Battery Management System

Abstract

Battery Management System A battery management system (BMS) configured to control the discharge current of a battery is provided. The BMS is configured to calculate a discharge energy of a battery for a time step based on the discharge current and the duration of the time step, and to calculate an accumulated discharge energy of the battery based on an accumulated discharge energy calculated for a previous time step and the discharge energy at 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 so that the discharge current does not exceed the discharge current limit. The BMS can control the charge current of the battery in a similar manner.

Description

[Technical Field]

[0001] The present disclosure relates to batteries, and more particularly to batteries for electric work vehicles and the like. [Background technology]

[0002] A battery (e.g., a cell or battery pack) generates heat when charging or discharging, so the flow of energy to / from the battery causes heating of the battery due to the battery's inherent resistance.

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

[0004] Typically, battery manufacturers specify safe operating limits for continuous power transfer from / to the battery. Additionally, battery manufacturers may specify pulsed power limits, where a large amount of power can be output from / into the battery for a given period of time.

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

[0006] According to a first aspect of the present disclosure, there is provided a battery management system configured to control a discharge current of a battery, the BMS comprising: Calculating a discharge energy of the battery for a time step based on the discharge current and the duration of the time step; calculating a stored discharge energy of the battery based on a stored discharge energy calculated for a previous time step and the discharge energy at the time step; determining a maximum discharge pulse current for a pulse having a duration based on a discharge pulse current lookup table of the BMS; calculating a maximum stored discharge energy of the battery based on the maximum discharge pulse current and the duration of the pulse; calculating a discharge current limit based on a ratio of the stored discharge energy to the maximum stored discharge energy, wherein the discharge current limit does not exceed the maximum discharge pulse current; and controlling the discharge current of the battery so that the discharge current does not exceed the discharge current limit.

[0007] The inventors have realized that the maximum discharge current value provided by a battery manufacturer's lookup table places limitations on how the battery can be operated. For example, a battery manufacturer may specify a value for a maximum pulse discharge current (the pulse is typically of relatively short duration, e.g., 2 or 30 seconds) and a separate value for a maximum discharge steady-state current (i.e., a safe operating limit for steady-state current discharge). The maximum discharge pulse current may be greater than the maximum discharge steady-state current, but the increased current is only suitable for operation for the specified duration of the current pulse (e.g., 2 or 30 seconds, depending on the specified pulse duration). In some cases, battery manufacturers specify different maximum discharge pulse currents for pulses of different durations (e.g., a first maximum discharge pulse current for a 2-second current pulse and a second, lower maximum discharge pulse current for a 30-second current pulse). In such cases, it may be difficult to determine a suitable operating current for a pulse of intermediate duration (e.g., operating with a 15-second current pulse) or a suitable operating duration for an intermediate current (i.e., a current between the maximum discharge pulse current and the maximum discharge steady-state current).

[0008] According to a first aspect, a BMS is provided that can determine a safe operating limit of a battery for pulse currents of longer duration than specified in a lookup table provided by a battery manufacturer. The BMS according to the first aspect calculates a discharge current limit by comparing the energy stored by discharging the battery with a maximum stored energy. The maximum stored discharge energy is calculated from a maximum discharge pulse current provided by the BMS lookup table. The difference between the stored discharge energy and the maximum stored discharge energy defines the remaining amount of energy the battery can safely store. Based on the energy difference, the BMS can determine a discharge current limit at which the battery can continue to operate. In practice, the BMS can enable the battery to safely operate at a discharge current greater than the maximum steady-state discharge current for a duration longer than the pulse duration associated with the maximum discharge pulse current.

[0009] According to a second aspect of the present disclosure, there is provided a battery management system (BMS) configured to control a charging current of a battery. The BMS comprises: calculating a charge energy of a battery for a time step based on the charge current of the battery and the duration of the time step; calculating a stored charge energy for the battery based on a stored charge energy calculated for a previous time step and the charge energy at the time step; determining a maximum charge pulse current for a pulse having a duration based on a charge pulse current lookup table of the BMS; calculating a maximum stored charge energy based on the maximum charge pulse current and the duration of the pulse; calculating a charge current limit based on a ratio of the stored charge energy to the maximum stored charge energy, wherein the charge current limit does not exceed the maximum charge pulse current; and controlling the charging current of the battery so that the charging current does not exceed the charging current limit.

[0010] It will be understood that a BMS can be provided to control the charging current of a battery. The BMS can control the charging current by comparing the stored charging energy with a maximum stored charging energy. Thus, the BMS can control the charging current according to a similar method to the BMS according to the first aspect.

[0011] According to a third aspect of the present disclosure, there is provided a machine. The machine may include a battery and a BMS according to the first and / or second aspects of the present disclosure. In some embodiments, the machine may be an electric work vehicle.

[0012] According to a fourth aspect of the present disclosure, there is provided a method for controlling a discharge current of a battery, the method comprising: Calculating a discharge energy of the battery for a time step based on the discharge current and the duration of the time step; calculating a stored discharge energy of the battery based on a stored discharge energy calculated for a previous time step and the discharge energy at the time step; determining a maximum discharge pulse current for a pulse having a duration based on a discharge pulse current lookup table of the BMS; calculating a maximum stored discharge energy of the battery based on the stored discharge pulse current and the duration of the pulse; calculating a discharge current limit based on a ratio of the stored discharge energy to the maximum stored discharge energy, wherein the discharge current limit does not exceed the maximum discharge pulse current; and controlling the discharge current of the battery so that the discharge current does not exceed the discharge current limit.

