Battery for cordless outdoor products

Abstract

The present disclosure relates to a heating system for a battery assembly configured to power a cordless power tool. In some embodiments, the heating system includes a temperature sensor configured to output one or more signals corresponding to a temperature of one or more battery cells of the battery assembly, a heater configured to heat the one or more battery cells, and a battery management system configured to determine the temperature of the one or more battery cells. In some embodiments, the one or more battery cells are configured to power the heater. In some embodiments, the battery management system is configured to activate the heater when the temperature of the one or more battery cells is less than a temperature threshold.

Description

Technical Field

[0001] This disclosure relates to a battery assembly, and more specifically to a battery assembly having a heater to warm a battery used in cordless outdoor products. Background Technology

[0002] Batteries power a variety of electric devices, including cordless power tools such as blowers and chainsaws. These devices may be exposed to cold environments (e.g., below 0°C). The internal chemistry of the battery may hinder efficient and safe charging in cold environments. Summary of the Invention

[0003] This disclosure describes a battery and a heating system configured to warm a battery assembly for use in cordless power tools. In some embodiments, the battery assembly includes battery cells. In some embodiments, the heating system includes a heater powered by the battery assembly, the heater being configured to warm the battery cells to a predetermined temperature. In some embodiments, a battery management system is configured to control the current flowing from the battery cells to the heater, and to control the current flowing from the charger to the battery cells. The batteries and heating systems disclosed herein can be used in a variety of cordless power tools, including but not limited to blowers (e.g., leaf blowers, snow blowers), chainsaws (e.g., sliding miter saws), drills, lawnmowers, hedge trimmers, cord trimmers, edge trimmers, and pressure washers.

[0004] In some embodiments, the heating system includes: a temperature sensor configured to output one or more signals corresponding to the temperature of one or more battery cells of the battery assembly; a heater configured to heat the one or more battery cells; and a battery management system configured to determine the temperature of the one or more battery cells. In some embodiments, the one or more battery cells are configured to supply power to the heater. In some embodiments, the battery management system is configured to activate the heater when the temperature of the one or more battery cells is below a temperature threshold.

[0005] In some embodiments, the battery management system is configured to prevent one or more battery cells from charging when the temperature of one or more battery cells is below a temperature threshold. In some embodiments, the battery management system is configured to allow one or more battery cells to charge when the temperature of one or more battery cells is greater than or equal to a temperature threshold.

[0006] In some embodiments, the heater includes a resistance heating element spaced less than 3 inches from the outer surface of one or more battery cells. In some embodiments, the resistance heating element is in direct contact with the outer surface of one or more battery cells. In some embodiments, the battery assembly includes a housing surrounding one or more battery cells, and at least a portion of the resistance heating element is disposed within the housing. In some embodiments, the battery assembly includes a housing surrounding one or more battery cells, and at least a portion of the resistance heating element is embedded in the peripheral wall of the housing. In some embodiments, the resistance heating element is formed of a material having a resistivity of less than or equal to 10⁻⁷ Ω·m at 20°C.

[0007] In some implementations, the battery assembly, heater, and battery management system are arranged inside the battery pack, and the battery pack is configured to be removably connected to the wireless power tool.

[0008] In some embodiments, a first signal among one or more signals corresponding to the temperature of one or more battery cells corresponds to the temperature of the coldest battery cell among the one or more battery cells. In some embodiments, a second signal among one or more signals corresponding to the temperature of one or more battery cells corresponds to the temperature of the hottest battery cell among the one or more battery cells.

[0009] In some embodiments, this disclosure includes a charging system for cordless power tools. In some embodiments, the charging system includes a battery assembly comprising one or more battery cells and configured to power the cordless power tool. In some embodiments, the charging system includes a heating system comprising: a temperature sensor configured to output a signal corresponding to the temperature of the one or more battery cells; and a battery management system configured to determine the temperature of the one or more battery cells. In some embodiments, the charging system includes a charger configured to charge the one or more battery cells. In some embodiments, the one or more battery cells are configured to power a heater. In some embodiments, the battery management system is configured to prevent charging of the one or more battery cells when the temperature of the one or more battery cells is below a first temperature threshold, and the battery management system is configured to activate the heater when the temperature of the one or more battery cells is below the first temperature threshold.

[0010] In some embodiments, the battery management system charges one or more battery cells at a first rate when the temperature of one or more battery cells is between a first temperature threshold and a second temperature threshold. In some embodiments, the battery management system charges one or more battery cells at a second rate when the temperature of one or more battery cells is greater than or equal to the second temperature threshold. In some embodiments, the first rate is less than or equal to 1 ampere, and the second rate is greater than or equal to 3 amperes. In some embodiments, the first temperature threshold is greater than or equal to 0°C. In some embodiments, the first temperature threshold is greater than or equal to 10°C.

[0011] In some embodiments, the charging system includes an ambient temperature sensor configured to output a signal corresponding to the ambient temperature. In some embodiments, the battery management system is configured to determine the temperature of one or more battery cells based on the ambient temperature.

