Batemo Pack Generator

Every Saturday, Thomas G. and Michael Bambula are excited to bring the developers on stage and provide you an extended read into various simulation topics.

by Filip Kozlik and Mario Jelovic

What’s the issue with battery packs?

Well, the simulation of battery packs is an interesting engineering task that gives you a lot of freedom to decide on battery cell type, number of cells, electrical cell configuration, design on thermoregulation concepts, assembly of battery modules, sizing of auxiliary and cooling devices, configuration of modules to a pack … and much more. You see, the freedom to decide might also turn into a burden when the quest for an optimum requires quite some complexity to be mastered. Only the brave? Not only, the Batemo Pack Generator enables you to assess new ideas, your way, without being bothered by electrochemistry, thermodynamics and math. The generator creates a link between basic pack design decisions and pack performance KPIs. You might have already thought about the following applications:

• Pack Design Study: Identify the optimal battery pack design for your application.
• Cell Technology Comparison: Learn which battery cell and housing type is the most suitable for you.
• Look Into The Future: See how your application can benefit from future cell technologies.
• Pack Cooling Analysis: Understand the consequences of using different cooling methods in your battery pack.
• Sensitivity Analysis: Quantify how battery pack parameter variations impact you design targets.

A guided workflow for the creation of battery packs

The collection of model generators in AVL CRUISE??M offers a special generator for battery modules and packs featuring cell models from Batemo. The Batemo Pack Generator follows CRUISE?M’s generator philosophy to enable a non-expert to setup a high fidelity battery model with a minimum number of inputs, quick and easy, within minutes (see Figure 1).

The creation of a battery pack model follows a guided workflow, walking you through a questionary to configure the setup. You start to select a cell, followed by the specification of the module, and finally you decide about the battery pack (see Figure 2). Here it is important to emphasize that you don’t follow the generator process in a blind-fold manner. You are continuously supported by graphical and text outputs giving you immediate feedback on what you do. When you are done, you are really done.

Many models call themselves advanced. The Batemo Back Generator proves this claim at three different levels. We use cell models from a validated library, thermal and electrical aspects on module and pack level are physically modeled and in case your setup deviates from the default options, you easily can adjust them in the CRUISE?M model topology editor. All you need for early phase concept studies.

How to generate battery pack in eight steps?

Step 1/8: Cell designSelect a battery cell to be used in the desired battery pack. We offer a choice between “Batemo cell library” and “Batemo cell custom”. The Batemo cell library will give you a list of validated cell models. Validated means that the cell behavior is proven against a standardized test protocol featuring steady and transient operations at different loads and temperatures. If you like you use a cell that’s not in the library we can connect you with the Batemo team and work on a custom cell model.

Step 2/8: Module design – mechanical

The module consists of cells, housing, auxiliaries, cooling, heating, and contacting. For that you are asked to specify the desired dimensions of the module, to select the housing material and thickness and to configure the size of the auxiliaries block and the way cells are packed into it. The auxiliaries block represents and contains the contactors, fuses, circuit boards, and all related electrical components. All these reduce the available volume in the battery module for cells.

Step 3/8: Module design – thermal ?

The question on cooling of battery module is not answered by one single answer. There is boundary conditions and constrains leading to all what system engineers can imagine. This step of the Batemo Pack Generator offers, as starting point, five different cooling options:

• Passive cooling: We assume that battery cells are positioned in a stationary fluid
• Passive cooling with heat sink: We consider a heat sink as additional block in the module supporting the cooling
• Forced cooling: We assume that the battery cells are positioned in a fluid in motion (there is forced advection)
• Forced cooling with heat sink: We consider a heat sink as additional block in the module supporting the cooling

• Liquid cooling with heat sink: We consider a heat sink as additional block in the module supporting the cooling

The selected cooling method affects the thermal model that is given as thermal boundary condition of the individual cells, it determines the required module cooling power, and thus the module efficiency. Beyond that, you have the option to specify a heat power applied to the module. Here, the heater is modeled as external power source that does not drain energy from cells.

Step 4/8: Module design – electrical

The module dimensions, the size of auxiliaries, the cooling and the heating blocks limit the number of cells that fit in the module. The generator does the math for you and calculates how many cells fit into it. Next, after having specified the number of cells in parallel, you get immediate feedback on the expected module capacity, current etc. Here it is highly recommended to take advantage of the three different graphical displays, the model visualization, the SOC-OCV and cell performance plots. What you see is what you get and, if you fine with it, the module configuration is done.

Step 5/8: Pack design – mechanical

The configuration of the pack starts and ends fairly simple. Decide how many modules you like to stack in length, width and height and configure a volume share for auxiliary and cooling devices.

Step 6/8: Pack design – electrical

The electrical setup of the pack asks you for one single number. How many modules do you like to operate in parallel. With that you finally configure the pack capacity and current as the performance plots are letting you know.

Step 7/8: Pack design – pack data

The configuration is done, almost, it’s time recheck the pack KPIs. The resulting mechanical and electrical pack characteristics are displayed and there is variety of graphs to evaluate the pack design.

Step 8/8: Pack design – initial conditions

Any simulation model that marches on in time needs a starting point. At the last page of the Batemo Pack Generator, you need to set initial state-of-charge, initial temperature, and if you like, a few settings on the cell state-of-health. With that you are all set and can click the finish button.

Pack Configuration Done – And now?

Once, the finish button in the Batemo Back Generator is clicked, it takes a few seconds, and a ready-to-run model is generated (see Figure 11). The model comprises a closed electrical network featuring a current source and the Batemo cell component. The latter is equipped with parameters that are the result of the pack configuration process you went through. The model additionally features several heat transfer and thermal mass components describing the heat transfer from the cells via the housing and potential heat sinks to the ambient. Again, the parameterization follows what was configured in the Batemo Pack Generator. No need to touch it.

How ready the model is to get started is shown in Figure 12. You get a pre-configured dashboard that allows an online inspection of the model by nothing else than clicking the run button. With that you can interactively play with the load and ambient conditions and see what your battery pack is doing, and eventually continue with more sophisticated simulation studies.

As much as we love to nerd out about simulation and read lengthy articles about it, we have to cut it short at this point.

We want to thank Filip Kozlik and Mario Jelovic for the insights and the impressive work that is performed day to day behind the scenes.

Real-world activities and their real-time limitations bring this Simulation Saturday to an end, but stay tuned for another one soon!

Cheers, Thomas and Michael

?What’s next:

You tell us!

• Which simulation topic are you particularly interested?
• What features would you love to see?
• What do you love or hate most about the tool(s) you use?

We love to hear all of it in the comments and encourage you to: - learn more on our product sites:?AVL Advanced Simulation Technologies Tools - try it:?Rescale - simulate for free via?AVL University Partnership Program as a student and academic researcher. - get in contact via [email protected] and [email protected]

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