[0013] It will be appreciated that the method according to the fourth aspect of the present disclosure may be performed by the BMS according to the first aspect and / or by the machine according to the third aspect.

[0014] According to a fifth aspect of the present disclosure, there is provided a method for controlling a charging current of a battery, the method comprising: calculating a charge energy of a battery for a time step based on the charge current of the battery and the duration of the time step; calculating a stored charge energy for the battery based on a stored charge energy calculated for a previous time step and the charge energy at the time step; determining a maximum charge pulse current for a pulse having a duration based on a charge pulse current lookup table of the BMS; calculating a maximum stored charge energy based on the charge / discharge pulse current and the duration of the pulse; calculating a charge current limit based on a ratio of the stored charge energy to the maximum stored charge energy, wherein the charge current limit does not exceed the maximum charge pulse current; and controlling the charging current of the battery so that the charging current does not exceed the charging current limit.

[0015] It will be appreciated that the method according to the fifth aspect of the present disclosure may be performed by the BMS according to the second aspect and / or by the machine according to the third aspect. [Brief explanation of the drawings]

[0016] Embodiments of the present disclosure will now be described with reference to the following non-limiting drawings.

[0017] [Figure 1] 1 shows a graph of a discharge current controlled by a BMS according to the present disclosure. [Figure 2] 10 shows a graph of accumulated discharge energy and maximum accumulated discharge energy calculated by a BMS according to the present disclosure. [Figure 3] 1 shows a graph of accumulated discharge energy and maximum accumulated discharge energy calculated by the BMS. [Figure 4]10 shows a graph of discharge current limits calculated by a BMS according to the present disclosure. [Figure 5] 10 shows a graph of discharge current limits calculated by a BMS according to the present disclosure. [Figure 6] 1 shows a graph of a discharge current controlled by a BMS according to the present disclosure. [Figure 7] 1 shows a graph of battery current controlled by a BMS according to the present disclosure. [Figure 8] 10 shows a graph of stored energy and maximum stored charge energy calculated by a BMS according to the present disclosure. [Figure 9] 1 shows a graph of battery current controlled by a BMS according to the present disclosure. [Figure 10] 10 shows a graph of charging current limits calculated by a BMS according to the present disclosure. [Figure 11] 1 shows a graph of battery current controlled by a BMS according to the present disclosure. [Figure 12] 1 is a graph of charging current weights and discharging current weights calculated by a BMS according to the present disclosure. [Figure 13] 13a, 13b and 13c show graphs of various arbitration methods for BMS. [Figure 14] 1 shows a block diagram of a method for controlling the discharge current of a battery according to an embodiment of the present disclosure. [Figure 15] 1 shows a block diagram of a method for controlling a charging current of a battery according to an embodiment of the present disclosure. [Figure 16] 1 illustrates a block diagram of a BMS connected to a battery according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0018] According to an embodiment of the present disclosure, a battery management system (BMS) 10 is provided. The BMS 10 is configured to control the discharge current of a battery 20. A block diagram of the BMS 10 and the battery 20 is shown in FIG. 16. According to an embodiment, the battery 20 may be a storage battery. The battery 20 and the BMS 10 may be provided as part of or connected to a machine 30, for example, an electric work machine.

[0019] BMS 10 may include various sensors (e.g., current sensors, voltage sensors, temperature sensors) to determine various operating parameters of battery 20 (e.g., state of charge, battery temperature, discharge / charge voltage, discharge / charge current, etc.). BMS 10 may also include a processor, controller, etc. configured to control the power output of battery 20. To control the power output of battery 20, BMS 10 may also include suitable circuitry (e.g., transistors, resistors, etc.) configured to control the power output of battery 20 in response to the power demands of external loads (e.g., power demands from machines connected to BMS 10 and battery 20).

[0020] The method of controlling the discharge current of battery 20 by BMS 10 will now be described with reference to Figures 1-6, which show graphs of the changes over time of various variables of BMS 10 and battery 20. In the graphs of Figures 1-6, the current that charges battery 20 (charging current) is shown as a positive current, while the current that discharges battery 20 (discharging current) is shown as a negative current.

[0021] FIG. 1 shows a graph of the discharge current (D) of a battery 20. The discharge current of the battery 20 varies over time in response to a square wave of required current (S). In the example of FIG. 1, the square wave of required discharge current is 3500 A for a duration of 60 seconds. FIG. 1 also shows the maximum discharge steady state current (M SS ) and maximum discharge pulse current (M P ) is also shown. In the embodiment of FIG. 1, for a pulse duration of 30 seconds, the maximum discharge pulse current M P is provided.

[0022] Maximum discharge steady state current (M SS ) may be a value associated with the battery 20 stored in the BMS 10. In some embodiments, the maximum discharge steady state current (M SS ) may be a value that varies with one or more of the battery's state of charge (SOC), battery temperature, and battery age. Thus, in some embodiments, the BMS 10 uses a discharge steady-state lookup table of the BMS 10 to determine the maximum discharge steady-state current (M SS ) can be determined.