[0012] In some implementations, the battery management system is configured to determine the temperature of one or more battery cells based on a thermal model. In other implementations, the battery management system is configured to adjust a temperature threshold based on the heating rate of one or more battery cells. Attached Figure Description

[0013] Figure 1 This is a system diagram of the charging system according to the implementation method;

[0014] Figure 2 This is a circuit diagram of the charging system according to the implementation method;

[0015] Figure 3 This is a block diagram of a charging system according to an implementation method;

[0016] Figure 4 This is a block diagram of a charging system according to an implementation method;

[0017] Figure 5A This is a system diagram of the heating system according to the implementation method;

[0018] Figure 5B This is a system diagram of the heating system according to the implementation method;

[0019] Figure 6 This is a system diagram of the heating system according to the implementation method;

[0020] Figure 7 This is a flowchart of the heating method according to the implementation method; and

[0021] Figure 8 This is a flowchart of a heating method according to an embodiment. Detailed Implementation

[0022] Batteries (such as lithium-ion batteries) are widely used in indoor household appliances because they are highly reliable, affordable, and typically have high power density. However, lithium-ion batteries exhibit reduced performance (e.g., charging and discharging rates) in cold environments (e.g., below 0°C). For example, users of cordless power tools (such as snow blowers or chainsaws) can bring the battery or the entire tool indoors for efficient and safe charging. This can be inconvenient, for example, if the user is not near their home or in an unheated garage. Charging lithium-ion batteries below, for example, -20°C can reduce battery life (e.g., capacitor life) over continuous charging cycles.

[0023] This disclosure includes a battery heating system configured to warm the battery assembly. Warming the battery assembly can mitigate capacitance reduction during charge and discharge cycles without increasing charging time in a manner that impacts user experience. Compared to battery heating systems present in, for example, electric vehicles, the heating system disclosed herein can have a lower size, weight, and power per unit area (SWaP) relative to battery power and capacitance. As discussed in more detail below, the low SWaP heater disclosed herein can warm the battery assembly without significantly affecting the weight or cost of cordless power tools.

[0024] Embodiments of this disclosure are described in detail with reference to embodiments illustrated in the accompanying drawings. References to “one embodiment,” “implementation,” “some embodiments,” etc., indicate that the described embodiments(s) may include a particular feature, structure, or characteristic, but each embodiment may not necessarily include that particular feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Additionally, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is believed that in conjunction with other embodiments, whether explicitly described or not, the influence of such feature, structure, or characteristic on it is within the knowledge of those skilled in the art.

[0025] For ease of description, spatial relative terms such as “below,” “under,” “lower,” “above,” “on,” “upper,” and “opposite” are used herein to describe the relationship between one element or feature and another, as shown in the figures. In addition to the orientations shown in the figures, the spatial relative terms are intended to cover different orientations of the device during use or operation. The device may be oriented in other ways (e.g., rotated 90 degrees or in other orientations), and the spatial relative descriptors used herein shall be interpreted accordingly.

[0026] As used herein, the terms “about” or “substantially” indicate a value of a given quantity that may vary based on a particular technique. Based on a particular technique, the terms “about” or “substantially” may indicate a value of a given quantity that varies, for example, within 1-15% of that value (e.g., ±1%, ±2%, ±5%, ±10%, or ±15% of that value). As used herein, the term “between” indicates an inclusive range.

[0027] The following examples are illustrative and not limiting examples of this implementation. Other suitable modifications and adjustments to various conditions and parameters that are commonly encountered in the art and will be obvious to those skilled in the art are within the spirit and scope of this disclosure.

[0028] In some implementations, for example, Figure 1 As shown, the charging environment 10 includes a cordless power tool 100, a battery assembly 200, a heater 220, and a charger 300. In some embodiments, the battery assembly 200 includes a housing 210 and one or more battery cells 205 disposed within the housing 210. In some embodiments, a battery management system 215 is configured, for example, to control the current between the charger 300 and the battery assembly 200 and / or between the battery assembly 200 and the heater 220. In some embodiments, the battery management system 215 includes, for example, a printed circuit board (PCB). The PCB can control the heating and charging of the battery assembly 200 by, for example, determining the temperature of the battery cells 205, comparing the temperature of the battery cells 205 with a threshold temperature, turning the heater 220 on or off, and closing or opening a charging switch to allow or prevent charging, respectively. In some embodiments, a temperature sensor 225 is connected to one or more battery cells 205 and is configured to output a signal to the battery management system 215 corresponding to the temperature of one or more battery cells 205. In some embodiments, the temperature sensor 225 includes one or more sensors. In some implementations, the battery management system 215 is configured to receive a signal corresponding to the temperature of one or more battery cells 205.

[0029] In some embodiments, the battery assembly 200 includes a plurality of temperature sensors 225 configured to output the temperature of one or more battery cells 205. In some embodiments, the battery assembly 200 includes a temperature sensor configured to output the ambient temperature.

