Thermal Analysis of New and Aged Battery Packs | Simscape Battery Essentials, Part 7 - MATLAB & Simulink
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    Thermal Analysis of New and Aged Battery Packs | Simscape Battery Essentials, Part 7

    From the series: Simscape Battery Essentials

    Simscape Battery™, a new product in R2022b, has been developed to provide a technology development framework that is assembled specifically to create a bridge between battery cell and battery system. The bridge directly supports upskilling as well as design exploration and design rigor, meaning you can navigate the battery system technology development cycle rapidly and with confidence. You will learn how to:

    1. Define the components and geometry of a battery pack that include fade characteristics (the degradation of resistance as a function of charging cycles).
    2. Make the battery pack parameters available in a MATLAB script and adjust the parameters to change parameterization from a “new” pack to an “aged” pack.
    3. Compare the responses of new and aged battery packs and show the degradation in voltage.

    Published: 20 Sep 2022

    Hello, everyone. My name is Graham Dudgeon and welcome to part seven in a series of videos where we'll provide insights and work examples on the use of Simscape battery, a new product in the Simscape portfolio. Simscape battery has been developed to provide a technology development framework that is assembled specifically to create a bridge between cell and system.

    This bridge directly supports upscaling as well as design exploration and design rigor, meaning you can navigate the technology development cycle rapidly and with confidence. Today, I'll discuss how we can perform thermal analysis of new and aged battery packs.

    So we'll start with the definition and creation of the battery pack model. I'm using this example, Build Model of Battery Pack with Cell Aging. And so this Matlab live script works through from cell through parallel assembly, module, module assembly, and pack. In parts 1 and 2 of this video series, I provided more detail on moving through this workflow.

    What I'll do today is highlight those aspects of the definition of the pack that enable us to model battery feed. So I'm just going to scroll down and stop at the appropriate points. So with the battery cell definition, what we need to do is we need to set the property, prm_fade, to equations and also thermal_port to model.

    We then create a parallel assembly. And, in this case, we're connecting three cells to create our parallel assembly. We then create our battery module, which consists of a series connection of four parallel assemblies. Next is our modular assembly. So we connect five modules in series.

    And when we get to our battery pack definition, we need to set the two thermal paths to cell-based thermal resistance because we're going to be adding a cooling element to this model. So what I'll do here is visualize the battery pack. You just highlight this and evaluate. We'll take a look.

    Here's our visualization with the simulation strategy highlighted. Let me just bring this to full screen. So you can see each parallel assembly has three cells. Module has four parallel assemblies connected in series. Module assembly has five modules connected in series. And then the pack has five module assemblies.

    You can see that each module has a single simulation strategy boundary, indicating that when we create the Simscape model, each module will be modeled as an individual cell model. We then build the Simscape model. So what I'm doing is I'm making a slight change to the build battery called here.

    You see I'm adding mask initial targets and mask parameters to variable names. What this will do is create a MATLAB script with data structures that contain the parameterization. I have already run this. So let me show you the battery pack.

    There's the pack model with positive and negative electrical terminals and various signal measurements, we just double click, and we bring this to full screen. Size module assemblies. Go on to the module assembly, clicking spacebar to go to full screen here.

    Five modules per module assembly and see we have the parameterization using data structures. The point I'd like to make here as I open up Fade, we have never included fades characteristics on this model, fades being the degradation of the capacity of the battery as a function of the number of cycles.

    Final point, we are exposing thermal ports. And you can see, we're connecting them together to a single thermal port. If I just work my way back up through, you can see we're doing the same connecting up to a single thermal port. Let me just zoom in on this.

    So there is a thermal port at the bottom. So it's a single port, in this case, where the thermal resistances have been connected together. And so our cooling model will be a lumped representation for more detail. And I have to do a more granular representation of cooling, which includes cooling plates. Please refer to part 3 in this video series.

    Well, OK, now that we've defined our pack and included these fade characteristics, let's take a look at how we now simulate new and aged battery packs. So we're using this example, Thermal Analysis for New and Aged Battery Packs. So let me just show you the simulation model first. We'll talk through the components of that.

    So here we have our battery pack. And so we have a lumped representation of a pipe. We're using a control mass flow rate pump to push cooling liquids through this pipe, and we have an appropriate control system here to manage that temperature. Constant load of 54 amps, and we'll simulate this model using a variable step solver.

    So now, we just step through the MATLAB live script. First thing we do is we set up our parameterization. So let me just quickly show you that MATLAB script which contains the data structures. So we've set the thermal resistance in the cooling path to 1.2. So that's for our new battery pack.

    So we run that simulation and make some measurements for the new pack. We then want to simulate an end-of-life battery pack. So we set it up so for every 100 discharge cycles, we are decreasing the thermal resistance by 5%. And then for the age pack, we're setting that thermal resistance from 1.2 to 5.

    We then set the number of cycles to be 999 for end-of-life and rerun the simulation. So let me just show you where this parameter end-of-life cycle goes. So we set the number of cycles in the cell model to that value. Then we rerun the simulation. Make some measurements on the age pack, and then we can take a look at some results.

    So you can see here the figure that's looking at the voltage response is a function of time for both the aged and the new pack. As you can see that the age pack has degraded as indicated by its decreased level of voltage.

    So let's recap what we've looked at today. First step was to create a battery pack, which included fade characteristics and set up the parameterization so that the data structures were contained within a MATLAB script. We then set up a simulation model with cooling and performed a comparison between a new pack and a degraded pack.

    And we specified the degraded pack through increasing the thermal resistance and indicating fade characteristics as a function of cycles and percentage reduction in thermal resistance. I hope you found this information useful. Thank you for listening.