[0023] Similarly, the maximum discharge pulse current (M P ) may be a value associated with the battery 20 stored in the BMS 10. In some embodiments, the maximum discharge pulse current (M P ) may be a value that varies with one or more of the battery's state of charge (SOC), battery temperature, and battery life. P ) is the specified maximum discharge pulse current (M P ) can operate the battery 20 at a specified pulse duration T p In some embodiments, the BMS 10 may be provided in combination with a plurality of maximum discharge pulse currents (M P ), and each maximum discharge pulse current (M P ) is the associated pulse duration T p and the pulse durations are of different lengths (associated M p Therefore, in some embodiments, the BMS 10 uses a discharge pulse lookup table of the BMS 10 to determine the maximum discharge pulse current (M P ) and pulse T p The associated duration of the

[0024] The maximum discharge steady-state current (M SS ) and maximum discharge pulse current (M PIt will be appreciated that the battery manufacturer may provide a voltage rating of the battery 20 for use with the BMS 10.

[0025] As can be seen from FIG. 1, the required current S is the maximum discharge steady-state current M SS is larger than the maximum discharge pulse current (M P ) is less than the required current S. Because the required current S is required for a duration longer than the specified length of the maximum discharge pulse current, the BMS 10 determines whether the battery 20 is in a maximum discharge steady state M. SS 1, the BMS 10 initially allows the battery 20 to discharge 100% of the required current. As the demand continues, the BMS 10 reduces the discharge current so that the total energy (i.e., thermal energy) stored by the battery 20 is not excessive. In accordance with the present disclosure, the BMS 10 determines the maximum discharge pulse current M for the battery. P Based on this, calculate the maximum energy that can be stored.

[0026] As shown in Figure 2, the BMS 10 measures the stored and discharged energy E D , and the maximum accumulated discharge energy M ED Calculate.

[0027] Maximum accumulated discharge energy M ED is the maximum discharge pulse current M P , and the maximum discharge pulse current M P According to this embodiment, the maximum energy that the battery 20 can store is calculated for the duration of the pulse associated with the battery 20. P The maximum discharge pulse current M P Thus, the maximum stored discharge energy M ED can be calculated according to: M ED =M P 2 xT p In some embodiments, the maximum stored discharge energy of battery 20 may also take into account steady-state energy losses associated with battery 20. Thus, in some embodiments, the maximum stored discharge energy may be calculated based on the maximum discharge pulse current, the duration of the pulse, and the steady-state energy loss of battery 20 for the duration of the pulse. In some embodiments, the steady-state energy loss may be a predetermined value associated with battery 20 or BMS 10.

[0028] In some embodiments, the steady state energy loss is determined by the maximum discharge steady state current M SS For example, in the embodiment of FIGS. 1-6, the battery 20 may be determined based on pulse T p The maximum discharge steady-state current M SS It is estimated that the energy generated by discharging the current at M SS 2 ×T P It can be calculated based on:

[0029] Thus, in the embodiment of Figures 1-6, the maximum accumulated discharge energy can be calculated as follows: M ED =(M P 2 xT p )-(M SS 2 xT p ) In the embodiment of FIGS. 1 to 6, the stored discharge energy E D is calculated when the BMS 10 controls the battery 20. The BMS 10 updates the controlled discharge current at regular time steps. In this way, the stored discharge energy E D is updated at each time step (Δt). Therefore, the accumulated discharge energy E D (n) (where n is an integer) is the accumulated discharge energy (E D(n-1)), and the discharge energy (E Δt ) is calculated based on

[0030] In the embodiment of FIGS. 1 to 6, the discharge energy (E Δt ) is calculated based on the square of the discharge current currently being output by battery 20 (D) and the duration of time step Δt. For example, in the embodiment of FIGS. 1-4, time step Δt may have a duration of 0.1 seconds. Thus, the accumulated discharge energy can be calculated as follows: E D (n)=(E D (n-1))+E Δt In some embodiments, the stored discharge energy E D (n) is calculated based on the discharge energy, the accumulated discharge energy of the previous time step, and the steady-state energy loss of the battery 20 at the time step. Taking the steady-state energy loss into account, in some cases, the accumulated discharge energy E D (n) can decrease between time steps.

[0031] For example, in the embodiment of FIGS. 1-6, the steady state energy loss of the battery 20 at a time step is calculated based on the maximum discharge steady state current M SS Thus, the steady-state energy loss is calculated based on M SS 2 × Δt.

[0032] Thus, in the embodiment of Figures 1-6, the accumulated discharge energy can be calculated as follows: E D (n)=(E D (n-1))+(D 2 xΔt)-(M SS 2 xΔt.) As can be seen from Figure 2, the accumulated discharge energy E Dincreases while a discharge current (D) is output from the battery 20. If the discharge current drops below the maximum steady state discharge current, the stored discharge energy decreases as the battery 20 dissipates the stored energy. As can be seen from FIGS. 1 and 2, the stored discharge energy E D As τ increases, the BMS 10 begins to limit the discharge current output by the battery 20. The process by which this control is implemented is discussed further below.

[0033] Figure 3 shows the accumulated discharge energy E D 4 is a graph showing the change in maximum accumulated discharge energy over time (also shown in FIG. 2). FIG. 4 shows the change in discharge current limit (L) over time along the same time axis as FIGS. 1 to 3. D ) is shown in the graph. D is the maximum accumulated discharge energy M ED , the accumulated discharge energy E D The BMS10 also ensures that the discharge current limit L D However, it also ensures that the maximum discharge pulse current specified by the BMS10 / battery manufacturer is not exceeded.