[0030] In some embodiments, the battery assembly 200 has a voltage between 10 volts and 120 volts. In some embodiments, the battery assembly 200 has a voltage less than 100 volts, less than 80 volts, less than 60 volts, less than 40 volts, or less than 20 volts. In some embodiments, the battery assembly 200 has a capacitance between 1 ampere-hour and 30 ampere-hours. In some embodiments, the battery assembly 200 has a capacitance less than 25 ampere-hours, less than 20 ampere-hours, less than 15 ampere-hours, less than 10 ampere-hours, or less than 5 ampere-hours. In some embodiments, the battery assembly has a capacitance less than 8 ampere-hours, less than 6 ampere-hours, less than 4 ampere-hours, or less than 2 ampere-hours. In some embodiments, the battery assembly 200 is configured to receive a charging current between 1 ampere and 8 amperes. In some embodiments, the battery assembly 200 is configured to receive a charging current between 1 ampere and 4 amperes or between 4 amperes and 8 amperes.

[0031] A relatively low charging rate (e.g., compared to 40 amps for a 30 amp-hour battery in an electric vehicle) is sufficient because users typically do not plan to operate the cordless power tool 100 shortly after the battery is depleted (e.g., 30 minutes). In contrast, electric vehicles require batteries capable of charging at high rates, minimizing the time the driver spends at charging stations, for example. Therefore, the heater 220 (e.g., a low-SWaP heater) can maintain an acceptable charging time, despite including the heating time when the battery assembly 200 is not charging. Although using the low-SWaP heater 220 increases charging time, it should not affect user satisfaction with the cordless power tool 100. Specifically, the increase in charging time introduced by the low-SWaP heater 220 will not affect the user experience because the charging time remains on the same order of magnitude as charging without heating. That is, if the charging time remains several hours, rather than, for example, several minutes, the user is unlikely to perceive the increase in charging time. In contrast, users of electric vehicles accustomed to, for example, a 40-minute charging time will be more likely to notice their charging time increasing to over an hour. In other words, any increase in charging time introduced by the low SWAP heater 220 is a fraction of the standard charging time (e.g., without heating).

[0032] In some embodiments, the battery assembly 200 is charged in a normalized charging time of less than 1.2, where the normalized charging time is the ratio between the charging time of the battery assembly 200 (including heating and charging time) and the standard calculated charging time (capacity, Ah / charging rate, A) without heating. The charging time of the battery assembly 200 includes the time spent heating the battery cell 205 from -20°C to a temperature threshold (e.g., a safe charging temperature) at an ambient temperature of -20°C. In other words, the time spent heating the battery assembly 200 (starting at a battery cell 205 temperature of -20°C and an ambient temperature of -20°C) and fully charging is less than 120% (i.e., 20% slower) of the standard calculated charging time (i.e., without heating). In some embodiments, the normalized charging time is between 1 and 1.05, between 1.05 and 1.1, between 1.1 and 1.15, or between 1.15 and 1.2. In some embodiments, as discussed in detail below, the normalized charging time is between 0.9 and 1.1.

[0033] In some embodiments, the battery assembly 200 weighs less than 20 pounds. In some embodiments, the battery assembly 200 weighs less than 15 pounds, less than 10 pounds, or less than 5 pounds. In some embodiments, the battery assembly 200 weighs less than 8 pounds, less than 6 pounds, less than 4 pounds, or less than 2 pounds. Increasing the weight of the battery assembly 200 may negatively impact the user experience, as users typically carry the cordless power tool 100 (e.g., a chainsaw, snow blower, or drill). Although the low-swap heater 220 may increase charging time, it maintains the weight of the cordless power tool 100 without the heater 220.

[0034] In some implementations, for example, Figure 2As shown, heater 220 is electrically connected to battery assembly 200, allowing current to flow from battery assembly 200 to heater 220. In some embodiments, battery cell 205 can safely discharge at temperatures lower than the safe charging temperature. For example, in some embodiments, battery cell 205 is manufactured to charge at temperatures greater than or equal to 0°C, but can safely discharge at temperatures as low as -20°C. Powering heater 220 from battery assembly 200 facilitates warming battery assembly 200 independently of the power supplied by charger 300 and utilizes the characteristics of the internal chemistry of battery assembly 200 (e.g., the difference between discharge and charge temperatures). In some embodiments, battery assembly 200 is more efficient than charger 300 in powering heater 220. In some embodiments, for example, battery assembly 200 has a higher power density than charger 300. In some embodiments, the instantaneous power supplied by battery assembly 200 to heater 220 is 5-15 times greater than the instantaneous power that charger 300 can supply to heater 220. For example, in some embodiments, the charger 300 is designed to supply power to the battery assembly 200 (e.g., with a lower power density than the battery assembly 200), but is not configured to also supply enough power to operate the heater 220.

[0035] In some embodiments, the battery management system 215 is electrically connected to the heater 220, the battery cell 205, and the temperature sensor 225. In some embodiments, the battery management system 215 is electrically connected to the charger 300. For example, the battery management system 215 may be configured to control (e.g., enable, throttle, stop) the current between the charger 300 and the battery assembly 200, and the current between the battery assembly 200 and the heater 220.

