Battery Pack Designing (Sizing+Simulation+Comparing+Calibration+Durability Analysis)

For this project, first we select a target application between 6 target load profiles. the following set of power profiles, representative of 1 year of operation each, are provided in MATLAB matrix format (.mat) as function of time where values are reported in [W] (positive = charge, negative = discharge) with an acquisition frequency of 1 Hz.

After selecting one of the target application between those proposed, we identified the requirements for the battery pack to fulfill the task. We chose and extracted a specific period (about one month long with overall neutral SOC variation) on which the sizing will be performed.

In the next step, we defined the required total energy and the maximum charge/discharge power capability for the battery packs. In addition, we performed the battery pack sizing by considering that SOC of the cells would be generally not exceeding 80% and 20% respectively in charge and discharge when executing the reference profile for the sake of durability and safety.

To evaluate the total energy required, a cumulative analysis is needed. The accumulated energy curve is plot below. It represents the amount of energy present inside the battery time-step per time-step.

Then we calculated the number of single cells to be comprised in each battery packs in order for it to fulfill the requirements calculated above, stating the resulting technical specifications in terms of overall volume and mass, total energy, maximum power and overall cost.

Once the battery pack is sized, we computed the corresponding SOC, Current, C-rate and Voltage profile vs time when executing the reference profile.

BATTERY PACK DURABILITY

In our project, It was asked to evaluate aging due to calendar life and cycle operations. The aging effects are evaluated via simplified experimental correlations taken from the literature.

the aging effects result in a capacity fading. So the nominal capacity of the cell (and so of the pack) will decrease time-step per time-step. This has been taken into account inside the model, updating the nominal capacity of the cell in each time-step of the calculation procedure (nominal capacity decrease will affect the SoC variation, as well as the ∆Charge and so the Ah_throughput). C-Rate needed in the calculation of cycling aging was also calculated inside the model. The capacity fade and the state of health (SoH) only due to cycle operations are shown in the following plot:

Also we analyzed two battery types for our project and in order to simulate charge and discharge operation of the battery packs, we calibrate the provided simplified model on the experimental curves provided for each of the single cells proposed.

We defined and Calculated all the needed parameters and the equilibrium potentials calculated via the Nernst’s Law. The experimental curves compared to the modeled curve are reported below:

Also for the two battery samples the voltage/current vs. time curves are reported as a function of the C_rate. For the cylindrical battery type the plots are :

PS:

• All The results and analysis extracted and done by MATLAB

• More information are available upon request