodiment of Figures 7 to 12 The embodiment of the present invention may use an arbitration strategy lookup table to determine a current weight (or charging current weight) which is used to scale the maximum charging pulse current M. PC .

[0129] The arbitration strategy lookup table may be based on the ratio E / M of the accumulated energy to the maximum accumulated charging energy. EC Output charging current weight W C In some embodiments, this may include using the arbitration strategy parameter k C In some embodiments, different arbitration strategy parameters k D , k C The arbitration strategy may be used to calculate the discharge current limit and the charge current limit separately, or the same arbitration strategy may be followed for both charging and discharging.

[0130] In some embodiments, the ratio E / M may also be combined EC The arbitration strategy parameter (k) is input into the arbitration strategy lookup table to determine the charging current weight W C arbitration strategy.

[0131] exist Figures 7 to 12 In the embodiment of FIG. 1 , the charging current weight W is used. C To scale the maximum charging pulse current M PC and the maximum charging steady-state current M SSTherefore, in some embodiments, the charging current limit L C It can be calculated as:

[0132] L C =W C x(M PC –M SSC )

[0133] Fig.12 shows the charging current weight W C and the discharge current weight W D The charging current weight and the discharging current weight may be based on the ratio (E / M) of the accumulated energy to the maximum accumulated charging energy. EC ) and the ratio of the accumulated energy to the maximum accumulated discharge energy (E / M ED ) is output by the arbitration strategy lookup table. Fig.12 The lieutenant general can understand that due to M P and M PC The value of is different, so during the charging pulse and the discharging pulse, the ratio E / M EC and the ratio E / M ED are different.

[0134] like Fig.11 As shown, the BMS 10 is configured to control the charging current of the battery 20 so that the battery current I does not exceed the charging current limit L C And does not exceed the discharge current limit L D Therefore, if Fig.11 As shown, the BMS 10 calculates the charging current limit value L according to the embodiment described above. C and the discharge current limit L D to reduce the current.

[0135] It should be understood that although the above description focuses on the calculation of the charging current limit, the ratio E / M EC (or E C / M EC ) can also be used to calculate the charging voltage limit for the battery 20. Therefore, the ratio E / M EC and the maximum charging pulse current M P The charging voltage limit is calculated by the associated maximum charging pulse voltage. The maximum charging pulse voltage may be provided by the battery manufacturer and stored in a suitable lookup table of the BMS 10.

[0136] Fig.14 FIG. 1 is a block diagram of a method 100 for controlling a discharge current of a battery 20 according to an embodiment of the present disclosure. The method may be performed by the BMS 10 described above.

[0137] In step 101 of the method, the BMS 10 calculates the discharge energy of the battery 20 within the time step based on the discharge current and the duration of the time step.

[0138] In step 102 of the method, the BMS 10 calculates the cumulative discharge energy of the battery 20 based on the cumulative discharge energy calculated for the previous time step and the discharge energy for the time step.

[0139] In step 103 of the method, the BMS 10 determines a maximum discharge pulse current of a pulse having a duration based on a discharge pulse current lookup table of the BMS 10 .

[0140] In step 104 of the method, the BMS 10 calculates the maximum accumulated discharge energy of the battery 20 based on the maximum discharge pulse current and the duration of the pulse.

[0141] In step 105 of the method, the BMS 10 calculates a discharge current limit value based on the ratio of the accumulated discharge energy to the maximum accumulated discharge energy. The discharge current limit value does not exceed the maximum discharge pulse current.

[0142] In step 106 of the method, the BMS 10 controls the discharge current of the battery 20 so that the discharge current does not exceed the discharge current limit.

[0143] It should be appreciated that the method 100 may incorporate additional steps / features in accordance with the embodiments of the BMS 10 described above.

[0144] Fig.15 FIG. 2 is a block diagram of a method 200 for controlling a charging current of a battery 20 according to an embodiment of the present disclosure. The method may be performed by the BMS 10 10 described above.

[0145] In step 201 of the method, the BMS 10 calculates the charging energy of the battery 20 within the time step based on the charging current and the duration of the time step.

[0146] In step 202 of the method, the BMS 10 calculates the cumulative charging energy of the battery 20 based on the cumulative charging energy calculated for the previous time step and the charging energy for the current time step.

[0147] In step 203 of the method, the BMS 10 determines a maximum charging pulse current of a pulse having a duration based on a charging pulse current lookup table of the BMS 10 .

[0148] In step 204 of the method, the BMS 10 calculates the maximum accumulated charging energy of the battery 20 based on the maximum charging pulse current and the duration of the pulse.