[0036] In some implementations, for example, Figure 2 As shown, the battery management system 215 is configured to switch between heating switch 224 and / or charging switch 302. For example, if the temperature of battery assembly 200 is below a threshold temperature, the battery management system 215 can close heating switch 224, thereby allowing current to flow between battery assembly 200 and heater 220. Furthermore, heater 220 can warm battery assembly 200 until it reaches the temperature threshold. If battery assembly 200 reaches the temperature threshold, heater 220 can open heating switch 224 and close charging switch 302 to allow current to flow between charger 300 and battery assembly 200. In some embodiments, heating switch 224 and / or charging switch 302 are field-effect transistors (e.g., MOSFETs). Heating switch 224 and charging switch 302 can be any type of switch operable to switch current between charger 300 and battery 200 and between battery 200 and heater 220.

[0037] In some implementations, for example, Figure 3 As shown, the battery assembly 200 is arranged inside the cordless power tool, and the battery assembly 200 is not removable. For example, in some embodiments, when the cordless power tool 100 is connected to the charger 300, the battery assembly 200 remains inside the cordless power tool 100, and the user cannot easily remove the battery assembly 200 (e.g., without the tool).

[0038] In some implementations, for example, Figure 4 As shown, battery assembly 200 is arranged inside battery pack 230, which is configured to be removably connected to cordless power tool 100 and charger 300. In some embodiments, battery cell 205, housing 210, battery management system 215 and / or temperature sensor 225 are arranged inside battery pack 230.

[0039] In some implementations, for example, Figures 3-4 As shown, the battery assembly 200 includes a housing 210 surrounding the battery cell 205. In some embodiments, the housing 210 is, for example, a polyvinyl chloride (PVC) enclosure (e.g., a shrink wrap). In some embodiments, the housing 210 is, for example, formed of rigid plastic.

[0040] In some implementations, for example, Figures 5A-5B As shown, the battery assembly is disposed inside the cordless power tool 100 and is not removable (as described above), and the heater 220 includes a heating element 222 inside the cordless power tool 100. In some embodiments, the heating element 222 includes one or more elements (e.g., a coil, a space heater, etc.). In some embodiments, for example, as... Figure 5A As shown, the heating element 222 is in direct contact with one or more battery cells 205. For example, in some embodiments, the heating element 222 is a coil wound around the battery cell 205. This direct contact between the heating element 222 and the battery cell 205 allows for simple and low-cost integration of the heater 220 into the battery assembly 200, where, for example, the battery assembly 200 is non-removable and therefore its visual appearance is concealed. In some embodiments, the direct contact (e.g., winding) between the heating element 222 and the battery cell 205 alleviates size / volume constraints on the battery assembly 200 because the heating element 222 is mounted directly to the exterior of the battery cell 205, rather than in a separate mounting location inside the cordless power tool 100.

[0041] In some implementations, for example, Figure 5BAs shown, heating element 222 is spaced apart from battery cell 205. In some embodiments, heating element 222 is, for example, a positive temperature coefficient (PTC) space heater. In some embodiments, heating element 222 is positioned approximately 0.5 inches to 3 inches from the exterior of battery cell 205. In some embodiments, heating element 222 is spaced 1 inch to 3 inches from the exterior of battery cell 205. In some embodiments, heating element 222 is spaced 2 inches to 3 inches from the exterior of battery cell 205. The spacing between heating element 222 and battery cell 205 can, for example, uniformly heat battery cell 205. The spacing between battery cell 205 and heating element 222 can reduce manufacturing complexity by positioning heating element 222 in an easily accessible (e.g., by hand) area inside cordless power tool 100.

[0042] In some implementations, for example, Figure 6 As shown, heater 220 includes a heating element 222 embedded within housing 210. Embedding the heating element 222 within housing 210 can reduce the increase in volume of battery assembly 200. For example, embedding the heating element 222 within the wall of housing 210 can make housing 210 thicker (compared to a housing without an embedded heating element), but the increased thickness can have a smaller impact on the volume of battery assembly 200 than the impact of increasing the internal volume of housing 210 to accommodate the heating element 222 and associated mounting features.

[0043] although Figures 5A-6 A battery assembly 200 is shown in either a removable or non-removable configuration; however, the heating element 222 disclosed herein, relative to, for example, the battery cell 205, can be applied to both removable and non-removable configurations. In some embodiments, for example, the battery cell 205 is embedded in a housing 210 in a non-removable configuration. In some embodiments, in both non-removable and removable configurations, the housing 210 isolates the battery cell 205 from potential damage (e.g., water leaking from a pump inside a pressure washer).

[0044] In some implementations, for example, Figure 6 As shown, the battery pack 230 includes an insulating portion 232, allowing a user to comfortably hold or touch the battery pack 230 when, for example, the heating element 222 is energized. In some embodiments, the insulating portion 232 includes one or more materials to absorb heat. For example, in some embodiments, the insulating portion 232 includes rubber, foam, plastic, and / or any other material to insulate the exterior of the battery assembly 200 (e.g., the part in contact with the user's hand) from the heat generated by the heater 220.

