In SAM 2020.2.29 r1, the specify cells option for sizing the battery is not working correctly for behind-the-meter (BTM) configurations (Residential, Commercial, or Third Party - Host Developer). We will fix this in the next update. In the meantime you can use the workaround described on GitHub.com to fix the problem:
github.com/NREL/SAM/issues/267
Best regards,
Paul.