[0149] In step 205 of the method, the BMS 10 calculates a charging current limit value based on the ratio of the accumulated charging energy to the maximum accumulated charging energy. The charging current limit value does not exceed the maximum charging pulse current.

[0150] In step 206 of the method, the BMS 10 controls the charging current of the battery 20 so that the charging current does not exceed the charging current limit.

[0151] It should be appreciated that the method 200 may incorporate additional steps / features in accordance with the embodiments of the BMS 10 described above.

[0152] Industrial Applicability

[0153] According to the present disclosure, a battery management system (BMS10) is provided. The BMS10 is configured to control the discharge current of a battery 20. According to this embodiment, the battery 20 may be a rechargeable battery. The battery 20 and the BMS10 may be provided as part of a machine 30 (e.g., an electric working machine).

[0154] The BMS10 according to the present disclosure determines the safe operating limit of the battery 20 for a pulse current (discharge or charge) that lasts longer than the duration specified in the lookup table provided by the battery manufacturer. The BMS10 of the first aspect calculates the discharge current limit and / or the charge current limit by comparing the energy accumulated by the discharge of the battery 20 with the maximum accumulated energy. The maximum accumulated energy is calculated based on the maximum pulse discharge current provided by the lookup table of the BMS10. The difference between the accumulated discharge energy and the maximum accumulated energy defines the remaining amount of energy that the battery 20 can safely accumulate. Based on the energy difference, the BMS10 can determine the discharge current limit or the charge current limit at which the battery 20 can continue to work. In fact, the BMS10 can allow the battery 20 to safely operate at a (charging or discharging) current higher than the specified maximum steady-state current for an extended period of time (i.e., a period of time longer than the pulse duration).

[0155] In some embodiments, the BMS 10 may also use an arbitration strategy lookup table to arbitrate between the maximum charge / discharge pulse current and the maximum charge / discharge steady-state current. In such embodiments, the arbitration strategy followed may be selected / modified to provide different power output curves, where different power output curves may be customized for various tasks to be performed by the machine 30.

Claims

1. A battery management system (BMS), the battery management system being configured to control a discharge current of a battery, wherein the BMS is configured to: Calculating a discharge energy of the battery within the time step based on the discharge current and the duration of the time step; calculating a cumulative discharge energy of the battery based on the cumulative discharge energy calculated for a previous time step and the discharge energy for the time step; determining a maximum discharge pulse current of a pulse having a duration based on a discharge pulse current lookup table of the BMS; calculating a maximum accumulated discharge energy of the battery based on the maximum discharge pulse current and the duration of the pulse; calculating a discharge current limit value based on a ratio of the cumulative discharge energy to the maximum cumulative discharge energy, wherein the discharge current limit value does not exceed the maximum discharge pulse current; as well as The discharge current of the battery is controlled so that the discharge current does not exceed the discharge current limit.

2. The BMS according to claim 1, wherein The discharge energy is calculated based on the discharge current square value and the duration of the time step.

3. The BMS according to claim 1 or claim 2, wherein calculating the cumulative discharge energy based on the discharge energy, the cumulative discharge energy in the previous time step, and the steady-state energy loss of the battery in the time step; and The maximum cumulative discharge energy of the battery is calculated based on the maximum discharge pulse current, the duration of the pulse, and the steady-state energy loss of the battery during the duration of the pulse.

4. The BMS according to claim 3, wherein The steady-state energy loss of the battery within the time step and / or within the duration of the pulse is calculated based on the maximum discharge steady-state current of the battery, wherein optionally The maximum discharge steady-state current of the battery is determined based on a discharge steady-state lookup table of the BMS.

5. The BMS according to any one of claims 1 to 4, wherein The discharge current limit is calculated based on the ratio of the maximum cumulative discharge energy to the cumulative discharge energy and the difference between the maximum discharge pulse current and the maximum discharge steady-state current of the battery, wherein optionally The maximum discharge steady-state current of the battery is determined based on a discharge steady-state lookup table of the BMS.

6. The BMS according to any one of claims 1 to 5, wherein Calculating the discharge current limit value based on the ratio of the accumulated discharge energy to the maximum accumulated discharge energy includes: inputting the ratio of the cumulative discharge energy to the maximum cumulative discharge energy into an arbitration strategy lookup table to obtain a discharge current weight; as well as The discharge current limit value is calculated based on the discharge current weight and the maximum discharge pulse current.

7. The BMS according to claim 6, wherein In conjunction with the ratio of the cumulative discharge energy to the maximum cumulative discharge energy, an arbitration strategy parameter is input into the arbitration strategy lookup table to determine an arbitration strategy for the discharge current weight.

