Practitioner-designed.Attorney-supervised by design.

Thermal Regulation System for a Modular Battery Assembly

Inventors: M. Okabe, L. Ferrer · Filed 14 March 2023

A thermal regulation system for a modular battery assembly includes a plurality of cell modules arranged in a stacked configuration, coolant channels disposed at the interfaces between adjacent modules, and a sensor that reports a temperature of the assembly a plurality of temperature sensors, each thermally coupled to a respective cell module. A controller receives the reported temperatures and modulates a coolant flow rate in response to a differential computed between cell modules that are not adjacent to one another, such that the control input varies with the thermal gradient of the assembly rather than with the resistance of a single interface.

[0001] The following describes systems and methods for regulating the temperature of an electrochemical storage assembly built from discrete cell modules, and is directed in particular to the selection of the measurement from which coolant flow is derived.

[0002] Thermal management of such assemblies has conventionally relied on a single assembly-level temperature, or on a differential taken across two modules sharing an interface. Either measurement reports the condition of one location rather than of the stack as a whole.

[0003] Aspects of the disclosure may be applied to vehicular traction batteries, to stationary grid-scale storage installations, to marine and aviation propulsion packs, and to any assembly in which cell modules are held in thermal communication with one another across shared interfaces. The particular application is not limiting, and the described control scheme is independent of cell chemistry.

[0004] As used herein, two cell modules are described as adjacent where they share a common interface, and as non-adjacent where at least one further cell module lies between them along the axis of the stack. The term coolant is used broadly and encompasses liquid, gaseous, and phase-change working fluids.

[0005] Where a range is recited, the range is intended to include the endpoints and each value falling within it, and no recitation of a preferred embodiment is intended to exclude any other embodiment falling within the scope of the appended claims.

[0006] Batteries assembled from discrete cell modules accumulate heat unevenly. A module near the center of a stack is bounded on both faces by further modules, each of which is itself generating heat, whereas a module at either end of the stack is bounded on one face by the enclosure and can reject heat to it. Under sustained load the resulting gradient persists and, in assemblies of any appreciable length, grows.

[0007] The consequence is not merely inefficiency. Cell degradation is strongly temperature dependent, and a pack whose central modules run persistently warmer than its outer modules will age unevenly. The assembly is thereafter limited by its weakest modules, which are the modules that were never adequately cooled.

[0008] Conventional systems address this condition by sensing temperature at a single representative module, or by comparing a pair of modules across a shared interface, and modulating coolant flow accordingly. Such an approach responds principally to the local thermal resistance of one interface, which is a quantity of limited diagnostic value.

[0009] A local measurement is a poor proxy for the condition of the stack. An interface may run warm because the module beside it is working hard, or because the coolant channel serving it is partially obstructed, and these two conditions call for opposite responses from the controller. Neither is distinguishable from the other on the evidence of a single adjacent-pair differential.

[0010] There accordingly remains a need for a control input that varies with the thermal gradient of the assembly considered as a whole, and that can be obtained from sensors already present in a conventional pack without additional instrumentation.

[0011] In one aspect, a thermal regulation system comprises a plurality of cell modules arranged in a stacked configuration, a coolant channel disposed between adjacent modules, a plurality of temperature sensors each thermally coupled to a respective module, and a controller configured to modulate a coolant flow rate in response to a temperature differential measured between non-adjacent modules.

[0012] Computing the differential across modules separated by at least one intervening module yields a quantity that varies with the thermal gradient of the assembly, rather than with the resistance of any single interface. The intervening module acts, in effect, as a thermal lever arm.

[0013] The disclosed arrangement anticipates conventional stacked designs and The disclosed arrangement differs from conventional stacked designs in that it derives its control input from modules that are not in direct thermal contact, and accordingly responds to the condition of the assembly rather than to the condition of one join within it.

[0014] In a further aspect, a method comprises receiving a first temperature from a first cell module, receiving a second temperature from a second cell module not adjacent to the first, computing a differential between them, and modulating a coolant flow rate in response to the differential.

[0015] This summary is provided to introduce a selection of concepts in simplified form. It is not intended to identify essential features of the claimed subject matter, nor to be used as an aid in determining the scope of the claimed subject matter.

[0037] Referring now to FIG. 1, a modular battery assembly 100 includes cell modules 110a through 110f arranged in a stacked configuration along a longitudinal axis. Coolant channels 120 are disposed at the interfaces between adjacent modules and are placed in fluid communication with a pump 130 and a heat exchanger 140. The number of modules shown is illustrative; assemblies of two modules and of several dozen are both contemplated.

[0038] Temperature sensors 150 are thermally coupled to each of the cell modules. In certain embodiments a sensor is coupled to an exterior face of each module housing; in other embodiments a sensor is embedded within the housing itself, in thermal contact with the cell stack. The particular placement is not limiting, provided the sensor reports a temperature representative of the module to which it is coupled.

[0039] The controller 160 receives temperature values from the sensors and computes one or more differentials. A differential is computed between a first cell module and a second cell module that is not adjacent to the first, such that at least one intervening cell module lies between them along the longitudinal axis. In the embodiment shown, differentials are computed between modules 110a and 110c, and between modules 110d and 110f.

[0040] In response to a computed differential exceeding a first threshold, the controller increases the coolant flow rate through the channels. In response to the differential falling below a second threshold, the controller reduces the flow rate. The first and second thresholds may be fixed, or may be determined as a function of ambient temperature, state of charge, commanded load, or a combination thereof.

[0041] Hysteresis between the first and second thresholds prevents the pump from cycling where the differential sits near a single boundary. In one embodiment the second threshold is set at approximately eighty percent of the first, though other separations may be adopted without departing from the scope of the disclosure.

Claims

1. 1.

   A thermal regulation system for a modular battery assembly, comprising: a plurality of cell modules arranged in a stacked configuration along a longitudinal axis; a coolant channel disposed between adjacent cell modules; a plurality of temperature sensors, each thermally coupled to a respective cell module; and a controller configured to modulate a coolant flow rate through the coolant channel in response to a temperature differential between cell modules a temperature differential between non-adjacent cell modules separated by at least one intervening cell module.

2. 2.

   The system of claim 1, wherein the controller increases the coolant flow rate in response to the temperature differential exceeding a first threshold.

3. 3.

   The system of claim 2, wherein the first threshold is determined as a function of at least one of ambient temperature, state of charge, and commanded load.

4. 4.

   The system of claim 1, further comprising a heat exchanger in fluid communication with the coolant channel and a pump configured to circulate coolant therethrough.

5. 5.

   The system of claim 1, wherein each temperature sensor is embedded within a housing of the respective cell module.

6. 6.

   A method of regulating temperature in a modular battery assembly, the method comprising: receiving a first temperature from a first cell module; receiving a second temperature from a second cell module not adjacent to the first cell module; computing a differential between the first temperature and the second temperature; and modulating a coolant flow rate in response to the differential.

7. 7.

   The method of claim 6, wherein the first and second cell modules are separated by at least one intervening cell module along a longitudinal axis of the assembly.