chosing the right Vnom, Qnom point in Shepherd model

Hello, I'm currently using the battery library in Simulink, based on the Shepherd model. When I input the nominal voltage values as specified in the datasheet, I notice that the curve accuracy diminishes after the nominal voltage range. However, when I manually select different points, I obtain a more accurate curve. Which approach is preferable: relying on the nominal voltage values provided in the datasheet or selecting my own points to achieve a more accurate representation of the battery's behavior?

Answer 1

[Ayush]

Hi Aymen,

A balanced approach here would be the most suitable for the most accurate representation of the battery's behaviour. Here is a step-by-step approach for the same:

1. To begin with, you can use the nominal voltage values from the battery's datasheet as they are the baseline standards and ensure that the initial model is as per the manufacturer's specifications.

2. You can then refine the model by analyzing the performance and identifying the critical points where the curve accuracy dips. Collect data or conduct tests in these identified areas to better understand the battery's behaviour.

3. Once done, you can then manually adjust the model by selecting the more accurate points, especially where the nominal values are dropping to ensure that the model capture the variations of your battery.

4. To validate the refined model, you can compare it with real-world data and confirm whether the modifications increase the accuracy of the battery's behaviour or not.

5. Continuously refine and validate the model to maintain its reliability and accuracy across different operating conditions and without introducing significant errors.

Some toolboxes that can increase this workflow's efficiency are referenced below:

Curve Fitting Toolbox: https://www.mathworks.com/help/curvefit/

Optimization Toolbox: https://www.mathworks.com/help/optim/

Simulink Design Optimization: https://www.mathworks.com/help/sldo/

Hope this helps!

[aymen mahmoudi]

thank you for Help

I find that Simulink battery model call the end of nominal area by nominal voltage. the nominal voltage mentionned in datasheet is not the the end of nominal voltage. for exemple for my battery model VL34570 the nominal voltage is 3.7 Volt, but the end of nominal voltage is 3.49 volt. so when simulink model ask for nominal voltage you need to write 3.49

[Ayush]

Hi Aymen,

Can you provide me the simulink model, if possible?

[aymen mahmoudi]

yes of course

this is the final comparaison of results between original and simulated

you can find datasheet and dataset of real curve of discharge

thanks for help