METHOD FOR HEATING A BATTERY WITH MIXED CHEMICALS

Abstract

A method for heating a mixed-chemistry battery (200) comprising a first battery cell (208) having a first chemistry and a second battery cell (210) having a second chemistry different from the first chemistry, the method comprising: monitoring the temperature of the mixed-chemistry battery (200); monitoring the first state of charge of the first battery cell (208); monitoring the second state of charge of the second battery cell (210); based on a determination that the temperature is below a minimum threshold, connecting a heating system (206) to supply electrical energy only to the first battery cell (208); based on a determination that the temperature is above an intermediate threshold greater than the minimum threshold, connecting the heating system (206) to supply electrical energy only to the second battery cell (210).and based on a determination that the temperature is above the intermediate threshold, connecting the heating system (206) to supply electrical energy to the first battery cell (208) and to the second battery cell (210); characterized in that the first chemistry is nickel-manganese-cobalt and the second chemistry is lithium-iron-phosphate; wherein, in the case that the temperature is above the intermediate threshold, the heating system (206) is only connected to supply electrical energy to the first battery cell (208) and to the second battery cell (210) if the first state of charge and the second state of charge differ from each other by less than 10%; and wherein the heating system (206) is also connected to supply electrical energy to the first battery cell (208) and to the second battery cell (210) if the temperature is between the minimum threshold and the intermediate threshold.

Description

INTRODUCTION The invention relates to batteries with mixed chemistry. More precisely, the invention relates to a method according to the preamble of claim 1 for heating a battery with mixed chemistry, as is known essentially from US 2014 / 0227568 A1. Further state of the art can also be found in the publications US 2017 / 0 346 089 A1 , JP 2004 - 39 523 A and DE 10 2019 112 552 A1 . Lithium-ion batteries are used in a wide variety of applications, from electric vehicles and household appliances to grid-connected devices. Generally, the term lithium-ion battery refers to a broad range of battery types, each of which charges and discharges through reactions between a lithium-containing metal oxide cathode and a graphite anode. A mixed-chemistry battery, as used here, is a lithium-ion battery that includes battery cells exhibiting at least two different chemical properties. Two of the most commonly used lithium-ion chemistries are nickel-manganese-cobalt (NCM) and lithium iron phosphate (LFP). Generally, LFP batteries are less expensive to manufacture than NCM batteries, and NCM batteries have higher rated power and energy density compared to LFP batteries. NCM batteries generally exhibit better performance at very low temperatures (i.e.,at temperatures below about twenty degrees Celsius) they perform better than LFP batteries. SUMMARY According to the invention, a method for heating a battery with mixed chemistry is presented, characterized by the features of claim 1. In addition to the one or more features described herein, the procedure also includes deactivating the heating system based on a determination that the temperature is above a maximum threshold. In addition to the one or more features described herein, the heating system includes one or more resistance heating layers arranged next to the second battery cell. In addition to the one or more features described herein, the heating system includes a cooling plate located next to the first battery cell and the second battery cell. Furthermore, a mixed-chemistry battery for a vehicle is described. The mixed-chemistry battery comprises a first battery cell having a first chemistry, a second battery cell having a second chemistry that differs from the first, and a sensor configured to measure the temperature of the mixed-chemistry battery. The mixed-chemistry battery also includes a heating system configured to heat the second battery cell and a battery monitoring system configured to selectively connect the heating system to at least one of the first and second battery cells based on the temperature of the mixed-chemistry battery. In addition to the one or more features described herein, the first chemistry is nickel-manganese-cobalt and the second chemistry is lithium-iron-phosphate. In addition to the one or more features described herein, the first battery cell is connected in series with the second battery cell. In addition to the one or more features described herein, the battery monitoring system is configured to connect the heating system only to the first battery cell based on the fact that the temperature is below a first threshold. In addition to the one or more features described herein, the battery monitoring system is configured to connect the heating system to the first battery cell and the second battery cell based on the temperature being at least a first threshold value. In addition to the one or more features described herein, the heating system includes one or more resistance heating layers arranged next to the second battery cell. In addition to the one or more features described herein, the heating system includes a cooling plate located next to