[0045] In some embodiments, the heating element 222 is made of a lightweight (e.g., atomic mass unit less than 80) and low resistivity metal alloy, such as copper (1.68 × 10⁻⁶ at 20°C). -8 Ω·m), aluminum (2.65×10 at 20℃) -8 Ω·m), iron (9.71×10 at 20℃) -8 (Ω·m) or any combination thereof (e.g., copper-nickel alloy). The lightweight and low resistivity heating element 222 reduces the power of the heater 220 and, conversely, reduces the need for the battery cell 205 to power the heater 220, while also reducing the increase in weight of the cordless power tool 100.

[0046] For example, in some embodiments, heater 220 is configured to draw less than 2 amps from battery cell 205. In some embodiments, heater is configured to draw less than 1.5 amps, less than 1 amp, or less than 0.5 amps from battery cell 205. Even small variations in current draw will affect the power of heater 220, as power is directly related to the square of current. Although a low-power heater 220 may require more time to warm battery cell 205, the increase in charging time will actually be negligible because, as mentioned above, the charging time remains within the same order of magnitude (e.g., several hours, rather than tens of hours), making it not alter the user experience.

[0047] In some embodiments, the heating element 222 is made of a high resistivity material and / or a metal alloy, such as carbon fiber (between 2 Ω·m and 20 Ω·m at 20°C) and nickel-chromium alloy (1.5 × 10⁻⁶ at 20°C). -6 (Ω·m). In some embodiments, the heating element 222 is a metal-ceramic heater (e.g., a PTC heater encapsulated as a heating plate) made of a high-resistivity material, such as a ceramic-metal composite. A heating element 222 made of a high-resistivity material can output similar power (e.g., heat) to a heating element 222 formed of a low-resistivity material because power is directly related to the square of the current and the resistance. A higher-resistivity heating element 222 can output similar power to a lower-resistivity heating element 222 while drawing less current (e.g., lower voltage). Lower current drawing (e.g., lower voltage) can reduce the weight increase of the cordless power tool 100 while generating sufficient heat to warm the battery cell 205.

[0048] As described above, the components discussed herein are operable to warm the battery cell 205, allowing the user to safely charge the battery assembly 200 in cold environments and mitigating the reduction in capacitance of the battery assembly 200 during charging cycles performed in cold environments. In some embodiments, for example, as Figure 7As shown, the battery management system 215 is configured to perform the battery heating method 700. In some embodiments, the battery heating method 700 is initialized when, for example, the battery assembly 200 is electrically connected to the charger 300.

[0049] In some embodiments, the battery heating method 700 determines the temperature of the battery cell 205. In some embodiments, the battery management system 215 determines the temperature of the battery cell 205 based on a signal output by the temperature sensor 225.

[0050] In some implementations, for example, temperature sensor 225 outputs a signal to battery management system 215 corresponding to the average temperature of battery assembly 200, the external temperature of one or more battery cells 205 arranged in battery assembly 200, ambient temperature, or any combination thereof.

[0051] For example, in some embodiments, temperature sensor 225 is configured to output the temperature of the coldest and / or hottest battery cell among one or more battery cells 205. For instance, a thermal map can identify which battery cells among one or more battery cells 205 are typically the coldest and hottest. During, for example, assembly of battery pack 230 or cordless power tool 100, temperature sensor 225 may be connected to the coldest and / or hottest battery cell among one or more battery cells 205 (based on the thermal map).

[0052] In some embodiments, the battery management system 215 includes a thermal model that dynamically estimates the average cell temperature and / or the temperature of each individual cell of one or more battery cells 205. In some embodiments, the thermal model includes, for example, a Kalman filter, a Markov process, and / or an uncertainty model (e.g., Gaussian, nonlinear) to estimate the cell temperature of one or more battery cells 205. In some embodiments, the battery management system 215 compares the estimated temperature from the thermal model, a heatmap, a signal from the temperature sensor 225 corresponding to the external cell temperature and / or ambient temperature, or any combination thereof. Accurately determining the temperature of one or more battery cells 205 can mitigate premature heating and / or charging, which can help reduce battery capacitance and lifespan during charge cycles.

[0053] In some implementations, the battery management system 215 determines whether the temperature of the battery cell 205 (710) is below a predetermined temperature threshold. If the temperature of the battery assembly 200 is below the predetermined temperature threshold, the heater 220 warms the battery cell 205 (715) and / or prevents the battery cell 205 from charging.

[0054] The threshold temperature may correspond to, for example, the minimum battery cell temperature required for charging. In some embodiments, the threshold temperature is 0°C. In some embodiments, the threshold temperature is between -20°C and 10°C. In some embodiments, the threshold temperature is between -20°C and -15°C, -15°C and -10°C, -10°C and -5°C, -5°C and 0°C, 0°C and 5°C, or 5°C and 10°C. For example, some manufacturers recommend avoiding charging the lithium battery when the battery cell 205 temperature is below 0°C and avoiding fast charging (e.g., 4 amps) when the battery cell 205 temperature is below 10°C. Conversely, warming the battery assembly 200 to, for example, 10°C (715°C) can facilitate earlier fast charging, thereby reducing the total charging time and mitigating the impact on the battery assembly 200's lifespan and capacitance.

