How can I limit SOC for a battery pack on the lower side

Hello,

Using MATLAB (R2024a), I have built a battery pack library (1 Pack having 20 Module Assemblies, each module assembly having 5 modules, each module assembly having 20 parallel assemblies, with each parallel assembly having 120 cells). Then, I am trying to simulate (using Simulink and simscape components), a system where this battery pack is connected to a resistance as load and monitoring current flowing out of the battery pack and temparature of the pack. The resolution for parallel assemble and module is "Lumped".

When I run this integrated model (this battery pack library with the battery thermal monitoring, current monitoring and boost DC-DC Converter with resistive load), the battery pack discharges. The SOC of the battery pack discharges and continues to fall even below 0.

How can I limit the SOC to 20% or 0%?

Kindly suggest a possible solution for my issue.

Thanks, and Regards,

Sameer Phatak

Answer 1

[Karanjot]

Hi Sameer,

If the SOC (State of Charge) falls below 0% in your simulation, it often indicates an issue with SOC estimation or model configuration. Here are some potential reasons and solutions:

• Ensure that the battery's capacity, internal resistance, and other parameters accurately reflect the real battery's characteristics.
• The algorithm used for SOC estimation might not be well-suited for the specific battery chemistry or application.
• Without proper control logic to limit discharge, the battery might continue to discharge even when SOC is low, leading to negative values.
• Implement a feedback mechanism to reduce or cut off the load when SOC approaches the minimum threshold.

I recommend going through the following documentation links:

https://www.mathworks.com/help/simscape-battery/ug/estimate-battery-soc-using-kalman-filter-example.html

https://www.mathworks.com/help/simscape-battery/ug/perform-controlled-charging-discharging-on-battery-module.html

I hope this helps!