[0034] In some embodiments, the stored discharge energy E D The maximum accumulated discharge energy M ED Ratio to (i.e., E D / M ED ) is an indication of the remaining energy (i.e., 1-E) that can be stored in the battery 20 without causing excessive heating. D / M ED ) can be used as the discharge current limit L D To calculate the ratio E D / ME D Using the maximum discharge pulse current M P can be scaled.

[0035] In some embodiments, the ratio E D / M ED Using the maximum discharge pulse current M Pand the maximum discharge steady-state current M SS In some embodiments, the BMS 10 ensures that the magnitude of the discharge current limit is greater than or equal to the maximum discharge steady-state current M SS Thus, in some embodiments, the discharge current limit L D can be calculated as: L D =(1-E D / M ED )x(M P -M SS )+M SS Therefore, as the stored discharge energy ED increases from zero, the discharge current limit LD decreases from the maximum discharge pulse current MP to the maximum discharge steady state current MSS.

[0036] In some embodiments, the BMS 10 can vary how it limits the discharge current when the current demand exceeds the maximum discharge steady state current MSS. For example, in some embodiments, the BMS 10 can vary the discharge current limit by adjusting the maximum discharge pulse current MSS. P From the maximum discharge steady-state current M SS In this way, it is sometimes desirable to change the M SS In order to maintain the ability to continue to supply current at a level above M, the BMS 10 may support a reduction in the instantaneous current required. In the example of a BMS 10 installed in an electric work vehicle, when the battery 20 is used to perform drive operations for the vehicle, a smooth transition may be desirable. That is, the maximum stored discharge energy M ED The sudden drop in acceleration due to reaching the maximum stored discharge energy M may give the user a "choppy" operating experience. In other embodiments, it may be desirable for the BMS 10 to increase the instantaneous power output. ED Such a method may then require a rapid reduction in the discharge current limit to avoid breaching the maximum discharge pulse limit M. P , and the maximum discharge steady-state current MSS The subsequent arbitration method can be selected / modified to provide different power output profiles that can be adapted for different tasks that are to be performed by the machine.

[0037] Thus, in some embodiments, the discharge current limit is the maximum discharge pulse current M P , and the discharge current weight W. The discharge current weight may be provided by an arbitration method lookup table.

[0038] The arbitration method lookup table is the ratio E of the accumulated discharge energy to the maximum accumulated discharge energy. D / M ED Based on this, the discharge current weight W D can be output.

[0039] In some embodiments, the discharge current weight W D To determine the arbitration method for D / M ED can also be combined with the above to input into the arbitration method lookup table.

[0040] In some embodiments, the arbitration method is such that the BMS 10 adjusts the discharge current to a maximum discharge pulse current M P From the maximum discharge steady-state current M SS (E D =M ED The method for reducing the concentration can be controlled until the concentration is reduced to 0.05%.

[0041] In one possible method to favor instantaneous output power, the BMS 10 can provide for a stored discharge energy that is less than the maximum stored discharge energy, and the discharge current limit is equal to the maximum discharge pulse current (i.e., E D <M ED When L D =M PWhen the stored discharge energy is equal to the maximum stored discharge energy, the BMS10 sets the discharge current limit to the maximum discharge steady-state current M SS (i.e., E D =M ED When L D =M SS This arbitration method may allow the battery 20 to deliver a discharge current above the maximum discharge steady state current for as long as possible. ED When E is reached, the arbitration method changes the discharge current limit step by step. D / M ED and discharge current weight W D An example of such a relationship is shown in Figure 13a. Because such a gradual change in discharge current may not be suitable for some applications, it may be desirable to provide other arbitration methods that result in a smoother transition (or ramp) between the maximum discharge pulse current and the maximum discharge steady-state current.

[0042] For example, in another possible way to support smooth variation of the discharge current, the discharge current weight W D is E D / M ED An example of such a relationship is shown in Figure 13b. In contrast to the method of Figure 13a, the arbitration method of Figure 13b reduces the discharge current limit L from the maximum discharge pulse current as soon as the battery 20 begins to store energy. D This provides a smoother transition to steady state discharge current, but may limit the power output by battery 20 in cases where the required power drops before the maximum stored discharge energy is reached.

[0043] A further possible arbitration method is shown in Figure 13c, where the discharge current weight W D In the method of Fig. 13a, the break point where the discharge current weight drops to zero is changed. D / M EDIt will be appreciated that the break point is at E = 1 (process variation). D / M ED In the embodiment of FIG. 13c, the break point is at E D / M ED = 0.5. In each case, the discharge current weight W D is the W at the break point D = 1, E D / M ED W at =1 D =0, linearly scaled.

[0044] In some embodiments, the arbitration method parameter K D Using the discharge current weight W D A break point may be selected where σ scales to zero. Thus, in some embodiments, the arbitration method may be as follows: E D / M ED <k D In the case of W D =1; and E D / M ED ≧k D In the case of W D =(1-E D / M ED ) / (1-k D ).