[0055] In some implementations, the battery management system 215 dynamically adjusts a temperature threshold based on, for example, the temperature of the battery cell 205 and / or the ambient temperature when the battery assembly 200 is connected to the charger 300. Dynamically adjusting the temperature threshold based on the initial temperature of the battery cell 205 balances the work done by the battery cell 205 to power the heater 220 with charging time and battery health. In one example, when the battery assembly 200 is connected to the charger 300, the temperature of the battery cell 205 is -20°C, and the battery management system 215 sets the temperature threshold to 0°C. In another example, when the battery assembly 200 is connected to the charger 300, the temperature of the battery cell 205 is -2°C, and the battery management system 215 sets the temperature threshold to 10°C.

[0056] In some implementations, when battery cell 205 is extremely cold (e.g., below -15°C), for the long-term health of battery cell 205, it is better to warm it to a low-temperature threshold (e.g., 0°C) so that heater 220 no longer draws power from battery cell 205, and battery cell 205 can begin to charge safely, even at a low rate (e.g., 1 amp). In one example, battery cell 205 is moderately cold (e.g., -2°C), and battery cell 205 powers heater 220 until the temperature of battery cell 205 reaches a fast-charging temperature threshold (e.g., 10°C). Because battery cell 205 has a higher initial temperature, battery cell 205 powers heater 220 to a higher threshold temperature without negatively impacting the health of battery cell 205, and then a higher charging rate (e.g., 4 amps) can be utilized to reduce charging time.

[0057] In another example, the ambient temperature is moderately cold (e.g., 5°C), but the battery cell 205 temperature is extremely cold (e.g., -20°C) (e.g., a user brings the battery assembly 200 into a garage where the ambient temperature is higher than the outside air temperature). Even if the battery cell 205 temperature is -20°C, the battery management system 215 can set a temperature threshold of 10°C. By taking the ambient temperature into account, the battery management system 215 can select a temperature threshold that balances the work done by the battery cell 205 to power the heater 220 with charging time and battery health.

[0058] In some embodiments, the battery management system 215 dynamically adjusts the threshold temperature during heating by taking into account, for example, the operating time spent heating the battery cell 205, the heating rate of the battery cell 205, the ambient temperature, deviations from the thermal model, deviations from the estimate (e.g., charging time, heating time), or any combination thereof. For example, in some embodiments, the battery management system 215 sets the temperature threshold to a first value (e.g., 10°C) upon initialization, but adjusts the temperature threshold to a second value (e.g., 0°C) after a predetermined threshold time (e.g., 30 minutes) to balance the work done by the battery cell 205 to power the heater 220 with the charging time and battery health.

[0059] In some implementations, if the battery management system 215 determines that the temperature of battery cell 205 710 is greater than or equal to a predetermined temperature threshold, then the battery management system determines whether heater 220 725 is turned on. If the battery management system 215 determines that heater 220 725 is on (e.g., by closing heating switch 224), then the battery management system 215 turns off heater 730 (e.g., by opening heating switch 224) and allows charger 300 to charge battery cell 205 735 (e.g., by closing charging switch 302). If the battery management system 215 determines that heater 220 725 is off, then the battery management system 215 allows charger 300 to charge battery cell 205 735 (e.g., by closing charging switch 302).

[0060] In some implementations, for example, Figure 8 As shown, the battery management system 215 is configured to perform a two-stage battery heating method 800. In some embodiments, the battery cell 205 is configured to charge at a first rate and a second rate. In some embodiments, the first rate is less than or equal to 1 ampere. In some embodiments, the second rate is greater than or equal to 2 amperes. In some embodiments, the second rate is greater than or equal to 3 amperes.

[0061] In some implementations, as described above, the battery management system 215 determines the temperature of one or more battery cells 205 based on signals output by the temperature sensor 225.

[0062] In some embodiments, the battery management system assesses whether the temperature of the 810 battery cell 205 is below a first predetermined threshold. In some embodiments, the first predetermined temperature corresponds to a safe temperature for charging at a standard charging rate (e.g., 1 ampere). In some embodiments, the first temperature threshold is 0°C. In some embodiments, the first temperature threshold is between -20°C and -5°C. In some embodiments, the threshold temperature is between -20°C and -15°C, -15°C and -10°C, or -10°C and -5°C.

[0063] In some embodiments, if the battery management system 215 assesses that the temperature of battery cell 205 is less than a first predetermined temperature threshold, the heater 220 warms battery cell 205 and / or the battery management system 215 prevents charging. In some embodiments, the battery management system 215 continues to receive signals corresponding to the temperature of battery cell 205 and determines the temperature of battery cell 205.