the first battery cell and the second battery cell. In addition to the one or more features described herein, the cooling plate is liquid-cooled and includes one or more valves controlled by the battery monitoring system based on the temperature of the mixed-chemistry battery. The aforementioned features and advantages, as well as other features and advantages of the invention, are readily apparent from the following detailed description in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Further features, advantages, and details are listed by way of example only in the following detailed description, which refers to the drawings, wherein: Fig. 1 is a schematic diagram illustrating a vehicle having a mixed-chemistry battery according to an exemplary embodiment; Fig. 2 is a block diagram illustrating a mixed-chemistry battery according to an exemplary embodiment; Fig. 3 is a schematic diagram illustrating a heating system for a mixed-chemistry battery according to an exemplary embodiment; Fig. 4 is a schematic diagram illustrating a heating system for a mixed-chemistry battery according to an exemplary embodiment; Fig. 5 is a schematic diagram illustrating a heating system for a mixed-chemistry battery according to an exemplary embodiment; Fig.Figure 6 is a schematic diagram illustrating a heating system for a mixed-chemistry battery according to an exemplary embodiment; Figure 7 is a flowchart illustrating a method for a heating system for a mixed-chemistry battery according to an exemplary embodiment; and Figure 8 is a flowchart illustrating another method for a heating system for a mixed-chemistry battery according to an exemplary embodiment. DETAILED DESCRIPTION To provide an overview of the aspects of the invention, embodiments of the invention include a mixed-chemistry battery comprising a first battery cell and a second battery cell. The first battery cell is a lithium-ion cell comprising a first chemistry whose state of charge (SOC) varies significantly depending on the open-circuit voltage (VOC), such as nickel-manganese-cobalt (NCM), nickel-cobalt-aluminum (NCA), lithium-ion manganese (LMO), lithium-cobalt (LCO), or the like. The second battery cell is a lithium-ion cell comprising a second chemistry whose SOC does not vary significantly based on its VOC level, such as lithium iron phosphate (LFP), lithium iron manganese phosphate (LFMP), sodium ions, or the like. As already mentioned, NCM batteries exhibit high volatility at very low temperatures (i.e.,At temperatures below approximately 20 degrees Celsius, mixed-chemistry batteries exhibit better performance than LFP batteries. Accordingly, in exemplary embodiments, the mixed-chemistry battery includes a heating system configured to warm the battery cells. In exemplary embodiments, the battery system is selectively powered by one or more of the battery cells, depending on the temperature of the mixed-chemistry battery. With reference to Fig. 1, a schematic diagram of a vehicle 100 for use in conjunction with one or more embodiments of the present invention is shown. The vehicle 100 comprises a mixed-chemistry battery 200. In one embodiment, the vehicle 100 is a hybrid vehicle that uses both an internal combustion engine and an electric motor, which is supplied by the mixed-chemistry battery 200. In another embodiment, the vehicle 100 is an electric vehicle that uses only electric motors, which are supplied by the mixed-chemistry battery 200. With reference to Fig. 2, a block diagram of a mixed-chemistry battery 200 is illustrated according to an exemplary embodiment. As illustrated, the mixed-chemistry battery 200 comprises a battery monitoring system 202, one or more sensors 204, a heating system 206, a first battery cell 208, and a second battery cell 210. In exemplary embodiments, the first battery cell 208 is one of several battery modules, each consisting of a number of cells of the same chemistry, and the second battery cell 210 is one of several battery modules, each consisting of a number of cells of a different chemistry. The battery modules can be connected in series, in parallel, or in a combination of both. The battery monitoring system 202 is configured to measure the temperature of the mixed-chemistry battery 200 via sensors 204. In one embodiment, the battery monitoring system 202 is configured to measure the state of charge (SOC) of both the first battery cell 208 and the second battery cell 210 via sensors 204 and performs other functions related to SOC estimation. In exemplary embodiments, the battery monitoring system 202 is configured to control the operation of the heating system 206 based at least on the temperature of the mixed-chemistry battery 200. In one embodiment, the heating system 206 comprises one or more switches and valves that are actuated by the battery monitoring system 202 to control which battery cells the heating system 206 supplies heat to and which battery cells supply power to the heating system 206. In exemplary embodiments, the battery monitoring system 202 comprises one or more general-purpose processors, central processing units, application-specific integrated circuits (ASICs), digital signal processors, field-programmable gate arrays (FPGAs), digital circuits, analog circuits, or combinations thereof. In one embodiment, the battery monitoring system 202 also comprises a memory that communicates with the processor and other components of the battery monitoring system 202. With reference