[0045] In some embodiments, an arbitration method lookup table can be generated based on the above relationship, where the arbitration method lookup table is D and E D / M ED Based on this, the discharge current weight is W D In the example of Figures 13a-13c, a linear relationship is used to generate the break points and E D / M ED It should be noted that the discharge current weight is scaled between W = 1 and W = 1. In other embodiments, a different relationship, e.g., a polynomial or other non-linear function, may be used to scale W = 1. D can be scaled.

[0046] In the embodiment of FIGS. 1 to 6, the discharge current weight W D Using the maximum discharge pulse current M P and the maximum discharge steady-state current M SS Thus, in some embodiments, the discharge current limit L D can be calculated as: L D =W D x(M P -M SS )+M SS Figure 4 shows that as the stored discharge energy increases (as shown in Figure 3), the maximum discharge pulse current M P The discharge current limit L D The graph shows:

[0047] The BMS10 discharge current D is equal to the discharge current limit L D Therefore, as shown in FIGS. 5 and 6, the discharge current limit L D drops below the required current S (see FIG. 1), the BMS 10 activates the discharge current limit L D The discharge current D is limited along the maximum discharge steady-state current M SS When it falls below the discharge current limit L D begins to increase, as shown in Figure 5.

[0048] Although the above description focuses on the calculation of the discharge current limit, the ratio E D / M ED It will be appreciated that the discharge voltage limit for battery 20 can also be calculated using the ratio E D / M ED , and the maximum discharge pulse current M P The maximum discharge pulse voltage may be provided by the battery manufacturer and stored in a suitable look-up table in the BMS 10.

[0049] A BMS 10 according to the present disclosure can also be used to control the charging current of the battery 20. In some embodiments, the BMS 10 can be used to control the charging and discharging current of the battery 20. That is, the BMS 10 can control the current input to and current output from the battery 20. Methods for controlling the charging and discharging current of the battery 20 by the BMS 10 will now be described with reference to FIGS. 7-12, which illustrate graphs of various variables of the BMS 10 and the battery 20 over time. In the graphs of FIGS. 7-12, the current that charges the battery 20 (charging current) is shown as a positive current, while the current that discharges the battery 20 (discharging current) is shown as a negative current. In the following description, the charging current and related variables of the BMS 10 are distinguished from the discharging current and related variables of the BMS 10 because the BMS 10 may apply different control methods to the charging and discharging of the battery 20.

[0050] FIG. 7 shows a graph of the current of the battery (I). The current of the battery 20 varies over time in response to a square wave of required current (S). In the example of FIG. 7, the square wave of required current (S) includes a square wave of required discharge current and a square wave of required charge current, similar to those in FIG. 1. The square wave of required current has a magnitude of 750 A for a duration of 60 seconds. FIG. 7 also shows the maximum discharge pulse current (M P ), Maximum charging steady state current (M SSC ), and maximum charging pulse current (M PC ) is also shown. In the embodiment of FIG. 7, the maximum discharge pulse current M P , and the maximum charging pulse current M PC are the pulse durations T P In another embodiment, the maximum discharge pulse current M P , and the maximum charging pulse current M PC The pulse duration for may be different.

[0051] Maximum charging steady state current (M SSC) may be a value associated with the battery 20 stored in the BMS 10. In some embodiments, the maximum charging steady state current (M SSC ) may be a value that varies with one or more of the battery's state of charge (SOC), battery temperature, and battery age. Thus, in some embodiments, the BMS 10 uses a charging steady state lookup table in the BMS 10 to determine the maximum charging steady state current (M SSC ) can be determined.

[0052] Similarly, the maximum charging pulse current (M PC ) may be a value associated with the battery 20 stored in the BMS 10. In some embodiments, the maximum charge pulse current (M PC ) may be a value that varies with one or more of the battery's state of charge (SOC), battery temperature, and battery life. For example, as shown in FIG. 7, the maximum charge pulse current (M PC ) increases as the battery 20 is discharged (i.e., as the battery SOC decreases). PC ) is the specified maximum charging pulse current (M PC ) for a specified pulse duration T p In some embodiments, the BMS 10 may be provided in combination with a plurality of maximum charging pulse currents (M PC ), and each maximum charging pulse current (M PC ) is the associated pulse duration T p and the pulse durations are of different lengths (associated M PC Therefore, in some embodiments, the BMS 10 uses a charge pulse lookup table in the BMS 10 to determine the maximum charge pulse current (M PC ) and pulse T p The associated duration of the

[0053] The maximum charging steady-state current (M SSC ) and maximum charging pulse current limit (M PCIt will be appreciated that the battery manufacturer may provide a battery voltage rating (V) for use with the BMS 10.

[0054] As can be seen from FIG. 7, the required current S is greater than the maximum charging steady state current M SS and the maximum charging pulse current (M PC ) is greater than the required current S for the specified duration T of the maximum charge pulse current. P Since the battery 20 is required for a longer duration than the maximum charging steady state current M SSC 7, the BMS 10 first determines the length of the period during which the battery 20 can be operated with a charging current exceeding the maximum charging pulse current M PC As long as the demand continues, the BMS 10 reduces the charging current S so that the total energy (i.e., thermal energy) stored by the battery 20 is not excessive. In accordance with the present disclosure, the BMS 10 PC Calculate the maximum energy that can be stored based on the maximum charging pulse current for

[0055] As shown in FIG. 8, the BMS 10 determines the stored energy E for the battery and the maximum stored charge energy M EC The stored energy E for the battery is calculated by multiplying the stored discharge energy E for the battery by the D (as described above), and the stored charge energy E for the battery C (i.e., E=E C +E D ) In this way, charging and discharging of battery 20 may be taken into account when calculating the charge current limit (or, indeed, the discharge current limit discussed above).