[0064] In some embodiments, if the battery management system 215 evaluates 810 that the temperature of the battery cell 205 is greater than or equal to a first predetermined temperature threshold, then the battery management system 215 allows the charger 300 to charge the battery cell 205 at a first rate (e.g., 1 ampere) 835. The battery management system may allow the charger 300 to charge the battery cell 205 at the first rate 835 by, for example, switching the charging switch 302 closed and sending a signal to the charger 300 to apply a predetermined charging current. In some embodiments, the battery management system 215 evaluates 825 whether the heater 220 is on. If the battery management system 215 evaluates 825 that the heater 220 is off, then the battery management system 215 allows the charger 300 to charge the battery cell 205 at the first rate 835. If the battery management system 215 evaluates 825 that the heater 220 is on, then the battery management system 215 turns off the heater 220 and allows the charger 300 to charge the battery cell 205 at the first rate 835. In some embodiments, even if the battery management system 215 assesses that the temperature of the battery cell 205 is greater than or equal to a first temperature threshold and assesses that the heater 220 is on, the battery management system 215 keeps the heater 220 on (e.g., without turning off the heating switch 224), so that the heater 220 continues to warm the battery cell 205 while the battery cell 205 is charging at a first rate. For example, in some embodiments, keeping the heater 220 on during charging allows the battery cell 205 to charge while continuing to warm towards a second threshold temperature that is safe for charging at a higher rate (e.g., 4 amps).

[0065] In some embodiments, while battery cell 205 is charging at a first rate 835, battery management system 215 continues to determine the temperature of battery cell 205 and evaluates the temperature of battery cell 205 against a second temperature threshold. In some embodiments, the second temperature threshold corresponds to a temperature safe for fast charging (e.g., 4 amps). In some embodiments, the second temperature threshold is 10°C. In some embodiments, the second temperature threshold is between -5°C and 20°C. In some embodiments, the second temperature threshold is between -5°C and 0°C, 0°C and 5°C, 5°C and 10°C, 10°C and 15°C, or 15°C and 20°C.

[0066] In some implementations, if the battery management system 215 assesses that the temperature of the 845 battery cell 205 is greater than or equal to a second temperature threshold, the battery management system 215 allows the battery cell 205 to be charged at a second rate (e.g., 4 amps) 850. The battery management system 215 can allow the battery cell 205 to be charged at the second rate 850, for example, by sending a signal to the charger 300 to increase the charging current to a predetermined charging current. For example, if the heater 220 remains on while the battery cell 205 is charging at a first rate (e.g., 1 amp), the battery management system 215 can turn off the heater 220 if the battery management system assesses that the temperature of the 845 battery cell 205 is greater than or equal to the second temperature threshold.

[0067] In some embodiments, even if the battery management system 215 prevents charging when the battery cell 205 is below a temperature threshold, the battery assembly 200 charges in a time similar to or less than the standard calculated charging time. For example, in some embodiments, the battery assembly 200 has an 8 amp-hour capacity and is configured to charge at a first rate of 1 amp and a second rate of 4 amps. Using standard charging time calculations (capacitance / charging rate), it would take approximately 8 hours to fully charge the 8 amp-hour battery assembly 200 (i.e., 8AH / 1A) at 1 amp, and approximately 2 hours to fully charge the 8 amp-hour battery assembly 200 (i.e., 8AH / 4A) at 4 amps.

[0068] For example, in some embodiments, battery assembly 200 is charged in a normalized charging time between 0.9 and 1.1 ampere-hours. For example, in some embodiments, battery assembly 200 includes an 8 ampere-hour battery (e.g., battery cell 205) and is configured to charge at a first rate of 1 ampere and a second rate of 4 amperes. In this example, the standard calculated charging rate is 8 hours. In some embodiments, heating and charging battery cell 205 may require 8.4 hours, where the initial battery cell temperature is -20°C and the ambient temperature is -20°C, thus the normalized charging time is 1.05 (i.e., 8.4h / 8h).

[0069] In another example, battery assembly 200 includes a 10 amp-hour battery (e.g., battery cell 205) and is configured to charge at a first rate of 1 amp when the temperature of battery cell 205 is greater than or equal to 0°C, and at a second rate of 4 amps when the temperature of battery cell 205 is greater than or equal to 10°C. In this example, the standard calculated charging rate is 10 hours. In this example, the temperature of battery cell 205 rises from -20°C to 0°C in 4 hours, and battery assembly 200 begins charging at 1 amp. In this example, battery assembly 200 charges at 1 amp for 3.6 hours while the temperature of battery cell 205 rises from 0°C to 10°C, and then battery assembly 200 begins charging at 4 amps. In this example, battery assembly 200 charges at 4 amps for 1.6 hours until it is fully charged, and the total heating and charging time is 9.2 hours. In this example, the normalized charging time is 0.92.

[0070] As described above, charging time can be reduced by increasing the power of heater 220 and conversely by reducing its size and weight. As discussed herein in conjunction with battery management system 215 and battery cell 205, the low SWAP heater 220 maintains charging time in cold environments while protecting capacitor and battery health.