to Fig. 3, a schematic diagram is shown illustrating a heating system for a mixed-chemistry battery 300 according to an exemplary embodiment. In exemplary embodiments, the mixed-chemistry battery 300 comprises a first battery set 302, comprising a plurality of first battery cells (not shown), and one or more second battery sets 310, each comprising a plurality of second battery cells 312. Each of the battery sets 302, 310 is electrically connected to one another via connectors 307, which may include wires and / or conductive plates. In one embodiment, the battery sets 302, 310 are connected to one another in a series configuration via the connectors 307. In another embodiment, the battery sets 302, 310 are connected to one another in a parallel configuration via the connectors 307. In exemplary embodiments, the mixed-chemistry battery 300 comprises a heating system including heating elements 314 arranged between the second battery cells 312. The heating elements 314 are resistance heating elements, which may include, but are not limited to, a positive temperature coefficient (PTC) resistance heater, aluminum foil, nickel foil, and the like. In exemplary embodiments, the heating elements 314 are interconnected by wires 301. In exemplary embodiments, the heating elements 314 are selectively connected to one or more of the first battery pack 302 and the second battery pack 310 via the actuation of switches 303, 304, 305, and 306. In exemplary embodiments, a battery monitoring system is configured to control the heating system via switches 303, 304, 305, and 306. In one embodiment, the heating system is configured to operate in three different modes. In the first mode, switch 303 is closed, switch 304 is open, switch 305 is open, and switch 306 is closed, so that the heating elements 314 are consequently configured to be supplied with power only from the first battery pack 302.In a second mode, switch 303 is open, switch 304 is closed, switch 305 is closed, and switch 306 is open, so that the heating elements 314 are consequently configured to be powered only from the second battery sets 310. In a third mode, switch 303 is closed, switch 304 is open, switch 305 is closed, and switch 306 is open, so that the heating elements 314 are consequently configured to be powered from both the first battery set 302 and the second battery sets 310. Furthermore, the heating system can be deactivated by opening switches 303, 304, 305, and 306. With reference to Fig. 4, a schematic diagram is shown illustrating a heating system for a mixed-chemistry battery 400 according to an exemplary embodiment. In exemplary embodiments, the mixed-chemistry battery 400 comprises a first battery set 402, comprising a plurality of first battery cells 403, and one or more second battery sets 404, each comprising a plurality of second battery cells 405. Each of the battery sets 402, 404 is electrically connected to one another via connectors 409, which may include wires and / or conductive plates. In one embodiment, the battery sets 402, 404 are connected to one another in a series configuration via the connectors 409. In exemplary embodiments, the mixed-chemistry battery 400 comprises a heating system comprising heating elements 406 arranged between the first battery cells 403 and heating elements 407 arranged between the second battery cells 405. The heating elements 406 and 407 are resistance heating elements, which may include, but are not limited to, a positive temperature coefficient (PTC) resistance heater, aluminum foil, nickel foil, and the like. In exemplary embodiments, the heating elements 406 and 407 are connected to each other by wires 408. In exemplary embodiments, the heating elements 406, 407 are selectively connected to one or more of the first battery set 402 and the second battery set 404 via the actuation of switches 410 and 411. In exemplary embodiments, a battery monitoring system is configured to control the heating system via switches 410 and 411. In one embodiment, the heating system is configured to operate in two different modes. In the first mode, switch 410 is closed and switch 411 is open, so that only the heating elements 407 are configured to be supplied with power from the first battery set 402 and the second battery set 404. In the second mode, switch 410 is open and switch 411 is closed, so that both heating elements 406, 407 are configured to be supplied with power from the first battery set 402 and the second battery set 404.Furthermore, the heating system can be deactivated by opening switches 410 and 411. With reference to Fig. 5, a schematic diagram is shown illustrating a heating system for a mixed-chemistry battery 500 according to an exemplary embodiment. In exemplary embodiments, the mixed-chemistry battery 500 comprises a plurality of first battery cells 503 and a plurality of second battery cells 505. Each of the battery cells 503, 505 is electrically connected to one another via connectors 509, which may include wires and / or conductive plates. In one embodiment, the battery cells 503, 505 are connected to one another in a series configuration via the connectors 509. In exemplary embodiments, the mixed-chemistry battery 500 comprises a heating system including heating elements 506 arranged between the battery cells 503 and 505. The heating elements 506 are resistance heating elements and may include, but are not limited to, a positive temperature coefficient (PTC) resistance