Method of thermal management of battery

Abstract

A thermal management method of a battery wherein the battery comprises at least one cell, and wherein a heating device is configured to heat the battery in response to a heating instruction. The method comprises the following steps: determining the charge state of the battery cell and the battery cell current of the battery cell; a first value of a first parameter of the heating device; a reference cell temperature of the cell; the maximum battery cell temperature and the minimum battery cell temperature of the battery cell are obtained. Under the condition that the maximum battery cell temperature is lower than a first threshold temperature; the minimum cell temperature of the cell is lower than a second threshold temperature; the charge state of the battery cell is higher than a charge state threshold value; the method also includes instructing a heating device to heat the electrical core.

Description

Technical Field

[0001] The present invention relates to the field of thermal management. Background Art

[0002] Operating a battery within its optimal temperature range is known to be beneficial for battery performance and reduces battery degradation. Operating a battery outside of its optimal temperature range can increase the rate at which battery health deteriorates. This can adversely affect the battery's capacity, charge and discharge rates, lifespan, and other performance characteristics.

[0003] It is known to use heating devices (e.g., heater pads) to warm batteries in an attempt to ensure that the battery is within its optimal temperature range before or during operation. Typically, the heating device is turned on until a threshold temperature is reached, at which point the heating device is turned off. The temperature measured is typically the temperature at or near the heating device, which may be different from the temperature of the battery cells. Summary of the Invention

[0004] Against this background, a method for thermal management of a battery is provided, wherein the battery includes at least one battery cell and wherein a heating device is configured to heat the battery in response to a heating instruction. The method includes determining a state of charge (SOC) of the battery cell; determining a cell current of the battery cell; determining a first value of a first parameter of the heating device; and determining a reference cell temperature of the battery cell. The method also includes determining a maximum cell temperature and a minimum cell temperature of the battery cell by comparing the cell current and the first value of the first parameter with test data correlating calibrated values of the cell current and the first parameter with one or more temperature errors. The method also includes determining a temperature of the heating device using the reference cell temperature, an ambient temperature, and a heat transfer coefficient of the heating device, and using the temperature of the heating device to determine a second value of the first parameter of the heating device. When the maximum cell temperature is below a first threshold temperature, the minimum cell temperature of the battery cell is below a second threshold temperature, and the SOC of the battery cell is above a SOC threshold, the method also includes instructing the heating device to heat the battery cell.

[0005] In this way, the heating of the battery cells can be controlled so that the battery cells are heated only when the battery cell temperature is within a range that requires heating and is safe. The heating of the battery cells can be further controlled so that heating occurs only when the state of charge of the battery is above a threshold, where the threshold can be the minimum state of charge that allows a machine powered by the battery to operate or perform certain functions. For example, in the case where the battery is powering an electric work vehicle, the state of charge threshold can be the minimum state of charge required for the electric work vehicle to travel to the charger. This method allows the battery to be maintained in a temperature range that is beneficial to reducing battery degradation or aging and improving battery performance. The method allows the heating to be controlled so that the heating device is enabled only when it is sufficiently beneficial and safe. In addition, the method can be performed by existing battery management software and controllers, saving money and increasing the ease of integration.

[0006] A thermal management device for a battery is also provided, wherein the battery includes at least one battery cell and the thermal management device includes a heating device configured to heat the battery in response to a heating instruction, and a controller. The thermal management device is configured to: determine the state of charge of the battery cell; determine a cell current of the battery cell; determine a first value of a first parameter of the heating device; and determine a reference cell temperature of the battery cell. The thermal management device is further configured to determine a maximum cell temperature and a minimum cell temperature of the battery cell by comparing the cell current and the first value of the first parameter with test data that correlates calibrated values of the cell current and the first parameter with one or more temperature errors. The thermal management device is further configured to determine a temperature of the heating device using the reference cell temperature, an ambient temperature, and a heat transfer coefficient of the heating device, and to use the temperature of the heating device to determine a second value of the first parameter of the heating device. The thermal management device is further configured to instruct the heating device to heat the battery cell when: the maximum cell temperature is below a first threshold temperature; the minimum cell temperature of the battery cell is below a second threshold temperature; and the state of charge of the battery cell is above a state of charge threshold. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0008] Figure 1 A flow chart illustrating thermal strategy logic according to an embodiment of the present invention is shown.

[0009] Figure 2 A flow chart illustrating a battery cell thermal model according to an embodiment of the present invention is shown.

[0010] Figure 3 A flow chart illustrating a heating device model according to an embodiment of the present invention is shown.

[0011] Figure 4A flow chart illustrating a combined cell thermal model and heater model according to an embodiment of the present invention is shown.