[0056] Maximum stored charge energy M EC is the maximum charging pulse current M PC , and the maximum charging pulse current M PC and associated pulse T PTherefore, the maximum stored charge energy M EC is the maximum accumulated discharge energy M ED For example, the maximum stored charge energy M EC can be calculated according to: M EC =M PC 2 xT p In some embodiments, the maximum stored charge energy of battery 20 may also take into account steady-state energy losses associated with battery 20. Thus, in some embodiments, the maximum stored charge energy may be calculated based on a maximum charge pulse current, a pulse duration, and a steady-state energy loss of battery 20 for the pulse duration. In some embodiments, the steady-state energy loss may be a predetermined value associated with battery 20 or BMS 10.

[0057] In some embodiments, the steady state energy loss is calculated based on the maximum charging steady state current M SSC For example, in the embodiment of FIGS. 7 to 12, the battery 20 may be determined based on pulse T p The maximum charging steady-state current M SSC It is estimated that the energy generated by charging the battery with current can be dissipated by M SSC 2 ×T P It can be calculated based on:

[0058] Thus, in the embodiment of Figures 7-12, the maximum stored charge energy can be calculated as follows: M EC =(M PC 2 xT p )-(M SSC 2 xT p ) In the embodiment of FIGS. 7-12, the stored charge energy E is calculated when the BMS 10 controls the battery 20. The BMS 10 updates the controlled charge current at regular time steps. Thus, the stored charge energy E is updated at each time step (Δt). Therefore, the stored discharge energy E(n) at the nth time step (where n is an integer) is calculated as the stored discharge energy (E D (n-1)), and the stored charge energy (E C (n-1)), and the discharge / charge energy at the time step (E Δt ) is calculated based on

[0059] In the embodiments of FIGS. 7-12, the charging energy (E Δt ) is calculated based on the square of the charging current currently being output by the battery 20 (I) and the duration of the time step Δt. For example, in the embodiment of FIGS. 7-12, the time step Δt may have a duration of 0.1 seconds. Thus, the stored energy can be calculated as follows: E(n)=(E(n-1))+E Δt In some embodiments, the stored energy E(n) is calculated based on the discharge / charge energy, the stored energy of the previous time step, and the steady-state energy loss of the battery 20 at the time step. Taking the steady-state energy loss into account, in some cases, the stored energy E(n) may decrease between time steps.

[0060] For example, in the embodiments of FIGS. 7-12, the steady state energy loss of battery 20 at a time step is calculated as the maximum discharge steady state current M of the battery depending on whether battery 20 is discharging or charging, respectively. SS , or the maximum charging steady-state current of the battery M SSC When charging the battery 20, the steady state energy loss can be calculated based on M SSC 2 × Δt.

[0061] As can be seen from Figure 8, the stored energy E increases while the battery 20 is being charged and when the battery 20 is being discharged. When the current I of the battery 20 reaches the maximum steady-state discharge current M SS , and the steady-state charging current M SSC If the stored energy E drops below a threshold defined by E = ∑ m ⁢ ⁢ ⁢ ⁢ ⁢ ⁢ ⁢ ⁢ E ... E ⁢ ⁢ ⁢ ⁢ ⁢ ⁢ ⁢ ⁢ E ⁢ ⁢ ⁢ �

[0062] Figures 9 and 10 show the battery current and charge current limit (L) versus time, following the same time axis as Figures 7 and 8. C ) is shown in the graph. C is the stored charge energy E C The maximum stored charge energy M EC In the embodiments of FIGS. 7 to 12, the charging current limit L C is the total accumulated discharge energy E D can also be taken into account. Thus, in the embodiments of Figures 7 to 12, the stored energy E can be expressed as the stored charge energy E C The BMS 10 also ensures that the charging current limit L C However, it also ensures that the maximum charge pulse current specified by the BMS10 / battery manufacturer is not exceeded.

[0063] Stored charge energy E C The maximum stored charge energy M EC Ratio to (i.e., E C / M EC ) or the maximum stored charge energy M of the stored energy E EC Ratio to E / M EC ) can be used as an indicator of the remaining energy that can be stored in battery 20 without causing excessive heat generation. Thus, in some embodiments, the discharge current limit LC To calculate the ratio (E C / M EC、 Or E / M EC ) to determine the maximum charging pulse current M PC can be scaled.

[0064] In some embodiments, the ratio (E C / M EC , or E / M EC ) to determine the maximum charging pulse current M PC and the maximum charging steady-state current M SSC Thus, in some embodiments, the charge current limit L C can be calculated as: L C =(E C / M EC )x(M PC -M SSC ) or L C =(E / M EC )x(M PC -M SSC ).

[0065] Therefore, the stored charge energy E C As increases from zero, the charging current limit L C is the maximum charging pulse current M PC From the maximum charging steady-state current M SSC decreases to.

[0066] Similar to the embodiment of FIGS. 1-6, the embodiment of FIGS. 7-12 can use an arbitration method lookup table to determine the current weight (or charge current weight), which can be used to determine the maximum charge pulse current M PC is scaled.