heater, aluminum foil, nickel foil, and the like. In exemplary embodiments, the heating elements 506 are interconnected by wires 508. In exemplary embodiments, the heating elements 506 are selectively connected to one or more of the first battery cells 503 and the second battery cells 505 via the actuation of switches 510 and 511. In exemplary embodiments, a battery monitoring system is configured to control the heating system via switches 510 and 511. In one embodiment, the heating system is configured to operate in two different modes. In the first mode, switch 510 is closed and switch 511 is open, so the heating elements 506 are consequently configured to be supplied with current only from the first battery cells 503. In the second mode, switch 510 is open and switch 511 is closed, so the heating elements 506 are consequently configured to be supplied with current from both the first battery cells 503 and the second battery cells 505.Furthermore, the heating system can be deactivated by opening switches 510 and 511. With reference to Fig. 6, a schematic diagram is shown illustrating a heating system for a mixed-chemistry battery 600 according to an exemplary embodiment. In exemplary embodiments, the mixed-chemistry battery 600 comprises a first battery set 602, comprising a plurality of first battery cells (not shown), and one or more second battery sets 610, each comprising a plurality of second battery cells 612. Each of the battery sets 602, 610 is electrically connected to one another via connectors 607, which may include wires and / or conductive plates. In one embodiment, the battery sets 602, 610 are connected to one another in a series configuration via the connectors 607. In exemplary embodiments, the mixed-chemistry battery 600 comprises a heating system including heating elements 614 arranged between the second battery cells 612. The heating elements 614 are resistance heating elements, which may include, but are not limited to, a positive temperature coefficient (PTC) resistance heater, aluminum foil, nickel foil, and the like. In exemplary embodiments, the heating elements 614 are interconnected by wires 601. In exemplary embodiments, the heating elements 614 are selectively connected to one or more of the first battery pack 602 and the second battery pack 610 via the actuation of switches 603, 604, 605, and 606. In exemplary embodiments, a battery monitoring system is configured to control the heating system via switches 603, 604, 605, and 606. In one embodiment, the heating system is configured to operate in three different modes. In the first mode, switch 603 is closed, switch 604 is open, switch 605 is open, and switch 606 is closed, so that the heating elements 614 are consequently configured to be supplied with power only from the first battery pack 602.In the second mode, switch 603 is open, switch 604 is closed, switch 605 is closed, and switch 606 is open, so the heating elements 614 are configured to be powered only from the second battery sets 610. In the third mode, switch 603 is closed, switch 604 is open, switch 605 is closed, and switch 606 is open, so the heating elements 614 are configured to be powered from both the first battery set 602 and the second battery sets 610. Furthermore, the heating system can be deactivated by opening switches 603, 604, 605, and 606. In exemplary embodiments, the heating system of the mixed-chemistry battery 600 also includes a cooling plate 620, which is arranged next to the first battery set 602 and the second battery sets 610. In exemplary embodiments, the cooling plate 620 is a metal cooling plate comprising one or more cooling channels through which cooling fluid can flow. The cooling plate 620 includes a fluid inlet 622 and a fluid outlet 624 and one or more valves 626. In exemplary embodiments, the valves 626 are controlled by the battery monitoring system to selectively control the flow of cooling fluid through the cooling plate 620. In one embodiment, the cooling plate 620 is used to heat the one or more battery sets 602, 610 by circulating a hot fluid through the cooling plate.In another embodiment, the cooling plate 620 is used to heat one or more battery sets 602, 610 by circulating a cool fluid through the cooling plate. With reference to Fig. 7, a flowchart is presented illustrating a method 700 for heating a mixed-chemistry battery according to an exemplary embodiment. The mixed-chemistry battery comprises a first battery cell having a first chemistry and a second battery cell having a second chemistry different from the first chemistry. In one embodiment, the first chemistry is nickel-manganese-cobalt and the second chemistry is lithium iron phosphate. In block 702, the method 700 comprises monitoring the temperature of the mixed-chemistry battery. In block 704, the method 700 comprises connecting a heating system to only the first battery cell based on a determination that the temperature is below a first threshold.In block 706, method 700 comprises connecting the heating system to the first battery cell and the second battery cell based on a determination that the temperature is at least the first threshold. In exemplary embodiments, the first threshold is approximately minus twenty degrees Celsius. With reference to Fig. 8, a flowchart is presented illustrating a method 800 for a heating system for a mixed-chemistry battery, according to an exemplary embodiment. The mixed-chemistry battery comprises a first battery