[0012] Figure 5 A flow chart illustrating a combined cell thermal model, heater model, and thermal strategy logic according to an embodiment of the present invention is shown.

[0013] Figure 6 Schematic diagrams showing battery modules, heater mats, and cooling plates are shown, for which methods according to embodiments of the present invention may be implemented.

[0014] Figure 7 A flow chart illustrating a heating device model according to an embodiment of the present invention is shown. Figure 7 A shows the model of the entire heating device, Figure 7 B shows the heat removal of the battery cell. Figure 7 C shows the heat rejection to the environment.

[0015] Figure 8 A flow chart illustrating thermal strategy logic according to an embodiment of the present invention is shown.

[0016] Figure 9 A flow chart illustrating thermal strategy logic with hysteresis according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0017] A method for thermal management of a battery is provided, wherein the battery includes at least one battery cell, may include more than one battery cell, and may include one or more modules, each module including one or more battery cells.

[0018] The heating device is configured to heat the battery in response to the heating instruction. The heating device may include any device configured to heat the battery, wherein the purpose of the heating device for heating the battery can be controlled. For example, the heating device can start and stop heating the battery. In certain embodiments, the heating device includes a heater pad that is configured to output heat when an electric current is applied. The heater pad may include a positive temperature coefficient (PTC) heater pad. The heater pad can be powered by the battery and can therefore draw current from the battery.

[0019] The method may allow one or more cells of a battery to be maintained within a certain temperature range, for example, by enabling or disabling a heating device. A battery management system (BMS) may determine and / or implement a thermal management method. In certain embodiments, where the battery includes more than one module, there may be one BMS for each module, wherein each BMS is configured to determine and / or implement a thermal management method for a corresponding module of the battery. In certain embodiments where the battery includes more than one module, there may be one heating device for each module.

[0020] The method may include using a cell thermal model (see 200, Figure 2 ), heating device model (300, Figure 3 ) and thermal strategy logic (100, Figure 1 The outputs of the cell thermal model 200 and the heater model 300 are used as inputs to the thermal strategy logic 100. The output of the thermal strategy logic 100 determines whether to instruct the heater to output heat. Hereinafter, enabling the heater includes enabling the heater to output heat. Activating the heater may include instructing the heater to begin heating, instructing the heater to continue heating, or providing no indication if the heater is already heating.

[0021] The cell thermal model 200 can be configured to determine the maximum and minimum cell temperatures of a battery module (where a battery may include one module or a battery may include more than one module, and where a battery module may include one or more cells). The maximum and minimum cell temperatures can account for temperature errors. The cell thermal model 200 will be discussed in more detail below.

[0022] The heating device model 300 can be configured to determine the temperature of the heating device and use the temperature of the heating device to determine a value of a first parameter of the heating device. The first parameter can indicate the thermal output of the heating device. For example, if the heating device comprises an electric heater pad, the first parameter can include current. If the heating device comprises an immersion heater or a liquid coolant system, the first parameter can include the output of a temperature sensor.

[0023] refer to Figure 1 , shows the thermal strategy logic 100. A maximum cell temperature 111, a minimum cell temperature 112, a first parameter value of a heating device 113, and a battery state of charge value 114 are used as inputs to the thermal strategy logic 100. In order for the thermal strategy logic 100 to determine that the heating device should be activated, various conditions need to be met. Figure 1The flowchart shown in illustrates situations where these conditions are met. The thermal strategy logic 100 compares the inputs to reference values or limits. In step 121, the thermal strategy logic 100 may compare the maximum cell temperature to an upper temperature threshold, in step 122, the minimum cell temperature to a lower temperature threshold, and in step 124, the state of charge value to a state of charge threshold. In step 130, a determination is made as to whether the maximum cell temperature is below the upper temperature threshold and the minimum cell temperature is below the lower temperature threshold. If the maximum cell temperature is below the upper temperature threshold and the minimum cell temperature is below the lower temperature threshold, the method proceeds to step 140. In step 140, a determination is made as to whether the state of charge value is above the state of charge threshold. If the state of charge value is above the state of charge threshold, the heating device may be enabled in step 150. If any of these conditions are not met, the heating device may not be enabled (even if the other conditions are met). Step 140 may also include, in step 123, comparing a first parameter value of the heating device 113 to a threshold when determining whether to enable the heating device. For example, if the maximum cell temperature is below an upper temperature threshold, the minimum cell temperature is below a lower temperature threshold, the state of charge value is above a state of charge threshold, and the first parameter value is below a first parameter threshold, then the heating device may be activated. Steps 121, 122, 123, and 124 may be performed in parallel or in any order. Steps 130 and 140 may be combined, performed in parallel, or performed in a different order.

