Battery area

Hi everyone, 

I am working on a battery model based on SAM. I managed to replicate the voltage model and I know have moved on to the thermal model. How is the battery area calculated? I can only find the volumetric density (Wh/L), but no correlation to the actual area.

Thanks in advance,

Niccolò Oggioni 

Hi Niccolò,

SAM's battery thermal model makes a simplifying assumption that the battery shape is a cube, so the battery area can be determined from its volume. That calculation is performed (internally) by the SAM user interface to calculate values of batt_length, batt_width, and batt_height as follows:



Note that we are making changes to the battery code, so in the next version of SAM (Fall 2020), batt_area will replace the length/width/height variables.

The code for the battery thermal model is in this file on GitHub.com (search "thermal"):

github.com/NREL/ssc/blob/develop/shared/lib_battery.cpp

Best regards,
Paul.

Hi,

thanks a lot for the answer! I have checked the file you linked and it really helped my work! There is one thing that I is confusing me. Is the heat generated by the battery calculated using the internal cell resistance (user input) or the equivalent battery resistance (function of the cells in series and number of strings)? 

best regards,

Niccolò

Dear Niccolò,

The battery thermal model uses the user input cell resistance value. If the voltage curve is for a battery pack rather than a single cell, then the resistance is the battery equivalent resistance.

Best regards,
Paul.