[0067] The arbitration method lookup table is the ratio of stored energy to maximum stored charge energy E / M EC Based on the charging current weight W C In some embodiments, this may involve outputting the arbitration method parameter k CIn some embodiments, different arbitration method parameters k D , k C can be used to calculate the discharge current limit and the charge current limit, respectively, or the same arbitration method can be followed after both charging and discharging.

[0068] In some embodiments, the charging current weight W C To determine the arbitration method for EC can also be combined with the above to input into the arbitration method lookup table.

[0069] In the embodiment of FIGS. 7 to 12, the charging current weight W C Using the maximum charging pulse current M PC and the maximum charging steady-state current M SS Thus, in some embodiments, the charging current limit L C can be calculated as: L C =W C x(M PC -M SSC ) Figure 12 shows the maximum stored charge energy (E / M EC ) and the ratio of the stored energy to the maximum stored discharge energy (E / M ED ) based on the ratio to the charging current weight W C and discharge current weight W D As can be seen from FIG. P and M PC Due to the different values ​​for , the ratio E / M EC and E / M ED is different.

[0070] As shown in Figure 11, the BMS 10 detects the battery current I as the charging current limit L C and does not exceed the discharge current limit L D11, the BMS 10 controls the charging current of the battery 20 so that it does not exceed the charging current limit L C and discharge current limit L D The current is decreased along the

[0071] 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 battery 20. Thus, the charging voltage limit is calculated using the ratio E / M EC , and the maximum charging pulse current M P The maximum charge pulse voltage may be provided by the battery manufacturer and stored in a suitable look-up table in the BMS 10.

[0072] 14 shows a block diagram of a method 100 for controlling the discharge current of a battery 20 according to an embodiment of the present disclosure. The method may be implemented by the BMS 10 described above.

[0073] In method step 101, the BMS 10 calculates the discharge energy of the battery 20 for a time step based on the discharge current and the duration of the time step.

[0074] In method step 102, the BMS 10 calculates the accumulated discharge energy of the battery 20 based on the accumulated discharge energy calculated for the previous time step and the discharge energy at the time step.

[0075] In method step 103, the BMS 10 determines a maximum discharge pulse current for a pulse having a duration based on the BMS 10 discharge pulse current lookup table.

[0076] In method step 104, the BMS 10 calculates the maximum stored discharge energy of the battery 20 based on the maximum discharge pulse current and the duration of the pulse.

[0077] In method step 105, the BMS 10 calculates a discharge current limit based on the ratio of the stored discharge energy to the maximum stored discharge energy, the discharge current limit not exceeding the maximum discharge pulse current.

[0078] In method step 106, the BMS 10 controls the discharge current of the battery 20 so that the discharge current does not exceed the discharge current limit.

[0079] It will be appreciated that the method 100 may incorporate additional steps / features along with the BMS 10 embodiments described above.

[0080] 15 shows a block diagram of a method 200 for controlling the charging current of the battery 20 according to an embodiment of the present disclosure. The method may be implemented by the BMS 10 described above.

[0081] In method step 201, the BMS 10 calculates the charge energy of the battery 20 for a time step based on the charge current and the duration of the time step.

[0082] In method step 202, the BMS 10 calculates the accumulated charge energy of the battery 20 based on the accumulated charge energy calculated for the previous time step and the charge energy at the time step.

[0083] In method step 203, the BMS 10 determines a maximum charge pulse current for a pulse having a duration based on the BMS 10 charge pulse current lookup table.

[0084] In method step 204, the BMS 10 calculates the maximum stored charge energy of the battery 20 based on the maximum charge pulse current and the duration of the pulse.

[0085] In method step 205, the BMS 10 calculates a charge current limit based on the ratio of stored charge energy to maximum charge / discharge energy, the charge current limit not exceeding the maximum charge pulse current.

[0086] In method step 206, the BMS 10 controls the charging current of the battery 20 so that the charging current does not exceed the charging current limit.

[0087] It will be appreciated that the method 200 may incorporate additional steps / features along the lines of the BMS 10 embodiments described above.

[0088] Industrial Applicability According to the present disclosure, a battery management system (BMS 10) is provided. The BMS 10 is configured to control the discharge current of a battery 20. According to an embodiment, the battery 20 may be a storage battery. The battery 20 and the BMS 10 may be provided as part of a machine 30, for example, an electric work machine.

[0089] The BMS 10 according to the present disclosure determines the safe operating limits of the battery 20 for pulse currents (discharge or charge) of longer duration than those specified in the look-up table provided by the battery manufacturer. The BMS 10 according to the first embodiment calculates the discharge current limit and / or charge current limit by comparing the energy stored by discharging the battery 20 with the maximum stored energy. The maximum stored energy is calculated from the maximum pulse discharge current provided by the look-up table of the BMS 10. The difference between the stored discharge energy and the maximum stored energy defines the remaining amount of energy the battery 20 can safely store. Based on the energy difference, the BMS 10 can determine the discharge current limit or charge current limit at which the battery 20 can continue to operate. In fact, the BMS 10 can safely operate the battery 20 at a current (charge or discharge) greater than the specified maximum steady-state current for an extended period of time (i.e., a period longer than the pulse duration).

[0090] In some embodiments, BMS 10 can also arbitrate between the maximum charge / discharge pulse current and the maximum charge / discharge steady-state current using an arbitration method lookup table. In such embodiments, the subsequent arbitration method can be selected / modified to provide different power output profiles that can be tailored for various tasks to be performed by machine 30.