[0024] In one embodiment, a method for thermal management of a battery is provided, wherein the battery includes at least one battery cell, and wherein a heating device is configured to heat the battery in response to a heating instruction. The method includes determining a state of charge of the battery cell; determining a cell current of the battery cell; determining a first value of a first parameter of the heating device; and determining a reference cell temperature of the battery cell. The method also includes determining a maximum cell temperature and a minimum cell temperature of the battery cell by comparing the cell current and the first value of the first parameter with test data that associates calibrated values of the cell current and the first parameter with one or more temperature errors. The method also includes determining a temperature of the heating device using the reference cell temperature, the ambient temperature, and a heat transfer coefficient of the heating device, and using the temperature of the heating device to determine a second value of the first parameter of the heating device.

[0025] When the maximum cell temperature is below a first threshold temperature, the minimum cell temperature of the cell is below a second threshold temperature, and the state of charge of the cell is above a state of charge threshold, the method further includes instructing the heating device to heat the cell. If the heating device is not yet enabled (i.e., not heating the cell), the step of instructing the heating device to heat the cell may include enabling the heating device. If the heating device is enabled (i.e., already heating the cell), the step of instructing the heating device to heat the cell may include instructing the heating device to continue heating. If one or more conditions are not met, i.e., when the maximum cell temperature is above a first threshold temperature, and / or the minimum cell temperature of the cell is above a second threshold temperature, and / or the state of charge of the cell is below the state of charge threshold, the method may further include instructing the heating device not to heat the cell. If the heating device has not yet heated the cell, the step of instructing the heating device not to heat the cell may include instructing the heating device to continue not heating the cell, or not providing instructions to the heating device. If the heating device is enabled (i.e., already heating the cell), the step of instructing the heating device not to heat the cell may include instructing the heating device to stop heating the cell.

[0026] In certain embodiments, when the maximum cell temperature is below a first threshold temperature, the minimum cell temperature of the cell is below a second threshold temperature, the state of charge of the cell is above a state of charge threshold, and the second value of the first parameter is below a threshold, the method includes instructing a heating device to heat the cell.

[0027] Iterations of the method can be performed at multiple times during the battery's life. For example, the method can be performed in a first iteration when the battery management system is turned on. The method can then be repeated at specific time intervals in subsequent iterations until the battery management system is turned off.

[0028] To aid explanation, the following description assumes that the heating device is an electric heater pad, such as a PTC heater pad, and that the first parameter is the input current to the heater pad. The heater pad is configured to emit heat in response to the input current. However, any heating device may be used, which may have a different first parameter.

[0029] As described above, the method may use the cell thermal model 200, whereby the method includes determining a maximum cell temperature and a minimum cell temperature of the cell by comparing the cell current and the first parameter with test data relating calibrated values of the cell current and the first parameter to one or more temperature errors (cell thermal model). Figure 2, shows a cell thermal model 200 according to certain embodiments of the present invention, wherein the heating device includes an electric heater pad. The inputs to the cell thermal model 200 are a BMS temperature measurement 211, a cell current 212, and a first value 213 of the heater pad input current (i.e., a first value of the first parameter). The BMS temperature measurement 211 may include the output of one or more temperature sensors from the battery. In the case where the battery includes more than one module, the BMS temperature measurement 211 may include the output of one or more temperature sensors from the module. The outputs of the cell thermal model 200 are a reference cell temperature 261, a maximum cell temperature 262, and a minimum cell temperature 263. The BMS temperature measurement 211 is used as a reference cell temperature. At 220, the cell current 212 and the first value 213 of the heater pad input current are used as input to calculate a positive temperature uncertainty. At 230, the positive temperature uncertainty is added to the BMS temperature measurement 211 to provide a maximum cell temperature 262. At 240 , the cell current 212 and the first value 213 of the heater pad input current are used as inputs to calculate a negative temperature uncertainty. At 250 , the negative temperature uncertainty is subtracted from the BMS temperature measurement 211 to provide a maximum cell temperature 262 .

[0030] At 220 and 240, positive temperature uncertainty and negative temperature uncertainty can be calculated using test data that associates the calibrated values of the cell current and the first parameter with one or more temperature errors. In other words, a calibrated error map is used to return the temperature error associated with the input cell current 211 and the input heater pad current 213. The calibrated error map can be generated from the test results. The error can indicate expected temperature variations (such as temperature variations between cells of a module, or uncertainty in heating the cells to a nominal temperature). The error can also indicate errors in upstream measurements, such as measurements made by a BMS.