[0071] It should be understood that the Detailed Description section, rather than the Summary and Abstract section, is intended to be used to interpret the claims. The Summary and Abstract section may set forth one or more, but not all, exemplary embodiments of this disclosure as conceived by the inventors, and is therefore not intended to limit this disclosure and the appended claims in any way.

[0072] The present disclosure has been described above using functional building blocks that illustrate the implementation of specified functions and their relationships. For ease of description, the boundaries of these functional building blocks are arbitrarily defined herein. Alternative boundaries can be defined as long as the specified functions and their relationships are properly performed.

[0073] The foregoing description of the specific embodiments so fully reveals the general nature of this disclosure that others, by applying knowledge within the scope of the art, can readily modify and / or adapt such specific embodiments for various applications without departing from the general concept of this disclosure, without excessive experimentation. Therefore, based on the teachings and guidance presented herein, such modifications and alterations are intended to fall within the meaning and scope of equivalents of the disclosed embodiments. It should be understood that the wording or terminology herein is for descriptive and not limiting purposes, and that the terminology or terminology of this specification should be interpreted by those skilled in the art based on the teachings and guidance.

[0074] The breadth and scope of this disclosure should not be limited by any of the exemplary embodiments described above, but should be defined solely by the appended claims and their equivalents.

Claims

1. A heating system for a battery assembly configured to power a cordless power tool, the heating system comprising: A temperature sensor configured to output one or more signals corresponding to the temperature of one or more battery cells of the battery assembly; A heater configured to heat the one or more battery cells; as well as A battery management system is configured to determine the temperature of the one or more battery cells. The one or more battery cells are configured to power the heater, and The battery management system is configured to activate the heater when the temperature of one or more battery cells is below a temperature threshold.

2. The heating system of claim 1, wherein the battery management system is configured to prevent the one or more battery cells from charging when the temperature of the one or more battery cells is less than the temperature threshold.

3. The heating system of claim 2, wherein the battery management system is configured to allow the one or more battery cells to charge when the temperature of the one or more battery cells is greater than or equal to the temperature threshold.

4. The heating system of claim 1, wherein the heater comprises a resistance heating element spaced less than 3 inches from the outer surface of the one or more battery cells.

5. The heating system according to claim 4, wherein the resistance heating element is in direct contact with the outer surface of the one or more battery cells.

6. The heating system of claim 4, wherein the battery assembly includes a housing surrounding the one or more battery cells, and wherein at least a portion of the resistance heating element is disposed inside the housing.

7. The heating system of claim 4, wherein the battery assembly includes a housing surrounding the one or more battery cells, and wherein at least a portion of the resistance heating element is embedded in the peripheral wall of the housing.

8. The heating system according to claim 4, wherein the resistance heating element comprises a component having a strength of less than or equal to 10 at 20°C. -7 Materials with resistivity of Ω·m are formed.

9. The heating system of claim 1, wherein the battery assembly, the heater, and the battery management system are arranged inside the battery pack, and wherein the battery pack is configured to be removably coupled to the cordless power tool.

10. The heating system of claim 1, wherein a first signal of the one or more signals corresponding to the temperature of the one or more battery cells corresponds to the temperature of the coldest battery cell among the one or more battery cells, and wherein a second signal of the one or more signals corresponding to the temperature of the one or more battery cells corresponds to the temperature of the hottest battery cell among the one or more battery cells.

11. A charging system for cordless power tools, comprising: A battery assembly, comprising one or more battery cells and configured to power the cordless power tool; Heating system, comprising: A temperature sensor configured to output a signal corresponding to the temperature of the one or more battery cells, and A battery management system configured to determine the temperature of the one or more battery cells; as well as A charger configured to charge the one or more battery cells. The one or more battery cells are configured to power the heater. The battery management system is configured to prevent the charging of the one or more battery cells when the temperature of the one or more battery cells is below a first temperature threshold. The battery management system is configured to activate the heater when the temperature of the one or more battery cells is below the first temperature threshold.

12. The charging system according to claim 11, wherein, When the temperature of one or more battery cells is greater than or equal to the first temperature threshold and less than the second temperature threshold, the battery management system charges the one or more battery cells at a first rate.

13. The charging system according to claim 12, wherein, When the temperature of one or more battery cells is greater than or equal to the second temperature threshold, the battery management system charges the one or more battery cells at a second rate.

14. The charging system according to claim 13, wherein, The first rate is less than or equal to 1 ampere, and the second rate is greater than or equal to 3 amperes.

15. The charging system of claim 11, wherein the first temperature threshold is greater than or equal to 0°C.

16. The charging system of claim 15, wherein the first temperature threshold is greater than or equal to 10°C.

17. The charging system of claim 11, further comprising an ambient temperature sensor configured to output a signal corresponding to the ambient temperature.

18. The charging system according to claim 17, wherein, The battery management system is configured to determine the temperature of the one or more battery cells based on the ambient temperature.

19. The charging system according to claim 11, wherein, The battery management system is configured to determine the temperature of the one or more battery cells based on a thermal model.

20. The charging system according to claim 11, wherein, The battery management system is configured to adjust the temperature threshold based on the heating rate of the one or more battery cells.

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