Claims

1. 1. A battery management system (BMS) configured to control a discharge current of a battery, the BMS comprising: calculating a discharge energy of the battery for a time step based on the discharge current and the duration of the time step; calculating a stored discharge energy of the battery based on a stored discharge energy calculated for a previous time step and the discharge energy at the time step; determining a maximum discharge pulse current for a pulse having a duration based on a discharge pulse current lookup table of the BMS; calculating a maximum stored discharge energy of the battery based on the stored discharge pulse current and the duration of the pulse; calculating a discharge current limit based on a ratio of the stored discharge energy to the maximum stored discharge energy, wherein the discharge current limit does not exceed the maximum discharge pulse current; and controlling the discharge current of the battery so that the discharge current does not exceed the discharge current limit.

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

3. the accumulated discharge energy is calculated based on the discharge energy, the accumulated discharge energy of the previous time step, and the steady state energy loss of the battery at the time step; 3. The BMS of claim 1, wherein the maximum stored discharge energy of the battery is calculated based on the maximum discharge pulse current, the duration of the pulse, and a steady-state energy loss of the battery for the duration of the pulse.

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

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

6. Calculating the discharge current limit based on a ratio of the stored discharge energy to the maximum stored discharge energy includes: inputting the ratio of the stored discharge energy to the maximum stored discharge energy into an arbitration method lookup table to obtain a discharge current weight; 6. The BMS according to claim 1, further comprising: calculating the discharge current limit based on the discharge current weight and the maximum discharge pulse current.

7. 7. The BMS of claim 6, wherein an arbitration method parameter is input into the arbitration method lookup table together with a ratio of the stored discharge energy to the maximum stored discharge energy to determine an arbitration method for the discharge current weight.

8. 1. A battery management system (BMS) configured to control a charging current of a battery, the BMS comprising: calculating a charge energy of the battery for a time step based on the charge current of the battery and the duration of the time step; calculating a stored charge energy for the battery based on a stored charge energy calculated for a previous time step and the charge energy at the time step; determining a maximum charge pulse current for a pulse having a duration based on a charge pulse current lookup table of the BMS; calculating a maximum stored charge energy based on the charge / discharge pulse current and the duration of the pulse; calculating a charge current limit based on a ratio of the stored charge energy to the maximum stored charge energy, wherein the charge current limit does not exceed the maximum charge pulse current; and controlling the charging current of the battery so that the charging current does not exceed the charging current limit.

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

10. the stored charge energy is calculated based on the charge energy, the stored charge energy of the previous time step, and a steady state energy loss of the battery at the time step; 10. The BMS of claim 8 or 9, wherein the maximum stored charge 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 for the duration of the pulse.

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

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

13. Calculating the charging current limit based on a ratio of the stored charging energy to the maximum stored charging energy comprises: inputting the ratio of the stored charge energy to the maximum stored charge energy into an arbitration method lookup table to obtain a charge current weight; Calculating the charging current limit based on the charging current weight and the maximum charging pulse current.

14. 14. The BMS of claim 13, wherein a charging arbitration method parameter is input into the arbitration method lookup table together with a ratio of the stored charge energy to the maximum stored charge energy to determine an arbitration method for the charging current weight.

15. The BMS further comprises:

8. The BMS according to claim 1 , configured to calculate a discharge voltage limit based on a ratio of the maximum stored discharge energy to the stored discharge energy, wherein the discharge voltage limit does not exceed a maximum discharge pulse voltage; and / or The BMS further comprises:

15. The BMS of claim 8, configured to calculate a charge voltage limit based on a ratio of the maximum stored charge energy to the stored charge energy, wherein the charge voltage limit does not exceed a maximum charge pulse voltage.

16. It is a machine, Battery, A BMS according to any one of claims 1 to 7, and / or A machine comprising a BMS according to any one of claims 8 to 15.

17. A method for controlling a discharge current of a battery, comprising: calculating a discharge energy of the battery for a time step based on the discharge current and the duration of the time step; calculating a stored discharge energy of the battery based on a stored discharge energy calculated for a previous time step and the discharge energy at the time step; determining a maximum discharge pulse current for a pulse having a duration based on a discharge pulse current lookup table of the BMS; calculating a maximum stored discharge energy of the battery based on the stored discharge pulse current and the duration of the pulse; calculating a discharge current limit based on a ratio of the stored discharge energy to the maximum stored discharge energy, wherein the discharge current limit does not exceed the maximum discharge pulse current; and controlling the discharge current of the battery so that the discharge current does not exceed the discharge current limit.

18. 1. A method for controlling a charging current of a battery, comprising: calculating a charge energy of the battery for a time step based on the charge current of the battery and the duration of the time step; calculating a stored charge energy for the battery based on a stored charge energy calculated for a previous time step and the charge energy at the time step; determining a maximum charge pulse current for a pulse having a duration based on a charge pulse current lookup table of the BMS; calculating a maximum stored charge energy based on the charge / discharge pulse current and the duration of the pulse; calculating a charge current limit based on a ratio of the stored charge energy to the maximum stored charge energy, wherein the charge current limit does not exceed the maximum charge pulse current; and controlling the charging current of the battery so that the charging current does not exceed the charging current limit.

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