[0031] The method may use a model of the heater, whereby the method uses the reference cell temperature, the ambient temperature, and a heat transfer coefficient of the heater to determine a temperature of the heater, and then uses the temperature of the heater to determine a second value of a first parameter of the heater. Figure 3 , shows a model 300 of a heating device according to some embodiments of the present invention, wherein the heating device includes an electric heater pad. Figure 3 The nth iteration of the heating device model 300 is shown. During battery use, the heating device model 300 may be executed at each of a plurality of consecutive time stamps. Figure 2The reference temperature 261 output by the cell thermal model 200 can be used as an input for the temperature parameter 310 of the nth iteration, where the temperature parameter 310 may include one or more of the average cell temperature, the ambient temperature, and the heat transfer coefficient of the heating device. The average cell temperature may be the average value of the cell temperatures of the battery. For example, when the battery includes more than one cell, the average cell temperature may be the average value of the reference cell temperature of each cell. When the battery includes more than one module and each module includes more than one cell, the average temperature may include the module temperature (the average value of the reference cell temperature of each cell of the module) or the battery temperature (the average value of the module temperature). The ambient temperature may be the temperature measured at the beginning of the battery's usage cycle, for example, when the BMS is turned on. Alternatively, the ambient temperature may be a calibrable parameter that can be set by the BMS or by the user. The heat transfer coefficient may be a calibrable parameter that can be set by the BMS or by the user. The temperature 330 of the heating device can be calculated using the temperature parameter of the nth iteration and the heater pad power value of the (n-1)th iteration of the heating device model. From the temperature 330, a second value of the first parameter of the heating device may be calculated 340. In case the heating device is an electric heater pad, a second value of the input current of the heater pad is calculated 340.

[0032] The heater model 300 can calculate the heater temperature based on a thermodynamic energy balance. In embodiments where the heater comprises an electric heater pad, the heater model can use the heater temperature to calculate a heater resistance value (e.g., based on calibration data that corresponds the resistance value to a calibrated heater temperature value). The heater resistance value can then be used to calculate the heater pad current based on the voltage (wherein the voltage can be measured or calibrated). In the case where the heater pad is powered by the battery or battery module, the voltage can be the battery voltage or the module voltage. The electric heater pad power can also be calculated for use as input 320 in the next iteration of the heater model.

[0033] Figure 4 The interaction between the cell thermal model 200 and the heater model 300 is shown. The output reference cell temperature 261 can be used as an input for the temperature parameter 310 of the heater model 300. The output second value 340 of the first parameter of the heater (e.g., input current) can be fed as input 213 to the next iteration of the cell thermal model 200. In other words, the input 213 of the nth iteration of the cell thermal model 200 (the first value 213 of the heater pad input current) is the output 340 of the (n-1)th iteration of the heater model 300 (the second value of the heater pad input current). For the first iteration of the cell thermal model 200, the input 213 can be a calibrated value or can be measured. For the first iteration of the heater model 300, the input 320 can be a calibrated value or can be measured.

[0034] Refer again Figure 1 The maximum and minimum cell temperatures 111 and 112 may be outputs 262 and 263 of the cell thermal model 200 . The value of the first parameter of the heating device 113 may be output 340 of the heating device model 300 . Figure 5 This diagram illustrates how the cell thermal model 200, the heater model 300, and the thermal strategy logic 100 can interact. At step 121, the maximum cell temperature 262 is compared to an upper temperature threshold. At step 122, the minimum cell temperature 263 is compared to a lower temperature threshold. At step 123, a first parameter of the heater is compared to a threshold. At step 124, the state of charge value 114 is compared to a state of charge threshold. At step 140, if all conditions are met, the heater is enabled at step 150.

[0035] As described above, the thermal strategy logic 100 may compare the maximum and minimum cell temperatures and the cell state of charge with reference values. If all three comparisons determine that the conditions for enabling heating have been met, the heating device may be enabled (if there are more than three conditions for enabling heating, the heating device may be enabled if all conditions are met). If one or more of the conditions are not met, heating is not enabled.

[0036] Compare the state of charge with a reference value (by Figure 1 and Figure 5 Step 124 of the embodiment may include comparing the minimum cell state of charge to a reference state of charge. If the minimum cell state of charge is higher than the reference state of charge, the state of charge condition has been met. If the minimum cell state of charge is lower than the reference state of charge, the state of charge condition has not been met and the heating device is not enabled. In one example, the reference state of charge may be 10% of the total capacity of the cell. In another example, the reference state of charge may be between 10% and 15% of the total capacity of the cell.