cell having a first chemistry and a second battery cell having a second chemistry that differs from the first chemistry. In one embodiment, the first chemistry is nickel-manganese-cobalt and the second chemistry is lithium-iron-phosphate. In block 802, the method 800 begins by monitoring the temperature of the mixed-chemistry battery, monitoring the state of charge of the first battery cell, and monitoring the state of charge of the second battery cell. In decision block 804, the method determines whether the temperature is below a minimum threshold. In one embodiment, the minimum threshold is approximately minus twenty degrees Celsius. Based on a determination that the temperature is below the minimum threshold, method 800 proceeds to block 806 and operates the mixed-chemistry battery heating system in a first operating mode. In exemplary embodiments, the first operating mode of the heating system comprises providing power to the heating system by connecting the heating system only to the first battery cell. While the heating system operates in the first operating mode, the temperature of the mixed-chemistry battery is monitored, and decision block 808 determines whether the temperature of the mixed-chemistry battery is below an intermediate threshold. In one embodiment, the intermediate threshold is approximately minus ten degrees Celsius. Based on a determination that the temperature of the mixed-chemistry battery is not below the intermediate threshold, method 800 proceeds to block 810 and operates the heating system of the mixed-chemistry battery in a second operating mode. In exemplary embodiments, the second operating mode of the heating system includes providing power to the heating system by connecting the heating system only to the second battery cell. While the heating system operates in the second operating mode, the state of charge of the first battery cell and a second state of charge of the second battery cell are monitored. Decision block 812 determines whether the difference between the first and second states of charge is less than a maximum offset. In exemplary embodiments, the maximum offset is less than ten percent. Based on a determination that the difference between the first and second states of charge is less than the maximum offset, the method proceeds to block 814 and operates the mixed-chemistry battery heating system in a third operating mode. Based on a determination that the difference between the first and second states of charge is greater than the maximum offset, method 800 returns to block 810 and continues operating the heating system in the second operating mode. Based on a determination that the temperature is at least the minimum threshold, Method 800 proceeds to Block 814 and operates the mixed-chemistry battery's heating system in a third operating mode. In exemplary embodiments, the third operating mode of the heating system includes supplying power to the heating system by connecting the heating system to the first battery cell and to the second battery cell. While the heating system is operating in the third operating mode, the temperature of the mixed-chemistry battery is monitored. In Decision Block 816, it is determined whether the temperature is above a maximum threshold. In exemplary embodiments, the maximum threshold is approximately twenty degrees Celsius. Based on a determination that the temperature is above the maximum threshold, Method 800 proceeds to Block 818 and the heating system is deactivated.Based on a determination that the temperature is below the maximum threshold, procedure 800 returns to block 814 and the heating system continues to operate in the third operating mode.

Claims

A method for heating a mixed-chemistry battery (200) comprising a first battery cell (208) having a first chemistry and a second battery cell (210) having a second chemistry different from the first chemistry, the method comprising: monitoring the temperature of the mixed-chemistry battery (200); monitoring the first state of charge of the first battery cell (208); monitoring the second state of charge of the second battery cell (210); based on a determination that the temperature is below a minimum threshold, connecting a heating system (206) to supply electrical energy only to the first battery cell (208); based on a determination that the temperature is above an intermediate threshold greater than the minimum threshold, connecting the heating system (206) to supply electrical energy only to the second battery cell (210).and based on a determination that the temperature is above the intermediate threshold, connecting the heating system (206) to supply electrical energy to the first battery cell (208) and to the second battery cell (210); characterized in that the first chemistry is nickel-manganese-cobalt and the second chemistry is lithium-iron-phosphate; wherein, in the case that the temperature is above the intermediate threshold, the heating system (206) is only connected to supply electrical energy to the first battery cell (208) and to the second battery cell (210) if the first state of charge and the second state of charge differ from each other by less than 10%; and wherein the heating system (206) is also connected to supply electrical energy to the first battery cell (208) and to the second battery cell (210) if the temperature is between the minimum threshold and the intermediate threshold.

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