8. A battery management system (BMS), the battery management system (BMS) being configured to control a charging current of a battery, wherein the BMS is configured to: calculating a charge energy of the battery within the time step based on the charge current of the battery and the duration of the time step; calculating a cumulative charging energy of the battery based on the cumulative charging energy calculated for a previous time step and the charging energy for the time step; Determining a maximum charging pulse current of a pulse having a duration based on a charging pulse current lookup table of the BMS; calculating a maximum accumulated charging energy based on the maximum charging pulse current and the duration of the pulse; calculating a charging current limit based on a ratio of the accumulated charging energy to the maximum accumulated charging energy, wherein the charging current limit does not exceed the maximum charging pulse current; as well as The charging current of the battery is controlled so that the charging current does not exceed the charging current limit.

9. The BMS according to claim 8, wherein The charging energy is calculated based on the charging current squared value and the duration of the time step.

10. The BMS according to claim 8 or claim 9, wherein calculating the cumulative charging energy based on the charging energy, the cumulative charging energy in the previous time step, and the steady-state energy loss of the battery in the time step; and The maximum cumulative charging energy of the battery is calculated based on the maximum discharge pulse current, the duration of the pulse, and the steady-state energy loss of the battery during the duration of the pulse.

11. The BMS according to claim 10, wherein The steady-state energy loss of the battery within the time step and / or within the duration of the pulse is calculated based on the maximum charging steady-state current of the battery, wherein optionally The maximum charging steady-state current of the battery is determined based on a charging steady-state lookup table of the BMS.

12. The BMS according to any one of claims 8 to 11, wherein The charging current limit is calculated based on the ratio of the maximum cumulative charging energy to the cumulative charging energy and the difference between the maximum charging pulse current and the maximum charging steady-state current of the battery, wherein optionally The maximum charging steady-state current of the battery is determined based on a charging steady-state lookup table of the BMS.

13. The BMS according to any one of claims 8 to 12, wherein Calculating the charging current limit value based on the ratio of the accumulated charging energy to the maximum accumulated charging energy includes: inputting the ratio of the accumulated charging energy to the maximum accumulated charging energy into an arbitration strategy lookup table to obtain a charging current weight; as well as The charging current limit value is calculated based on the charging current weight and the maximum charging pulse current.

14. The BMS according to claim 13, wherein In combination with the ratio of the accumulated charging energy to the maximum accumulated charging energy, a charging arbitration strategy parameter is input into the arbitration strategy lookup table to determine an arbitration strategy for the charging current weight.

15. The BMS according to any one of claims 1 to 7, wherein the BMS is further configured to: Calculating a discharge voltage limit value based on a ratio of the maximum cumulative discharge energy to the cumulative discharge energy, wherein the discharge voltage limit value does not exceed a maximum discharge pulse voltage; and / or The BMS according to any one of claims 8 to 14, wherein the BMS is further configured to: A charging voltage limit value is calculated based on a ratio of the maximum cumulative charging energy to the cumulative charging energy, wherein the charging voltage limit value does not exceed a maximum charging pulse voltage.

16. A machine, comprising: Battery; The BMS according to any one of claims 1 to 7; and / or A BMS according to any one of claims 8 to 15.

17. A method for controlling a discharge current of a battery, the method comprising: Calculating a discharge energy of the battery within the time step based on the discharge current and the duration of the time step; calculating a cumulative discharge energy of the battery based on the cumulative discharge energy calculated for a previous time step and the discharge energy for the time step; determining a maximum discharge pulse current of a pulse having a duration based on a discharge pulse current lookup table of the BMS; calculating a maximum accumulated discharge energy of the battery based on the maximum discharge pulse current and the duration of the pulse; calculating a discharge current limit value based on a ratio of the cumulative discharge energy to the maximum cumulative discharge energy, wherein the discharge current limit value does not exceed the maximum discharge pulse current; as well as The discharge current of the battery is controlled so that the discharge current does not exceed the discharge current limit.

18. A method for controlling a charging current of a battery, the method comprising: calculating a charging energy of the battery within the time step based on the charging current of the battery and the duration of the time step; calculating a cumulative charging energy of the battery based on the cumulative charging energy calculated for a previous time step and the charging energy for the time step; Determine the maximum charging pulse current of the pulse having the duration based on the charging pulse current lookup table of the BMS; calculating a maximum accumulated charging energy based on the maximum charging pulse current and the duration of the pulse; calculating a charging current limit based on a ratio of the accumulated charging energy to the maximum accumulated charging energy, wherein the charging current limit does not exceed the maximum charging pulse current; as well as The charging current of the battery is controlled so that the charging current does not exceed the charging current limit.

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