[0037] Compare the maximum cell temperature with a reference value (given by Figure 1 and Figure 5Step 121 of the present invention may include comparing the maximum cell temperature of the battery cell to an upper temperature threshold. If the maximum cell temperature of the battery cell is below the upper temperature threshold, the upper temperature condition has been met. If the maximum cell temperature of the battery cell is not below the upper temperature threshold, the upper temperature condition is not met and the heating device is not enabled. When the maximum cell temperature approaches the upper temperature threshold, a hysteresis may be applied to prevent the heating device from being repeatedly enabled and disabled (i.e., if the cell temperature fluctuates very close to the temperature threshold, unnecessary actuation is prevented). In one example, the upper temperature threshold may be between 30°C and 60°C. In one example, a hysteresis of between 5°C and 10°C may be applied. In another example, a hysteresis of between 5% and 10% of the upper temperature threshold may be applied.

[0038] Compare the minimum cell temperature with a reference value (given by Figure 1 and Figure 5 Step 122 of the present invention may include comparing the minimum cell temperature of the battery cell with a lower temperature threshold. If the minimum cell temperature of the battery cell is lower than the lower temperature threshold, the lower temperature condition has been met. If the minimum cell temperature of the battery cell is not lower than the lower temperature threshold, the lower temperature condition is not met and the heating device is not enabled. When the minimum cell temperature approaches the lower temperature threshold, a hysteresis may be applied to prevent the heating device from being repeatedly enabled and disabled. In one example, the lower temperature threshold may be 10°C. In one example, the lower temperature threshold may be between 0°C and 10°C. In one example, a hysteresis of between 5°C and 10°C may be applied.

[0039] These comparisons may be performed in any order or in parallel.If a condition is not met, then no subsequent comparisons may be performed for that iteration of the method (or at that timestamp).

[0040] In embodiments where the heating device includes an electric heater pad, the thermal strategy logic 100 may further include comparing the heater pad current to a threshold. This may include checking whether the heater pad current is below a current threshold. Otherwise, this may include subtracting the heater pad current from the battery's discharge current limit and checking whether the current difference is above an operating current threshold, where the operating current threshold is the minimum discharge current available for the battery-powered machine to operate.

[0041] The cell thermal model 200 can be executed for a single cell, for a battery module comprising more than one cell, or for a battery comprising more than one battery module, each of which comprises more than one cell. When executing the cell thermal model 200 for a single cell, temperature uncertainties can be calculated based on test data corresponding to individual cell temperature errors associated with a first parameter value. The output maximum and minimum cell temperatures can reflect these expected errors. When executing the cell thermal model 200 for a battery module comprising more than one cell, temperature uncertainties can be calculated based on test data corresponding to variations in cell temperatures across the module associated with the first parameter value. For example, cells within a module may heat at different rates depending on their position relative to a heating device, cooling pathways, or other factors. The output maximum and minimum cell temperatures can be the expected maximum cell temperature and the maximum cell temperature of the multiple cells, respectively. When executing the cell thermal model 200 for a battery comprising more than one battery module, temperature uncertainties can be calculated based on test data corresponding to variations in cell temperatures within each module of the battery associated with the value of the first parameter. For example, modules within a battery may be heated at different rates depending on their location relative to a heating device, cooling pathways, or other factors. The output maximum and minimum cell temperatures may be the expected maximum cell temperature for the plurality of modules and the maximum cell temperature for the plurality of modules, respectively.

[0042] The heating device model 300 may obtain an input of a reference cell temperature from one or more cell thermal models implemented for the cell, or for the module, or for the battery.

[0043] The thermal strategy logic 100 can be executed for a single cell, or for a battery module including more than one cell, or for a battery including more than one battery module, where each battery module includes more than one cell. In the case where the thermal strategy logic 100 is executed for a single cell, the minimum cell state of charge, maximum cell temperature, and minimum cell temperature used as inputs in the thermal strategy logic 100 may correspond to that particular cell. The maximum and minimum cell temperatures are outputs from the cell thermal model 200 executed on the cell (i.e., they are the reference cell temperature plus positive uncertainty and minus negative uncertainty, respectively). In the case where the thermal strategy logic 100 is executed for a battery module including more than one cell, the minimum cell state of charge, maximum cell temperature, and minimum cell temperature used as inputs in the thermal strategy logic 100 may correspond to the entire module. The minimum cell state of charge may be the minimum cell state of charge of more than one cell. The maximum cell temperature used in the thermal strategy logic 100 may be the maximum output of the cell thermal model 200 executed for more than one cell individually, or may be the output of the cell thermal model 200 executed for the module as a whole (see above). The minimum cell temperature used in the thermal strategy logic 100 may be the minimum output of the cell thermal model 200 executed for more than one cell individually, or may be the output of the cell thermal model 200 executed for the module as a whole (see above). In the case where the thermal strategy logic 100 is executed for a battery including more than one module, the minimum cell state of charge, maximum cell temperature, and minimum cell temperature used as inputs in the thermal strategy logic 100 may correspond to the entire battery. The minimum cell state of charge may be the minimum cell state of charge of the cells of more than one module. The maximum cell temperature used in the thermal strategy logic 100 may be the maximum output of the cell thermal model 200 executed for more than one cell individually, or may be the maximum output of the cell thermal model 200 executed for each module as a whole, or may be the output of the cell thermal model 200 executed for the battery as a whole. The minimum cell temperature used in the thermal strategy logic 100 may be the minimum output of the cell thermal model 200 executed for more than one cell individually, or may be the maximum output of the cell thermal model 200 executed for each module, or may be the output of the cell thermal model 200 executed for the battery as a whole.

[0044] The thermal strategy logic 100 may also check the value of the priority channel, contactor or relay status, current limit, or other parameters. Additionally, in some embodiments, the thermal strategy logic 100 may check that the bus contactor is closed, where the bus contactor needs to be closed to activate the heater pad. In some embodiments, the thermal strategy logic 100 may check that the bus disconnect warning is not active. In some embodiments, the thermal strategy logic 100 may check whether the pre-charge has completed successfully. The thermal strategy logic 100 may perform other checks before enabling the heating device.

[0045] As described above, the cell thermal model 200, the heating device model 300, and the thermal strategy logic 100 can be executed for a cell, module, or battery. The heating device can be configured to heat a cell, module, or battery. In the case where the heating device is configured to heat a cell or module, there can be more than one heating device for the battery. For example, if the heating device is configured to heat a module and the battery includes more than one module, then there can be one heating device for each module of the battery. In the case where each module includes more than one cell, the method for thermal management of the module as a whole can take into account the minimum and maximum cell temperatures of each cell and / or the temperature difference across more than one cell of the module. For example, the calculation of uncertainty can take into account the temperature difference between more than one cell of the module. However, for the module as a whole, the heating device can be enabled or disabled.

[0046] In some embodiments, the heating device may include an electric heater pad, such as a PTC heater pad. The battery may be passively cooled or actively cooled. In addition, there may be a cooling system for the battery, such as a cooling plate or a liquid coolant loop. In the case where the battery is passively cooled or in the case where the battery is actively cooled, the heating device model may also receive as input the coolant temperature and the coolant heat transfer coefficient. The heating device model may calculate the input power to the heater pad, the heat rejection to the battery cell or module, and the heat rejection to the cooling system or to the surrounding environment. This will refer to Figure 6 and Figure 7 Provide a description.

[0047] As described above, the heating device model can estimate the heating device temperature through a thermodynamic energy balance. In the example, where the heating device includes a PTC electric heater pad, the heater pad can be assumed to be 2D. In this example, it can be assumed that the heat from the heater generates a cooling path to the battery cell or a cooling plate, and the interaction of the heater pad with any housing or other components is ignored. This example is Figure 6, where a battery module 610 including cells is heated by a heater pad 620 located between the module 610 and a coolant plate 630. Heat can be transferred between the coolant plate 630 and the surrounding atmosphere. The heat generated by the heater pad can be given by:

[0048]

[0049] Among them I PTC is the current consumption of the heater pad and V module is the voltage of the battery module 610 (where the battery powers the heater pad). The heat transferred from the heater pad 620 to the module 610 can be given by:

[0050]

[0051] where h PTC cell is the heat transfer coefficient between the heater pad 620 and the cells of the module 610, A PTC cell is the interface area between the heater pad 620 and the module 610, T PTC is the temperature of the heater pad 620, and T cell is the temperature of module 610. Similarly, the heat transferred from the heater pad 620 to the cooling path via the cooling plate 630 can be given by:

[0052]

[0053] Among them, h PTC amb is the heat transfer coefficient between the heater pad and the surrounding atmosphere, A PTC amb is the interface area between the heater pad 620 and the coolant plate 630, T PTC is the temperature of the heater pad 620, and T amb is the ambient temperature. amb The measurement can be taken when the battery management system is on. In one example, the battery can be used to power an electric vehicle, and T amb The measurement can be performed with the vehicle's key on.

[0054] Reference Figure 7 , shows an example of a heating device model 700 that incorporates heat rejection into the environment. Figure 7 A shows a high level model of the heating device 700. The three main blocks are heat removal to the module or cell 710, heater input power 720, and heat removal to the environment 730. Figure 7 B and Figure 7C shows blocks 710 and 730 in more detail. Figure 7 A, block 710 may calculate This is passed to the final output 760, which is the heat rejected to the cell (or module). Block 720 outputs the heating device input power 721. Block 730 can calculate This is passed to the final output 780, which is the heat rejected to the surrounding environment or cooling path. At 740, the heat rejection to the cell is subtracted from the input power of the heating device. and heat rejection to the environment The temperature of the heating device is calculated at 750. The temperature of the heating device is output at 770 and is also passed back to blocks 710 and 730. Figure 7 B shows block 710. The input may be the cell temperature 711 which is subtracted from the temperature of the heating device at 712 (passed back to block 750) to provide the temperature difference (T) between the heating device and the cell at 713. PTC -T cell ). In 716, Is to use the temperature difference 713, heating surface area 714 (A PTC cell ) and the heat transfer coefficient between the heating device and the battery cell is 715 (h PTC cell ) is calculated. Figure 7 Block 730 is shown in C. The input may be the ambient temperature 731 which is subtracted from the temperature of the heating device at 732 (passed back to block 750) to provide the temperature difference (T) between the heating device and the environment at 733. PTC -T amb ). At 736, Is to use the temperature difference 733, heating surface area 734 (A PTC amb ) and the heat transfer coefficient between the heating device and the environment 735 (h PTC amb ) to calculate.

[0055] Figure 8An example of thermal strategy logic 800 is shown, in which the heating device includes an electric heater pad and the first parameter is the heater pad current. At Boolean operation 813, the maximum cell temperature 811 is compared to an upper cell temperature threshold 812. If the maximum cell temperature 811 is lower than the upper cell temperature threshold 812, a "true" output is output; if the maximum cell temperature 811 is higher than the upper cell temperature threshold 812, a "false" output is output. At Boolean operation 823, the minimum cell temperature 821 is compared to a lower cell temperature threshold 822. If the minimum cell temperature 821 is lower than the lower cell temperature threshold 822, a "true" output is output; if the minimum cell temperature 821 is higher than the lower cell temperature threshold 822, a "false" output is output. If both 813 and 823 output "true", then Boolean operation 814 outputs "true". If either or both 813 and 823 output "false", then Boolean operation 814 outputs "false". At 833, the heater pad current 832 is subtracted from the current limit 831. At Boolean operation 835, the current difference is compared to the current reserve 834. If the current difference is greater than the current reserve, "true" is output, and if the current difference is less than the current reserve, "false" is output. In Boolean operation 843, the minimum cell state of charge 841 is compared to the state of charge threshold 842. If the minimum cell state of charge 841 is greater than the state of charge threshold, operation 843 outputs "true", and if the minimum cell state of charge 841 is less than the state of charge threshold, operation 843 outputs "false". If operations 814, 835 and 843 all output "true", then Boolean operation 850 outputs "true". If Boolean operation 850 outputs "true", then a signal is output at 860 to instruct the heater pad to heat the cell (or module). If one or more of operations 814, 835 and 843 output "false", then Boolean operation 850 outputs "false". If the Boolean operation 850 outputs "false," then a signal is output at 860 to instruct the heater pad not to heat the cell (or module). The Boolean operations 814 and 850 may occur in parallel or in combination.

[0056] Figure 9 Shown with Figure 8 Thermal strategy logic 800 is shown similar to thermal strategy logic 900, but with hysteresis added to the lower cell temperature threshold 822. Hysteresis upper limit 824 and hysteresis lower limit 825 are input to 826 along with the signal to heater pad 860. The hysteresis calculated at 826 is added to the lower cell temperature threshold at 827. This sum is then input to operation 823. Hysteresis may also be added to the upper cell temperature threshold 812.

[0057] The heating device may include other heating devices instead of the heater pad, such as a thermoelectric heat pump (or Peltier heater), immersion heating, a liquid heating loop or air heating. For example, an immersion heating element may use a valve to control the heating of an individual battery module. The methods for these devices will be similar, but different first parameters may be used. When an electric current is applied, the Peltier heater transfers heat from one side of the device to the other. The direction of heat transfer depends on the direction of the current. Typically, a Peltier heater includes alternating p-type and n-type semiconductors arranged between two thermally conductive plates. Similar to the heater pad, the first parameter may include the applied current. The thermal strategy logic may compare the current to a threshold, where a current below the threshold is a condition for enabling the heating device. For immersion heating, a liquid heating loop or air heating, the first parameter may include the flow rate (flow regulation may occur via a valve) or an output from a temperature sensor.

[0058] According to an embodiment of the present invention, a thermal management device for a battery is provided, wherein the battery includes at least one battery cell, and wherein the thermal management device includes a heating device configured to heat the battery in response to a heating instruction. The thermal management device also includes a controller. The thermal management device is configured to perform any of the methods discussed herein. The thermal management device may include a battery management system configured to determine a thermal strategy and control the heating device.

[0059] In one embodiment, a battery can be used to power an electric work vehicle. The battery can include more than one module, each module including more than one battery cell, and each module being provided with a heating device. The battery management system can be configured to individually control each heating device.

Claims

1. A method for thermal management of a battery, wherein the battery comprises at least one battery cell, and wherein a heating device is configured to heat the battery in response to a heating instruction, the method comprising: determining a state of charge of the battery cell; determining a cell current of the cell; determining a first value of a first parameter of the heating device; determining a reference cell temperature of the cell; determining a maximum cell temperature and a minimum cell temperature of the battery cell by comparing the cell current and the first value of the first parameter to test data correlating calibrated values of the cell current and the first parameter with one or more temperature errors; as well as determining a temperature of the heating device using the reference cell temperature, an ambient temperature, and a heat transfer coefficient of the heating device, and determining a second value of the first parameter of the heating device using the temperature of the heating device; In the following cases: The maximum battery cell temperature is lower than a first threshold temperature; The minimum cell temperature of the cell is lower than a second threshold temperature; and The state of charge of the battery cell is higher than a state of charge threshold; The method further includes instructing the heating device to heat the battery cell.

2. The method according to claim 1, wherein in the following cases: The maximum battery cell temperature is lower than a first threshold temperature; The minimum cell temperature of the cell is lower than a second threshold temperature; The state of charge of the battery cell is higher than a state of charge threshold; and the second value of the first parameter is below a threshold; The method further includes instructing the heating device to heat the battery cell.

3. The method according to claim 1 or 2, wherein in the following cases: The maximum battery cell temperature is higher than a first threshold temperature; or The minimum cell temperature of the cell is higher than a second threshold temperature; or The state of charge of the battery cell is lower than a state of charge threshold; The method further includes instructing the heating device to not heat the battery cell.

4. The method according to any one of the preceding claims, wherein in the following cases: The maximum battery cell temperature is higher than a first threshold temperature; or The minimum cell temperature of the cell is higher than a second threshold temperature; or The state of charge of the battery cell is lower than a state of charge threshold; or the second value of the first parameter is above a threshold; The method further includes instructing the heating device to not heat the battery cell.

5. A method according to any one of the preceding claims, wherein hysteresis is added to the first threshold temperature.

6. The method according to any of the preceding claims, wherein hysteresis is added to the second threshold temperature.

7. The method of any one of the preceding claims, wherein determining the temperature of the heating device using the reference cell temperature, the ambient temperature, and the heat transfer coefficient of the heating device comprises: The heat transfer from the heating device to the battery cell is calculated, and the heat transfer from the heating device to the environment is calculated.

8. A method according to any preceding claim, wherein the first parameter comprises an input current.

9. The method of claim 8, wherein the heating device comprises a heater pad configured to emit heat in response to an input current.

10. The method of claim 9, wherein the battery comprises one or more battery modules, each of the battery modules comprising more than one battery cell, and wherein the heating device comprises a heater pad for each battery module, each heater pad being configured to heat the battery module.

11. The method of claim 8, wherein the heating device comprises a thermoelectric heat pump.

12. The method of any one of claims 1 to 7, wherein the heating device comprises a fluid heating system. The method of claim 12 , wherein the first parameter comprises flow rate.

14. A thermal management device for a battery, wherein the battery comprises at least one battery cell, and wherein the thermal management device comprises a heating device configured to heat the battery in response to a heating instruction, and a controller, wherein the thermal management device is configured to: determining a state of charge of the battery cell; determining a cell current of the cell; determining a first value of a first parameter of the heating device; determining a reference cell temperature of the cell; determining a maximum cell temperature and a minimum cell temperature of the battery cell by comparing the cell current and the first value of the first parameter to test data correlating calibrated values of the cell current and the first parameter with one or more temperature errors; as well as determining a temperature of the heating device using the reference cell temperature, an ambient temperature, and a heat transfer coefficient of the heating device, and determining a second value of the first parameter of the heating device using the temperature of the heating device; In the following cases: The maximum battery cell temperature is lower than a first threshold temperature; The minimum cell temperature of the cell is lower than a second threshold temperature; and The state of charge of the battery cell is higher than a state of charge threshold; The thermal management device is further configured to instruct the heating device to heat the battery cell.

15. The thermal management device of claim 14, wherein in the following cases: The maximum battery cell temperature is lower than a first threshold temperature; The minimum cell temperature of the cell is lower than a second threshold temperature; The state of charge of the battery cell is higher than a state of charge threshold; and the second value of the first parameter is below a threshold; The thermal management device is further configured to instruct the heating device to heat the battery cell.

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